GPS Ocean Reflection Experiment (GORE) Wind Explorer (WindEx) Instrument Design and Development

NASA Astrophysics Data System (ADS)

Ganoe, G.

2004-12-01

This paper describes the design and development of the WindEx instrument, and the technology implemented by it. The important design trades will be covered along with the justification for the options selected. An evaluation of the operation of the instrument, and plans for continued development and enhancements will also be given. The WindEx instrument consists of a processor that receives data from an included GPS Surface reflection receiver, and computes ocean surface wind speeds in real time utilizing an algorithm developed at LaRC by Dr. Stephen J. Katzberg. The WindEx performs a windspeed server function as well as acting as a repository for the client moving map applications, and providing a web page with instructions on the installation and use of the WindEx system. The server receives the GPS reflection data produced by the receiver, performs wind speed processing, then makes the wind speed data available as a moving map display to requesting client processors on the aircraft network. The client processors are existing systems used by the research personnel onboard. They can be configured to be WINDEX clients by downloading the Java client application from the WINDEX server. The client application provides a graphical display of a moving map that shows the aircraft position along with the position of the reflection point from the surface of the ocean where the wind speed is being estimated, and any coastlines within the field of view. Information associated with the reflection point includes the estimated wind speed, and a confidence factor that gives the researcher an idea about the reliability of the wind speed measurement. The instrument has been installed on one of NOAA's Hurricane Hunters, a Gulfstream IV, whose nickname is "Gonzo". Based at MacDill AFB, Florida, "Gonzo" flies around the periphery of the storm deploying GPS-based dropsondes which measure local winds. The dropsondes are the "gold-standard" for determining surface winds, but can only be deployed sparingly. The GPS WindEx system allows for a continuous map between dropsonde releases as well as monitoring the ocean surface for suspicious areas. The GPS technique is insensitive to clouds or rain and can give information concerning surface conditions not available to the flight crew.

Initial Studies of the Bidirectional Reflectance Distribution Function of Multi-Walled Carbon Nanotube Structures for Stray Light Control Applications

NASA Technical Reports Server (NTRS)

Butler, J. J.; Tveekrem, J. L.; Quijada, M. A.; Getty, S. A.; Hagopian, J. G.; Georglev, G. T.

2010-01-01

The presentation examines the application of low reflectance surfaces in optical instruments, multi-walled carbon nanotubes (MWCNTs), research objects, MWCNT samples, measurement of 8 deg. directional/hemispherical reflectance, measurement of bidirectional reflectance distribution function (BRDF), and what is current the "blackest ever black".

ASTER Waves

NASA Technical Reports Server (NTRS)

2000-01-01

The pattern on the right half of this image of the Bay of Bengal is the result of two opposing wave trains colliding. This ASTER sub-scene, acquired on March 29, 2000, covers an area 18 kilometers (13 miles) wide and 15 kilometers (9 miles) long in three bands of the reflected visible and infrared wavelength region. The visible and near-infrared bands highlight surface waves due to specular reflection of sunlight off of the wave faces.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

Enabling High Performance Instruments for UV Astronomy and Space Exploration with ALD

NASA Technical Reports Server (NTRS)

Greer, F.; Hoenk, M. E.; Jones, T. J.; Jacquot, B. C.; Monacos, S.; Nikzad, S.; Hamden, E.; Schiminovich, D.

2011-01-01

Benefits of Atomic Layer Deposition (ALD) for UV instruments and application are: (1) Ultrathin, highly conformal, and uniform films over arbitrarily large surface area (2) High quality films (density, roughness, conductivity, etc.) (3) Angstrom level control of stoichiometry, interfaces, and surface properties (3a) Multilayer nanolaminates/nanocomposites (3b) Low temperature surface engineering UV flight applications enabled by ALD. (1) Anti -reflective coatings/Mirrors/Filters/Optics for UV/Vis/NIR Detectors (2) Surface Passivation for III -N detectors

Enabling High Performance Instruments for Astronomy and Space Exploration and ALD

NASA Technical Reports Server (NTRS)

Greer, Frank; Lee, M. C.; Hoenk, M. E.; Jones, T. J.; Jacquot, B. C.; Dickie, M.; Monacos, S.; Nikzad, S.; Day, P.; Leduc, R.;

The Retrieval of Aerosol Optical Thickness Using the MERIS Instrument

NASA Astrophysics Data System (ADS)

Mei, L.; Rozanov, V. V.; Vountas, M.; Burrows, J. P.; Levy, R. C.; Lotz, W.

2015-12-01

Retrieval of aerosol properties for satellite instruments without shortwave-IR spectral information, multi-viewing, polarization and/or high-temporal observation ability is a challenging problem for spaceborne aerosol remote sensing. However, space based instruments like the MEdium Resolution Imaging Spectrometer (MERIS) and the successor, Ocean and Land Colour Instrument (OLCI) with high calibration accuracy and high spatial resolution provide unique abilities for obtaining valuable aerosol information for a better understanding of the impact of aerosols on climate, which is still one of the largest uncertainties of global climate change evaluation. In this study, a new Aerosol Optical Thickness (AOT) retrieval algorithm (XBAER: eXtensible Bremen AErosol Retrieval) is presented. XBAER utilizes the global surface spectral library database for the determination of surface properties while the MODIS collection 6 aerosol type treatment is adapted for the aerosol type selection. In order to take the surface Bidirectional Reflectance Distribution Function (BRDF) effect into account for the MERIS reduce resolution (1km) retrieval, a modified Ross-Li mode is used. The AOT is determined in the algorithm using lookup tables including polarization created using Radiative Transfer Model SCIATRAN3.4, by minimizing the difference between atmospheric corrected surface reflectance with given AOT and the surface reflectance calculated from the spectral library. The global comparison with operational MODIS C6 product, Multi-angle Imaging SpectroRadiometer (MISR) product, Advanced Along-Track Scanning Radiometer (AATSR) aerosol product and the validation using AErosol RObotic NETwork (AERONET) show promising results. The current XBAER algorithm is only valid for aerosol remote sensing over land and a similar method will be extended to ocean later.

Reflections of ions in electrostatic analyzers: a case study with New Horizons/Solar Wind Around Pluto.

PubMed

Randol, B M; Ebert, R W; Allegrini, F; McComas, D J; Schwadron, N A

2010-11-01

Electrostatic analyzers (ESAs), in various forms, are used to measure plasma in a range of applications. In this article, we describe how ions reflect from the interior surfaces of an ESA, the detection of which constitutes a fundamentally nonideal response of ESAs. We demonstrate this effect by comparing laboratory data from a real ESA-based space instrument, the Solar Wind Around Pluto (SWAP) instrument, aboard the NASA New Horizons spacecraft, to results from a model based on quantum mechanical simulations of particles reflected from the instrument's surfaces combined with simulations of particle trajectories through the instrument's applied electrostatic fields. Thus, we show, for the first time, how reflected ions in ESAs lead to nonideal effects that have important implications for understanding the data returned by these instruments, as well as for designing new low-background ESA-based instruments. Specifically, we show that the response of SWAP widens considerably below a level of 10(-3) of the peak response. Thus, a direct measurement of a plasma distribution with SWAP will have an energy-dependent background on the order of ≤10(-3) of the peak of the signal due to that distribution. We predict that this order of magnitude estimate for the background applies to a large number of ESA-based instruments because ESAs operate using a common principle. However, the exact shape of the energy-dependent response will be different for different instruments. The principle of operation is that ions outside the ideal range of energy-per-charge are deflected into the walls of the ESA. Therefore, we propose that a new design paradigm is necessary to mitigate the effect of ion reflections and thus accurately and directly measure the energy spectrum of a plasma using ESAs. In this article, we build a framework for minimizing the effect of ion reflections in the design of new ESAs. Through the use of existing computer simulation software, a design team can use our method to quantify the amount of reflections in their instrument and iteratively change design parameters before fabrication, conserving resources. A possible direction for the new design paradigm is having nonsolid walls of the ESA, already used in some applications.

Reflections of ions in electrostatic analyzers: A case study with New Horizons/Solar Wind Around Pluto

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randol, B. M.; Ebert, R. W.; Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas 78228

Electrostatic analyzers (ESAs), in various forms, are used to measure plasma in a range of applications. In this article, we describe how ions reflect from the interior surfaces of an ESA, the detection of which constitutes a fundamentally nonideal response of ESAs. We demonstrate this effect by comparing laboratory data from a real ESA-based space instrument, the Solar Wind Around Pluto (SWAP) instrument, aboard the NASA New Horizons spacecraft, to results from a model based on quantum mechanical simulations of particles reflected from the instrument's surfaces combined with simulations of particle trajectories through the instrument's applied electrostatic fields. Thus, wemore » show, for the first time, how reflected ions in ESAs lead to nonideal effects that have important implications for understanding the data returned by these instruments, as well as for designing new low-background ESA-based instruments. Specifically, we show that the response of SWAP widens considerably below a level of 10{sup -3} of the peak response. Thus, a direct measurement of a plasma distribution with SWAP will have an energy-dependent background on the order of {<=}10{sup -3} of the peak of the signal due to that distribution. We predict that this order of magnitude estimate for the background applies to a large number of ESA-based instruments because ESAs operate using a common principle. However, the exact shape of the energy-dependent response will be different for different instruments. The principle of operation is that ions outside the ideal range of energy-per-charge are deflected into the walls of the ESA. Therefore, we propose that a new design paradigm is necessary to mitigate the effect of ion reflections and thus accurately and directly measure the energy spectrum of a plasma using ESAs. In this article, we build a framework for minimizing the effect of ion reflections in the design of new ESAs. Through the use of existing computer simulation software, a design team can use our method to quantify the amount of reflections in their instrument and iteratively change design parameters before fabrication, conserving resources. A possible direction for the new design paradigm is having nonsolid walls of the ESA, already used in some applications.« less

Exploring Mercury's Surface in UltraViolet from Orbit

NASA Astrophysics Data System (ADS)

Izenberg, N.

2017-12-01

The MESSENGER Mission's Ultraviolet and Visible Spectrometer (UVVS) component of its Mercury Atmosphere and Surface Composition Spectrometer (MASCS) instrument obtained approximately 4600 point observations of Mercury's surface in middle ultraviolet (MUV; 210 nm - 300 nm) and far ultraviolet (FUV; 119.1 - 122.5 nm and 129.2 - 131.5 nm) wavelengths over the course of its orbital mission, mostly in Mercury's southern hemisphere. Given the very low (<1 to 2 wt %) average abundance of iron in the silicates of Mercury observed by multiple MESSENGER instruments, the near- to middle-ultraviolet wavelengths encompassing the oxygen metal charge transfer band (<400 nm), which is more sensitive to the presence of iron than the classic 1 micron absorption band, provides potentially useful additional compositional insight into the top layer of Mercury's regolith. The presence of nano- and microphase carbon also has potentially significant expression in the ultraviolet, and the interplay and variation between carbon and iron in mercury surface materials is an active area of investigation. Analysis of middle-UV surface reflectance and parameters appear to support the presence of varying amounts of carbon in different spectral or geologic units on Mercury. Far-UV reflectance data is currently under-utilized, but analysis of lunar surface by the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) indicate that the data are sensitive to both composition and space weathering. The far-UV reflectance from MASCS may provide similar information for the Mercury surface, complementing results from longer wavelengths. MESSENGER data products for surface reflectance include middle-UV reflectance spectra, ultraviolet far-UV reflectance values, combined middle-UV through near-infrared spectra (210 nm - 1450 nm), a global `spectral cube' of near-UV to near-IR, and an upcoming UV spectral cube.

In-Situ VIS/NIR Measurements of Space Environment Effects on Spacecraft Surfaces

NASA Astrophysics Data System (ADS)

Bedard, D.; Seitzer, P.; Willison, A.; Somers, P.

2016-09-01

Laboratory material characterization experiments have shown that passive observational techniques that measure the spectral energy distribution of reflected sunlight from spacecraft and space debris could potentially be used to determine an object's surface compositional make-up and even possibly its orientation. Such techniques, if proven to be reliable and consistent, would represent non-intrusive and cost effective tools that would benefit the overall space situational awareness (SSA) mission. However, to date, observations using either colour photometry or spectrophotometry to determine surface material characteristics of such objects have not produced encouraging results. One common problem that has plagued these attempts is the lack of understanding on how the spectral reflectance of the spacecraft surfaces evolves with time. There are a number of spacecraft materials whose spectral reflectance characteristics have been studied before and after spaceflight in LEO; there are no measurements on how the space environment gradually modifies the spectral scattering characteristics of these materials as a function of time. Furthermore, there are little or no in-situ observations of environmental effects on individually identifiable materials in MEO and GEO. This complicates the task of interpreting the spectral measurements of spatially unresolved spacecraft and orbital debris. This paper presents instrument concepts whose sole purpose will be to acquire on-orbit spectral reflectance measurements, at different observational geometries, of either witness samples or materials covering the surface of the host spacecraft. Such instruments could be flown as a hosted payload on an operational GEO satellite or as a dedicated payload on a microsatellite. Measurements would be acquired over the lifetime of the satellite and would observe how the spectral reflectance characteristics evolve during its lifetime. Furthermore, installation of one of the proposed instruments on multiple satellites would provide an opportunity to study the variation in space environment effects on the surfaces of spacecraft located in different orbital regimes, such as LEO, MEO, and GEO.

Diffusely Reflecting Paints Containing TFE

NASA Technical Reports Server (NTRS)

Shai, M. C.; Schutt, J. B.

1985-01-01

Highly reflective, diffused coatings developed by incorporating polytetrafluoroethylene (TFE) pigment with alcohol-soluble binders. Alcohol and binder mixed together in blender before adding TFE. TFE preferably outgassed in mechanical-pump vacuum for typical interval of 4 hours before adding to liquid. Like wetting agent, vacuum treatment helps to prevent clumping of TFE and eases dispersion throughout mixture. Mixture blended for 3 to 5 minutes before used. Coatings useful on reflectance-standard surfaces for calibrating radiometric instruments in both laboratory and field. Paints washable and usable as optical reference surfaces.

Diffuse Reflectance Mid-Infrared Spectroscopy as a Tool for the Identification of Surface Contamination on Sandblasted Metals

NASA Technical Reports Server (NTRS)

Powell, Louis G.; Barber, Tye E.; Neu, John T.; Nerren, Billy H.

1997-01-01

The SOC 400 Surface Inspection Machine/Infrared (SIMIR) is a small, ruggedized Fourier transform infrared spectrometer having dedicated diffuse reflectance optics. The SOC 400 was designed for the purpose of detecting (qualitatively and quantitatively) oil stains on the inside surface of solid rocket motor casings in the as-sandblasted and cleaned condition at levels approaching 1 mg. sq ft. The performance of this instrument is described using spectral mapping techniques.

Workshop on Innovative Instrumentation for the In Situ Study of Atmosphere-Surface Interactions on Mars

NASA Technical Reports Server (NTRS)

Fegley, Bruce, Jr. (Editor); Waenke, Heinrich (Editor)

1992-01-01

The speakers in the first session of the workshop addressed some of the continuing enigmas regarding the atmospheric composition, surface composition, and atmosphere-surface interactions on Mars; provided a description of a database of proposed payloads and instruments for SEI missions that is scheduled to be accessible in 1993; discussed potential uses of atmospheric imaging from landed stations on Mars; and advocated the collection and employment of high-spectral-resolution reflectance and emission data.

The effect of surface anisotropy and viewing geometry on the estimation of NDVI from AVHRR

USGS Publications Warehouse

Meyer, David; Verstraete, M.; Pinty, B.

1995-01-01

Since terrestrial surfaces are anisotropic, all spectral reflectance measurements obtained with a small instantaneous field of view instrument are specific to these angular conditions, and the value of the corresponding NDVI, computed from these bidirectional reflectances, is relative to the particular geometry of illumination and viewing at the time of the measurement. This paper documents the importance of these geometric effects through simulations of the AVHRR data acquisition process, and investigates the systematic biases that result from the combination of ecosystem-specific anisotropies with instrument-specific sampling capabilities. Typical errors in the value of NDVI are estimated, and strategies to reduce these effects are explored. -from Authors

Use of the densiometer to estimate density of forest canopy on permanent sample plots.

Treesearch

Gerald S. Strickler

1959-01-01

An instrument known as the spherical densiometer has been found adaptable to permanent-plot estimates of relative canopy closure or density in forest and range ecological studies. The device is more compact and simpler to use than previous ocular-type instruments. Because the instrument has a curved reflecting surface which results in observations from lateral as well...

Front lighted optical tooling method and apparatus

DOEpatents

Stone, W.J.

1983-06-30

An optical tooling method and apparatus uses a front lighted shadowgraphic technique to enhance visual contrast of reflected light. The apparatus includes an optical assembly including a fiducial mark, such as cross hairs, reflecting polarized light with a first polarization, a polarizing element backing the fiducial mark and a reflective surface backing the polarizing element for reflecting polarized light bypassing the fiducial mark and traveling through the polarizing element. The light reflected by the reflecting surface is directed through a second pass of the polarizing element toward the frontal direction with a polarization differing from the polarization of the light reflected by the fiducial mark. When used as a tooling target, the optical assembly may be mounted directly to a reference surface or may be secured in a mounting, such as a magnetic mounting. The optical assembly may also be mounted in a plane defining structure and used as a spherometer in conjunction with an optical depth measuring instrument.

A novel X-ray diffractometer for studies of liquid-liquid interfaces.

PubMed

Murphy, Bridget M; Greve, Matthais; Runge, Benjamin; Koops, Christian T; Elsen, Annika; Stettner, Jochim; Seeck, Oliver H; Magnussen, Olaf M

2014-01-01

The study of liquid-liquid interfaces with X-ray scattering methods requires special instrumental considerations. A dedicated liquid surface diffractometer employing a tilting double-crystal monochromator in Bragg geometry has been designed. This diffractometer allows reflectivity and grazing-incidence scattering measurements of an immobile mechanically completely decoupled liquid sample, providing high mechanical stability. The available energy range is from 6.4 to 29.4 keV, covering many important absorption edges. The instrument provides access in momentum space out to 2.54 Å(-1) in the surface normal and out to 14.8 Å(-1) in the in-plane direction at 29.4 keV. Owing to its modular design the diffractometer is also suitable for heavy apparatus such as vacuum chambers. The instrument performance is described and examples of X-ray reflectivity studies performed under in situ electrochemical control and on biochemical model systems are given.

Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hierlemann, A.; Hill, M.; Ricco, A.J.

We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseousmore » analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.« less

Surface inspection using FTIR spectroscopy

NASA Technical Reports Server (NTRS)

Powell, G. L.; Smyrl, N. R.; Williams, D. M.; Meyers, H. M., III; Barber, T. E.; Marrero-Rivera, M.

1995-01-01

The use of reflectance Fourier transform infrared (FTIR) spectroscopy as a tool for surface inspection is described. Laboratory instruments and portable instruments can support remote sensing probes that can map chemical contaminants on surfaces with detection limits under the best of conditions in the sub-nanometer range, i.e.. near absolute cleanliness, excellent performance in the sub-micrometer range, and useful performance for films tens of microns thick. Examples of discovering and quantifying contamination such as mineral oils and greases, vegetable oils, and silicone oils on aluminum foil, galvanized sheet steel, smooth aluminum tubing, and sandblasted 7075 aluminum alloy and D6AC steel. The ability to map in time and space the distribution of oil stains on metals is demonstrated. Techniques associated with quantitatively applying oils to metals, subsequently verifying the application, and non-linear relationships between reflectance and the quantity oil are described.

Bi-directional Reflectance of Icy Surface Analogs: A Dual Approach

NASA Astrophysics Data System (ADS)

Quinones, Juan Manuel; Vides, Christina; Nelson, Robert M.; Boryta, Mark; Mannat, Ken s.

2018-01-01

Bi-directional reflectance measurements of analogs for planetary regolith have provided insight into the surface properties of planetary satellites and small bodies. Because Aluminum Oxide (Al2O3) and water ice share a similar hexagonal crystalline structure, the former has been used in laboratory experiments to simulate the regolith of both icy and dusty planetary bodies. By measuring various sizes of well sorted size fractions of Al2O3, the reflectance phase curve and porosity of a planetary regolith can be determined. We have designed an experiment to test the laboratory measurements produced by Nelson et al. (2000). Additionally, we made reflectance measurements for other alkali-halide compounds that could be used for applications beyond astronomy and planetary science.In order to provide an independent check on the Nelson et al. data, we designed an instrument with a different configuration. While both instruments take bidirectional reflectance measurements, our instrument, the Rigid Photometric Goniometer (RPG), is fixed at a phase angle of 5° and detects the scattered light with a photomultiplier tube (PMT). The PMT current is then measured with an electrometer. Following the example of Nelson et al., we measured the bidirectional reflectance of Al2O3 particulate size fractions between 0.1

Simulation of Hyperspectral Images

NASA Technical Reports Server (NTRS)

Richsmeier, Steven C.; Singer-Berk, Alexander; Bernstein, Lawrence S.

2004-01-01

A software package generates simulated hyperspectral imagery for use in validating algorithms that generate estimates of Earth-surface spectral reflectance from hyperspectral images acquired by airborne and spaceborne instruments. This software is based on a direct simulation Monte Carlo approach for modeling three-dimensional atmospheric radiative transport, as well as reflections from surfaces characterized by spatially inhomogeneous bidirectional reflectance distribution functions. In this approach, "ground truth" is accurately known through input specification of surface and atmospheric properties, and it is practical to consider wide variations of these properties. The software can treat both land and ocean surfaces, as well as the effects of finite clouds with surface shadowing. The spectral/spatial data cubes computed by use of this software can serve both as a substitute for, and a supplement to, field validation data.

Development of a Novel Multispectral Instrument for Handheld and UAS Measurements of Surface Albedo; First Applications for Glaciers in the Peruvian Andes and for Nevada's Black Rock Desert

NASA Astrophysics Data System (ADS)

Boehmler, J. M.; Stevens, C.; Arnott, W. P.; Watts, A.; All, J.; Schmitt, C. G.

2017-12-01

Accurate atmospheric aerosol characteristics derived from satellite measurements are needed over a variety of land surfaces. Nonhomogeneous and bright surface reflectance across California and Nevada may be a contributing factor in the discrepancies observed between ground based and satellite-retrieved atmospheric aerosol optical depth (AOD). We developed and deployed a compact and portable instrument to measure albedo to evaluate a major factor that influences the accuracy of AOD retrievals. The instrument will be operated on an unmanned aircraft system (UAS) to control areal averaging for comparison with satellite derived albedo from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS). A handheld version of the instrument was mounted on a trekking pole and used for obtaining in situ glacier albedo measurements in the Cordillera Blanca of Peru during the summer of 2017. The instrument weighs approximately 433 g and consists of two parts, a mountable, payload portion (300 g) which houses the sensors, and a handheld screen (133 g) to display real-time data from the payload portion. Both parts are powered by a 9V battery and run on a Teensy 3.6/3.2 microcontroller. To retrieve albedo, two micro-spectrometers manufactured by Hamamatsu Photonics, each with a spectral range of 340 -780 nm, are utilized; one for obtaining the downwelling solar radiation and the other for measuring the solar radiation reflected from the surface. Additional components on the instrument include temperature, pressure and humidity sensors with a one second time response; a GPS for position and altitude; an infrared sensor to measure ground temperature; a digital level and compass for orienting the instrument; a camera for taking photos of the sky and surface; a radio for two-way communication between the screen display and sensor payload; and a micro SD card for recording data. We will present the instrument design along with surface albedo measurements for glaciers of the Peruvian Andes in hand held operation, and for the Black Rock Desert of Nevada in UAS operation.

Variability in Surface BRDF at Different Spatial Scales (30m-500m) Over a Mixed Agricultural Landscape as Retrieved from Airborne and Satellite Spectral Measurements

NASA Technical Reports Server (NTRS)

Roman, Miguel O.; Gatebe, Charles K.; Schaaf, Crystal B.; Poudyal, Rajesh; Wang, Zhuosen; King, Michael D.

2012-01-01

Over the past decade, the role of multiangle 1 remote sensing has been central to the development of algorithms for the retrieval of global land surface properties including models of the bidirectional reflectance distribution function (BRDF), albedo, land cover/dynamics, burned area extent, as well as other key surface biophysical quantities represented by the anisotropic reflectance characteristics of vegetation. In this study, a new retrieval strategy for fine-to-moderate resolution multiangle observations was developed, based on the operational sequence used to retrieve the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5 reflectance and BRDF/albedo products. The algorithm makes use of a semiempirical kernel-driven bidirectional reflectance model to provide estimates of intrinsic albedo (i.e., directional-hemispherical reflectance and bihemispherical reflectance), model parameters describing the BRDF, and extensive quality assurance information. The new retrieval strategy was applied to NASA's Cloud Absorption Radiometer (CAR) data acquired during the 2007 Cloud and Land Surface Interaction Campaign (CLASIC) over the well-instrumented Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site in Oklahoma, USA. For the case analyzed, we obtained approx.1.6 million individual surface bidirectional reflectance factor (BRF) retrievals, from nadir to 75deg off-nadir, and at spatial resolutions ranging from 3 m - 500 m. This unique dataset was used to examine the interaction of the spatial and angular 18 characteristics of a mixed agricultural landscape; and provided the basis for detailed assessments of: (1) the use of a priori knowledge in kernel-driven BRDF model inversions; (2) the interaction between surface reflectance anisotropy and instrument spatial resolution; and (3) the uncertainties that arise when sub-pixel differences in the BRDF are aggregated to a moderate resolution satellite pixel. Results offer empirical evidence concerning the influence of scale and spatial heterogeneity in kernel-driven BRDF models; providing potential new insights into the behavior and characteristics of different surface radiative properties related to land/use cover change and vegetation structure.

Variability in Surface BRDF at Different Spatial Scales (30 m-500 m) Over a Mixed Agricultural Landscape as Retrieved from Airborne and Satellite Spectral Measurements

NASA Technical Reports Server (NTRS)

Roman, Miguel O.; Gatebe, Charles K.; Schaaf, Crystal B.; Poudyal, Rajesh; Wang, Zhousen; King, Michael D.

2011-01-01

Over the past decade, the role of multiangle remote sensing has been central to the development of algorithms for the retrieval of global land surface properties including models of the bidirectional reflectance distribution function (BRDF), albedo, land cover/dynamics, burned area extent, as well as other key surface biophysical quantities represented by the anisotropic reflectance characteristics of vegetation. In this study, a new retrieval strategy for fine-to-moderate resolution multiangle observations was developed, based on the operational sequence used to retrieve the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5 reflectance and BRDF/albedo products. The algorithm makes use of a semiempirical kernel-driven bidirectional reflectance model to provide estimates of intrinsic albedo (i.e., directional-hemispherical reflectance and bihemispherical reflectance), model parameters describing the BRDF, and extensive quality assurance information. The new retrieval strategy was applied to NASA's Cloud Absorption Radiometer (CAR) data acquired during the 2007 Cloud and Land Surface Interaction Campaign (CLASIC) over the well-instrumented Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site in Oklahoma, USA. For the case analyzed, we obtained approx.1.6 million individual surface bidirectional reflectance factor (BRF) retrievals, from nadir to 75 off-nadir, and at spatial resolutions ranging from 3 m - 500 m. This unique dataset was used to examine the interaction of the spatial and angular characteristics of a mixed agricultural landscape; and provided the basis for detailed assessments of: (1) the use of a priori knowledge in kernel-driven BRDF model inversions; (2) the interaction between surface reflectance anisotropy and instrument spatial resolution; and (3) the uncertain ties that arise when sub-pixel differences in the BRDF are aggregated to a moderate resolution satellite pixel. Results offer empirical evidence concerning the influence of scale and spatial heterogeneity in kernel-driven BRDF models; providing potential new insights into the behavior and characteristics of different surface radiative properties related to land/use cover change and vegetation structure.

AIS-2 radiometry and a comparison of methods for the recovery of ground reflectance

NASA Technical Reports Server (NTRS)

Conel, James E.; Green, Robert O.; Vane, Gregg; Bruegge, Carol J.; Alley, Ronald E.; Curtiss, Brian J.

1987-01-01

A field experiment and its results involving Airborne Imaging Spectrometer-2 data are described. The radiometry and spectral calibration of the instrument are critically examined in light of laboratory and field measurements. Three methods of compensating for the atmosphere in the search for ground reflectance are compared. It was found that laboratory determined responsitivities are 30 to 50 percent less than expected for conditions of the flight for both short and long wavelength observations. The combined system atmosphere surface signal to noise ratio, as indexed by the mean response divided by the standard deviation for selected areas, lies between 40 and 110, depending upon how scene averages are taken, and is 30 percent less for flight conditions than for laboratory. Atmospheric and surface variations may contribute to this difference. It is not possible to isolate instrument performance from the present data. As for methods of data reduction, the so-called scene average or log-residual method fails to recover any feature present in the surface reflectance, probably because of the extreme homogeneity of the scene.

Alternatives to SiOx for protective scan mirror coatings in remote sensing instruments

NASA Astrophysics Data System (ADS)

MacDonald, Michael E.

1999-09-01

Mirrors in remote sensing instruments require durable dielectric coatings, both to prevent oxidation of the reflective surface and to protect it during cleaning. IR absorption bands within widely-used SiOx coatings produce scene radiance and instrument background variations as a function of scan mirror angle which motivate the search for possible substitute materials. In this work several candidate coatings are evaluated including CeF3, HfO2, MgF2 SrF2, and Y2O3. This evaluation consists of reflectance, adhesion, and durability measurements of mirrors with an aluminum reflective surface over-coated with these materials. S-polarized and P- polarized reflectance measurements are presented between 2 and 20 micrometers for incidence angles between 40 and 50 degrees. This angular range is sufficient to scan the earth disk from geostationary orbit. Additional measurements at 45 degrees incidence are presented between 2 and 55 micrometers , covering the IR wavelength range of interest for earth radiation budget sensors. Comparisons are drawn with measurements of scan- mirror witness samples from the imaging and sounding instruments used in the Geostationary Operational Environmental Satellite (GOES). These witness samples exhibit reflectance variations arising from IR absorption bands in the SiOx protective coatings used in these mirrors. The spectral characteristics of several of the alternate materials are found to be quite attractive, however durable coatings of some of these materials require elevated deposition temperature which are incompatible with the nickel-coated beryllium scan mirror substrate construction used in GOES. This work present the achievable reflectance and durability of these alternate dielectric protective coatings at the deposition temperature constraints imposed by the scan mirror substrate. The prospects for substituting one of these coatings for SiOx are evaluated, and contrasted with the capability of radiometric calibration techniques to deal with the reflectance variations produced by SiOx coatings.

Tandem transmission/reflection mode XRD instrument including XRF for in situ measurement of Martian rocks and soils

NASA Astrophysics Data System (ADS)

Delhez, Robert; Van der Gaast, S. J.; Wielders, Arno; de Boer, J. L.; Helmholdt, R. B.; van Mechelen, J.; Reiss, C.; Woning, L.; Schenk, H.

2003-02-01

The mineralogy of the surface material of Mars is the key to disclose its present and past life and climates. Clay mineral species, carbonates, and ice (water and CO2) are and/or contain their witnesses. X-ray powder diffraction (XRPD) is the most powerful analytical method to identify and quantitatively characterize minerals in complex mixtures. This paper discusses the development of a working model of an instrument consisting of a reflection mode diffractometer and a transmission mode CCD-XRPD instrument, combined with an XRF module. The CCD-XRD/XRF instrument is analogous to the instrument for Mars missions developed by Sarrazin et al. (1998). This part of the tandem instrument enables "quick and dirty" analysis of powdered (!) matter to monitor semi-quantitatively the presence of clay minerals as a group, carbonates, and ices and yields semi-quantitative chemical information from X-ray fluorescence (XRF). The reflection mode instrument (i) enables in-situ measurements of rocks and soils and quantitative information on the compounds identified, (ii) has a high resolution and reveals large spacings for accurate identification, in particular of clay mineral species, and (iii) the shape of the line profiles observed reveals the kind and approximate amounts of lattice imperfections present. It will be shown that the information obtained with the reflection mode diffractometer is crucial for finding signs of life and changes in the climate on Mars. Obviously this instrument can also be used for other extra-terrestrial research.

ALR - Laser altimeter for the ASTER deep space mission. Simulated operation above a surface with crater

NASA Astrophysics Data System (ADS)

de Brum, A. G. V.; da Cruz, F. C.; Hetem, A., Jr.

2015-10-01

To assist in the investigation of the triple asteroid system 2001-SN263, the deep space mission ASTER will carry onboard a laser altimeter. The instrument was named ALR and its development is now in progress. In order to help in the instrument design, with a view to the creation of software to control the instrument, a package of computer programs was produced to simulate the operation of a pulsed laser altimeter with operating principle based on the measurement of the time of flight of the travelling pulse. This software Simulator was called ALR_Sim, and the results obtained with its use represent what should be expected as return signal when laser pulses are fired toward a target, reflect on it and return to be detected by the instrument. The program was successfully tested with regard to some of the most common situations expected. It constitutes now the main workbench dedicated to the creation and testing of control software to embark in the ALR. In addition, the Simulator constitutes also an important tool to assist the creation of software to be used on Earth, in the processing and analysis of the data received from the instrument. This work presents the results obtained in the special case which involves the modeling of a surface with crater, along with the simulation of the instrument operation above this type of terrain. This study points out that the comparison of the wave form obtained as return signal after reflection of the laser pulse on the surface of the crater with the expected return signal in the case of a flat and homogeneous surface is a useful method that can be applied for terrain details extraction.

Saturn's Titan: Searching for Surface Change

NASA Astrophysics Data System (ADS)

Nelson, R. M.; Kamp, L.; Matson, D. L.; Boryta, M. D.; Leader, F.; Baines, K. H.; Lopes, R.; Smythe, W. D.; Jauman, R.; Sotin, C.; Clark, R. N.; Cruikshank, D. P.; Drosart, P.; Hapke, B. W.; Buratti, B. J.; Brown, R. H.; Sicardy, B.; Lunine, J. I.; Combes, M.; Belucci, G.; Biebring, J.; Capaccioni, M.; Cerroni, P.; Corodini, A.; Formisano, V.; Filacchione, G.; Langevin, Y.; McCord, T.; Mennella, V.; Nicholson, P.

2007-12-01

The VIMS instrument on the Cassini spacecraft observes the surface of Titan through spectral 'windows' in its atmosphere where methane, the principal absorbing gas is transmitting. We previously have used VIMS to document changes in spectral reflectance and that have occurred on Titan's surface during Cassini's orbital tour at (latitude 26S, longitude 78W), (AGU spring meeting 2007). Having removed the possibility that the observed changes are either an atmospheric phenomenon or are the result of viewing angle (phase) effects, we conclude that physical changes in the chemistry or structure of the surface must be occurring. The size of the region suggests it may exceed the size of the largest active volcanic areas in the solar system. We now have explored additional sections of Titan's surface and have developed new techniques for locating surface changes over time. While some additional candidate areas for surface activity are suggested, confirmation is possible with the support of additional instruments on the Cassini Orbiter, particularly the radar instrument. The principal difficulty in implementing a coordinated program of observations with both instruments is due to the radar instrument's higher spatial resolution but small footprint on the surface relative to VIMS. In addition, the two instruments can not be used simultaneously on the same pass. Overlapping coverage will only be available after repeated flybys during Cassini's extended mission. This work done at JPL/CALTECH under contract with NASA

GOSAT and OCO-2 Inter-comparison on Measured Spectral Radiance and Retrieved Carbon Dioxide

NASA Astrophysics Data System (ADS)

Kataoka, F.; Kuze, A.; Shiomi, K.; Suto, H.; Crisp, D.; Bruegge, C. J.; Schwandner, F. M.

2016-12-01

TANSO-FTS onboard GOSAT and grating spectrometer on OCO-2 use different measurement techniques to measure carbon dioxide (CO2) and molecular oxygen (O2). Both instruments observe sunlight reflected from the Earth's surface in almost the same spectral range. As a first step in cross calibrating these two instruments, we compared spectral radiance observations within the three short wave infrared (SWIR) spectral bands centered on the O2 A-band (O2A), the weak CO2 band near 1.6 microns (Weak-CO2) and 2.06 micons (Strong-CO2) bands at temporally coincident and spatially collocated points. In this work, we reconciled the different size of the footprints and evaluated at various types of surface targets such as ocean, desert and forest. For radiometric inter-comparisons, we consider long term instrument sensitivity degradation in orbit and differences in viewing geometry and associated differences in surface bidirectional reflectance distribution function (BRDF). Measured spectral radiances agree very well within 5% for all bands. This presentation will summarize these comparisons of GOSAT and OCO-2 spectral radiance observations and associated estimates of carbon dioxide and related parameters retrieved with the same algorithm at matchup points. We will also discuss instrument related uncertainties from various target observations.

A data base of geologic field spectra

NASA Technical Reports Server (NTRS)

Kahle, A. B.; Goetz, A. F. H.; Paley, H. N.; Alley, R. E.; Abbott, E. A.

1981-01-01

It is noted that field samples measured in the laboratory do not always present an accurate picture of the ground surface sensed by airborne or spaceborne instruments because of the heterogeneous nature of most surfaces and because samples are disturbed and surface characteristics changed by collection and handling. The development of new remote sensing instruments relies on the analysis of surface materials in their natural state. The existence of thousands of Portable Field Reflectance Spectrometer (PFRS) spectra has necessitated a single, all-inclusive data base that permits greatly simplified searching and sorting procedures and facilitates further statistical analyses. The data base developed at JPL for cataloging geologic field spectra is discussed.

Improved Mirror Coatings for Use in the Lyman Ultraviolet to Enhance Astronomical Instrument Capabilities

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; Del Hoyo, Javier; Boris, David R.; Walton, Scott

2017-01-01

This paper will describe efforts at developing broadband mirror coatings with high performance that will extend from infrared wavelengths down to the Far-Ultraviolet (FUV) spectral region. These mirror coatings would be realized by passivating the surface of freshly made aluminum coatings with XeF2 gas in order to form a thin AlF3 overcoat that will protect the aluminum from oxidation and, hence, realize the high-reflectance of this material down to its intrinsic cut-off wavelength of 90 nm. Improved reflective coatings for optics, particularly in the FUV region (90-120 nm), could yield dramatically more sensitive instruments and permit more instrument design freedom.

Improved mirror coatings for use in the Lyman Ultraviolet to enhance astronomical instrument capabilities

NASA Astrophysics Data System (ADS)

Quijada, Manuel A.; del Hoyo, Javier; Boris, David R.; Walton, Scott G.

2017-09-01

This paper will describe efforts at developing broadband mirror coatings with high performance that will extend from infrared wavelengths down to the Far-Ultraviolet (FUV) spectral region. These mirror coatings would be realized by passivating the surface of freshly made aluminum coatings with fluorine ions in order to form a thin AlF3 overcoat that will protect the aluminum from oxidation and, hence, realize the high-reflectance of this material down to its intrinsic cut-off wavelength of 90 nm. Improved reflective coatings for optics, particularly in the FUV region (90-120 nm), could yield dramatically more sensitive instruments and permit more instrument design freedom.

Hyperspectral Fluorescence and Reflectance Imaging Instrument

NASA Technical Reports Server (NTRS)

Ryan, Robert E.; O'Neal, S. Duane; Lanoue, Mark; Russell, Jeffrey

2008-01-01

The system is a single hyperspectral imaging instrument that has the unique capability to acquire both fluorescence and reflectance high-spatial-resolution data that is inherently spatially and spectrally registered. Potential uses of this instrument include plant stress monitoring, counterfeit document detection, biomedical imaging, forensic imaging, and general materials identification. Until now, reflectance and fluorescence spectral imaging have been performed by separate instruments. Neither a reflectance spectral image nor a fluorescence spectral image alone yields as much information about a target surface as does a combination of the two modalities. Before this system was developed, to benefit from this combination, analysts needed to perform time-consuming post-processing efforts to co-register the reflective and fluorescence information. With this instrument, the inherent spatial and spectral registration of the reflectance and fluorescence images minimizes the need for this post-processing step. The main challenge for this technology is to detect the fluorescence signal in the presence of a much stronger reflectance signal. To meet this challenge, the instrument modulates artificial light sources from ultraviolet through the visible to the near-infrared part of the spectrum; in this way, both the reflective and fluorescence signals can be measured through differencing processes to optimize fluorescence and reflectance spectra as needed. The main functional components of the instrument are a hyperspectral imager, an illumination system, and an image-plane scanner. The hyperspectral imager is a one-dimensional (line) imaging spectrometer that includes a spectrally dispersive element and a two-dimensional focal plane detector array. The spectral range of the current imaging spectrometer is between 400 to 1,000 nm, and the wavelength resolution is approximately 3 nm. The illumination system consists of narrowband blue, ultraviolet, and other discrete wavelength light-emitting-diode (LED) sources and white-light LED sources designed to produce consistently spatially stable light. White LEDs provide illumination for the measurement of reflectance spectra, while narrowband blue and UV LEDs are used to excite fluorescence. Each spectral type of LED can be turned on or off depending on the specific remote-sensing process being performed. Uniformity of illumination is achieved by using an array of LEDs and/or an integrating sphere or other diffusing surface. The image plane scanner uses a fore optic with a field of view large enough to provide an entire scan line on the image plane. It builds up a two-dimensional image in pushbroom fashion as the target is scanned across the image plane either by moving the object or moving the fore optic. For fluorescence detection, spectral filtering of a narrowband light illumination source is sometimes necessary to minimize the interference of the source spectrum wings with the fluorescence signal. Spectral filtering is achieved with optical interference filters and absorption glasses. This dual spectral imaging capability will enable the optimization of reflective, fluorescence, and fused datasets as well as a cost-effective design for multispectral imaging solutions. This system has been used in plant stress detection studies and in currency analysis.

Mars surface chemistry investigated with the MOx probe: A 1-kg optical microsensor-based chemical analysis instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ricco, A.J.; Butler, M.A.; Grunthaner, F.J.

The authors have designed and built the prototype of an instrument that will use fiber optic micromirror-based chemical sensors to investigate the surprising reactivity of martian soil reported by several Viking Lander Experiments in the mid 1970s. The MOx (Mars Oxidant Experiment) Instrument, which will probe the reactivity of the near-surface martian atmosphere as well as soil, utilizes an array of chemically sensitive thin films including metals, organometallics, and organic dyes to produce a pattern of reflectivity changes characteristic of the species interacting with these sensing layers. The 850-g system includes LED light sources, optical fiber light guides, silicon micromachinedmore » fixtures, a line-array CCD detector, control-and-measurement electronics, microprocessor, memory, interface, batteries, and housing. This instrument monitors real-time reflectivities from an array of {approximately}200 separate micromirrors. The unmanned Russian Mars 96 mission is slated to carry the MOx Instrument along with experiments from several other nations. The principles of the chemically sensitive micromirror upon which this instrument is based will be described and preliminary data for reactions of micromirrors with oxidant materials believed to be similar to those on Mars will be presented. The general design of the instrument, including Si micromachined components, as well as the range of coatings and the rationale for their selection, will be discussed as well.« less

GOME-2 Tropospheric Ozone Profile Retrievals from Joint UV/Visible Measurement

NASA Astrophysics Data System (ADS)

Liu, X.; Zoogman, P.; Chance, K.; Cai, Z.; Nowlan, C. R.; Huang, G.; Gonzalez Abad, G.

2016-12-01

It has been shown from sensitivity studies that adding visible measurements in the Chappuis ozone band to UV measurements in the Hartley/Huggins ozone bands can significantly enhance retrieval sensitivity to lower tropospheric ozone from backscattered solar radiances due to deeper photon penetration in the visible to the surface than in the ultraviolet. The first NASA EVI (Earth Venture Instrument) TEMPO (Tropospheric Emissions: Monitoring of Pollution) instrument is being developed to measure backscattered solar radiation in two channels ( 290-490 and 540-740 nm) and make atmospheric pollution measurements over North America from the Geostationary orbit. However, this retrieval enhancement has yet to be demonstrated from existing measurements due to the weak ozone absorption in the visible and strong interferences from surface reflectance and aerosols and the requirement of accurate radiometric calibration across different spectral channels. We present GOME-2 retrievals from joint UV/visible measurements using the SAO ozone profile retrieval algorithm, to directly explore the retrieval improvement in lower tropospheric ozone from additional visible measurements. To reduce the retrieval interference from surface reflectance, we add characterization of surface spectral reflectance in the visible based on combining EOFs (Empirical Orthogonal Functions) derived from ASTER and other surface reflectance spectra with MODIS BRDF climatology into the ozone profile algorithm. The impacts of various types of aerosols and surface BRDF on the retrievals will be investigated. In addition, we will also perform empirical radiometric calibration of the GOME-2 data based on radiative transfer simulations. We will evaluate the retrieval improvement of joint UV/visible retrieval over the UV retrieval based on fitting quality and validation against ozonesonde observations.

Auger spectroscopic examination of MgF2-coated Al mirrors before and after UV irradiation

NASA Technical Reports Server (NTRS)

Heaney, J. B.; Herzig, H.; Osantowski, J. F.

1977-01-01

Magnesium fluoride protected Al films were studied since these mirrors are commonly used in astronomical instruments whenever a highly reflecting optical surface is required in the wavelength region from 1100 A to 2000 A. Freshly prepared samples of evaporated Al + 250-A thick MgF2 on glass were analyzed by Auger electron spectroscopy in conjunction with surface erosion by Ar(+) ion bombardment before and after UV irradiation. The analysis showed that a very thin layer of surface contamination and not bulk photolysis in the MgF2 film was reponsible for the irradiation-induced reflectance loss. Postirradiation polishing with a mild calcium carbonate abrasive can restore a mirror's reflectance by removing the photolyzed surface film without disturbing the MgF2 layer.

Combined measurement of directional Raman scattering and surface-plasmon-polariton cone from adsorbates on smooth planar gold surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nyamekye, Charles K. A.; Weibel, Stephen C.; Bobbitt, Jonathan M.

Directional-surface-plasmon-coupled Raman scattering (directional RS) has the combined benefits of surface plasmon resonance and Raman spectroscopy, and provides the ability to measure adsorption and monolayer-sensitive chemical information. Directional RS is performed by optically coupling a 50-nm gold film to a Weierstrass prism in the Kretschmann configuration and scanning the angle of the incident laser under total internal reflection. The collected parameters on the prism side of the interface include a full surface-plasmon-polariton cone and the full Raman signal radiating from the cone as a function of incident angle. An instrument for performing directional RS and a quantitative study of themore » instrumental parameters are herein reported. To test the sensitivity and quantify the instrument parameters, self-assembled monolayers and 10 to 100-nm polymer films are studied. The signals are found to be well-modeled by two calculated angle-dependent parameters: three-dimensional finite-difference time-domain calculations of the electric field generated in the sample layer and projected to the far-field, and Fresnel calculations of the reflected light intensity. This is the first report of the quantitative study of the full surface-plasmon-polariton cone intensity, cone diameter, and directional Raman signal as a function of incident angle. We propose that directional RS is a viable alternative to surface plasmon resonance when added chemical information is beneficial.« less

Combined measurement of directional Raman scattering and surface-plasmon-polariton cone from adsorbates on smooth planar gold surfaces

DOE PAGES

Nyamekye, Charles K. A.; Weibel, Stephen C.; Bobbitt, Jonathan M.; ...

2017-09-15

Directional-surface-plasmon-coupled Raman scattering (directional RS) has the combined benefits of surface plasmon resonance and Raman spectroscopy, and provides the ability to measure adsorption and monolayer-sensitive chemical information. Directional RS is performed by optically coupling a 50-nm gold film to a Weierstrass prism in the Kretschmann configuration and scanning the angle of the incident laser under total internal reflection. The collected parameters on the prism side of the interface include a full surface-plasmon-polariton cone and the full Raman signal radiating from the cone as a function of incident angle. An instrument for performing directional RS and a quantitative study of themore » instrumental parameters are herein reported. To test the sensitivity and quantify the instrument parameters, self-assembled monolayers and 10 to 100-nm polymer films are studied. The signals are found to be well-modeled by two calculated angle-dependent parameters: three-dimensional finite-difference time-domain calculations of the electric field generated in the sample layer and projected to the far-field, and Fresnel calculations of the reflected light intensity. This is the first report of the quantitative study of the full surface-plasmon-polariton cone intensity, cone diameter, and directional Raman signal as a function of incident angle. We propose that directional RS is a viable alternative to surface plasmon resonance when added chemical information is beneficial.« less

Earth's UV Reflectivity Data from the Ozone Monitoring Instrument on EOS-Aura

NASA Astrophysics Data System (ADS)

Larko, D. E.; Mao, J.; Herman, J. R.; Huang, L.; Qin, W.; Labow, G. J.; Lloyd, S. A.; DeLand, M. T.

2011-12-01

The Lambert Equivalent Reflectivity (LER), derived from satellite ultraviolet (UV) radiance measurements, represents the equivalent scene reflectivity of the Earth's surface and atmosphere without Rayleigh scattering. It provides a better opportunity to quantify variations of the planetary reflectance and albedo associated with snow/ice, atmospheric aerosols and clouds, since UV reflectance is very low over most land surfaces and water. LER values at 340 nm from the Ozone Monitoring Instrument (OMI) on EOS-Aura have been generated as a new product from the OMI TO3 ozone retrieval algorithm and provided to users in HDF format. The wide field of view of OMI (~2200 km) provides complete global coverage every day with 13 km x 24 km resolution at nadir. These data are then mapped to 1 degree x 1 degree latitude-longitude grid as daily and monthly means for weather and climate studies. The OMI LER data set has been used to validate other UV LER data sets from NOAA and NASA polar orbiting satellites, and has been combined with these data sets to construct a continuous long-term data record of terrestrial UV reflectivity. This paper will present details about the data processing and format of the OMI LER product. Applications of this data set in global climate studies will be demonstrated and discussed in this presentation.

Influence of Aerosols And Surface Reflectance On NO2 Retrieval Over China From 2005 to 2015

NASA Astrophysics Data System (ADS)

Liu, M.; Lin, J.

2016-12-01

Satellite observation is a powerful way to analysis annual and seasonal variations of nitrogen dioxide (NO2). However, much retrieval of vertical column densities (VCDs) of normally do not explicitly account for aerosol optical effects and surface reflectance anisotropy that vary with space and time. In traditional retrieval, aerosols' effects are often considered as cloud. However, China has complicated aerosols type and aerosol loading. Their optical properties may be very different from the cloud. Furthermore, China has undergone big changes in land use type in recent 10 years. Traditional climatology surface reflectance data may not have representation. In order to study spatial-temporal variation of and influences of these two factors on variations and trends, we use an improved retrieval method of VCDs over China, called the POMINO, based on measurements from the Ozone Monitoring Instrument (OMI), and we compare the results of without aerosol, without surface reflectance treatments and without both to the original POMINO product from 2005 to 2015. Furthermore, we will study correspondent spatial-temporal variations of aerosols, represented by MODIS aerosol optical depth (AOD) data and CALIOP extinction data; surface reflectance, represented by MODIS bidirectional reflectance distribution function (BRDF) data.

A passive low frequency instrument for radio wave sounding the subsurface oceans of the Jovian icy moons: An instrument concept

NASA Astrophysics Data System (ADS)

Hartogh, P.; Ilyushin, Ya. A.

2016-10-01

Exploration of subsurface oceans on Jovian icy moons is a key issue of the icy moons' geology. Electromagnetic wave propagation is the only way to probe their icy mantles from the orbit. In the present paper, a principal concept of a passive interferometric instrument for deep sounding of the icy moons' crust is proposed. Its working principle is measuring and correlating Jupiter's radio wave emissions with reflections from the deep sub-surface of the icy moons. A number of the functional aspects of the proposed experiment are studied, in particular, impact of the wave scattering on the surface terrain on the instrument performance and digital sampling of the noisy signal. Results of the test of the laboratory prototype of the instrument are also presented in the paper.

Cloud Retrieval Information Content Studies with the Pre-Aerosol, Cloud and ocean Ecosystem (PACE) Ocean Color Imager (OCI)

NASA Astrophysics Data System (ADS)

Coddington, Odele; Platnick, Steven; Pilewskie, Peter; Schmidt, Sebastian

2016-04-01

The NASA Pre-Aerosol, Cloud and ocean Ecosystem (PACE) Science Definition Team (SDT) report released in 2012 defined imager stability requirements for the Ocean Color Instrument (OCI) at the sub-percent level. While the instrument suite and measurement requirements are currently being determined, the PACE SDT report provided details on imager options and spectral specifications. The options for a threshold instrument included a hyperspectral imager from 350-800 nm, two near-infrared (NIR) channels, and three short wave infrared (SWIR) channels at 1240, 1640, and 2130 nm. Other instrument options include a variation of the threshold instrument with 3 additional spectral channels at 940, 1378, and 2250 nm and the inclusion of a spectral polarimeter. In this work, we present cloud retrieval information content studies of optical thickness, droplet effective radius, and thermodynamic phase to quantify the potential for continuing the low cloud climate data record established by the MOderate Resolution and Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) missions with the PACE OCI instrument (i.e., non-polarized cloud reflectances and in the absence of midwave and longwave infrared channels). The information content analysis is performed using the GEneralized Nonlinear Retrieval Analysis (GENRA) methodology and the Collection 6 simulated cloud reflectance data for the common MODIS/VIIRS algorithm (MODAWG) for Cloud Mask, Cloud-Top, and Optical Properties. We show that using both channels near 2 microns improves the probability of cloud phase discrimination with shortwave-only cloud reflectance retrievals. Ongoing work will extend the information content analysis, currently performed for dark ocean surfaces, to different land surface types.

ICESAT Laser Altimeter Pointing, Ranging and Timing Calibration from Integrated Residual Analysis

NASA Technical Reports Server (NTRS)

Luthcke, Scott B.; Rowlands, D. D.; Carabajal, C. C.; Harding, D. H.; Bufton, J. L.; Williams, T. A.

2003-01-01

On January 12, 2003 the Ice, Cloud and land Elevation Satellite (ICESat) was successfully placed into orbit. The ICESat mission carries the Geoscience Laser Altimeter System (GLAS), which has a primary measurement of short-pulse laser- ranging to the Earth s surface at 1064nm wavelength at a rate of 40 pulses per second. The instrument has collected precise elevation measurements of the ice sheets, sea ice roughness and thickness, ocean and land surface elevations and surface reflectivity. The accurate geolocation of GLAS s surface returns, the spots from which the laser energy reflects on the Earth s surface, is a critical issue in the scientific application of these data. Pointing, ranging, timing and orbit errors must be compensated to accurately geolocate the laser altimeter surface returns. Towards this end, the laser range observations can be fully exploited in an integrated residual analysis to accurately calibrate these geolocation/instrument parameters. ICESat laser altimeter data have been simultaneously processed as direct altimetry from ocean sweeps along with dynamic crossovers in order to calibrate pointing, ranging and timing. The calibration methodology and current calibration results are discussed along with future efforts.

Online Resource for Earth-Observing Satellite Sensor Calibration

NASA Technical Reports Server (NTRS)

McCorkel, J.; Czapla-Myers, J.; Thome, K.; Wenny, B.

2015-01-01

The Radiometric Calibration Test Site (RadCaTS) at Railroad Valley Playa, Nevada is being developed by the University of Arizona to enable improved accuracy and consistency for airborne and satellite sensor calibration. Primary instrumentation at the site consists of ground-viewing radiometers, a sun photometer, and a meteorological station. Measurements made by these instruments are used to calculate surface reflectance, atmospheric properties and a prediction for top-of-atmosphere reflectance and radiance. This work will leverage research for RadCaTS, and describe the requirements for an online database, associated data formats and quality control, and processing levels.

Measuring Thicknesses of Coatings on Metals

NASA Technical Reports Server (NTRS)

Cotty, Glenn M., Jr.

1986-01-01

Digital light sensor and eddy-current sensor measure thickness without contact. Surface of Coating reflects laser beam to optical sensor. Position of reflected spot on sensor used by microcomputer to calculate coating thickness. Eddy-current sensor maintains constant distance between optical sensor and metal substrate. When capabilities of available components fully exploited, instrument measures coatings from 0.001 to 6 in. (0.0025 to 15 cm) thick with accuracy of 1 part in 4,000. Instrument readily incorporated in automatic production and inspection systems. Used to inspect thermal-insulation layers, paint, and protective coatings. Also used to control application of coatings to preset thicknesses.

The case for a modern multiwavelength, polarization-sensitive LIDAR in orbit around Mars

USGS Publications Warehouse

Brown, Adrian J.; Michaels, Timothy I.; Byrne, Shane; Sun, Wenbo; Titus, Timothy N.; Colaprete, Anthony; Wolff, Michael J.; Videen, Gorden; Grund, Christian J.

2014-01-01

We present the scientific case to build a multiple-wavelength, active, near-infrared (NIR) instrument to measure the reflected intensity and polarization characteristics of backscattered radiation from planetary surfaces and atmospheres. We focus on the ability of such an instrument to enhance, perhaps revolutionize, our understanding of climate, volatiles and astrobiological potential of modern-day Mars.

Laer-induced Breakdown Spectroscopy Instrument for Element Analysis of Planetary Surfaces

NASA Technical Reports Server (NTRS)

Blacic, J.; Pettit, D.; Cremers, D.; Roessler, N.

1993-01-01

One of the most fundamental pieces of information about any planetary body is the elemental and mineralogical composition of its surface materials. We are developing an instrument to obtain such data at ranges of up to several hundreds of meters using the technique of Laser-Induced Breakdown Spectroscopy (LIBS). We envision our instrument being used from a spacecraft in close rendezvous with small bodies such as comets and asteroids, or deployed on surface-rover vehicles on large bodies such as Mars and the Moon. The elemental analysis is based on atomic emission spectroscopy of a laser-induced plasma or spark. A pulsed, diode pumped Nd:YAG laser of several hundred millijoules optical energy is used to vaporize and electronically excite the constituent elements of a rock surface remotely located from the laser. Light emitted from the excited plasma is collected and introduced to the entrance slit of a small grating spectrometer. The spectrally dispersed spark light is detected with either a linear photo diode array or area CCD array. When the latter detector is used, the optical and spectrometer components of the LIBS instrument can also be used in a passive imaging mode to collect and integrate reflected sunlight from the same rock surface. Absorption spectral analysis of this reflected light gives mineralogical information that provides a remote geochemical characterization of the rock surface. We performed laboratory calibrations in air and in vacuum on standard rock powders to quantify the LIBS analysis. We performed preliminary field tests using commercially available components to demonstrate remote LIBS analysis of terrestrial rock surfaces at ranges of over 25 m, and we have demonstrated compatibility with a six-wheeled Russian robotic rover vehicle. Based on these results, we believe that all major and most minor elements expected on planetary surfaces can be measured with absolute accuracy of 10-15 percent and much higher relative accuracy. We have performed preliminary systems analysis of a LIBS instrument to evaluate probable mass and power requirements; results of this analysis are summarized.

Hand-held optical imager (Gen-2): improved instrumentation and target detectability

PubMed Central

Gonzalez, Jean; DeCerce, Joseph; Erickson, Sarah J.; Martinez, Sergio L.; Nunez, Annie; Roman, Manuela; Traub, Barbara; Flores, Cecilia A.; Roberts, Seigbeh M.; Hernandez, Estrella; Aguirre, Wenceslao; Kiszonas, Richard

2012-01-01

Abstract. Hand-held optical imagers are developed by various researchers towards reflectance-based spectroscopic imaging of breast cancer. Recently, a Gen-1 handheld optical imager was developed with capabilities to perform two-dimensional (2-D) spectroscopic as well as three-dimensional (3-D) tomographic imaging studies. However, the imager was bulky with poor surface contact (∼30%) along curved tissues, and limited sensitivity to detect targets consistently. Herein, a Gen-2 hand-held optical imager that overcame the above limitations of the Gen-1 imager has been developed and the instrumentation described. The Gen-2 hand-held imager is less bulky, portable, and has improved surface contact (∼86%) on curved tissues. Additionally, the forked probe head design is capable of simultaneous bilateral reflectance imaging of both breast tissues, and also transillumination imaging of a single breast tissue. Experimental studies were performed on tissue phantoms to demonstrate the improved sensitivity in detecting targets using the Gen-2 imager. The improved instrumentation of the Gen-2 imager allowed detection of targets independent of their location with respect to the illumination points, unlike in Gen-1 imager. The developed imager has potential for future clinical breast imaging with enhanced sensitivity, via both reflectance and transillumination imaging. PMID:23224163

Integration of a Spectral Domain Optical Coherence Tomography System into a Surgical Microscope for Intraoperative Imaging

PubMed Central

Ehlers, Justis P.; Tao, Yuankai K.; Farsiu, Sina; Maldonado, Ramiro; Izatt, Joseph A.

2011-01-01

Purpose. To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging. Methods. A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board–approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting. Results. High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes). Conclusions. High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon. PMID:21282565

Integration of a spectral domain optical coherence tomography system into a surgical microscope for intraoperative imaging.

PubMed

Ehlers, Justis P; Tao, Yuankai K; Farsiu, Sina; Maldonado, Ramiro; Izatt, Joseph A; Toth, Cynthia A

2011-05-16

To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging. A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board-approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting. High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes). High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon.

Development of Hyperspectral Remote Sensing Capability For the Early Detection and Monitoring of Harmful Algal Blooms (HABs) in the Great Lakes

NASA Technical Reports Server (NTRS)

Lekki, John; Anderson, Robert; Nguyen, Quang-Viet; Demers, James; Leshkevich, George; Flatico, Joseph; Kojima, Jun

2013-01-01

Hyperspectral imagers have significant capability for detecting and classifying waterborne constituents. One particularly appropriate application of such instruments in the Great Lakes is to detect and monitor the development of potentially Harmful Algal Blooms (HABs). Two generations of small hyperspectral imagers have been built and tested for aircraft based monitoring of harmful algal blooms. In this paper a discussion of the two instruments as well as field studies conducted using these instruments will be presented. During the second field study, in situ reflectance data was obtained from the Research Vessel Lake Guardian in conjunction with reflectance data obtained with the hyperspectral imager from overflights of the same locations. A comparison of these two data sets shows that the airborne hyperspectral imager closely matches measurements obtained from instruments on the lake surface and thus positively supports its utilization for detecting and monitoring HABs.

Site-specific ultrasound reflection properties and superficial collagen content of bovine knee articular cartilage

NASA Astrophysics Data System (ADS)

Laasanen, Mikko S.; Saarakkala, Simo; Töyräs, Juha; Rieppo, Jarno; Jurvelin, Jukka S.

2005-07-01

Previous quantitative 2D-ultrasound imaging studies have demonstrated that the ultrasound reflection measurement of articular cartilage surface sensitively detects degradation of the collagen network, whereas digestion of cartilage proteoglycans has no significant effect on the ultrasound reflection. In this study, the first aim was to characterize the ability of quantitative 2D-ultrasound imaging to detect site-specific differences in ultrasound reflection and backscattering properties of cartilage surface and cartilage-bone interface at visually healthy bovine knee (n = 30). As a second aim, we studied factors controlling ultrasound reflection properties of an intact cartilage surface. The ultrasound reflection coefficient was determined in time (R) and frequency domains (IRC) at medial femoral condyle, lateral patello-femoral groove, medial tibial plateau and patella using a 20 MHz ultrasound imaging instrument. Furthermore, cartilage surface roughness was quantified by calculating the ultrasound roughness index (URI). The superficial collagen content of the cartilage was determined using a FT-IRIS-technique. A significant site-dependent variation was shown in cartilage thickness, ultrasound reflection parameters, URI and superficial collagen content. As compared to R and IRC, URI was a more sensitive parameter in detecting differences between the measurement sites. Ultrasound reflection parameters were not significantly related to superficial collagen content, whereas the correlation between R and URI was high. Ultrasound reflection at the cartilage-bone interface showed insignificant site-dependent variation. The current results suggest that ultrasound reflection from the intact cartilage surface is mainly dependent on the cartilage surface roughness and the collagen content has a less significant role.

ICESat Laser Altimeter Pointing, Ranging and Timing Calibration from Integrated Residual Analysis: A Summary of Early Mission Results

NASA Technical Reports Server (NTRS)

Lutchke, Scott B.; Rowlands, David D.; Harding, David J.; Bufton, Jack L.; Carabajal, Claudia C.; Williams, Teresa A.

2003-01-01

On January 12, 2003 the Ice, Cloud and land Elevation Satellite (ICESat) was successfUlly placed into orbit. The ICESat mission carries the Geoscience Laser Altimeter System (GLAS), which consists of three near-infrared lasers that operate at 40 short pulses per second. The instrument has collected precise elevation measurements of the ice sheets, sea ice roughness and thickness, ocean and land surface elevations and surface reflectivity. The accurate geolocation of GLAS's surface returns, the spots from which the laser energy reflects on the Earth's surface, is a critical issue in the scientific application of these data Pointing, ranging, timing and orbit errors must be compensated to accurately geolocate the laser altimeter surface returns. Towards this end, the laser range observations can be fully exploited in an integrated residual analysis to accurately calibrate these geolocation/instrument parameters. Early mission ICESat data have been simultaneously processed as direct altimetry from ocean sweeps along with dynamic crossovers resulting in a preliminary calibration of laser pointing, ranging and timing. The calibration methodology and early mission analysis results are summarized in this paper along with future calibration activities

VIIRS ZEMAX and FORTRAN Polarization Models

NASA Technical Reports Server (NTRS)

Waluschka, Eugene; Meister, Gerhard; Voss, Kenneth; Moyer, David

2007-01-01

The Visible/Infrared Imager/Radiometer Suite (VIIRS) collects visible/infrared imagery and radiometric data. The radiometric requirements are such that the instrument's polarization sensitivity must be very well understood. This paper presents the ZEMAX and FORTRAN polarization ray trace models of the instrument's visible light path. This will include the measured optical surface reflectance data, the bandpass shapes and a comparison of the results of the two models.

Radiative Properties of Smoke and Aerosol Over Land Surfaces

NASA Technical Reports Server (NTRS)

King, Michael D.

2000-01-01

This talk discusses smoke and aerosol's radiative properties with particular attention to distinguishing the measurement over clear sky from clouds over land, sea, snow, etc. surfaces, using MODIS Airborne Simulator data from (Brazil, arctic sea ice and tundra and southern Africa, west Africa, and other ecosystems. This talk also discusses the surface bidirectional reflectance using Cloud Absorption Radiometer, BRDF measurements of Saudi Arabian desert, Persian Gulf, cerrado and rain forests in Brazil, sea ice, tundra, Atlantic Ocean, Great Dismal Swamp, Kuwait oil fire smoke. Recent upgrades to instrument (new TOMS UVA channels at 340 and 380 planned use in Africa (SAFARI 2000) and possibly for MEIDEX will also be discussed. This talk also plans to discuss the spectral variation of surface reflectance over land and the sensitivity of off-nadir view angles to correlation between visible near-infrared reflectance for use in remote sensing of aerosol over land.

An Overview of the Topography of Mars from the Mars Orbiter Laser Altimeter (MOLA)

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.

2000-01-01

The Mars Global Surveyor (MGS) spacecraft has now completed more than half of its one-Mars-year mission to globally map Mars. During the MGS elliptical and circular orbit mapping phases, the Mars Orbiter Laser Altimeter (MOLA), an instrument on the MGS payload, has collected over 300 million precise elevation measurements. MOLA measures the range from the MGS spacecraft to the Martian surface and to atmospheric reflections. Range is converted to topography through knowledge of the MGS spacecraft orbit. Ranges from MOLA have resulted in a precise global topographic map of Mars. The instrument has also provided measurements of the width of the backscattered optical pulse and of the 1064 nm reflectivity of the Martian surface and atmosphere. The range resolution of the MOLA instrument is 37.5 cm and the along-track resolution of MOLA ground shots is approx. 300 m; the across-track spacing depends on latitude and time in the mapping orbit. The best current topographic grid has a spatial resolution of approx. 1/16 deg and vertical accuracy of approx. one meter. Additional information is contained in the original extended abstract.

Microwave based civil structure inspection device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sohns, C.W.; Bible, D.W.

1994-06-01

A microwave based ``wall probe`` has been developed which is capable of nondestructive evaluation of architectural structures. By using microwaves in the 8 to 12 GHz range this probing instrument can detect subsurface characteristics through concrete, brick, wood or other building materials to depths in excess of 12 inches. The instrument interrogates a structure from a single side by transmitting a microwave signal into the surface at some angle of incidence and receiving the reflected signal some distance away on the same side of the structure. The transmitted signal is partially reflected at each internal boundary of different dielectric constant,more » giving a composite reflection which contains information from each internal layer. The reflected composite signal is compared in phase and amplitude to the transmitted signal and that reading is considered the ``signature`` of the structure under test. Computer algorithms analyze the signature for recognizable features and nonstandard construction.« less

Radiometric calibration stability and inter-calibration of solar-band instruments in orbit using the moon

USGS Publications Warehouse

Stone, T.C.

2008-01-01

With the increased emphasis on monitoring the Earth's climate from space, more stringent calibration requirements are being placed on the data products from remote sensing satellite instruments. Among these are stability over decade-length time scales and consistency across sensors and platforms. For radiometer instruments in the solar reflectance wavelength range (visible to shortwave infrared), maintaining calibration on orbit is difficult due to the lack of absolute radiometric standards suitable for flight use. The Moon presents a luminous source that can be viewed by all instruments in Earth orbit. Considered as a solar diffuser, the lunar surface is exceedingly stable. The chief difficulty with using the Moon is the strong variations in the Moon's brightness with illumination and viewing geometry. This mandates the use of a photometric model to compare lunar observations, either over time by the same instrument or between instruments. The U.S. Geological Survey in Flagstaff, Arizona, under NASA sponsorship, has developed a model for the lunar spectral irradiance that explicitly accounts for the effects of phase, the lunar librations, and the lunar surface reflectance properties. The model predicts variations in the Moon's brightness with precision ???1% over a continuous phase range from eclipse to the quarter lunar phases. Given a time series of Moon observations taken by an instrument, the geometric prediction capability of the lunar irradiance model enables sensor calibration stability with sub-percent per year precision. Cross-calibration of instruments with similar passbands can be achieved with precision comparable to the model precision. Although the Moon observations used for intercomparison can be widely separated in phase angle and/or time, SeaWiFS and MODIS have acquired lunar views closely spaced in time. These data provide an example to assess inter-calibration biases between these two instruments.

Sun Glint and Sea Surface Salinity Remote Sensing

NASA Technical Reports Server (NTRS)

Dinnat, Emmanuel P.; LeVine, David M.

2007-01-01

A new mission in space, called Aquarius/SAC-D, is being built to measure the salinity of the world's oceans. Salinity is an important parameter for understanding movement of the ocean water. This circulation results in the transportation of heat and is important for understanding climate and climate change. Measuring salinity from space requires precise instruments and a careful accounting for potential sources of error. One of these sources of error is radiation from the sun that is reflected from the ocean surface to the sensor in space. This paper examines this reflected radiation and presents an advanced model for describing this effect that includes the effects of ocean waves on the reflection.

Improved Lyman Ultraviolet Astronomy Capabilities through Enhanced Coatings

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; del Hoyo, Javier; Boris, David; Walton, Scott

2017-01-01

This paper will describe efforts at developing broadband mirror coatings with high performance that will extend from infrared wavelengths down to the Far-Ultraviolet (FUV) spectral region. These mirror coatings would be realized by passivating the surface of freshly made aluminum coatings with XeF2 gas in order to form a thin AlF$_3$ overcoat that will protect the aluminum from oxidation and, hence, realize the high-reflectance of this material down to its intrinsic cut-off wavelength of 90 nm. Improved reflective coatings for optics, particularly in the FUV region (90-120 nm), could yield dramatically more sensitive instruments and permit more instrument design freedom.

DSCOVR_EPIC_L2_TO3_01

Atmospheric Science Data Center

2018-04-23

... the long term time series of ozone data from OMI and SBUV instruments. Scene Reflectivity (clouds, aerosolos, and surface) is derived as ... available and are expected to support a wide range of scientific studies. Project Title:  DSCOVR ...

Calibration of the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

NASA Technical Reports Server (NTRS)

Thome, Kurtis; Barnes, Robert; Baize, Rosemary; O'Connell, Joseph; Hair, Jason

2010-01-01

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) plans to observe climate change trends over decadal time scales to determine the accuracy of climate projections. The project relies on spaceborne earth observations of SI-traceable variables sensitive to key decadal change parameters. The mission includes a reflected solar instrument retrieving at-sensor reflectance over the 320 to 2300 nm spectral range with 500-m spatial resolution and 100-km swath. Reflectance is obtained from the ratio of measurements of the earth s surface to those while viewing the sun relying on a calibration approach that retrieves reflectance with uncertainties less than 0.3%. The calibration is predicated on heritage hardware, reduction of sensor complexity, adherence to detector-based calibration standards, and an ability to simulate in the laboratory on-orbit sources in both size and brightness to provide the basis of a transfer to orbit of the laboratory calibration including a link to absolute solar irradiance measurements.

White-Light, Dispersed-Fringe Interferometric Keratometer

NASA Technical Reports Server (NTRS)

Hochberg, Eric B.; Baroth, Edmund C.

1992-01-01

Proposed keratometer based on scheme involving spectral dispersal of white-light interference fringes. Instrument operates in "snapshot" mode: no scanning necessary, not necessary to immobilize patient's eye. Insensitive to vibration, involves no phase shifting, and has variable sensitivity. Intended primarily for use in medical assessments of human corneas, also used to measure shapes of animal corneas, lenses, and other aspherical or spherical reflective or partly reflective surfaces.

Sea Ice Remote Sensing Using Surface Reflected GPS Signals

NASA Technical Reports Server (NTRS)

Komjathy, Attila; Maslanik, James; Zavorotny, Valery U.; Axelrad, Penina; Katzberg, Stephen J.

2000-01-01

This paper describes a new research effort to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. Our experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and freshwater ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska indicating correlation between forward-scattered GPS returns and RADARSAT backscattered measurements.

Software for Simulation of Hyperspectral Images

NASA Technical Reports Server (NTRS)

Richtsmeier, Steven C.; Singer-Berk, Alexander; Bernstein, Lawrence S.

2002-01-01

A package of software generates simulated hyperspectral images for use in validating algorithms that generate estimates of Earth-surface spectral reflectance from hyperspectral images acquired by airborne and spaceborne instruments. This software is based on a direct simulation Monte Carlo approach for modeling three-dimensional atmospheric radiative transport as well as surfaces characterized by spatially inhomogeneous bidirectional reflectance distribution functions. In this approach, 'ground truth' is accurately known through input specification of surface and atmospheric properties, and it is practical to consider wide variations of these properties. The software can treat both land and ocean surfaces and the effects of finite clouds with surface shadowing. The spectral/spatial data cubes computed by use of this software can serve both as a substitute for and a supplement to field validation data.

Handheld directional reflectometer: an angular imaging device to measure BRDF and HDR in real time

NASA Astrophysics Data System (ADS)

Mattison, Phillip R.; Dombrowski, Mark S.; Lorenz, James M.; Davis, Keith J.; Mann, Harley C.; Johnson, Philip; Foos, Bryan

1998-10-01

Many applications require quantitative measurements of surface light scattering, including quality control on production lines, inspection of painted surfaces, inspection of field repairs, etc. Instruments for measuring surface scattering typically fall into two main categories, namely bidirectional reflectometers, which measure the angular distribution of scattering, and hemispherical directional reflectometers, which measure the total scattering into the hemisphere above the surface. Measurement of the bi-directional reflectance distribution function (BRDF) gives the greatest insight into how light is scattered from a surface. Measurements of BRDF, however, are typically very lengthy measurements taken by moving a source and detector to map the scattering. Since BRDF has four angular degrees of freedom, such measurements can require hours to days to complete. Instruments for measuring BRDF are also typically laboratory devices, although a field- portable bi-directional reflectometer does exist. Hemispherical directional reflectance (HDR) is a much easier measurement to make, although care must be taken to use the proper methodology when measuring at wavelengths beyond 10 micrometer, since integrating spheres (typically used to make such measurements) are very energy inefficient and lose their integrating properties at very long wavelengths. A few field- portable hemispherical directional reflectometers do exist, but typically measure HDR only at near-normal angles. Boeing Defense and Space Group and Surface Optics Corporation, under a contract from the Air Force Research Laboratory, have developed a new hand-held instrument capable of measuring both BRDF and HDR using a unique, patented angular imaging technique. A combination of an hemi-ellipsoidal mirror and an additional lens translate the angular scatter from a surface into a two-dimensional spatial distribution, which is recorded by an imaging array. This configuration fully maps the scattering from a half-hemisphere above the surface with more than 30,000 angularly-resolved points and update rates to 60 measurements per second. The instrument then computes HDR from the measured BDR. For ease of use, the instrument can also compare both the BRDF and HDR to preset limits, generating a Pass/Fail indicator for HDR and a high-acceptable-low image display of BRDF. Beam incidence elevation is variable from normal incidence ((theta) equals 0 degrees) to 5 degrees off grazing ((theta) equals 85 degrees), while scattering is measured to nearly 90 degrees off normal. Such capability is extremely important for any application requiring knowledge of surface appearance at oblique viewing angles. The current instrument operates over the range of 3 micrometer to 12 micrometer, with extension into the visible band possible.

A Microwave Pressure Sounder

NASA Technical Reports Server (NTRS)

Flower, D. A.; Peckham, G. E.

1978-01-01

An instrument to measure atmospheric pressure at the earth's surface from an orbiting satellite would be a valuable addition to the expanding inventory of remote sensors. The subject of this report is such an instrument - the Microwave Pressure Sounder (MPS). It is shown that global-ocean coverage is attainable with sufficient accuracy, resolution and observational frequency for meteorological, oceanographic and climate research applications. Surface pressure can be deduced from a measurement of the absorption by an atmospheric column at a frequency in the wing of the oxygen band centered on 60 GHz. An active multifrequency instrument is needed to make this measurement with sufficient accuracy. The selection of optimum operating frequencies is based upon accepted models of surface reflection, oxygen, water vapor and cloud absorption. Numerical simulation using a range of real atmospheres defined by radiosonde observations were used to validate the frequency selection procedure. Analyses are presented of alternative system configurations that define the balance between accuracy and achievable resolution.

INERTIAL INSTRUMENT SYSTEM FOR AERIAL SURVEYING.

USGS Publications Warehouse

Brown, Russell H.; Chapman, William H.; Hanna, William F.; Mongan, Charles E.; Hursh, John W.

1987-01-01

The purpose of this report is to describe an inertial guidance or navigation system that will enable use of relatively light aircraft for efficient data-gathering in geologgy, hydrology, terrain mapping, and gravity-field mapping. The instrument system capitalizes not only on virtual state-of-the-art inertial guidance technology but also on similarly advanced technology for measuring distance with electromagnetic radiating devices. The distance measurement can be made with a transceiver beamed at either a cooperative taget, with a specially designed reflecting surface, or a noncooperative target, such as the Earth's surface. The instrument system features components that use both techniques. Thus, a laser tracker device, which updates the inertial guidance unit or navigator in flight, makes distance measurements to a retroreflector target mounted at a ground-control point; a laser profiler device, beamed vertically downward, makes distance measurements to the Earth's surface along a path that roughly mirrors the aircraft flight path.

New portable instrument for combined reflectance, time-resolved and steady-state luminescence measurements on works of art

NASA Astrophysics Data System (ADS)

Romani, Aldo; Grazia, Chiara; Anselmi, Chiara; Miliani, Costanza; Brunetti, Brunetto Giovanni

2011-06-01

In this paper a new compact and portable instrument for combined reflectance, time-resolved and steady-state fluorescence is presented. All the optical parts of the apparatus, carefully described in the text, were chosen after an extensive market survey in order to obtain the best performances coupled with the smallest dimensions. This instrument through the use of a dedicated multiple fiber optic probe, allows the complete photophysical behaviors of investigated materials to be collected from the same point of the analyzed surface. In this way, the resultant instrumental setup is a portable device, usable in situ for non destructive and non invasive diagnostic purposes in the field of cultural heritage. Preliminary results concerning organic dyes characterization, which is the main application of luminescence-based diagnostic techniques in artworks, are presented and compared with those previously obtained using separate devices. Concerning reflectance data, improvements in the deep detectable UV spectral range have been achieved switching from the integrating sphere of the old instrument to bifurcated optical fibers used as probe in the new one. Special attention was devoted to test the instrument capability in order to obtain the true emission spectrum, corrected for the selfabsorption effect, for which good results were found. This particular experimental procedure is strongly recommended, by a diagnostic point of view, to avoid distortions in the instrumental responses, namely the spectral shape and emission maximum wavelength of a fluorophore as function of the color saturation.

The optical design of the G-CLEF Spectrograph: the first light instrument for the GMT

NASA Astrophysics Data System (ADS)

Ben-Ami, Sagi; Epps, Harland; Evans, Ian; Mueller, Mark; Podgorski, William; Szentgyorgyi, Andrew

2016-08-01

The GMT-Consortium Large Earth Finder (G-CLEF), the first major light instrument for the GMT, is a fiber-fed, high-resolution echelle spectrograph. In the following paper, we present the optical design of G-CLEF. We emphasize the unique solutions derived for the spectrograph fiber-feed: the Mangin mirror that corrects the cylindrical field curvature, the implementation of VPH grisms as cross dispersers, and our novel solution for a multi-colored exposure meter. We describe the spectrograph blue and red cameras comprised of 7 and 8 elements respectively, with one aspheric surface in each camera, and present the expected echellogram imaged on the instrument focal planes. Finally, we present ghost analysis and mitigation strategy that takes into account both single reflection and double reflection back scattering from various elements in the optical train.

The current development status of the Orbiting Carbon Observatory (OCO) instrument optical design

NASA Technical Reports Server (NTRS)

Haring, Robert; Sutin, Brian; Crisp, David; Pollock, Randy; Sundstrand, Hamilton

2005-01-01

The status of the OCO instrument optical design is presented in this paper. The optical bench assembly comprises three cooled grating spectrometers coupled to an all-reflective telescope/relay system. Dichroic beam splitters are used to separate the light from a common telescope into the three spectral bands. The three bore sighted spectrometers allow the total column CO2 absorption path to be corrected for optical path and surface pressure uncertainties, aerosols, and water vapor. The design of the instrument is based on classic flight proven technologies.

The Effects of Surface Roughness on the Apparent Thermal and Optical Properties of the Moon

NASA Astrophysics Data System (ADS)

Rubanenko, L.; Hayne, P. O.; Paige, D. A.

2017-12-01

The thermal inertia and albedo of airless planetary bodies such as the Moon can be inferred by measuring the surface temperatures and solar reflectance. However, roughness below the instrument resolution can affect these measured parameters. Scattering and IR emission from warm slopes onto colder slopes change the surface cooling rate, while shadowing and directional scattering change the reflectance. The importance of these effects grows with increasing solar incidence and emission angles, and during solar eclipses during which the insolation decreases rapidly. The high-quality data gathered by the Lunar Reconnaissance Orbiter (LRO) mission during the last seven years provides us with a unique opportunity to study these effects. Previous works have either adopted a simplified roughness model composed of a single slope, or an illumination model that does not account for subsurface conduction. Our approach incorporates data with simulations conducted using a coupled thermal and illumination model. First, we model the surface temperature distribution below the instrument resolution, considering two realizations: a cratered surface and a Gaussian random surface. Then, we fit the rough surface brightness temperature distribution to that of a flat surface with effective thermal and optical properties to find they differ from the original properties by up to 20% due to the added surface roughness. In the future, this will help to better constrain the intrinsic physical properties of the surface on both the Moon and Mercury and also other airless bodies such as asteroids.

Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces

PubMed Central

Goldschmidt, Benjamin S.; Rudy, Anna M.; Nowak, Charissa A.; Tsay, Yowting; Whiteside, Paul J. D.; Hunt, Heather K.

2016-01-01

Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive. PMID:27500652

Accounting for surface reflectance in the derivation of vertical column densities of NO2 from airborne imaging DOAS

NASA Astrophysics Data System (ADS)

Meier, Andreas Carlos; Schönhardt, Anja; Richter, Andreas; Bösch, Tim; Seyler, André; Constantin, Daniel Eduard; Shaiganfar, Reza; Merlaud, Alexis; Ruhtz, Thomas; Wagner, Thomas; van Roozendael, Michel; Burrows, John. P.

2016-04-01

Nitrogen oxides, NOx (NOx = NO + NO2) play a key role in tropospheric chemistry. In addition to their directly harmful effects on the respiratory system of living organisms, they influence the levels of tropospheric ozone and contribute to acid rain and eutrophication of ecosystems. As they are produced in combustion processes, they can serve as an indicator for anthropogenic air pollution. In the late summers of 2014 and 2015, two extensive measurement campaigns were conducted in Romania by several European research institutes, with financial support from ESA. The AROMAT / AROMAT-2 campaigns (Airborne ROmanian Measurements of Aerosols and Trace gases) were dedicated to measurements of air quality parameters utilizing newly developed instrumentation at state-of-the-art. The experiences gained will help to calibrate and validate the measurements taken by the upcoming Sentinel-S5p mission scheduled for launch in 2016. The IUP Bremen contributed to these campaigns with its airborne imaging DOAS (Differential Optical Absorption Spectroscopy) instrument AirMAP (Airborne imaging DOAS instrument for Measurements of Atmospheric Pollution). AirMAP allows retrieving spatial distributions of trace gas columns densities in a stripe below the aircraft. The measurements have a high spatial resolution of approximately 30 x 80 m2 (along x across track) at a typical flight altitude of 3000 m. Supported by the instrumental setup and the large swath, gapless maps of trace gas distributions above a large city, like Bucharest or Berlin, can be acquired within a time window of approximately two hours. These properties make AirMAP a valuable tool for the validation of trace gas measurements from space. DOAS retrievals yield the density of absorbers integrated along the light path of the measurement. The light path is altered with a changing surface reflectance, leading to enhanced / reduced slant column densities of NO2 depending on surface properties. This effect must be considered in the derivation of air mass factors used to convert the measurements into vertical columns. Due to the high-resolution measurements, no data product of surface reflectance with sufficient spatial resolution is available. Thus the surface reflectance is estimated from AirMAP's own spectra. In this work the results of the research flights will be presented. The study focuses on the validation of AirMAP's measurements by comparison to other ground-based platforms like (mobile) MAX-DOAS measurements. Conclusions will be drawn on the quality of the measurements, their applicability for satellite data validation and possible improvements for future measurements.

ASTER Mexicali

NASA Technical Reports Server (NTRS)

2000-01-01

Dramatic differences in land use patterns are highlighted in this image of the U.S.-Mexico border. Lush, regularly gridded agricultural fields on the U.S. side contrast with the more barren fields of Mexico This June 12, 2000, sub-scene combines visible and near infrared bands, displaying vegetation in red. The town of Mexicali-Calexico spans the border in the middle of the image; El Centro, California, is in the upper left. Watered by canals fed from the Colorado River, California's Imperial Valley is one of the country's major fruit and vegetable producers. This image covers an area 24 kilometers (15 miles) wide and 30 kilometers (19 miles) long in three bands of the reflected visible and infrared wavelength region.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

Luminance-based specular gloss characterization.

PubMed

Leloup, Frédéric B; Pointer, Michael R; Dutré, Philip; Hanselaer, Peter

2011-06-01

Gloss is a feature of visual appearance that arises from the directionally selective reflection of light incident on a surface. Especially when a distinct reflected image is perceptible, the luminance distribution of the illumination scene above the sample can strongly influence the gloss perception. For this reason, industrial glossmeters do not provide a satisfactory gloss estimation of high-gloss surfaces. In this study, the influence of the conditions of illumination on specular gloss perception was examined through a magnitude estimation experiment in which 10 observers took part. A light booth with two light sources was utilized: the mirror image of only one source being visible in reflection by the observer. The luminance of both the reflected image and the adjacent sample surface could be independently varied by separate adjustment of the intensity of the two light sources. A psychophysical scaling function was derived, relating the visual gloss estimations to the measured luminance of both the reflected image and the off-specular sample background. The generalization error of the model was estimated through a validation experiment performed by 10 other observers. In result, a metric including both surface and illumination properties is provided. Based on this metric, improved gloss evaluation methods and instruments could be developed.

Absolute surface reconstruction by slope metrology and photogrammetry

NASA Astrophysics Data System (ADS)

Dong, Yue

Developing the manufacture of aspheric and freeform optical elements requires an advanced metrology method which is capable of inspecting these elements with arbitrary freeform surfaces. In this dissertation, a new surface measurement scheme is investigated for such a purpose, which is to measure the absolute surface shape of an object under test through its surface slope information obtained by photogrammetric measurement. A laser beam propagating toward the object reflects on its surface while the vectors of the incident and reflected beams are evaluated from the four spots they leave on the two parallel transparent windows in front of the object. The spots' spatial coordinates are determined by photogrammetry. With the knowledge of the incident and reflected beam vectors, the local slope information of the object surface is obtained through vector calculus and finally yields the absolute object surface profile by a reconstruction algorithm. An experimental setup is designed and the proposed measuring principle is experimentally demonstrated by measuring the absolute surface shape of a spherical mirror. The measurement uncertainty is analyzed, and efforts for improvement are made accordingly. In particular, structured windows are designed and fabricated to generate uniform scattering spots left by the transmitted laser beams. Calibration of the fringe reflection instrument, another typical surface slope measurement method, is also reported in the dissertation. Finally, a method for uncertainty analysis of a photogrammetry measurement system by optical simulation is investigated.

Simultaneous measurement of X-ray specular reflection and off-specular diffuse scattering from liquid surfaces using a two-dimensional pixel array detector: the liquid-interface reflectometer of BL37XU at SPring-8.

PubMed

Yano, Yohko F; Uruga, Tomoya; Tanida, Hajime; Toyokawa, Hidenori; Terada, Yasuko; Yamada, Hironari

2010-07-01

An X-ray reflectometer for simultaneous measurement of specular and off-specular reflection of liquid surfaces is described. The reflectometer, equipped with a two-dimensional single X-ray photon-counting pixel array detector obtained the full range of X-ray specular and off-specular reflections in an extremely short time (1 s). Both the specular and off-specular reflection of water exhibited good agreement with the predicted capillary-wave theory within the appropriate instrumental resolution. The approach is also demonstrated on an aqueous solution of 1-dodecyl-3-methylimidazolium chloride. The monolayer in which the dodecyl chain faces upwards and the Cl(-) anion locates next to the imidazolium ring formed on the water surface was found to be laterally homogeneous. The use of a pixel array detector will be particularly powerful for in situ measurements to investigate both out-of-plane and in-plane structures simultaneously, not only for liquid surfaces but also for other thin films.

The Absolute Reflectance and New Calibration Site of the Moon

NASA Astrophysics Data System (ADS)

Wu, Yunzhao; Wang, Zhenchao; Cai, Wei; Lu, Yu

2018-05-01

How bright the Moon is forms a simple but fundamental and important question. Although numerous efforts have been made to answer this question such as use of sophisticated electro-optical measurements and suggestions for calibration sites, the answer is still debated. An in situ measurement with a calibration panel on the surface of the Moon is crucial for obtaining the accurate absolute reflectance and resolving the debate. China’s Chang’E-3 (CE-3) “Yutu” rover accomplished this type of measurement using the Visible-Near Infrared Spectrometer (VNIS). The measurements of the VNIS, which were at large emission and phase angles, complement existing measurements for the range of photometric geometry. The in situ reflectance shows that the CE-3 landing site is very dark with an average reflectance of 3.86% in the visible bands. The results are compared with recent mission instruments: the Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC), the Spectral Profiler (SP) on board the SELENE, the Moon Mineralogy Mapper (M3) on board the Chandrayaan-1, and the Chang’E-1 Interference Imaging Spectrometer (IIM). The differences in the measurements of these instruments are very large and indicate inherent differences in their absolute calibration. The M3 and IIM measurements are smaller than LROC WAC and SP, and the VNIS measurement falls between these two pairs. When using the Moon as a radiance source for the on-orbit calibration of spacecraft instruments, one should be cautious about the data. We propose that the CE-3 landing site, a young and homogeneous surface, should serve as the new calibration site.

Determination of in-flight AVIRIS spectral, radiometric, spatial and signal-to-noise characteristics using atmospheric and surface measurements from the vicinity of the rare-earth-bearing carbonatite at Mountain Pass, California

NASA Technical Reports Server (NTRS)

Green, Robert O.; Vane, Gregg; Conel, James E.

1988-01-01

An assessment of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) performance was made for a flight over Mountain Pass, California, July 30, 1987. The flight data were reduced to reflectance using an empirical algorithm which compensates for solar, atmospheric and instrument factors. AVIRIS data in conjunction with surface and atmospheric measurements acquired concurrently were used to develop an improved spectral calibration. An accurate in-flight radiometric calibration was also performed using the LOWTRAN 7 radiative transfer code together with measured surface reflectance and atmospheric optical depths. A direct comparison with coincident Thematic Mapper imagery of Mountain Pass was used to demonstrate the high spatial resolution and good geometric performance of AVIRIS. The in-flight instrument noise was independently determined with two methods which showed good agreement. A signal-to-noise ratio was calculated using data from a uniform playa. This ratio was scaled to the AVIRIS reference radiance model, which provided a basis for comparison with laboratory and other in-flight signal-to-noise determinations.

Design and validation of a multiplexed low coherence interferometry instrument for in vivo clinical measurement of microbicide gel thickness distribution

PubMed Central

Drake, Tyler K.; DeSoto, Michael G.; Peters, Jennifer J.; Henderson, Marcus H.; Murtha, Amy P.; Katz, David F.; Wax, Adam

2011-01-01

We present a multiplexed, Fourier-domain low coherence interferometry (mLCI) instrument for in vivo measurement of intravaginal microbicide gel coating thickness distribution over the surface of the vaginal epithelium. The mLCI instrument uses multiple delivery fibers to acquire depth resolved reflection profiles across large scanned tissue areas. Here mLCI has been adapted into an endoscopic system with a custom imaging module for simultaneous, co-registered measurements with fluorimetric scans of the same surface. The resolution, optical signal-to-noise, and cross-talk of the mLCI instrument are characterized to evaluate performance. Validation measurements of gel thickness are made using a calibration socket. Initial results from a clinical study are presented to show the in vivo capability of the dual-modality system for assessing the distribution of microbicide gel vehicles in the lower human female reproductive tract. PMID:22025989

Rock Layers in Lower Mound in Gale Crater

NASA Image and Video Library

2011-07-22

Mars scientists have several important hypotheses about how these minerals may reflect changes in the amount of water on the surface of Mars. The Mars Science Laboratory rover, Curiosity, will use its full suite of instruments to study these minerals.

Simulation of radar reflectivity and surface measurements of rainfall

NASA Technical Reports Server (NTRS)

Chandrasekar, V.; Bringi, V. N.

1987-01-01

Raindrop size distributions (RSDs) are often estimated using surface raindrop sampling devices (e.g., disdrometers) or optical array (2D-PMS) probes. A number of authors have used these measured distributions to compute certain higher-order RSD moments that correspond to radar reflectivity, attenuation, optical extinction, etc. Scatter plots of these RSD moments versus disdrometer-measured rainrates are then used to deduce physical relationships between radar reflectivity, attenuation, etc., which are measured by independent instruments (e.g., radar), and rainrate. In this paper RSDs of the gamma form as well as radar reflectivity (via time series simulation) are simulated to study the correlation structure of radar estimates versus rainrate as opposed to RSD moment estimates versus rainrate. The parameters N0, D0 and m of a gamma distribution are varied over the range normally found in rainfall, as well as varying the device sampling volume. The simulations are used to explain some possible features related to discrepancies which can arise when radar rainfall measurements are compared with surface or aircraft-based sampling devices.

Principal Components Analysis of Reflectance Spectra from the Mars Exploration Rover Opportunity

NASA Technical Reports Server (NTRS)

Mercer, C. M.; Cohen, B. A.

2010-01-01

In the summer of 2007 a global dust storm on Mars effectively disabled Opportunity's Miniature Thermal Emission Spectrometer (Mini-TES), the primary instrument used by the Athena Science Team to identify locally unique rocks on the Martian surface. The science team needs another way to distinguish interesting rocks from their surroundings on a tactical timescale. This study was designed to develop the ability to identify locally unique rocks on the Martian surface remotely using the Mars Exploration Rovers' Panoramica Camera (PanCam) instrument. Meridiani bedrock observed by Opportunity is largely characterized by sulfate-rich sandstones and hematite spherules. Additionally, loose fragments of bedrock and "cobbles" of foreign origin collet on the surface, some of which are interpreted as meteorites.

Polarised Multiangular Reflectance Measurements Using the Finnish Geodetic Institute Field Goniospectrometer

PubMed Central

Suomalainen, Juha; Hakala, Teemu; Peltoniemi, Jouni; Puttonen, Eetu

2009-01-01

The design, operation, and properties of the Finnish Geodetic Institute Field Goniospectrometer (FIGIFIGO) are presented. FIGIFIGO is a portable instrument for the measurement of surface Bidirectional Reflectance Factor (BRF) for samples with diameters of 10 – 50 cm. A set of polarising optics enable the measurement of linearly polarised BRF over the full solar spectrum (350 – 2,500 nm). FIGIFIGO is designed mainly for field operation using sunlight, but operation in a laboratory environment is also possible. The acquired BRF have an accuracy of 1 – 5% depending on wavelength, sample properties, and measurement conditions. The angles are registered at accuracies better than 2°. During 2004 – 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe. The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces. PMID:22412342

Overview on grating developments at ESA

NASA Astrophysics Data System (ADS)

Guldimann, B.; Deep, A.; Vink, R.; Harnisch, B.; Kraft, S.; Sierk, B.; Bazalgette, G.; Bézy, J.-L.

2017-11-01

In the frame of recent studies and missions, ESA has been performing various pre-developments of optical gratings for instruments operating at wavelengths from the UV up to the SWIR. The instrument requirements of Sentinel-4, Sentinel-5, CarbonSat and FLEX are driving the need for advanced designs and technologies leading to gratings with high efficiency, high spectral resolution, low stray light and low polarization sensitivities. Typical ESA instruments (e.g. Sciamachy, GOME, MERIS, OLCI, NIRSpec) were and are based on ruled gratings or gratings manufactured with one holographic photoresist mask layer which is transferred to an optical substrate (e.g. glass, glass ceramic) with dry etching methods and subsequently either coated with a reflective coating or used as a mold for replication. These manufacturing methods lead to blazed grating profiles with a metallic reflective surface. The vast majority of spectrometers on ground are still based on such gratings. In general, gratings based on grooved metallic surfaces tend for instance to polarize the incoming light significantly and are therefore not always suitable for ESA's needs of today. Gratings made for space therefore evolved to many other designs and concepts which will be reported in this paper.

Application of Reflected Global Navigation Satellite System (GNSS-R) Signals in the Estimation of Sea Roughness Effects in Microwave Radiometry

NASA Technical Reports Server (NTRS)

Voo, Justin K.; Garrison, James L.; Yueh, Simon H.; Grant, Michael S.; Fore, Alexander G.; Haase, Jennifer S.; Clauss, Bryan

2010-01-01

In February-March 2009 NASA JPL conducted an airborne field campaign using the Passive Active L-band System (PALS) and the Ku-band Polarimetric Scatterometer (PolSCAT) collecting measurements of brightness temperature and near surface wind speeds. Flights were conducted over a region of expected high-speed winds in the Atlantic Ocean, for the purposes of algorithm development for salinity retrievals. Wind speeds encountered were in the range of 5 to 25 m/s during the two weeks deployment. The NASA-Langley GPS delay-mapping receiver (DMR) was also flown to collect GPS signals reflected from the ocean surface and generate post-correlation power vs. delay measurements. This data was used to estimate ocean surface roughness and a strong correlation with brightness temperature was found. Initial results suggest that reflected GPS signals, using small low-power instruments, will provide an additional source of data for correcting brightness temperature measurements for the purpose of sea surface salinity retrievals.

Using Neural Networks to Improve the Performance of Radiative Transfer Modeling Used for Geometry Dependent Surface Lambertian-Equivalent Reflectivity Calculations

NASA Technical Reports Server (NTRS)

Fasnacht, Zachary; Qin, Wenhan; Haffner, David P.; Loyola, Diego; Joiner, Joanna; Krotkov, Nickolay; Vasilkov, Alexander; Spurr, Robert

2017-01-01

Surface Lambertian-equivalent reflectivity (LER) is important for trace gas retrievals in the direct calculation of cloud fractions and indirect calculation of the air mass factor. Current trace gas retrievals use climatological surface LER's. Surface properties that impact the bidirectional reflectance distribution function (BRDF) as well as varying satellite viewing geometry can be important for retrieval of trace gases. Geometry Dependent LER (GLER) captures these effects with its calculation of sun normalized radiances (I/F) and can be used in current LER algorithms (Vasilkov et al. 2016). Pixel by pixel radiative transfer calculations are computationally expensive for large datasets. Modern satellite missions such as the Tropospheric Monitoring Instrument (TROPOMI) produce very large datasets as they take measurements at much higher spatial and spectral resolutions. Look up table (LUT) interpolation improves the speed of radiative transfer calculations but complexity increases for non-linear functions. Neural networks perform fast calculations and can accurately predict both non-linear and linear functions with little effort.

Elevation Measurement Profile of Mars

NASA Technical Reports Server (NTRS)

1999-01-01

The elevation measurements were collected by the Mars Orbiter Laser Altimeter (MOLA) aboard Global Surveyor during the spring and summer of 1998, as the spacecraft orbited Mars in an interim elliptical orbit. MOLA sends laser pulses toward the planet and measures the precise amount of time before the reflected signals are received back at the instrument. From this data, scientists can infer surface and cloud heights.

During its mapping of the north polar cap, the MOLA instrument also made the first direct measurement of cloud heights on the red planet. Reflections from the atmosphere were obtained at altitudes from just above the surface to more than nine miles (approximately 15 kilometers) on about 80 percent of the laser profiles. Most clouds were observed at high latitudes, at the boundary of the ice cap and surrounding terrain.

Clouds observed over the polar cap are likely composed of carbon dioxide that condenses out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamic structure probably caused by winds interacting with surface topography, much as occurs on Earth when winds collide with mountains to produce turbulence.

The principal investigator for MOLA is Dr. David E. Smith of Goddard. The MOLA instrument was designed and built by the Laser Remote Sensing Branch of Laboratory for Terrestrial Physics at Goddard. The Mars Global Surveyor Mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for the NASA Office of Space Science.

Infrared Surface Temperature Measurements in the Presence of Reflected Radiation

DTIC Science & Technology

1990-08-01

33 11. Photograph of l-in. Blackbody Radiator .................................. 34 12. Radiosity (B...amount of radiation reaching the detector will be proportional to the radiosity (B) of the target, and will be a function of the optical path, target...emissivity, and geometry of the instrument. The radiosity is the rate at which energy streams away from the target surface and is the sum of the

NASA ER-2 Doppler radar reflectivity calibration for the CAMEX project

NASA Technical Reports Server (NTRS)

Caylor, I. J.; Heymsfield, G. M.; Bidwell, S. W.; Ameen, S.

1994-01-01

The NASA ER-2 Doppler radar (EDOP) was flown aboard the ER-2 high-altitude aircraft in September and October 1993 for the Convection and Moisture Experiment. During these flights, the first reliable reflectivity observations were performed with the EDOP instrument. This report details the procedure used to convert real-time engineering data into calibrated radar reflectivity. Application of the calibration results produces good agreement between the EDOP nadir pointing reflectivity and ground truth provided by a National Weather Service WSR-88D radar. The rms deviation between WSR-88D and EDOP is 6.9 dB, while measurements of the ocean surface backscatter coefficient are less than 3 dB from reported scatterometer coefficients. After an initial 30-minute period required for the instrument to reach thermal equilibrium, the radar is stable to better than 0.25 dB during flight. The range performance of EDOP shows excellent agreement with aircraft altimeter and meteorological sounding data.

Active multispectral reflection fingerprinting of persistent chemical agents

NASA Astrophysics Data System (ADS)

Tholl, H. D.; Münzhuber, F.; Kunz, J.; Raab, M.; Rattunde, M.; Hugger, S.; Gutty, F.; Grisard, A.; Larat, C.; Papillon, D.; Schwarz, M.; Lallier, E.; Kastek, M.; Piatkowski, T.; Brygo, F.; Awanzino, C.; Wilsenack, F.; Lorenzen, A.

2017-10-01

Remote detection of toxic chemicals of very low vapour pressure deposited on surfaces in form of liquid films, droplets or powder is a capability that is needed to protect operators and equipment in chemical warfare scenarios and in industrial environments. Infrared spectroscopy is a suitable means to support this requirement. Available instruments based on passive emission spectroscopy have difficulties in discriminating the infrared emission spectrum of the surface background from that of the contamination. Separation of background and contamination is eased by illuminating the surface with a spectrally tune-able light source and by analyzing the reflectivity spectrum. The project AMURFOCAL (Active Multispectral Reflection Fingerprinting of Persistent Chemical Agents) has the research topic of stand-off detection and identification of chemical warfare agents (CWAs) with amplified quantum cascade laser technology in the long-wave infrared spectral range. The project was conducted under the Joint Investment Programme (JIP) on CBRN protection funded through the European Defence Agency (EDA). The AMURFOCAL instrument comprises a spectrally narrow tune-able light source with a broadband infrared detector and chemometric data analysis software. The light source combines an external cavity quantum cascade laser (EC-QCL) with an optical parametric amplifier (OPA) to boost the peak output power of a short laser pulse tune-able over the infrared fingerprint region. The laser beam is focused onto a target at a distance between 10 and 20 m. A 3D data cube is registered by tuning the wavelength of the laser emission while recording the received signal scattered off the target using a multi-element infrared detector. A particular chemical is identified through the extraction of its characteristic spectral fingerprint out of the measured data. The paper describes the AMURFOCAL instrument, its functional units, and its principles of operation.

Space-Based Remote Sensing of Atmospheric Aerosols: The Multi-Angle Spectro-Polarimetric Frontier

NASA Technical Reports Server (NTRS)

Kokhanovsky, A. A.; Davis, A. B.; Cairns, B.; Dubovik, O.; Hasekamp, O. P.; Sano, I.; Mukai, S.; Rozanov, V. V.; Litvinov, P.; Lapyonok, T.;

10 Years of Asian Dust Storm Observations from SeaWiFS: Source, Pathway, and Interannual Variability

NASA Technical Reports Server (NTRS)

Hsu, N. Christina; Tsay, S.-C.; King, M.D.; Jeong, M.-J.

2008-01-01

In this paper, we will demonstrate the capability of a new satellite algorithm to retrieve aerosol optical thickness and single scattering albedo over bright-reflecting surfaces such as urban areas and deserts. Such retrievals have been difficult to perform using previously available algorithms that use wavelengths from the mid-visible to the near IR because they have trouble separating the aerosol signal from the contribution due to the bright surface reflectance. The new algorithm, called Deep Blue, utilizes blue-wavelength measurements from instruments such as SeaWiFS and MODIS to infer the properties of aerosols, since the surface reflectance over land in the blue part of the spectrum is much lower than for longer wavelength channels. We have validated the satellite retrieved aerosol optical thickness with data from AERONET sunphotometers over desert and semi-desert regions. The comparisons show reasonable agreements between these two. These new satellite products will allow scientists to determine quantitatively the aerosol properties near sources using high spatial resolution measurements from SeaWiFS and MODIS-like instruments. The multiyear satellite measurements (1998 - 2007) from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with these dust outbreaks in East Asia. The monthly averaged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures

NASA Astrophysics Data System (ADS)

Kestell, John D.; Mudiyanselage, Kumudu; Ye, Xinyi; Nam, Chang-Yong; Stacchiola, Dario; Sadowski, Jerzy; Boscoboinik, J. Anibal

2017-10-01

This paper describes the design and construction of a compact, "user-friendly" polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, from the surface bound species. A spectral frequency range between 1000 cm-1 and 4000 cm-1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ˜2 min at 4 cm-1 resolution, we have also acquired higher resolution spectra at 0.25 cm-1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a "vacuum suitcase" that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.

Polarized Optical Scattering Measurements of Metallic Nanoparticles on a Thin Film Silicon Wafer

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Liu, Tze-An; Fu, Wei-En

2009-09-01

Light scattering has shown its powerful diagnostic capability to characterize optical quality surfaces. In this study, the theory of bidirectional reflectance distribution function (BRDF) was used to analyze the metallic nanoparticles' sizes on wafer surfaces. The BRDF of a surface is defined as the angular distribution of radiance scattered by the surface normalized by the irradiance incident on the surface. A goniometric optical scatter instrument has been developed to perform the BRDF measurements on polarized light scattering on wafer surfaces for the diameter and distribution measurements of metallic nanoparticles. The designed optical scatter instrument is capable of distinguishing various types of optical scattering characteristics, which are corresponding to the diameters of the metallic nanoparticles, near surfaces by using the Mueller matrix calculation. The metallic nanoparticle diameter of measurement is 60 nm on 2 inch thin film wafers. These measurement results demonstrate that the polarization of light scattered by metallic particles can be used to determine the size of metallic nanoparticles on silicon wafers.

Preliminary spectral and geologic analysis of Landsat-4 Thematic Mapper data, Wind River Basin area, Wyoming

NASA Technical Reports Server (NTRS)

Conel, J. E.; Lang, H. R.; Paylor, E. D.; Alley, R. E.

1985-01-01

A Landsat-4 Thematic Mapper (TM) image of the Wind River Basin area in Wyoming is currently under analysis for stratigraphic and structural mapping and for assessment of spectral and spatial characteristics using visible, near infrared, and short wavelength infrared bands. To estimate the equivalent Lambertian surface reflectance, TM radiance data were calibrated to remove atmospheric and instrumental effects. Reflectance measurements for homogeneous natural and cultural targets were acquired about one year after data acquisition. Calibration data obtained during the analysis were used to calculate new gains and offsets to improve scanner response for earth science applications. It is shown that the principal component images calculated from the TM data were the result of linear transformations of ground reflectance. In images prepared from this transform, the separation of spectral classes was independent of systematic atmospheric and instrumental factors. Several examples of the processed images are provided.

Changes in cloud and aerosol cover (1980-2006) from reflectivity time series using SeaWiFS, N7-TOMS, EP-TOMS, SBUV-2, and OMI radiance data

NASA Astrophysics Data System (ADS)

Herman, J. R.; Labow, G.; Hsu, N. C.; Larko, D.

2009-01-01

The amount of solar radiation reflected back to space or reaching the Earth's surface is primarily governed by the amount of cloud cover and, to a much lesser extent, by Rayleigh scattering, aerosols, and various absorbing gases (e.g., O3, NO2, H2O). A useful measure of the effect of cloud plus aerosol cover is given by the amount that the 331 nm Lambert Equivalent Reflectivity (LER) of a scene exceeds the surface reflectivity for snow/ice-free scenes after Rayleigh scattering has been removed. Twenty-eight years of reflectivity data are available by overlapping data from several satellites: N7 (Nimbus 7, TOMS; 331 nm) from 1979 to 1992, SBUV-2 series (Solar Backscatter Ultraviolet, NOAA; 331 nm) 1985 to 2007, EP (Earth-Probe, TOMS; 331 nm) 1997 to 2006, SW (SeaWiFS; 412 nm) 1998 to 2006, and OMI (Ozone Measuring Instrument; 331 nm) 2004-2007. Only N7 and SW have a sufficiently long data record, Sun-synchronous orbits, and are adequately calibrated for long-term reflectivity trend estimation. Reflectivity data derived from these instruments and the SBUV-2 series are compared during the overlapping years. Key issues in determining long-term reflectivity changes that have occurred during the N7 and SW operating periods are discussed. The largest reflectivity changes in the 412 nm SW LER and 331 nm EP LER are found to occur near the equator and are associated with a large El Nino-Southern Oscillation event. Most other changes that have occurred are regional, such as the apparent cloud decrease over northern Europe since 1998. The fractional occurrence (fraction of days) of high reflectivity values over Hudson Bay, Canada (snow/ice and clouds) appears to have decreased when comparing reflectivity data from 1980 to 1992 to 1997-2006, suggesting shorter duration of ice in Hudson Bay since 1980.

Estimation of shortwave hemispherical reflectance (albedo) from bidirectionally reflected radiance data

NASA Technical Reports Server (NTRS)

Starks, Patrick J.; Norman, John M.; Blad, Blaine L.; Walter-Shea, Elizabeth A.; Walthall, Charles L.

1991-01-01

An equation for estimating albedo from bidirectional reflectance data is proposed. The estimates of albedo are found to be greater than values obtained with simultaneous pyranometer measurements. Particular attention is given to potential sources of systematic errors including extrapolation of bidirectional reflectance data out to a view zenith angle of 90 deg, the use of inappropriate weighting coefficients in the numerator of the albedo equation, surface shadowing caused by the A-frame instrumentation used to measure the incoming and outgoing radiation fluxes, errors in estimates of the denominator of the proposed albedo equation, and a 'hot spot' contribution in bidirectional data measured by a modular multiband radiometer.

Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

NASA Astrophysics Data System (ADS)

Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

2018-01-01

Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

Combining total internal reflection sum frequency spectroscopy spectral imaging and confocal fluorescence microscopy.

PubMed

Allgeyer, Edward S; Sterling, Sarah M; Gunewardene, Mudalige S; Hess, Samuel T; Neivandt, David J; Mason, Michael D

2015-01-27

Understanding surface and interfacial lateral organization in material and biological systems is critical in nearly every field of science. The continued development of tools and techniques viable for elucidation of interfacial and surface information is therefore necessary to address new questions and further current investigations. Sum frequency spectroscopy (SFS) is a label-free, nonlinear optical technique with inherent surface specificity that can yield critical organizational information on interfacial species. Unfortunately, SFS provides no spatial information on a surface; small scale heterogeneities that may exist are averaged over the large areas typically probed. Over the past decade, this has begun to be addressed with the advent of SFS microscopy. Here we detail the construction and function of a total internal reflection (TIR) SFS spectral and confocal fluorescence imaging microscope directly amenable to surface investigations. This instrument combines, for the first time, sample scanning TIR-SFS imaging with confocal fluorescence microscopy.

Light-scattering measurements of optical thin-film components at 157 and 193 nm

NASA Astrophysics Data System (ADS)

Gliech, Stefan; Steinert, Jorg; Duparre, Angela

2002-06-01

An instrument for total backscattering and forward-scattering measurements of optical coating components at 157 and 193 nm is described. The system is operated in both vacuum and nitrogen purge gas. An excimer laser as well as a deuterium lamp can be used as a radiation source. Suppression of the background signal level to 1 part in 106 permits measurements even of low-scatter samples such as superpolished substrates and antireflection coatings. Results of investigations of antireflective and highly reflective multilayers and CaF2 substrates reveal scattering from surface and interface roughness as well as from the volume of the substrate material. First steps to extend the instrument for angle-resolved scatter, transmittance, and reflectance measurements are described.

Considerations in the Design of Future Planetary Laser Altimeters

NASA Astrophysics Data System (ADS)

Smith, D. E.; Neumann, G. A.; Mazarico, E.; Zuber, M. T.; Sun, X.

2017-12-01

Planetary laser altimeters have generally been designed to provide high accuracy measurements of the nadir range to an uncooperative surface for deriving the shape of the target body, and sometimes specifically for identifying and characterizing potential landing sites. However, experience has shown that in addition to the range measurement, other valuable observations can be acquired, including surface reflectance and surface roughness, despite not being given high priority in the original altimeter design or even anticipated. After nearly 2 decades of planetary laser altimeter design, the requirements are evolving and additional capabilities are becoming equally important. The target bodies, once the terrestrial planets, are now equally asteroids and moons that in many cases do not permit simple orbital operations due to their small mass, radiation issues, or spacecraft fuel limitations. In addition, for a number of reasons, it has become necessary to perform shape determination from a much greater range, even thousands of kilometers, and thus ranging is becoming as important as nadir altimetry. Reflectance measurements have also proved important for assessing the presence of ice, water or CO2, and laser pulse spreading informed knowledge of surface roughness; all indicating a need for improved instrument capability. Recently, the need to obtain accurate range measurement to laser reflectors on landers or on a planetary surface is presenting new science opportunities but for which current designs are far from optimal. These changes to classic laser altimetry have consequences for many instrument functions and capabilities, including beam divergence, laser power, number of beams and detectors, pixelation, energy measurements, pointing stability, polarization, laser wavelengths, and laser pulse rate dependent range. We will discuss how a new consideration of these trades will help make lidars key instruments to execute innovative science in future planetary missions.

The Southwest Research Institute ultraviolet reflectance chamber (SwURC): a far ultraviolet reflectometer

NASA Astrophysics Data System (ADS)

Winters, Gregory S.; Retherford, Kurt D.; Davis, Michael W.; Escobedo, Stephen M.; Bassett, Eric C.; Patrick, Edward L.; Nagengast, Maggie E.; Fairbanks, Matthew H.; Miles, Paul F.; Parker, Joel W.; Gladstone, G. Randall; Slater, David C.; Stern, S. Alan

2012-10-01

We designed and assembled a highly capable UV reflectometer chamber and data acquisition system to provide bidirectional scattering data of various surfaces and materials. This chamber was initially conceived to create laboratory-based UV reflectance measurements of water frost on lunar soil/regolith simulants, to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project ("LAMP") instrument on-board the NASA Lunar Reconnaissance Orbiter spacecraft. A deuterium lamp illuminates surfaces and materials at a fixed 45° incident beam angle over the 115 to 200 nm range via a monochromator, while a photomultiplier tube detector is scanned to cover emission angles -85° to +85° (with a gap from -60° to -30°, due to the detector blocking the incident beam). Liquid nitrogen cools the material/sample mount when desired. The chamber can be configured to test a wide range of samples and materials using sample trays and holders. Test surfaces to date include aluminum mirrors, water ice, reflectance standards, and frozen mixtures of water and lunar soil/regolith stimulant. Future UV measurements planned include Apollo lunar samples, meteorite samples, other ices, minerals, and optical surfaces. Since this chamber may well be able to provide useful research data for groups outside Southwest Research Institute, we plan to take requests from and collaborate with others in the UV and surface reflection research community.

GPS Ocean Reflection Experiment on Spartan 251

NASA Technical Reports Server (NTRS)

Garrison, James L; Russo, Angela; Mickler, Dave; Armatys, Michael; Ferebee, Melvin J.

1999-01-01

It has recently been demonstrated that the GPS signal which has reflected from the ocean surface contains useful geophysical data from which the sea surface wind speed and other parameters can be extracted. This can be used for remote sensing, similar to present day use of radar altimeters or scatterometers, but with significantly smaller instrumentation because of the utilization of the existing GPS broadcast signal for illumination. Several campaigns of aircraft experimentation have been completed demonstrating this technique and reflected GPS data has been reliably collected from 25 km altitude on a balloon. However, there has not yet been a demonstration that the reflected GPS signal can be detected from orbit with sufficient signal to noise ratio (SNR) to make useful remote sensing measurements. A technology demonstration experiment was planned for a Space Shuttle flight in the late 2000 using the Spartan 251 recoverable carrier. This experiment would also have been the first flight validation of the PiVoT GPS receiver developed in house at the Goddard Space Flight Center. The "open-architecture" design of this receiver would allow the software modifications to be made which control code-correlator spacing to map out the shape of the reflected signal waveform, which is the most basic data product generated by this instrumentation. A moderate gain left-hand circularly polarized antenna, constructed from an array of off-the-shelf hemispherical antennas was to be used to give approximately 3 to 6 dB of additional gain. Preliminary SNR predictions have been done indicating that this antenna would offer sufficient gain to record waveform measurements. A system level description of the experiment instrumentation, including the receiver, antenna and data storage and retrieval will be given. The visibility of GPS reflections over the mission duration of several hours will be studied, including the effects of the limited beamwidth of the antenna. Spartan 251 has now been postponed with the earliest opportunity in the year 2002. The results of this study however, have been 2 used to further the define the requirements and expected performance of reflected GPS receivers in orbit. Several other space flight opportunities are being considered based upon this new information.

ASTER Paris

NASA Technical Reports Server (NTRS)

2000-01-01

The Eiffel Tower and its shadow can be seen next to the Seine in the left middle of this ASTER image of Paris. Based on the length of the shadow and the solar elevation angle of 59 degrees, we can calculate its height as 324 meters (1,054 feet), compared to its actual height of 303 meters (985 feet). Acquired on July 23, 2000, this image covers an area 23 kilometers (15 miles) wide and 20 kilometers (13 miles) long in three bands of the reflected visible and infrared wavelength region. Known as the City of Light, Paris has been extolled for centuries as one of the great cities of the world. Its location on the Seine River, at a strategic crossroads of land and river routes, has been the key to its expansion since the Parisii tribe first settled here in the 3rd century B.C.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

Lessons Learned from GOSAT; Instrument Design, Calibration, Operation, Data Processing, and International Collaboration

NASA Astrophysics Data System (ADS)

Kuze, A.; Suto, H.; Shiomi, K.; Nakajima, M.

2012-12-01

Advantage of satellite observation is its ability to monitor long term and global distribution with a single instrument. Ozone observation from space has been successful for long term monitoring purposes. Monitoring gradual increase and distribution of greenhouse gases in the troposphere with sub-percent accuracy has become a challenging subject. Interference of cloud and aerosol in radiative transfer has to be corrected for troposphere measurement. Accurate O2-A band measurement can retrieve surface pressure and aerosol distribution property. We have selected a Fourier Transform spectrometer (FTS) to achieve high throughput and wide spectral coverage with uniform spectral resolution. On the other hand, it is difficult to modulate short wave such as 0.76μm and avoid micro vibration interference. Prelaunch, we took special care to select optical components of excellent surface quality and isolate vibration. Design parameters such as IFOV, spectral resolution, observation interval within limited satellite resources must be carefully optimized. Greenhouse gases Observing SATellite (GOSAT) has been providing global high spectral resolution data for almost 4 years. Instrument performance, radiometric calibration, radiative transfer calculation and laboratory spectroscopy are all important. The first step was to reduce bias of column-averaged dry air mole fractions (the Level 2 product) of CO2 and CH4 (XCO2 and XCH4) and validate using well calibrated data such as TCCON. After 2 years of operation, latitudinal distribution of zonal mean and seasonal variation at these sites can be measured with better than 2ppm accuracy. However, validations are limited to ideal conditions. Next step is to evaluate consistency of measured values from long periods since launch, different surface types, and various input radiance with different instrument gain. For long term radiometric calibration, we have uses vicarious, onboard solar diffuser, and lunar calibration data. Over the ocean we target sun glint (specular reflection) points, where the surface reflectance is not uniform or randomly distributed. Over the desert area, where surface reflectance is high and dust layers extend to high altitude, we have to use lower gain to avoid saturation and multiple scattering is complicated. For both ocean high albedo targets, validation data of XCO2 and XCH4 are limited. Validation by airplane become accurate but extrapolation is needed above flight attitude. Comparison of surface pressure between retrieved data and a priori model forecast fields is useful. For such kind of consistency, measurement must be very linear within wide dynamic range. After launch, we are re-evaluating the linearity of the detector, analog circuit and AD converters using a lab-model on the ground. Since launch, we have received feedback about the radiance spectra data from many data users of diverse institutes. We have gathered many calibration and validation data from international collaboration. We have modified the Level 1 algorithm and instrument calibrations several times. We are currently measuring the grid point of the Earth's surface, but the sampling for source and sink retrieval has not been optimized yet. We will present how we have solved problems, which portions of the instrument design we should modify, and items that we have not understood well yet.

A fiber-coupled displacement measuring interferometer for determination of the posture of a reflective surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Shuai; Hu, Peng-Cheng, E-mail: hupc@hit.edu.cn; Ding, Xue-Mei, E-mail: X.M.Ding@outlook.com

A fiber-coupled displacement measuring interferometer capable of determining of the posture of a reflective surface of a measuring mirror is proposed. The newly constructed instrument combines fiber-coupled displacement and angular measurement technologies. The proposed interferometer has advantages of both the fiber-coupled and the spatially beam-separated interferometer. A portable dual-position sensitive detector (PSD)-based unit within this proposed interferometer measures the parallelism of the two source beams to guide the fiber-coupling adjustment. The portable dual PSD-based unit measures not only the pitch and yaw of the retro-reflector but also measures the posture of the reflective surface. The experimental results of displacement calibrationmore » show that the deviations between the proposed interferometer and a reference one, Agilent 5530, at two different common beam directions are both less than ±35 nm, thus verifying the effectiveness of the beam parallelism measurement. The experimental results of angular calibration show that deviations of pitch and yaw with the auto-collimator (as a reference) are less than ±2 arc sec, thus proving the proposed interferometer’s effectiveness for determination of the posture of a reflective surface.« less

Effects of Surface BRDF on the OMI Cloud and NO2 Retrievals: A New Approach Based on Geometry-Dependent Lambertian Equivalent Reflectivity (GLER) Derived from MODIS

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander; Qin, Wenhan; Krotkov, Nickolay; Lamsal, Lok; Spurr, Robert; Haffner, David; Joiner, Joanna; Yang, Eun-Su; Marchenko, Sergey

2017-01-01

The Ozone Monitoring Instrument (OMI) cloud and NO2 algorithms use a monthly gridded surface reflectivity climatology that does not depend upon the observation geometry. In reality, reflection of incoming direct and diffuse solar light from land or ocean surfaces is sensitive to the sun sensor geometry. This dependence is described by the bidirectional reflectance distribution function (BRDF). To account for the BRDF, we propose to use a new concept of geometry-dependent Lambertian equivalent reflectivity (GLER). Implementation within the existing OMI cloud and NO2 retrieval infrastructure requires changes only to the input surface reflectivity database. GLER is calculated using a vector radiative transfer model with high spatial resolution BRDF information from MODIS over land and the Cox Munk slope distribution over ocean with a contribution from water-leaving radiance. We compare GLER and climatological LER at 466 nm, which is used in the OMI O2-O2cloud algorithm to derive effective cloud fractions. A detailed comparison of the cloud fractions and pressures derived with climatological and GLERs is carried out. GLER and corresponding retrieved cloud products are then used as input to the OMI NO2 algorithm. We find that replacing the climatological OMI-based LERs with GLERs can increase NO2 vertical columns by up to 50 % in highly polluted areas; the differences include both BRDF effects and biases between the MODIS and OMI-based surface reflectance data sets. Only minor changes to NO2 columns (within 5 %) are found over unpolluted and overcast areas.

Cloud information content analysis of multi-angular measurements in the oxygen A-band: application to 3MI and MSPI

NASA Astrophysics Data System (ADS)

Merlin, G.; Riedi, J.; Labonnote, L. C.; Cornet, C.; Davis, A. B.; Dubuisson, P.; Desmons, M.; Ferlay, N.; Parol, F.

2015-12-01

The vertical distribution of cloud cover has a significant impact on a large number of meteorological and climatic processes. Cloud top altitude and cloud geometrical thickness are then essential. Previous studies established the possibility of retrieving those parameters from multi-angular oxygen A-band measurements. Here we perform a study and comparison of the performances of future instruments. The 3MI (Multi-angle, Multi-channel and Multi-polarization Imager) instrument developed by EUMETSAT, which is an extension of the POLDER/PARASOL instrument, and MSPI (Multi-angles Spectro-Polarimetric Imager) develoloped by NASA's Jet Propulsion Laboratory will measure total and polarized light reflected by the Earth's atmosphere-surface system in several spectral bands (from UV to SWIR) and several viewing geometries. Those instruments should provide opportunities to observe the links between the cloud structures and the anisotropy of the reflected solar radiation into space. Specific algorithms will need be developed in order to take advantage of the new capabilities of this instrument. However, prior to this effort, we need to understand, through a theoretical Shannon information content analysis, the limits and advantages of these new instruments for retrieving liquid and ice cloud properties, and especially, in this study, the amount of information coming from the A-Band channel on the cloud top altitude (CTOP) and geometrical thickness (CGT). We compare the information content of 3MI A-Band in two configurations and that of MSPI. Quantitative information content estimates show that the retrieval of CTOP with a high accuracy is possible in almost all cases investigated. The retrieval of CGT seems less easy but possible for optically thick clouds above a black surface, at least when CGT > 1-2 km.

Preliminary studies leading toward the development of a LIDAR bathymetry mapping instrument

NASA Astrophysics Data System (ADS)

Hill, John M.; Krenek, Brendan D.; Kunz, Terry D.; Krabill, William; Stetina, Fran

1993-02-01

The National Aeronautics and Space Administration (NASA) at Goddard Space Flight Center (GSFC) has developed a laser ranging device (LIDAR) which provides accurate and timely data of earth features. NASA/GSFC recently modified the sensor to include a scanning capability to produce LIDAR swaths. They have also integrated a Global Positioning System (GPS) and an Inertial Navigation System (INS) to accurately determine the absolute aircraft location and aircraft attitude (pitch, yaw, and roll), respectively. The sensor has been flown in research mode by NASA for many years. The LIDAR has been used in different configurations or modes to acquire such data as altimetry (topography), bathymetry (water depth), laser-induced fluorosensing (tracer dye movements, oil spills and oil thickness, chlorophyll and plant stress identification), forestry, and wetland discrimination studies. NASA and HARC are developing a commercial version of the instrument for topographic mapping applications. The next phase of the commercialization project will be to investigate other applications such as wetlands mapping and coastal bathymetry. In this paper we report on preliminary laboratory measurements to determine the feasibility of making accurate depth measurements in relatively shallow water (approximately 2 to 6 feet deep) using a LIDAR system. The LIDAR bathymetry measurements are relatively simple in theory. The water depth is determined by measuring the time interval between the water surface reflection and the bottom surface reflection signals. Depth is then calculated by dividing by the index of refraction of water. However, the measurements are somewhat complicated due to the convolution of the water surface return signal with the bottom surface return signal. Therefore in addition to the laboratory experiments, computer simulations of the data were made to show these convolution effects in the return pulse waveform due to: (1) water depth, and (2) changes in bottom surface reflectivity.

Preliminary Studies Leading Toward the Development of a LIDAR Bathymetry Mapping Instrument

NASA Technical Reports Server (NTRS)

Hill, John M.; Krenek, Brendan D.; Kunz, Terry D.; Krabill, William; Stetina, Fran

1993-01-01

The National Aeronautics and Space Administration (NASA) at Goddard Space Flight Center (GSFC) has developed a laser ranging device (LIDAR) which provides accurate and timely data of earth features. NASA/GSFC recently modified the sensor to include a scanning capability to produce LIDAR swaths. They have also integrated a Global Positioning System (GPS) and an Inertial Navigation System (INS) to accurately determine the absolute aircraft location and aircraft attitude (pitch, yaw, and roll), respectively. The sensor has been flown in research mode by NASA for many years. The LIDAR has been used in different configurations or modes to acquire such data as altimetry (topography), bathymetry (water depth), laser-induced fluorosensing (tracer dye movements, oil spills and oil thickness, chlorophyll and plant stress identification), forestry, and wetland discrimination studies. NASA and HARC are developing a commercial version of the instrument for topographic mapping applications. The next phase of the commercialization project will be to investigate other applications such as wetlands mapping and coastal bathymetry. In this paper we report on preliminary laboratory measurements to determine the feasibility of making accurate depth measurements in relatively shallow water (approximately 2 to 6 feet deep) using a LIDAR system. The LIDAR bathymetry measurements are relatively simple in theory. The water depth is determined by measuring the time interval between the water surface reflection and the bottom surface reflection signals. Depth is then calculated by dividing by the index of refraction of water. However, the measurements are somewhat complicated due to the convolution of the water surface return signal with the bottom surface return signal. Therefore in addition to the laboratory experiments, computer simulations of the data were made to show these convolution effects in the return pulse waveform due to: (1) water depth, and (2) changes in bottom surface reflectivity.

Development and field testing of a Light Aircraft Oil Surveillance System (LAOSS)

NASA Technical Reports Server (NTRS)

Burns, W.; Herz, M. J.

1976-01-01

An experimental device consisting of a conventional TV camera with a low light level photo image tube and motor driven polarized filter arrangement was constructed to provide a remote means of discriminating the presence of oil on water surfaces. This polarized light filtering system permitted a series of successive, rapid changes between the vertical and horizontal components of reflected polarized skylight and caused the oil based substances to be more easily observed and identified as a flashing image against a relatively static water surface background. This instrument was flight tested, and the results, with targets of opportunity and more systematic test site data, indicate the potential usefulness of this airborne remote sensing instrument.

POlarized Light Angle Reflectance Instrument I Polarized Incidence (POLAR:I)

NASA Technical Reports Server (NTRS)

Sarto, Anthony W.; Woldemar, Christopher M.; Vanderbilt, V. C.

1989-01-01

The light scattering properties of leaves are used as input data for models which mathematically describe the transport of photons within plant canopies. Polarization measurements may aid in the investigation of these properties. This paper describes an instrument for rapidly determining the bidirectional light scattering properties of leaves illuminated by linearly polarized light. Results for one species, magnolia, show large differences in the bidirectional light scattering properties depending whether or not the electric vector E is parallel to the foliage surface.

High Resolution Surface Geometry and Albedo by Combining Laser Altimetry and Visible Images

NASA Technical Reports Server (NTRS)

Morris, Robin D.; vonToussaint, Udo; Cheeseman, Peter C.; Clancy, Daniel (Technical Monitor)

2001-01-01

The need for accurate geometric and radiometric information over large areas has become increasingly important. Laser altimetry is one of the key technologies for obtaining this geometric information. However, there are important application areas where the observing platform has its orbit constrained by the other instruments it is carrying, and so the spatial resolution that can be recorded by the laser altimeter is limited. In this paper we show how information recorded by one of the other instruments commonly carried, a high-resolution imaging camera, can be combined with the laser altimeter measurements to give a high resolution estimate both of the surface geometry and its reflectance properties. This estimate has an accuracy unavailable from other interpolation methods. We present the results from combining synthetic laser altimeter measurements on a coarse grid with images generated from a surface model to re-create the surface model.

Comparison of cloud optical depth and cloud mask applying BRDF model-based background surface reflectance

NASA Astrophysics Data System (ADS)

Kim, H. W.; Yeom, J. M.; Woo, S. H.

2017-12-01

Over the thin cloud region, satellite can simultaneously detect the reflectance from thin clouds and land surface. Since the mixed reflectance is not the exact cloud information, the background surface reflectance should be eliminated to accurately distinguish thin cloud such as cirrus. In the previous research, Kim et al (2017) was developed the cloud masking algorithm using the Geostationary Ocean Color Imager (GOCI), which is one of significant instruments for Communication, Ocean, and Meteorology Satellite (COMS). Although GOCI has 8 spectral channels including visible and near infra-red spectral ranges, the cloud masking has quantitatively reasonable result when comparing with MODIS cloud mask (Collection 6 MYD35). Especially, we noticed that this cloud masking algorithm is more specialized in thin cloud detections through the validation with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data. Because this cloud masking method was concentrated on eliminating background surface effects from the top-of-atmosphere (TOA) reflectance. Applying the difference between TOA reflectance and the bi-directional reflectance distribution function (BRDF) model-based background surface reflectance, cloud areas both thick cloud and thin cloud can be discriminated without infra-red channels which were mostly used for detecting clouds. Moreover, when the cloud mask result was utilized as the input data when simulating BRDF model and the optimized BRDF model-based surface reflectance was used for the optimized cloud masking, the probability of detection (POD) has higher value than POD of the original cloud mask. In this study, we examine the correlation between cloud optical depth (COD) and its cloud mask result. Cloud optical depths mostly depend on the cloud thickness, the characteristic of contents, and the size of cloud contents. COD ranges from less than 0.1 for thin clouds to over 1000 for the huge cumulus due to scattering by droplets. With the cloud optical depth of CALIPSO, the cloud masking result can be more improved since we can figure out how deep cloud is. To validate the cloud mask and the correlation result, the atmospheric retrieval will be computed to compare the difference between TOA reflectance and the simulated surface reflectance.

Preliminary Error Budget for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

NASA Technical Reports Server (NTRS)

Thome, Kurtis; Gubbels, Timothy; Barnes, Robert

2011-01-01

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) plans to observe climate change trends over decadal time scales to determine the accuracy of climate projections. The project relies on spaceborne earth observations of SI-traceable variables sensitive to key decadal change parameters. The mission includes a reflected solar instrument retrieving at-sensor reflectance over the 320 to 2300 nm spectral range with 500-m spatial resolution and 100-km swath. Reflectance is obtained from the ratio of measurements of the earth s surface to those while viewing the sun relying on a calibration approach that retrieves reflectance with uncertainties less than 0.3%. The calibration is predicated on heritage hardware, reduction of sensor complexity, adherence to detector-based calibration standards, and an ability to simulate in the laboratory on-orbit sources in both size and brightness to provide the basis of a transfer to orbit of the laboratory calibration including a link to absolute solar irradiance measurements. The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe high-accuracy, long-term climate change trends and to use decadal change observations as the most critical method to determine the accuracy of climate change projections such as those in the IPCC Report. A rigorously known accuracy of both decadal change observations as well as climate projections is critical in order to enable sound policy decisions. The CLARREO Project will implement a spaceborne earth observation mission designed to provide rigorous SI traceable observations (i.e., radiance, reflectance, and refractivity) that are sensitive to a wide range of key decadal change variables, including: 1) Surface temperature and atmospheric temperature profile 2) Atmospheric water vapor profile 3) Far infrared water vapor greenhouse 4) Aerosol properties and anthropogenic aerosol direct radiative forcing 5) Total and spectral solar irradiance 6) Broadband reflected and emitted radiative fluxes 7) Cloud properties 8) Surface albedo There are two methods the CLARREO mission will rely on to achieve these critical decadal change benchmarks: direct and reference inter-calibration. A quantitative analysis of the strengths and weaknesses of the two methods has led to the recommended CLARREO mission approach. The project consists of two satellites launched into 90-degree, precessing orbits separated by 90 degrees. The instrument suite receiver on each spacecraft includes one emitted infrared spectrometer, two reflected solar spectrometers: dividing the spectrum from ultraviolet through near infrared, and one global navigation receiver for radio occultation. The measurements will be acquired for a period of three years minimum, with a five-year lifetime goal, enabling follow-on missions to extend the climate record over the decades needed to understand climate change. The current work concentrates on the reflected solar instrument giving an overview of its design and calibration approach. The calibration description includes the approach to achieving an SI-traceable system on orbit. The calibration overview is followed by a preliminary error budget based on techniques currently in place at the National Institute of Standards and Technology (NIST).

Landsat-7 ETM+ On-Orbit Reflective-Band Radiometric Stability and Absolute Calibration

NASA Technical Reports Server (NTRS)

Markham, Brian L.; Thome, Kurtis J.; Barsi, Julia A.; Kaita, Ed; Helder, Dennis L.; Barker, John L.

2003-01-01

The Landsat-7 spacecraft carries the Enhanced Thematic Mapper Plus (ETM+) instrument. This instrument images the Earth land surface in eight parts of the electromagnetic spectrum, termed spectral bands. These spectral images are used to monitor changes in the land surface, so a consistent relationship, i.e., calibration, between the image data and the Earth surface brightness, is required. The ETM+ has several on- board calibration devices that are used to monitor this calibration. The best on-board calibration source employs a flat white painted reference panel and has indicated changes of between 0.5% to 2% per year in the ETM+ response, depending on the spectral band. However, most of these changes are believed to be caused by changes in the reference panel, as opposed to changes in the instrument's sensitivity. This belief is based partially on on-orbit calibrations using instrumented ground sites and observations of "invariant sites", hyper-arid sites of the Sahara and Arabia. Changes determined from these data sets indicate are 0.1% - 0.6% per year. Tests and comparisons to other sensors also indicate that the uncertainty of the calibration is at the 5% level.

Results of an analytical study of spacecraft deposition contamination by internal reflection spectroscopy. [(haze on spacecraft windows from space debris)

NASA Technical Reports Server (NTRS)

Mookherji, T.

1976-01-01

Outgassing, deposition, and desorption kinetics of silicone compounds, are examined as examples of optical surface contaminants of spacecraft windows. Their behavior in a space environment after exposure to ultraviolet radiation is also examined. The use of internal reflection spectroscopy is shown to provide a viable means of real-time, in-situ identification of contaminants of orbiting spacecraft. The instrumental techniques are proposed as the basis of further investigations and the development of flight hardware.

Correcting Bidirectional Effects in Remote Sensing Reflectance from Coastal Waters

NASA Astrophysics Data System (ADS)

Stamnes, K. H.; Fan, Y.; Li, W.; Voss, K. J.; Gatebe, C. K.

2016-02-01

Understanding bidirectional effects including sunglint is important for GEO-CAPE for several reasons: (i) correct interpretation of ocean color data; (ii) comparing consistency of spectral radiance data derived from space observations with a single instrument for a variety of illumination and viewing conditions; (iii) merging data collected by different instruments operating simultaneously. We present a new neural network (NN) method to correct bidirectional effects in water-leaving radiance for both Case 1 and Case 2 waters. We also discuss a new BRDF and 2D sun-glint model that was validated by comparing simulated surface reflectances with Cloud Absorption Radiometer (CAR) data. Finally, we present an extension of our marine bio-optical model to the UV range that accounts for the seasonal dependence of the inherent optical properties (IOPs).

Use of Airborne Hyperspectral Data in the Simulation of Satellite Images

NASA Astrophysics Data System (ADS)

de Miguel, Eduardo; Jimenez, Marcos; Ruiz, Elena; Salido, Elena; Gutierrez de la Camara, Oscar

2016-08-01

The simulation of future images is part of the development phase of most Earth Observation missions. This simulation uses frequently as starting point images acquired from airborne instruments. These instruments provide the required flexibility in acquisition parameters (time, date, illumination and observation geometry...) and high spectral and spatial resolution, well above the target values (as required by simulation tools). However, there are a number of important problems hampering the use of airborne imagery. One of these problems is that observation zenith angles (OZA), are far from those that the misisons to be simulated would use.We examine this problem by evaluating the difference in ground reflectance estimated from airborne images for different observation/illumination geometries. Next, we analyze a solution for simulation purposes, in which a Bi- directional Reflectance Distribution Function (BRDF) model is attached to an image of the isotropic surface reflectance. The results obtained confirm the need for reflectance anisotropy correction when using airborne images for creating a reflectance map for simulation purposes. But this correction should not be used without providing the corresponding estimation of BRDF, in the form of model parameters, to the simulation teams.

A BRDF-BPDF database for the analysis of Earth target reflectances

NASA Astrophysics Data System (ADS)

Breon, Francois-Marie; Maignan, Fabienne

2017-01-01

Land surface reflectance is not isotropic. It varies with the observation geometry that is defined by the sun, view zenith angles, and the relative azimuth. In addition, the reflectance is linearly polarized. The reflectance anisotropy is quantified by the bidirectional reflectance distribution function (BRDF), while its polarization properties are defined by the bidirectional polarization distribution function (BPDF). The POLDER radiometer that flew onboard the PARASOL microsatellite remains the only space instrument that measured numerous samples of the BRDF and BPDF of Earth targets. Here, we describe a database of representative BRDFs and BPDFs derived from the POLDER measurements. From the huge number of data acquired by the spaceborne instrument over a period of 7 years, we selected a set of targets with high-quality observations. The selection aimed for a large number of observations, free of significant cloud or aerosol contamination, acquired in diverse observation geometries with a focus on the backscatter direction that shows the specific hot spot signature. The targets are sorted according to the 16-class International Geosphere-Biosphere Programme (IGBP) land cover classification system, and the target selection aims at a spatial representativeness within the class. The database thus provides a set of high-quality BRDF and BPDF samples that can be used to assess the typical variability of natural surface reflectances or to evaluate models. It is available freely from the PANGAEA website (doi:10.1594/PANGAEA.864090). In addition to the database, we provide a visualization and analysis tool based on the Interactive Data Language (IDL). It allows an interactive analysis of the measurements and a comparison against various BRDF and BPDF analytical models. The present paper describes the input data, the selection principles, the database format, and the analysis tool

The Effect of Incident Light Polarization on Vegetation Bidirectional Reflectance Factor

NASA Technical Reports Server (NTRS)

Georgiev, Georgi T.; Thome, Kurt; Ranson, Kurtis J.; King, Michael D.; Butler, James J.

2010-01-01

The Laboratory-based Bidirectional Reflectance Factor (BRF) polarization study of vegetation is presented in this paper. The BRF was measured using a short-arc Xenon lamp/monochromator assembly producing an incoherent, tunable light source with a well-defined spectral bandpass at visible and near-infrared wavelengths of interest at 470 nm and 870 nm and coherent light source at 1.656 microns. All vegetation samples were measured using P and S linearly polarized incident light over a range of incident and scatter angles. By comparing these results, we quantitatively examine how the BRF of the samples depends on the polarization of the incident light. The differences are significant, depend strongly on the incident and scatter angles, and can be as high as 120% at 67 deg incident and 470nm. The global nature of Earth's processes requires consistent long-term calibration of all instruments involved in data retrieval. The BRF defines the reflection characteristics of Earth surface. It provides the reflectance of a target in a specific direction as a function of illumination and viewing geometry. The BRF is a function of wavelength and reflects the structural and optical properties of the surface. Various space and airborne radiometric and imaging remote sensing instruments are used in the remote sensing characterization of vegetation canopies and soils, oceans, or especially large pollution sources. The satellite data is validated through comparison with airborne, ground-based and laboratory-based data in an effort to fully understand the vegetation canopy reflectance, The Sun's light is assumed to be unpolarized at the top of the atmosphere; however it becomes polarized to some degree due to atmospheric effects by the time it reaches the vegetation canopy. Although there are numerous atmospheric correction models, laboratory data is needed for model verification and improvement.

[A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

PubMed

Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

2015-07-01

Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable.

Microwave reflectometer ionization sensor

NASA Technical Reports Server (NTRS)

Seals, Joseph; Fordham, Jeffrey A.; Pauley, Robert G.; Simonutti, Mario D.

1993-01-01

The development of the Microwave Reflectometer Ionization Sensor (MRIS) Instrument for use on the Aeroassist Flight Experiment (AFE) spacecraft is described. The instrument contract was terminated, due to cancellation of the AFE program, subsequent to testing of an engineering development model. The MRIS, a four-frequency reflectometer, was designed for the detection and location of critical electron density levels in spacecraft reentry plasmas. The instrument would sample the relative magnitude and phase of reflected signals at discrete frequency steps across 4 GHz bandwidths centered at four frequencies: 20, 44, 95, and 140 GHz. The sampled data would be stored for later processing to calculate the distance from the spacecraft surface to the critical electron densities versus time. Four stepped PM CW transmitter receivers were located behind the thermal protection system of the spacecraft with horn antennas radiating and receiving through an insulating tile. Techniques were developed to deal with interference, including multiple reflections and resonance effects, resulting from the antenna configuration and operating environment.

Uncertainty in vegetation products derived from field spectral measurements: an error budget approach

NASA Astrophysics Data System (ADS)

Anderson, K.; Dungan, J. L.

2008-12-01

One of the biggest challenges in the use of proximal remote sensing methods continues to be the accurate, reproducible characterisation of natural surface reflectance properties measured in the solar radiation environment. Complexities in such measurements arise from differences in instrument type, field-of-view, atmospheric conditions, solar illumination and measurement angles and uncertainty in the calibration of reference sources used. Three GER 1500 spectroradiometers were used to measure the reflectance of a short sward grass canopy. A full laboratory assessment was first carried out to characterise instrument uncertainty. Wavelength-dependent patterns in noise equivalent delta radiances (NEdL) were similar for all three instruments, (less than 1 W m-2 sr μm-1 in the range 400-1000 nm). The spectroradiometers were then used in the field, each in a single-beam configuration and two in a dual-field- of-view configuration to compare their field reproducibility to laboratory measurements. Hemispherical-conical reflectance factors (HCRF) were collected in clear sky conditions of a grass (Pennisetum clandestinum) canopy. Two measurement dates were used where skies were clean (diffuse-to-global (DG) irradiance ratios < 0.13) and stable (standard deviation in DG < 0.001). Spectra were collected at nadir during the two- hour period spanning solar noon with a 2° range in solar zenith angles. A reproducible method was used which enabled positioning of instruments to within 1° precision in the azimuthal direction and with no movement in zenithal position. Ten measurements were taken with each sensor head, from a calibrated optical grade Spectralon panel (99% reflecting), the grass target, and a control surface -- a grey, 75% Spectralon panel. After each sequence the sensor heads were changed. On each date, the sequence of measurements was repeated. Field results showed standard uncertainties (u) of less than 0.01 (SD in HCRF) for the grey panel and less than 0.015 for vegetation. The grey panel data showed a wavelength- dependent pattern, similar to the NEdL laboratory trend, but subsequent error propagation of laboratory- derived NEdL through to a reflectance factor showed that the laboratory characterisation was unable to account for all of the uncertainty measured in the field. Therefore the estimate of u gained from field data more closely represents the reproducibility of measurements where atmospheric, solar zenith and instrument-related uncertainties are combined. Results on vegetation u showed a stronger wavelength dependency with higher standard uncertainties beyond the vegetation red-edge than in visible wavelengths (maximum = 0.015 at 800 nm, and 0.004 at 550nm). The results demonstrate that standard uncertainties of field reflectance data have a spectral dependence and exceed laboratory-derived estimates of instrument "noise". Uncertainty of this type must be taken into account when statistically testing for differences in field spectra. Improved reporting of standard uncertainties from field experiments will foster progress in remote sensing science.

Development and Testing of the New Surface LER Climatology for OMI UV Aerosol Retrievals

NASA Technical Reports Server (NTRS)

Gupta, Pawan; Torres, Omar; Jethva, Hiren; Ahn, Changwoo

2014-01-01

Ozone Monitoring Instrument (OMI) onboard Aura satellite retrieved aerosols properties using UV part of solar spectrum. The OMI near UV aerosol algorithm (OMAERUV) is a global inversion scheme which retrieves aerosol properties both over ocean and land. The current version of the algorithm makes use of TOMS derived Lambertian Equivalent Reflectance (LER) climatology. A new monthly climatology of surface LER at 354 and 388 nm have been developed. This will replace TOMS LER (380 nm and 354nm) climatology in OMI near UV aerosol retrieval algorithm. The main objectives of this study is to produce high resolution (quarter degree) surface LER sets as compared to existing one degree TOMS surface LERs, to product instrument and wavelength consistent surface climatology. Nine years of OMI observations have been used to derive monthly climatology of surface LER. MODIS derived aerosol optical depth (AOD) have been used to make aerosol corrections on OMI wavelengths. MODIS derived BRDF adjusted reflectance product has been also used to capture seasonal changes in the surface characteristics. Finally spatial and temporal averaging techniques have been used to fill the gaps around the globes, especially in the regions with consistent cloud cover such as Amazon. After implementation of new surface data in the research version of algorithm, comparisons of AOD and single scattering albedo (SSA) have been performed over global AERONET sites for year 2007. Preliminary results shows improvements in AOD retrievals globally but more significance improvement were observed over desert and bright locations. We will present methodology of deriving surface data sets and will discuss the observed changes in retrieved aerosol properties with respect to reference AERONET measurements.

Accounting for the effects of surface BRDF on satellite cloud and trace-gas retrievals: a new approach based on geometry-dependent Lambertian equivalent reflectivity applied to OMI algorithms

NASA Astrophysics Data System (ADS)

Vasilkov, Alexander; Qin, Wenhan; Krotkov, Nickolay; Lamsal, Lok; Spurr, Robert; Haffner, David; Joiner, Joanna; Yang, Eun-Su; Marchenko, Sergey

2017-01-01

Most satellite nadir ultraviolet and visible cloud, aerosol, and trace-gas algorithms make use of climatological surface reflectivity databases. For example, cloud and NO2 retrievals for the Ozone Monitoring Instrument (OMI) use monthly gridded surface reflectivity climatologies that do not depend upon the observation geometry. In reality, reflection of incoming direct and diffuse solar light from land or ocean surfaces is sensitive to the sun-sensor geometry. This dependence is described by the bidirectional reflectance distribution function (BRDF). To account for the BRDF, we propose to use a new concept of geometry-dependent Lambertian equivalent reflectivity (LER). Implementation within the existing OMI cloud and NO2 retrieval infrastructure requires changes only to the input surface reflectivity database. The geometry-dependent LER is calculated using a vector radiative transfer model with high spatial resolution BRDF information from the Moderate Resolution Imaging Spectroradiometer (MODIS) over land and the Cox-Munk slope distribution over ocean with a contribution from water-leaving radiance. We compare the geometry-dependent and climatological LERs for two wavelengths, 354 and 466 nm, that are used in OMI cloud algorithms to derive cloud fractions. A detailed comparison of the cloud fractions and pressures derived with climatological and geometry-dependent LERs is carried out. Geometry-dependent LER and corresponding retrieved cloud products are then used as inputs to our OMI NO2 algorithm. We find that replacing the climatological OMI-based LERs with geometry-dependent LERs can increase NO2 vertical columns by up to 50 % in highly polluted areas; the differences include both BRDF effects and biases between the MODIS and OMI-based surface reflectance data sets. Only minor changes to NO2 columns (within 5 %) are found over unpolluted and overcast areas.

Accounting for the Effects of Surface BRDF on Satellite Cloud and Trace-Gas Retrievals: A New Approach Based on Geometry-Dependent Lambertian-Equivalent Reflectivity Applied to OMI Algorithms

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander; Qin, Wenhan; Krotkov, Nickolay; Lamsal, Lok; Spurr, Robert; Haffner, David; Joiner, Joanna; Yang, Eun-Su; Marchenko, Sergey

2017-01-01

Most satellite nadir ultraviolet and visible cloud, aerosol, and trace-gas algorithms make use of climatological surface reflectivity databases. For example, cloud and NO2 retrievals for the Ozone Monitoring Instrument (OMI) use monthly gridded surface reflectivity climatologies that do not depend upon the observation geometry. In reality, reflection of incoming direct and diffuse solar light from land or ocean surfaces is sensitive to the sun-sensor geometry. This dependence is described by the bidirectional reflectance distribution function (BRDF). To account for the BRDF, we propose to use a new concept of geometry-dependent Lambertian equivalent reflectivity (LER). Implementation within the existing OMI cloud and NO2 retrieval infrastructure requires changes only to the input surface reflectivity database. The geometry-dependent LER is calculated using a vector radiative transfer model with high spatial resolution BRDF information from the Moderate Resolution Imaging Spectroradiometer (MODIS) over land and the Cox-Munk slope distribution over ocean with a contribution from water-leaving radiance. We compare the geometry-dependent and climatological LERs for two wavelengths, 354 and 466 nm, that are used in OMI cloud algorithms to derive cloud fractions. A detailed comparison of the cloud fractions and pressures derived with climatological and geometry-dependent LERs is carried out. Geometry-dependent LER and corresponding retrieved cloud products are then used as inputs to our OMI NO2 algorithm. We find that replacing the climatological OMI-based LERs with geometry-dependent LERs can increase NO2 vertical columns by up to 50% in highly polluted areas; the differences include both BRDF effects and biases between the MODIS and OMI-based surface reflectance data sets. Only minor changes to NO2 columns (within 5 %) are found over unpolluted and overcast areas.

Generating a Long-Term Land Data Record from the AVHRR and MODIS Instruments

NASA Technical Reports Server (NTRS)

Pedelty, Jeffrey; Devadiga, Sadashiva; Masuoka, Edward; Brown, Molly; Pinzon, Jorge; Tucker, Compton; Vermote, Eric; Prince, Stephen; Nagol, Jyotheshwar; Justice, Christopher;

Multistage Passive Cooler for Spaceborne Instruments

NASA Technical Reports Server (NTRS)

Rodriquez, Jose I.

2007-01-01

A document describes a three-stage passive radiative cooler for a cryogenic spectrometer to be launched into a low orbit around the Moon. This cooler is relatively lightweight and compact, and its basic design is scalable and otherwise adaptable to other applications in which there are requirements for cooling instrumentation in orbit about planets. The cooler includes multiple lightweight flat radiator blades alternating with cylindrical parabolic infrared reflectors. The radiator blades are oriented at an angle chosen to prevent infrared loading from the Moon limb at the intended orbital altitude and attitude. The reflectors are shaped and oriented to position their foci outside the radiator surfaces. There are six radiator-blade/reflector pairs - two pairs for each stage of cooling. The radiator blades and reflectors are coated on their front and back surfaces with materials having various infrared emissivities, infrared reflectivities, and solar reflectivities so as to maximize infrared radiation to cold outer space and minimize inadvertent solar heating. The radiator blades and reflectors are held in place by a lightweight support structure, the components of which are designed to satisfy a complex combination of thermal and mechanical requirements.

Inference of Surface Chemical and Physical Properties Using Mid-Infrared (MIR) Spectral Observations

NASA Technical Reports Server (NTRS)

Roush, Ted L.

2016-01-01

Reflected or emitted energy from solid surfaces in the solar system can provide insight into thermo-physical and chemical properties of the surface materials. Measurements have been obtained from instruments located on Earth-based telescopes and carried on several space missions. The characteristic spectral features commonly observed in Mid-Infrared (MIR) spectra of minerals will be reviewed, along with methods used for compositional interpretations of MIR emission spectra. The influence of surface grain size, and space weathering processes on MIR emissivity spectra will also be discussed. Methods used for estimating surface temperature, emissivity, and thermal inertias from MIR spectral observations will be reviewed.

Osmium coated diffraction grating in the Space Shuttle environment - Performance

NASA Technical Reports Server (NTRS)

Torr, M. R.

1985-01-01

Samples coated with osmium were flown on the early Shuttle test flights, and on the return of these samples, the osmium coating was found to have disappeared, evidently due to the oxidation of the material in the atomic oxygen atmosphere. An instrument flown on the Spacelab 1 mission comprised an array of five spectrometers covering the extreme ultraviolet (EUV) to near-IR wavelengths. The EUV spectrometer contained an osmium-coated reflective grating located fairly deep within the instruments. Here, results of an assessment of the reflectivity and stability of the osmium surface over the course of the ten-day mission are reported. It is concluded that the osmium reflective coating remained stable relative to the spectrometer coated with MgF2 over the course of the mission. In addition, the ratio of sensitivity of these two spectrometers did not change in any major way from the time of the laboratory calibration until the time of flight two years later. Any changes are within the 50-percent calibration uncertainty.

ASTER Suez Canal

NASA Technical Reports Server (NTRS)

2000-01-01

One of the most important waterways in the world, the Suez Canal runs north to south across the Isthmus of Suez in northeastern Egypt. This image of the canal covers an area 36 kilometers (22 miles) wide and 60 kilometers (47 miles) long in three bands of the reflected visible and infrared wavelength region. It shows the northern part of the canal, with the Mediterranean Sea just visible in the upper right corner. The Suez Canal connects the Mediterranean Sea with the Gulf of Suez, an arm of the Red Sea. The artificial canal provides an important shortcut for ships operating between both European and American ports and ports located in southern Asia, eastern Africa, and Oceania. With a length of about 195 kilometers (121 miles) and a minimum channel width of 60 meters (197 feet), the Suez Canal is able to accommodate ships as large as 150,000 tons fully loaded. Because no locks interrupt traffic on this sea level waterway, the transit time only averages about 15 hours. ASTER acquired this scene on May 19, 2000.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

ASTER Gibraltar

NASA Technical Reports Server (NTRS)

2000-01-01

The Strait of Gibraltar separates Spain from Morocco. This image, acquired on July 5, 2000, covers an area 34 kilometers (21 miles) wide and 59 kilometers (37 miles) long in three bands of the reflected visible and infrared wavelength region. The promontory on the eastern side of the conspicuous Spanish port is the Rock of Gibraltar. Once one of the two classical Pillars of Hercules, the Rock was crowned with silver columns by Phoenician mariners to mark the limits of safe navigation for the ancient Mediterranean peoples. The rocky promontory still commands the western entrance to the Mediterranean Sea. The rocky limestone and shale ridge rises abruptly from the sea, to a maximum elevation of 426 meters (1,398 feet). A British colony, Gibraltar occupies a narrow strip of land at the southernmost tip of the Iberian Peninsula. It is separated from the Spanish mainland by a neutral zone contained on a narrow, sandy isthmus. Because of its strategic location and formidable topography, Gibraltar serves mainly as a British fortress. Most of its sparse land is taken up by air and naval installations, and the civilian population is small.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

BOREAS RSS-20 POLDER C-130 Measurements of Surface BRDF

NASA Technical Reports Server (NTRS)

Leroy, Marc; Hall, Forrest G. (Editor); Nickerson, Jaime (Editor); Smith, David E. (Technical Monitor)

2000-01-01

This Boreal Ecosystem-Atmosphere Study (BOREAS) Remote Sensing Science (RSS)-20 data set contains measurements of surface bidirectional reflectance distribution function (BRDF) made by the polarization and Directionality of Earth reflectances (POLDER) instrument over several surface types (pine, spruce, fen) of the BOREAS southern study area (SSA) during the 1994 intensive field campaigns (IFCs). Single-point BRDF values were acquired either from the NASA Ames Research Center (ARC) C-130 aircraft or from a NASA Wallops Flight Facility (WFF) helicopter. A related data set collected from the helicopter platform is available as is POLDER imagery acquired from the C-130. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures

DOE PAGES

Kestell, John D.; Mudiyanselage, Kumudu; Ye, Xinyi; ...

2017-10-01

This article describes the design and construction of a compact, “user-friendly” polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, frommore » the surface bound species. A spectral frequency range between 1000 cm -1 and 4000 cm -1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ~2 min at 4 cm -1 resolution, we have also acquired higher resolution spectra at 0.25 cm -1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a “vacuum suitcase” that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.« less

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kestell, John D.; Mudiyanselage, Kumudu; Ye, Xinyi

This article describes the design and construction of a compact, “user-friendly” polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, frommore » the surface bound species. A spectral frequency range between 1000 cm -1 and 4000 cm -1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ~2 min at 4 cm -1 resolution, we have also acquired higher resolution spectra at 0.25 cm -1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a “vacuum suitcase” that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.« less

An Acoustic-Instrumented Mine for Studying Subsequent Burial

DTIC Science & Technology

2007-01-01

seawater . A strong reflection from the transducer face therefore indicates sediment flush with the mine surface (i.e., the mine surface is buried...variations in seawater sound speed and urethane sound speed that create a slight acoustic impedance mismatch at the water-urethane in- terface. The water...following was used: w. = \\//,„/2f/« TTH, U, T;Sinh( kh ) /„• = 0.237 0.52 /„, is the wave friction factor, Uw is the wave orbital velocity

Computation of diffuse sky irradiance from multidirectional radiance measurements

NASA Technical Reports Server (NTRS)

Ahmad, Suraiya P.; Middleton, Elizabeth M.; Deering, Donald W.

1987-01-01

Accurate determination of the diffuse solar spectral irradiance directly above the land surface is important in characterizing the reflectance properties of these surfaces, especially vegetation canopies. This determination is also needed to infer the net radiation budget of the earth-atmosphere system above these surfaces. An algorithm is developed here for the computation of hemispheric diffuse irradiance using the measurements from an instrument called PARABOLA, which rapidly measures upwelling and downwelling radiances in three selected wavelength bands. The validity of the algorithm is established from simulations. The standard reference data set of diffuse radiances of Dave (1978), obtained by solving the radiative transfer equation numerically for realistic atmospheric models, is used to simulate PARABOLA radiances. Hemispheric diffuse irradiance is estimated from a subset of simulated radiances by using the algorithm described. The algorithm is validated by comparing the estimated diffuse irradiance with the true diffuse irradiance of the standard data set. The validations include sensitivity studies for two wavelength bands (visible, 0.65-0.67 micron; near infrared, 0.81-0.84 micron), different atmospheric conditions, solar elevations, and surface reflectances. In most cases the hemispheric diffuse irradiance computed from simulated PARABOLA radiances and the true irradiance obtained from radiative transfer calculations agree within 1-2 percent. This technique can be applied to other sampling instruments designed to estimate hemispheric diffuse sky irradiance.

Investigating Bidirectional Reflectance in the Los Angeles Megacity Using CLARS Multiangle and Hyperspectral Measurements

NASA Astrophysics Data System (ADS)

Zeng, Z. C.; Natraj, V.; Pongetti, T.; Shia, R. L.; Sander, S. P.; Yung, Y. L.

2017-12-01

The surface reflectance is a key ingredient in the remote sensing of surface and atmospheric properties from space. The determination of atmospheric composition, including greenhouse gas (GHG) and aerosol concentrations, from reflected sunlight requires accurate knowledge of the contribution from the underlying surface. Over megacity areas, such as the Los Angeles (LA) basin, which are major sources of GHGs and anthropogenic aerosols, the quantification of surface reflectance is challenging due to the associated complex land use types. In this study, we investigate the bidirectional reflectance in the Los Angeles megacity area using multiangle and hyperspectral radiance measurements from the California Laboratory for Atmospheric Remote Sensing (CLARS). The CLARS facility is located near the top of Mt. Wilson, at an altitude of 1670 m a.s.l., overlooking the LA megacity area with an FTS operating since 2011 to continuously monitor the GHGs and near-surface aerosols in the basin. The CLARS-FTS offers continuous high-resolution spectral measurements in the visible, near infrared and shortwave infrared spectral regions. The CLARS measurements mimic the off-nadir viewing of a low-Earth orbiting instrument, such as GOSAT and OCO-2, but with daily viewing capability. Eight surface targets with different land use types, including urban parks, industrial and residential areas, are selected in this study. The surface reflectance for specific solar incident and viewing angles is calculated by dividing, for non-absorbing spectral channels on clear days (such that gas and aerosol extinction can be ignored), the observed radiance reflected from surface targets by the observed irradiance. The non-linear Rahman-Pinty-Verstraete (RPV) model is used to model the Bidirectional Reflectance Distribution Function (BRDF) by fitting the multiangle and hyperspectral measurements. By evaluating the retrieved RPV parameters, we find that the RPV model provides a good representation of the BRDF in the LA megacity area. The fitted RPV parameters and their dependence on wavelength provides quantification of BRDF and potentially contributes towards reducing uncertainties in retrievals of GHGs and aerosols in megacity from space.

The UV reflectance of Patroclus: Exploring the surface composition and origins of Jupiter Trojans

NASA Astrophysics Data System (ADS)

Molyneux, Pippa

2017-08-01

(617) Patroclus is a binary system comprising two almost equally sized Trojan asteroids, Patroclus and Menoetius. (617) Patroclus has never been observed in the UV spectral region, which contains important diagnostic features of major Trojan surface constituents inferred from fits to visible-near IR spectra. Previous spectral observations have not been spatially resolved, precluding a direct spectral comparison of the two bodies. We propose to obtain full surface UV reflectance maps of both Patroclus and Menoetius using the STIS G230L mode, to search for characteristic absorption features of silicates, carbons/graphites and NH3, which together make up the major inferred Jupiter Trojan surface constituents, and for signs of ''spectral bluing'' that occurs for space-weathered objects. The Jupiter Trojans are believed to represent the most readily accessible Kuiper Belt material in the solar system, having been scattered from that region to their current orbits following a dynamical instability. A direct spectral comparison of Patroclus and Menoetius, indicating whether the objects share a common origin and evolution, will explore the hypothesis that the system is a rare binary survivor of this scattering. (617) Patroclus is also a target of the upcoming Lucy mission, and constraints on surface composition would represent a valuable input to instrument configuration and observation planning work for the mission. As Lucy will not carry a UV instrument, the proposed observations would remain unique and complementary to the results of the mission.

Design of a dynamic biofilm imaging cell for white-light interferometric microscopy

NASA Astrophysics Data System (ADS)

Larimer, Curtis; Brann, Michelle; Suter, Jonathan D.; Addleman, R. Shane

2017-11-01

In microbiology research, there is a strong need for next-generation imaging and sensing instrumentation that will enable minimally invasive and label-free investigation of soft, hydrated structures, such as in bacterial biofilms. White-light interferometry (WLI) can provide high-resolution images of surface topology without the use of fluorescent labels but is not typically used to image biofilms because there is insufficient refractive index contrast to induce reflection from the biofilm's interface. The soft structure and water-like bulk properties of hydrated biofilms make them difficult to characterize in situ, especially in a nondestructive manner. We build on our prior description of static biofilm imaging and describe the design of a dynamic growth flow cell that enables monitoring of the thickness and topology of live biofilms over time using a WLI microscope. The microfluidic system is designed to grow biofilms in dynamic conditions and to create a reflective interface on the surface while minimizing disruption of fragile structures. The imaging cell was also designed to accommodate limitations imposed by the depth of focus of the microscope's objective lens. Example images of live biofilm samples are shown to illustrate the ability of the flow cell and WLI instrument to (1) support bacterial growth and biofilm development, (2) image biofilm structure that reflects growth in flow conditions, and (3) monitor biofilm development over time nondestructively. In future work, the apparatus described here will enable surface metrology measurements (roughness, surface area, etc.) of biofilms and may be used to observe changes in biofilm structure in response to changes in environmental conditions (e.g., flow velocity, availability of nutrients, and presence of biocides). This development will open opportunities for the use of WLI in bioimaging.

Design of a dynamic biofilm imaging cell for white-light interferometric microscopy

DOE PAGES

Larimer, Curtis; Brann, Michelle; Suter, Jonathan D.; ...

2017-05-10

In microbiology research there is a strong need for next generation imaging and sensing instrumentation that will enable minimally invasive and label-free investigation of soft, hydrated structures such as in bacterial biofilms. White light interferometry (WLI) can provide high resolution images of surface topology without the use of fluorescent labels but is not typically used to image biofilms because there is insufficient refractive index contrast to induce reflection from the biofilm’s interface. The soft structure and water-like bulk properties of hydrated biofilms make them difficult to characterize in situ, especially in a non-destructive manner. In this report, we build onmore » our prior description of static biofilm imaging and describe the design of a dynamic imaging flow cell that enables monitoring the thickness and topology of live biofilms over time using a WLI microscope. The microfluidic system is specifically designed to create a reflective interface on the surface of biofilms while minimizing disruption of fragile structures. The imaging cell was also designed to accommodate limitations imposed by the depth of focus of the microscope’s objective lens. Example images of live biofilm samples are shown in order to illustrate the ability of the flow cell and WLI instrument to 1) support bacterial growth and biofilm development, 2) image biofilm structure that reflects growth in flow conditions, and 3) monitor biofilm development over time non-destructively. In future work, the apparatus described here will enable surface metrology measurements (roughness, surface area, etc.) of biofilms and may be used to observe changes in biofilm structure in response to changes in environmental conditions (e.g., flow velocity, availability of nutrients, and presence of biocides). Furthermore, this development will open new opportunities for the use of WLI in bioimaging.« less

Design of a dynamic biofilm imaging cell for white-light interferometric microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larimer, Curtis; Brann, Michelle; Suter, Jonathan D.

In microbiology research there is a strong need for next generation imaging and sensing instrumentation that will enable minimally invasive and label-free investigation of soft, hydrated structures such as in bacterial biofilms. White light interferometry (WLI) can provide high resolution images of surface topology without the use of fluorescent labels but is not typically used to image biofilms because there is insufficient refractive index contrast to induce reflection from the biofilm’s interface. The soft structure and water-like bulk properties of hydrated biofilms make them difficult to characterize in situ, especially in a non-destructive manner. In this report, we build onmore » our prior description of static biofilm imaging and describe the design of a dynamic imaging flow cell that enables monitoring the thickness and topology of live biofilms over time using a WLI microscope. The microfluidic system is specifically designed to create a reflective interface on the surface of biofilms while minimizing disruption of fragile structures. The imaging cell was also designed to accommodate limitations imposed by the depth of focus of the microscope’s objective lens. Example images of live biofilm samples are shown in order to illustrate the ability of the flow cell and WLI instrument to 1) support bacterial growth and biofilm development, 2) image biofilm structure that reflects growth in flow conditions, and 3) monitor biofilm development over time non-destructively. In future work, the apparatus described here will enable surface metrology measurements (roughness, surface area, etc.) of biofilms and may be used to observe changes in biofilm structure in response to changes in environmental conditions (e.g., flow velocity, availability of nutrients, and presence of biocides). Furthermore, this development will open new opportunities for the use of WLI in bioimaging.« less

The Multiple Altimeter Beam Experimental Lidar (MABEL), an Airborne Simulator for the ICESat-2 Mission

NASA Technical Reports Server (NTRS)

McGill, Matthew; Markus, Thorsten; Scott, V. Stanley; Neumann, Thomas

2012-01-01

The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission is currently under development by NASA. The primary mission of ICESat-2 will be to measure elevation changes of the Greenland and Antarctic ice sheets, document changes in sea ice thickness distribution, and derive important information about the current state of the global ice coverage. To make this important measurement, NASA is implementing a new type of satellite-based surface altimetry based on sensing of laser pulses transmitted to, and reflected from, the surface. Because the ICESat-2 measurement approach is different from that used for previous altimeter missions, a high-fidelity aircraft instrument, the Multiple Altimeter Beam Experimental Lidar (MABEL), was developed to demonstrate the measurement concept and provide verification of the ICESat-2 methodology. The MABEL instrument will serve as a prototype for the ICESat-2 mission and also provides a science tool for studies of land surface topography. This paper outlines the science objectives for the ICESat-2 mission, the current measurement concept for ICESat-2, and the instrument concept and preliminary data from MABEL.

Coupled thermo-elastic and optical performance analyses of a reflective baffle for the BepiColombo laser altimeter (BELA) receiver

NASA Astrophysics Data System (ADS)

Heesel, E.; Weigel, T.; Lochmatter, P.; Rugi Grond, E.

2017-11-01

For the BepiColombo mission, the extreme thermal environment around Mercury requires good heat shields for the instruments. The BepiColombo Laser altimeter (BELA) Receiver will be equipped with a specular reflective baffle in order to limit the solar power impact. The design uses a Stavroudis geometry with alternating elliptical and hyperbolic vanes to reflect radiation at angles >38° back into space. The thermal loads on the baffle lead to deformations, and the resulting changes in the optical performance can be modeled by ray-tracing. Conventional interfaces, such as Zernike surface fitting, fail to provide a proper import of the mechanical distortions into optical models. We have studied alternative models such as free form surface representations and compared them to a simple modeling approach with straight segments. The performance merit is presented in terms of the power rejection ratio and the absence of specular stray-light.

Modelling of XCO₂ Surfaces Based on Flight Tests of TanSat Instruments.

PubMed

Zhang, Li Li; Yue, Tian Xiang; Wilson, John P; Wang, Ding Yi; Zhao, Na; Liu, Yu; Liu, Dong Dong; Du, Zheng Ping; Wang, Yi Fu; Lin, Chao; Zheng, Yu Quan; Guo, Jian Hong

2016-11-01

The TanSat carbon satellite is to be launched at the end of 2016. In order to verify the performance of its instruments, a flight test of TanSat instruments was conducted in Jilin Province in September, 2015. The flight test area covered a total area of about 11,000 km² and the underlying surface cover included several lakes, forest land, grassland, wetland, farmland, a thermal power plant and numerous cities and villages. We modeled the column-average dry-air mole fraction of atmospheric carbon dioxide (XCO₂) surface based on flight test data which measured the near- and short-wave infrared (NIR) reflected solar radiation in the absorption bands at around 760 and 1610 nm. However, it is difficult to directly analyze the spatial distribution of XCO₂ in the flight area using the limited flight test data and the approximate surface of XCO₂, which was obtained by regression modeling, which is not very accurate either. We therefore used the high accuracy surface modeling (HASM) platform to fill the gaps where there is no information on XCO₂ in the flight test area, which takes the approximate surface of XCO₂ as its driving field and the XCO₂ observations retrieved from the flight test as its optimum control constraints. High accuracy surfaces of XCO₂ were constructed with HASM based on the flight's observations. The results showed that the mean XCO₂ in the flight test area is about 400 ppm and that XCO₂ over urban areas is much higher than in other places. Compared with OCO-2's XCO₂, the mean difference is 0.7 ppm and the standard deviation is 0.95 ppm. Therefore, the modelling of the XCO₂ surface based on the flight test of the TanSat instruments fell within an expected and acceptable range.

GLORI: A GNSS-R Dual Polarization Airborne Instrument for Land Surface Monitoring

PubMed Central

Motte, Erwan; Zribi, Mehrez; Fanise, Pascal; Egido, Alejandro; Darrozes, José; Al-Yaari, Amen; Baghdadi, Nicolas; Baup, Frédéric; Dayau, Sylvia; Fieuzal, Remy; Frison, Pierre-Louis; Guyon, Dominique; Wigneron, Jean-Pierre

2016-01-01

Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a remote sensing tool, which is complementary to traditional monostatic radars, for the retrieval of geophysical parameters related to surface properties. In the present paper, we describe a new polarimetric GNSS-R system, referred to as the GLObal navigation satellite system Reflectometry Instrument (GLORI), dedicated to the study of land surfaces (soil moisture, vegetation water content, forest biomass) and inland water bodies. This system was installed as a permanent payload on a French ATR42 research aircraft, from which simultaneous measurements can be carried out using other instruments, when required. Following initial laboratory qualifications, two airborne campaigns involving nine flights were performed in 2014 and 2015 in the Southwest of France, over various types of land cover, including agricultural fields and forests. Some of these flights were made concurrently with in situ ground truth campaigns. Various preliminary applications for the characterisation of agricultural and forest areas are presented. Initial analysis of the data shows that the performance of the GLORI instrument is well within specifications, with a cross-polarization isolation better than −15 dB at all elevations above 45°, a relative polarimetric calibration accuracy better than 0.5 dB, and an apparent reflectivity sensitivity better than −30 dB, thus demonstrating its strong potential for the retrieval of land surface characteristics. PMID:27213393

GLORI: A GNSS-R Dual Polarization Airborne Instrument for Land Surface Monitoring.

PubMed

Motte, Erwan; Zribi, Mehrez; Fanise, Pascal; Egido, Alejandro; Darrozes, José; Al-Yaari, Amen; Baghdadi, Nicolas; Baup, Frédéric; Dayau, Sylvia; Fieuzal, Remy; Frison, Pierre-Louis; Guyon, Dominique; Wigneron, Jean-Pierre

2016-05-20

Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a remote sensing tool, which is complementary to traditional monostatic radars, for the retrieval of geophysical parameters related to surface properties. In the present paper, we describe a new polarimetric GNSS-R system, referred to as the GLObal navigation satellite system Reflectometry Instrument (GLORI), dedicated to the study of land surfaces (soil moisture, vegetation water content, forest biomass) and inland water bodies. This system was installed as a permanent payload on a French ATR42 research aircraft, from which simultaneous measurements can be carried out using other instruments, when required. Following initial laboratory qualifications, two airborne campaigns involving nine flights were performed in 2014 and 2015 in the Southwest of France, over various types of land cover, including agricultural fields and forests. Some of these flights were made concurrently with in situ ground truth campaigns. Various preliminary applications for the characterisation of agricultural and forest areas are presented. Initial analysis of the data shows that the performance of the GLORI instrument is well within specifications, with a cross-polarization isolation better than -15 dB at all elevations above 45°, a relative polarimetric calibration accuracy better than 0.5 dB, and an apparent reflectivity sensitivity better than -30 dB, thus demonstrating its strong potential for the retrieval of land surface characteristics.

The surface elevation table: marker horizon method for measuring wetland accretion and elevation dynamics

USGS Publications Warehouse

Callaway, John C.; Cahoon, Donald R.; Lynch, James C.

2014-01-01

Tidal wetlands are highly sensitive to processes that affect their elevation relative to sea level. The surface elevation table–marker horizon (SET–MH) method has been used to successfully measure these processes, including sediment accretion, changes in relative elevation, and shallow soil processes (subsidence and expansion due to root production). The SET–MH method is capable of measuring changes at very high resolution (±millimeters) and has been used worldwide both in natural wetlands and under experimental conditions. Marker horizons are typically deployed using feldspar over 50- by 50-cm plots, with replicate plots at each sampling location. Plots are sampled using a liquid N2 cryocorer that freezes a small sample, allowing the handling and measurement of soft and easily compressed soils with minimal compaction. The SET instrument is a portable device that is attached to a permanent benchmark to make high-precision measurements of wetland surface elevation. The SET instrument has evolved substantially in recent decades, and the current rod SET (RSET) is widely used. For the RSET, a 15-mm-diameter stainless steel rod is pounded into the ground until substantial resistance is achieved to establish a benchmark. The SET instrument is attached to the benchmark and leveled such that it reoccupies the same reference plane in space, and pins lowered from the instrument repeatedly measure the same point on the soil surface. Changes in the height of the lowered pins reflect changes in the soil surface. Permanent or temporary platforms provide access to SET and MH locations without disturbing the wetland surface.

Coordinated Analyses of Antarctic Sediments as Mars Analog Materials Using Reflectance Spectroscopy and Current Flight-Like Instruments for CheMin, SAM and MOMA

NASA Technical Reports Server (NTRS)

Bishop, Janice L.; Franz, Heather B.; Goetz, Walter; Blake, David F.; Freissinet, Caroline; Steininger, Harald; Goesmann, Fred; Brinckerhoff, William B.; Getty, Stephanie; Pinnick, Veronica T.;

Prototype Global Burnt Area Algorithm Using a Multi-sensor Approach

NASA Astrophysics Data System (ADS)

López Saldaña, G.; Pereira, J.; Aires, F.

2013-05-01

One of the main limitations of products derived from remotely-sensed data is the length of the data records available for climate studies. The Advanced Very High Resolution Radiometer (AVHRR) long-term data record (LTDR) comprises a daily global atmospherically-corrected surface reflectance dataset at 0.05Deg spatial resolution and is available for the 1981-1999 time period. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument has been on orbit in the Terra platform since late 1999 and in Aqua since mid 2002; surface reflectance products, MYD09CMG and MOD09CMG, are available at 0.05Deg spatial resolution. Fire is strong cause of land surface change and emissions of greenhouse gases around the globe. A global long-term identification of areas affected by fire is needed to analyze trends and fire-clime relationships. A burnt area algorithm can be seen as a change point detection problem where there is an abrupt change in the surface reflectance due to the biomass burning. Using the AVHRR-LTDR and the aforementioned MODIS products, a time series of bidirectional reflectance distribution function (BRDF) corrected surface reflectance was generated using the daily observations and constraining the BRDF model inversion using a climatology of BRDF parameters derived from 12 years of MODIS data. The identification of the burnt area was performed using a t-test in the pre- and post-fire reflectance values and a change point detection algorithm, then spectral constraints were applied to flag changes caused by natural land processes like vegetation seasonality or flooding. Additional temporal constraints are applied focusing in the persistence of the affected areas. Initial results for years 1998 to 2002, show spatio-temporal coherence but further analysis is required and a formal rigorous validation will be applied using burn scars identified from high-resolution datasets.

Portable spotter for fluorescent contaminants on surfaces

DOEpatents

Schuresko, Daniel D.

1980-01-01

A portable fluorescence-based spotter for polynuclear aromatic hydrocarbon contamination on personnel and work area surfaces under ambient lighting conditions is provided. This instrument employs beam modulation and phase sensitive detection for discriminating between fluorescence from organic materials from reflected background light and inorganic fluorescent material. The device uses excitation and emission filters to provide differentiation between classes of aromatic organic compounds. Certain inorganic fluorescent materials, including heavy metal compounds, may also be distinguished from the organic compounds, despite both having similar optical properties.

Industrial Tape

NASA Technical Reports Server (NTRS)

1986-01-01

Scotch Brand Tape 364 was developed for NASA by 3M Company to protect electrical instrumentation coils and fluid lines from rocket launch blast conditions. It is an aluminized glass cloth tape which can withstand very high temperatures, is easily applied to compound surfaces, has excellent solar energy reflectance, and does not present an electrostatic hazard. It has potential automotive, transportation, and building construction applications.

GLORI (GLObal navigation satellite system Reflectometry Instrument): A New Airborne GNSS-R receiver for land surface applications

NASA Astrophysics Data System (ADS)

Motte, Erwan; Zribi, Mehrez; Fanise, Pascal

2015-04-01

GLORI (GLObal navigation satellite system Reflectometry Instrument) is a new receiver dedicated to the airborne measurement of surface parameters such as soil moisture and biomass above ground and sea state (wave height and direction) above oceans. The instrument is based on the PARIS concept [Martin-Neira, 1993] using both the direct and surface-reflected L-band signals from the GPS constellation as a multistatic radar source. The receiver is based on one up-looking and one down-looking dual polarization hemispherical active antennas feeding a low-cost 4-channel SDR direct down-conversion receiver tuned to the GPS L1 frequency. The raw measurements are sampled at 16.368MHz and stored as 2-bit, IQ binary files. In post-processing, GPS acquisition and tracking are performed on the direct up-looking signal while the down-looking signal is processed blindly using tracking parameters from the direct signal. The obtained direct and reflected code-correlation waveforms are the basic observables for geophysical parameters inversion. The instrument was designed to be installed aboard the ATR42 experimental aircraft from the French SAFIRE fleet as a permanent payload. The long term goal of the project is to provide real-time continuous surface information for every flight performed. The aircraft records attitude information through its Inertial Measurement Unit and a commercial GPS receiver records additional information such as estimated doppler and code phase, receiver location, satellites azimuth and elevation. A series of test flights were performed over both the Toulouse and Gulf of Lion (Mediterranean Sea) regions during the period 17-21 Nov 2014 together with the KuROS radar [Hauser et al., 2014]. Using processing methods from the literature [Egido et al., 2014], preliminary results demonstrate the instrument sensitivity to both ground and ocean surface parameters estimation. A dedicated scientific flight campaign is planned at the end of second quarter 2015 with collocated measurement of biomass and soil moisture ground truth in order to better characterize the instrument sensitivity to geophysical parameters. The instrument will be improved in the meanwhile including the optimization of data processing and the better integration of external data (GPS commercial receiver, Attitude) into the receiver. M.Martin-Neira. A Passive reflectometry and interferometry system (PARIS): Application to ocean altimetry. ESA J., 17:331-355, 1993 Hauser, D.; Caudal, G.; Le Gac, C.; Valentin, R.; Delaye, L.; Tison, C., "KuROS: A new airborne Ku-band Doppler radar for observation of the ocean surface," Geoscience and Remote Sensing Symposium (IGARSS), 2014 IEEE International , vol., no., pp.282,285, 13-18 July 2014 Egido, A.; Paloscia, S.; Motte, E.; Guerriero, L.; Pierdicca, N.; Caparrini, M.; Santi, E.; Fontanelli, G.; Floury, N., "Airborne GNSS-R Polarimetric Measurements for Soil Moisture and Above-Ground Biomass Estimation," Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of , vol.7, no.5, pp.1522,1532, May 2014

Soil Moisture Sensing Using Reflected GPS Signals: Description of the GPS Soil Moisture Product.

NASA Astrophysics Data System (ADS)

Larson, Kristine; Small, Eric; Chew, Clara

2015-04-01

As first demonstrated by the GPS reflections group in 2008, data from GPS networks can be used to monitor multiple parameters of the terrestrial water cycle. The GPS L-band signals take two paths: (1) the "direct" signal travels from the satellite to the antenna, which is typically located 2-3 meters above the ground; (2) the reflected signal interacts with the Earth's surface before traveling to the antenna. The direct signal is used by geophysicists and surveyors to measure the position of the antenna, while the effects of reflected signals are a source of error. If one focuses on the reflected signal rather than the positioning observables, one has a method that is sensitive to surface soil moisture (top 5 cm), vegetation water content, and snow depth. This method - known as GPS Interferometric Reflectometry (GPS-IR) - has a footprint of ~1000 m2 for most GPS sites. This is intermediate in scale to most in situ and satellite observations. A significant advantage of GPS-IR is that data from existing GPS networks can be used without any changes to the instrumentation. This means that there is a new source of cost-effective instrumentation for satellite validation and climate studies. This presentation will provide an overview of the GPS-IR methodology with an emphasis on the soil moisture product. GPS water cycle products are currently produced on a daily basis for a network of ~500 sites in the western United States; results are freely available at http://xenon.colorado.edu/portal. Plans to expand the GPS-IR method to the network of international GPS sites will also be discussed.

Comparison of Sentinel-2A and Landsat-8 Nadir BRDF Adjusted Reflectance (NBAR) over Southern Africa

NASA Astrophysics Data System (ADS)

Li, J.; Roy, D. P.; Zhang, H.

2016-12-01

The Landsat satellites have been providing moderate resolution imagery of the Earth's surface for over 40 years with continuity provided by the Landsat 8 and planned Landsat 9 missions. The European Space Agency Sentinel-2 satellite was successfully launched into a polar sun-synchronous orbit in 2015 and carries the Multi Spectral Instrument (MSI) that has Landsat-like bands and acquisition coverage. These new sensors acquire images at view angles ± 7.5° (Landsat) and ± 10.3° (Sentinel-2) from nadir that result in small directional effects in the surface reflectance. When data from adjoining paths, or from long time series are used, a model of the surface anisotropy is required to adjust observations to a uniform nadir view (primarily for visual consistency, vegetation monitoring, or detection of subtle surface changes). Recently a generalized approach was published that provides consistent Landsat view angle corrections to provide nadir BRDF-adjusted reflectance (NBAR). Because the BRDF shapes of different terrestrial surfaces are sufficiently similar over the narrow 15° Landsat field of view, a fixed global set of MODIS BRDF spectral model parameters was shown to be adequate for Landsat NBAR derivation with little sensitivity to the land cover type, condition, or surface disturbance. This poster demonstrates the application of this methodology to Sentinel-2 data over a west-east transect across southern Africa. The reflectance differences between adjacent overlapping paths in the forward and backward scatter directions are quantified for both before and after BRDF correction. Sentinel-2 and Landsat-8 reflectance and NBAR inter-comparison results considering different stages of cloud and saturation filtering, and filtering to reduce surface state differences caused by acquisition time differences, demonstrate the utility of the approach. The relevance and limitations of the corrections for providing consistent moderate resolution reflectance are discussed.

But Does It Work? Reflective Activities, Learning Outcomes and Instrumental Learning in Continuing Professional Development

ERIC Educational Resources Information Center

Roessger, Kevin M.

2015-01-01

This paper examines the relationship between reflective practice and instrumental learning within the context of continuing professional development (CPD). It is argued that instrumental learning is a unique process of adult learning, and reflective practice's impact on learning outcomes in instrumental learning contexts remains unclear. A…

Clouds and the Earth's Radiant Energy System (CERES) Data Products for Climate Research

NASA Technical Reports Server (NTRS)

Kato, Seiji; Loeb, Norman G.; Rutan, David A.; Rose, Fred G.

2015-01-01

NASA's Clouds and the Earth's Radiant Energy System (CERES) project integrates CERES, Moderate Resolution Imaging Spectroradiometer (MODIS), and geostationary satellite observations to provide top-of-atmosphere (TOA) irradiances derived from broadband radiance observations by CERES instruments. It also uses snow cover and sea ice extent retrieved from microwave instruments as well as thermodynamic variables from reanalysis. In addition, these variables are used for surface and atmospheric irradiance computations. The CERES project provides TOA, surface, and atmospheric irradiances in various spatial and temporal resolutions. These data sets are for climate research and evaluation of climate models. Long-term observations are required to understand how the Earth system responds to radiative forcing. A simple model is used to estimate the time to detect trends in TOA reflected shortwave and emitted longwave irradiances.

Laboratory and airborne techniques for measuring fluoresence of natural surfaces

NASA Technical Reports Server (NTRS)

Stoertz, G. E.; Hemphill, W. R.

1972-01-01

Techniques are described for obtaining fluorescence spectra from samples of natural surfaces that can be used to predict spectral regions in which these surfaces would emit solar-stimulated or laser-stimulated fluorescence detectable by remote sensor. Scattered or reflected stray light caused large errors in spectrofluorometer analysis or natural sample surfaces. Most spurious light components can be eliminated by recording successive fluorescence spectra for each sample, using identical instrument settings, first with an appropriate glass or gelatin filter on the excitation side of the sample, and subsequently with the same filter on the emission side of the sample. This technique appears more accurate than any alternative technique for testing the fluorescence of natural surfaces.

2010 CEOS Field Reflectance Intercomparisons Lessons Learned

NASA Technical Reports Server (NTRS)

Thome, Kurtis; Fox, Nigel

2011-01-01

This paper summarizes lessons learned from the 2009 and 2010 joint field campaigns to Tuz Golu, Turkey. Emphasis is placed on the 2010 campaign related to understanding the equipment and measurement protocols, processing schemes, and traceability to SI quantities. Participants in both 2009 and 2010 used an array of measurement approaches to determine surface reflectance. One lesson learned is that even with all of the differences in collection between groups, the differences in reflectance are currently dominated by instrumental artifacts including knowledge of the white reference. Processing methodology plays a limited role once the bi-directional reflectance of the white reference is used rather than a hemispheric-directional value. The lack of a basic set of measurement protocols, or best practices, limits a group s ability to ensure SI traceability and the development of proper error budgets. Finally, rigorous attention to sampling methodology and its impact on instrument behavior is needed. The results of the 2009 and 2010 joint campaigns clearly demonstrate both the need and utility of such campaigns and such comparisons must continue in the future to ensure a coherent set of data that can span multiple sensor types and multiple decades.

Solution algorithm of dwell time in slope-based figuring model

NASA Astrophysics Data System (ADS)

Li, Yong; Zhou, Lin

2017-10-01

Surface slope profile is commonly used to evaluate X-ray reflective optics, which is used in synchrotron radiation beam. Moreover, the measurement result of measuring instrument for X-ray reflective optics is usually the surface slope profile rather than the surface height profile. To avoid the conversion error, the slope-based figuring model is introduced introduced by processing the X-ray reflective optics based on surface height-based model. However, the pulse iteration method, which can quickly obtain the dell time solution of the traditional height-based figuring model, is not applied to the slope-based figuring model because property of the slope removal function have both positive and negative values and complex asymmetric structure. To overcome this problem, we established the optimal mathematical model for the dwell time solution, By introducing the upper and lower limits of the dwell time and the time gradient constraint. Then we used the constrained least squares algorithm to solve the dwell time in slope-based figuring model. To validate the proposed algorithm, simulations and experiments are conducted. A flat mirror with effective aperture of 80 mm is polished on the ion beam machine. After iterative polishing three times, the surface slope profile error of the workpiece is converged from RMS 5.65 μrad to RMS 1.12 μrad.

Spectroscopic observations of the Moon at the lunar surface

NASA Astrophysics Data System (ADS)

Wu, Yunzhao; Hapke, Bruce

2018-02-01

The Moon's reflectance spectrum records many of its important properties. However, prior to Chang'E-3 (CE-3), no spectra had previously been measured on the lunar surface. Here we show the in situ reflectance spectra of the Moon acquired on the lunar surface by the Visible-Near Infrared Spectrometer (VNIS) onboard the CE-3 rover. The VNIS detected thermal radiation from the lunar regolith, though with much shorter wavelength range than typical thermal radiometer. The measured temperatures are higher than expected from theoretical model, indicating low thermal inertia of the lunar soil and the effects of grain facet on soil temperature in submillimeter scale. The in situ spectra also reveal that 1) brightness changes visible from orbit are related to the reduction in maturity due to the removal of the fine and weathered particles by the lander's rocket exhaust, not the smoothing of the surface and 2) the spectra of the uppermost soil detected by remote sensing exhibit substantial differences with that immediately beneath, which has important implications for the remote compositional analysis. The reflectance spectra measured by VNIS not only reveal the thermal, compositional, and space-weathering properties of the Moon but also provide a means for the calibration of optical instruments that view the surface remotely.

Remote-sensing reflectance determinations in the coastal ocean environment: impact of instrumental characteristics and environmental variability.

PubMed

Toole, D A; Siegel, D A; Menzies, D W; Neumann, M J; Smith, R C

2000-01-20

Three independent ocean color sampling methodologies are compared to assess the potential impact of instrumental characteristics and environmental variability on shipboard remote-sensing reflectance observations from the Santa Barbara Channel, California. Results indicate that under typical field conditions, simultaneous determinations of incident irradiance can vary by 9-18%, upwelling radiance just above the sea surface by 8-18%, and remote-sensing reflectance by 12-24%. Variations in radiometric determinations can be attributed to a variety of environmental factors such as Sun angle, cloud cover, wind speed, and viewing geometry; however, wind speed is isolated as the major source of uncertainty. The above-water approach to estimating water-leaving radiance and remote-sensing reflectance is highly influenced by environmental factors. A model of the role of wind on the reflected sky radiance measured by an above-water sensor illustrates that, for clear-sky conditions and wind speeds greater than 5 m/s, determinations of water-leaving radiance at 490 nm are undercorrected by as much as 60%. A data merging procedure is presented to provide sky radiance correction parameters for above-water remote-sensing reflectance estimates. The merging results are consistent with statistical and model findings and highlight the importance of multiple field measurements in developing quality coastal oceanographic data sets for satellite ocean color algorithm development and validation.

Preferred mirror coatings for UV, visible, and IR space optical instruments

NASA Astrophysics Data System (ADS)

Heaney, James B.; Kauder, Lonny R.; Freese, Scott C.; Quijada, Manuel A.

2012-09-01

This paper will review the suitability of the common four types of reflecting surfaces - Ag, Al, Au and Be - for use aboard satellite borne remote sensing and astrophysical observatories, from the uv to far-ir spectral bands. The choice of appropriate protecting and reflectance enhancing overcoats for these reflecting metals will be discussed. Laboratory test data and optical diagnostic techniques used to verify durability of the selected coatings in a terrestrial storage environment and their sensitivity to a space radiation and cold temperature environment will be presented. For some of the selected coatings, a connection will be made between pre-launch laboratory quality checks and post-launch performance on orbit.

ARC-1990-AC91-2010

NASA Image and Video Library

1990-12-08

Range : 50,000 miles This multispectral map of Australia, and surrounding seas was obtained by the Galileo spacecraft's Near Infrared Mapping Spectrometer shortly after closest approach. The image shows various ocean, land and atmospheric cloud features as they appear in three of the 408 infrared colors or wavelengths sensed by the instrument. The wavelength of 0.873 micron, represented as blue in the photo, shows regions of enhanced liquid water absorption, i.e. the Pacific and Indian oceans. The 0.984-micron band, represented as red, shows areas of enhanced ground reflection as on the Australian continent. This wavelength is also s ensitive to the reflectivity of relatively thick clouds. The 0.939-micron wavelength, shown as green, is a strong water-vapor-absorbing band, and is used to accentuate clouds lying above the strongly absorbing lower atmosphere. When mixed with the red indicator of cloud reflection, the green produces a yellowish hue; this indicates thick clouds. The distinctive purplish color off the northeast coast marks the unusually shallow waters of the Great Barrier Reef and the Coral Sea. Here the blue denoting water absorption combines with the red denoting reflection from coral and surface marine organisms to produce thiss unusual color. The Near Infrared Mapping Spectrometer (NIMS) on the Galileo spacecraft is a combines mapping (imaging) and spectral instrument. It can sense 408 contiguous wavelengths from 0.7 micron (deep red) to 5.2 microns, and can construct a map or image by mechanical scanning. It can spectroscopically analyze atmospheres and surfaces and construct thermal and chemical maps.

Radiometric Calibration Techniques for Signal-of-Opportunity Reflectometers

NASA Technical Reports Server (NTRS)

Piepmeier, Jeffrey R.; Shah, Rashmi; Deshpande, Manohar; Johnson, Carey

2014-01-01

Bi-static reflection measurements utilizing global navigation satellite service (GNSS) or other signals of opportunity (SoOp) can be used to sense ocean and terrestrial surface properties. End-to-end calibration of GNSS-R has been performed using well-characterized reflection surface (e.g., water), direct path antenna, and receiver gain characterization. We propose an augmented approach using on-board receiver electronics for radiometric calibration of SoOp reflectometers utilizing direct and reflected signal receiving antennas. The method calibrates receiver and correlator gains and offsets utilizing a reference switch and common noise source. On-board electronic calibration sources, such as reference switches, noise diodes and loop-back circuits, have shown great utility in stabilizing total power and correlation microwave radiometer and scatterometer receiver electronics in L-band spaceborne instruments. Application to SoOp instruments is likely to bring several benefits. For example, application to provide short and long time scale calibration stability of the direct path channel, especially in low signal-to-noise ratio configurations, is directly analogous to the microwave radiometer problem. The direct path channel is analogous to the loopback path in a scatterometer to provide a reference of the transmitted power, although the receiver is independent from the reflected path channel. Thus, a common noise source can be used to measure the gain ratio of the two paths. Using these techniques long-term (days to weeks) calibration stability of spaceborne L-band scatterometer and radiometer has been achieved better than 0.1. Similar long-term stability would likely be needed for a spaceborne reflectometer mission to measure terrestrial properties such as soil moisture.

Spectral decomposition of AVIRIS data

NASA Technical Reports Server (NTRS)

Gaddis, Lisa; Soderblom, Laurence; Kieffer, Hugh; Becker, Kris; Torson, Jim; Mullins, Kevin

1993-01-01

A set of techniques is presented that uses only information contained within a raw Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) scene to estimate and to remove additive components such as multiple scattering and instrument dark current. Multiplicative components (instrument gain, topographic modulation of brightness, atmospheric transmission) can then be normalized, permitting enhancement, extraction, and identification of relative reflectance information related to surface composition and mineralogy. The technique for derivation of additive-component spectra from a raw AVIRIS scene is an adaption of the 'regression intersection method' of Crippen. This method uses two surface units that are spatially extensive, and located in rugged terrain. For a given wavelength pair, subtraction of the derived additive component from individual band values will remove topography in both regions in a band/band ratio image. Normalization of all spectra in the scene to the average scene spectrum then results in cancellation of multiplicative components and production of a relative-reflectance scene. The resulting AVIRIS product contains relative-reflectance features due to mineral absorption that depart from the average spectrum. These features commonly are extremely weak and difficult to recognize, but they can be enhanced by using two simple 3-D image-processing tools. The validity of these techniques will be demonstrated by comparisons between relative-reflectance AVIRIS spectra and those derived by using JPL standard calibrations. The AVIRIS data used in this analysis were acquired over the Kelso Dunes area (34 deg 55' N, 115 deg 43' W) of the eastern Mojave Desert, CA (in 1987) and the Upheaval Dome area (38 deg 27' N, 109 deg 55' W) of the Canyonlands National Park, UT (in 1991).

Design, Fabrication, Optical Testing, and Performance of Diamond Machined Aspheric Mirrors for Ground-Based Near-IR Astronomy

NASA Technical Reports Server (NTRS)

Ohl, Raymond G.; Mink, Ronald; Chambers, V. John; Connelly, Joseph A.; Mentzell, J. Eric; Tveekrem, June L.; Howard, Joseph M.; Preuss, Werner; Schroeder, Mechthild; Sohn, Alex;

Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing

PubMed Central

Seidel, Felix; Schläpfer, Daniel; Nieke, Jens; Itten, Klaus I.

2008-01-01

This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (Δτλaer) and compared to the available measuring sensitivity of the sensor (NEΔLλsensor). This is done for multiple signal-to-noise ratios (SNR) and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions. PMID:27879801

Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing.

PubMed

Seidel, Felix; Schläpfer, Daniel; Nieke, Jens; Itten, Klaus I

2008-03-18

This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (Δτ λ aer ) and compared to the available measuring sensitivity of the sensor (NE ΔL λ sensor ). This is done for multiple signal-to-noise ratios (SNR) and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions.

Enhanced-Adhesion Multi-Walled Carbon Nanotubes on Titanium Substrates for Stray Light Control

NASA Technical Reports Server (NTRS)

Hagopian, John; Getty, Stephanie; Quijada, Manuel

2012-01-01

Carbon nanotubes previously grown on silicon have extremely low reflectance, making them a good candidate for stray light suppression. Silicon, however, is not a good structural material for stray light components such as tubes, stops, and baffles. Titanium is a good structural material and can tolerate the 700 C nanotube growth process. The ability to grow carbon nanotubes on a titanium substrate that are ten times blacker than the current NASA state-of-the-art paints in the visible to near infrared spectra has been achieved. This innovation will allow significant improvement of stray light performance in scientific instruments or any other optical system. This innovation is a refinement of the utilization of multiwalled carbon nano tubes for stray light suppression in spaceflight instruments. The innovation is a process to make the surface darker and improve the adhesion to the substrate, improving robustness for spaceflight use. Bright objects such as clouds or ice scatter light off of instrument structures and components and make it difficult to see dim objects in Earth observations. A darker material to suppress this stray light has multiple benefits to these observations, including enabling scientific observations not currently possible, increasing observational efficiencies in high-contrast scenes, and simplifying instruments and lowering their cost by utilizing fewer stray light components and achieving equivalent performance. The prior art was to use commercially available black paint, which resulted in approximately 4% of the light being reflected (hemispherical reflectance or total integrated scatter, or TIS). Use of multiwalled carbon nanotubes on titanium components such as baffles, entrance aperture, tubes, and stops, can decrease this scattered light by a factor of ten per bounce over the 200-nm to 2,500-nm wavelength range. This can improve system stray light performance by orders of magnitude. The purpose of the innovation is to provide an enhanced stray light control capability by making a blacker surface treatment for typical stray light control components. Since baffles, stops, and tubes used in scientific observations often undergo loads such as vibration, it was critical to develop this surface treatment on structural materials. The innovation is to optimize the carbon nanotube growth for titanium, which is a strong, lightweight structural material suitable for spaceflight use. The titanium substrate carbon nanotubes are more robust than those grown on silicon and allow for easier utilization. They are darker than current surface treatments over larger angles and larger wavelength range. The primary advantage of titanium substrate is that it is a good structural material, and not as brittle as silicon.

An improved methodology for heliostat testing and evaluation at the Plataforma Solar de Almería

NASA Astrophysics Data System (ADS)

Monterreal, Rafael; Enrique, Raúl; Fernández-Reche, Jesús

2017-06-01

The optical quality of a heliostat basically quantifies the difference between the scattering effects of the actual solar radiation reflected on its optical surface, compared to the so called canonical dispersion, that is, the one reflected on an optical surface free of constructional errors (paradigm). However, apart from the uncertainties of the measuring process itself, the value of the optical quality must be independent of the measuring instrument; so, any new measuring techniques that provide additional information about the error sources on the heliostat reflecting surface would be welcome. That error sources are responsible for the final optical quality value, with different degrees of influence. For the constructor of heliostats it will be extremely useful to know the value of the classical sources of error and their weight on the overall optical quality of a heliostat, such as facets geometry or focal length, as well as the characteristics of the heliostat as a whole, i.e., its geometry, focal length, facets misalignment and also the possible dependence of these effects with mechanical and/or meteorological factors. It is the goal of the present paper to unfold these optical quality error sources by exploring directly the reflecting surface of the heliostat with the help of a laser-scanner device and link the result with the traditional methods of heliostat evaluation at the Plataforma Solar de Almería.

Instrument for measurement of vacuum in sealed thin wall packets

DOEpatents

Kollie, T.G.; Thacker, L.H.; Fine, H.A.

1993-10-05

An instrument is described for the measurement of vacuum within sealed packets, the packets having a wall sufficiently thin that it can be deformed by the application of an external vacuum to small area thereof. The instrument has a detector head for placement against the deformable wall of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall, with this deformation or lift monitored by the application of light as via a bifurcated light pipe. Retro-reflected light through the light pipe is monitored with a photo detector. An abrupt change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the vacuum applied through the head to achieve this initiation of movement is equal to the vacuum within the packet. In a preferred embodiment a vacuum reference plate is placed beneath the packet to ensure that no deformation occurs on the reverse surface of the packet. A packet production line model is also described. 3 figures.

Instrument for measurement of vacuum in sealed thin wall packets

DOEpatents

Kollie, Thomas G.; Thacker, Louis H.; Fine, H. Alan

1993-01-01

An instrument for the measurement of vacuum within sealed packets 12, the packets 12 having a wall 14 sufficiently thin that it can be deformed by the application of an external vacuum to small area thereof. The instrument has a detector head 18 for placement against the deformable wall 14 of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall 14, with this deformation or lift monitored by the application of light as via a bifurcated light pipe 20. Retro-reflected light through the light pipe is monitored with a photo detector 26. An abrupt change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the vacuum applied through the head 18 to achieve this initiation of movement is equal to the vacuum Within the packet 12. In a preferred embodiment a vacuum reference plate 44 is placed beneath the packet 12 to ensure that no deformation occurs on the reverse surface 16 of the packet. A packet production line model is also described.

Radiometric calibration of the reflective bands of NS001-Thematic Mapper Simulator (TMS) and modular multispectral radiometers (MMR)

NASA Technical Reports Server (NTRS)

Markham, Brian L.; Wood, Frank M., Jr.; Ahmad, Suraiya P.

1988-01-01

The NS001 Thematic Mapper Simulator scanner (TMS) and several modular multispectral radiometers (MMRs) are among the primary instruments used in the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). The NS001 has a continuously variable gain setting. Calibration of the NS001 data is influenced by drift in the dark current level of up to six counts during a mirror scan at typical gain settings. The MMR instruments are being used in their 1 deg FOV configuration on the helicopter and 15 deg FOV on the ground.

Land surface temperature measurements from EOS MODIS data

NASA Technical Reports Server (NTRS)

Wan, Zhengming

1995-01-01

A significant progress has been made in TIR instrumentation which is required to establish the spectral BRDF/emissivity knowledge base of land-surface materials and to validate the land-surface temperature (LST) algorithms. The SIBRE (spectral Infrared Bidirectional Reflectance and Emissivity) system and a TIR system for measuring spectral directional-hemispherical emissivity have been completed and tested successfully. Optical properties and performance features of key components (including spectrometer, and TIR source) of these systems have been characterized by integrated use of local standards (blackbody and reference plates). The stabilization of the spectrometer performance was improved by a custom designed and built liquid cooling system. Methods and procedures for measuring spectral TIR BRDF and directional-hemispheric emissivity with these two systems have been verified in sample measurements. These TIR instruments have been used in the laboratory and the field, giving very promising results. The measured spectral emissivities of water surface are very close to the calculated values based on well established water refractive index values in published papers. Preliminary results show that the TIR instruments can be used for validation of the MODIS LST algorithm in homogeneous test sites. The beta-3 version of the MODIS LST software is being prepared for its delivery scheduled in the early second half of this year.

Diffractive optics technology and the NASA Geostationary Earth Observatory (GEO)

NASA Technical Reports Server (NTRS)

Morris, G. Michael; Michaels, Robert L.; Faklis, Dean

1992-01-01

Diffractive (or binary) optics offers unique capabilities for the development of large-aperture, high-performance, light-weight optical systems. The Geostationary Earth Observatory (GEO) will consist of a variety of instruments to monitor the environmental conditions of the earth and its atmosphere. The aim of this investigation is to analyze the design of the GEO instrument that is being proposed and to identify the areas in which diffractive (or binary) optics technology can make a significant impact in GEO sensor design. Several potential applications where diffractive optics may indeed serve as a key technology for improving the performance and reducing the weight and cost of the GEO sensors have been identified. Applications include the use of diffractive/refractive hybrid lenses for aft-optic imagers, diffractive telescopes for narrowband imaging, subwavelength structured surfaces for anti-reflection and polarization control, and aberration compensation for reflective imaging systems and grating spectrometers.

Radargrams Indicating Ice-Rich Subsurface Deposit

NASA Image and Video Library

2016-11-22

These two images show data acquired by the Shallow Radar (SHARAD) instrument while passing over two ground tracks in a part of Mars' Utopia Planitia region where the orbiting, ground-penetrating radar detected subsurface deposits rich in water ice. The instrument on NASA's Mars Reconnaissance Orbiter emits radio waves and times their echo off of radio-reflective surfaces and interfaces on Mars. The white arrows indicate a subsurface reflector interpreted as the bottom of the ice-rich deposit. The deposit is about as large in area as the state of New Mexico and contains about as much water as Lake Superior. The horizontal scale bar indicates 40 kilometers (25 miles) along the ground track of the radar, as flown by the orbiter overhead. The vertical scale bar indicates a return time of one microsecond for the reflected radio signal, equivalent to a distance of about 90 meters (295 feet). http://photojournal.jpl.nasa.gov/catalog/PIA21137

Comparison of Newly Acquired Lunar Spectra with the Titanium Abundance Maps Derived from Clementine

NASA Technical Reports Server (NTRS)

Holsclaw, G. M.; McClintock, W. E.; Robinson, M. S.

2005-01-01

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) is one of seven science instruments onboard NASA's MESSENGER mission, currently en-route to the planet Mercury. One of MASCS s components, referred to as the Visible and Near Infrared Spectrograph (VIRS), will record reflectance spectra of the surface in order to characterize the mineralogy of the planet [1]. The lunar highlands and the average mercurian crust are proposed to be compositionally similar [i.e. 2]. In preparation to interpret VIRS reflectance spectra of Mercury to be first obtained in 2008, the Moon has been observed with an engineering model of the VIRS from a ground-based telescope. In this study, the ultraviolet and visible region of the spectrum is compared with titanium content in the lunar regolith.

Instrumentation for remote sensing solar radiation from light aircraft.

PubMed

Howard, J A; Barton, I J

1973-10-01

The paper outlines the instrumentation needed to study, from a light aircraft, the solar radiation reflected by ground surfaces and the incoming solar radiation. A global shortwave radiometer was mounted on the roof of the aircraft and a specially designed mount was used to support a downward pointing 70-mm aerial camera, a downward pointing narrow-beam pyranometer, and, sometimes, a downward pointing global shortwave pyranometer. Calibration factors were determined for the three pyranometers by comparison with a standard Angstrom compensation pyrheliometer. Results have indicated trends in the albedos of major plant communities and have shown that the calculated albedo values vary according to whether the downward pointing instrument is narrow-beam or global. Comparisons were also made with albedos measured on the ground.

A study of the effect of clinical washing decontamination process on corrosion resistance of Martensitic Stainless Steel 420.

PubMed

Xu, Yunwei; Huang, Zhihong; Corner, George

2016-09-28

Corrosion of surgical instruments provides a seat for contamination and prevents proper sterilisation, placing both patients and medical staff at risk of infection. Corrosion can also compromise the structural integrity of instruments and lead to mechanical failure in use. It is essential to understand the various factors affecting corrosion resistance of surgical instruments and how it can be minimised.This paper investigates the effect on corrosion resistance from the clinical washing decontamination (WD) process, specifically by studying the changes in surface roughness and Cr/Fe ratio. Results indicate that the WD process provides a positive effect on smooth polished samples, while a lesser positive effect was observed on rough reflection reduced samples.

Testing the potential of multi-spectral remote sensing for retrospectively estimating fire severity in African savannahs

Treesearch

Alistair M.S. Smith; Martin J. Wooster; Nick A. Drake; Frederick M. Dipotso; Michael J. Falkowski; Andrew T. Hudak

2005-01-01

The remote sensing of fire severity is a noted goal in studies of forest and grassland wildfires. Experiments were conducted to discover and evaluate potential relationships between the characteristics of African savannah fires and post-fire surface spectral reflectance in the visible to shortwave infrared spectral region. Nine instrumented experimental fires were...

An algorithm for hyperspectral remote sensing of aerosols: 1. Development of theoretical framework

NASA Astrophysics Data System (ADS)

Hou, Weizhen; Wang, Jun; Xu, Xiaoguang; Reid, Jeffrey S.; Han, Dong

2016-07-01

This paper describes the first part of a series of investigations to develop algorithms for simultaneous retrieval of aerosol parameters and surface reflectance from a newly developed hyperspectral instrument, the GEOstationary Trace gas and Aerosol Sensor Optimization (GEO-TASO), by taking full advantage of available hyperspectral measurement information in the visible bands. We describe the theoretical framework of an inversion algorithm for the hyperspectral remote sensing of the aerosol optical properties, in which major principal components (PCs) for surface reflectance is assumed known, and the spectrally dependent aerosol refractive indices are assumed to follow a power-law approximation with four unknown parameters (two for real and two for imaginary part of refractive index). New capabilities for computing the Jacobians of four Stokes parameters of reflected solar radiation at the top of the atmosphere with respect to these unknown aerosol parameters and the weighting coefficients for each PC of surface reflectance are added into the UNified Linearized Vector Radiative Transfer Model (UNL-VRTM), which in turn facilitates the optimization in the inversion process. Theoretical derivations of the formulas for these new capabilities are provided, and the analytical solutions of Jacobians are validated against the finite-difference calculations with relative error less than 0.2%. Finally, self-consistency check of the inversion algorithm is conducted for the idealized green-vegetation and rangeland surfaces that were spectrally characterized by the U.S. Geological Survey digital spectral library. It shows that the first six PCs can yield the reconstruction of spectral surface reflectance with errors less than 1%. Assuming that aerosol properties can be accurately characterized, the inversion yields a retrieval of hyperspectral surface reflectance with an uncertainty of 2% (and root-mean-square error of less than 0.003), which suggests self-consistency in the inversion framework. The next step of using this framework to study the aerosol information content in GEO-TASO measurements is also discussed.

Portable laser-induced breakdown spectroscopy/diffuse reflectance hybrid spectrometer for analysis of inorganic pigments

NASA Astrophysics Data System (ADS)

Siozos, Panagiotis; Philippidis, Aggelos; Anglos, Demetrios

2017-11-01

A novel, portable spectrometer, combining two analytical techniques, laser-induced breakdown spectroscopy (LIBS) and diffuse reflectance spectroscopy, was developed with the aim to provide an enhanced instrumental and methodological approach with regard to the analysis of pigments in objects of cultural heritage. Technical details about the hybrid spectrometer and its operation are presented and examples are given relevant to the analysis of paint materials. Both LIBS and diffuse reflectance spectra in the visible and part of the near infrared, corresponding to several neat mineral pigment samples, were recorded and the complementary information was used to effectively distinguish different types of pigments even if they had similar colour or elemental composition. The spectrometer was also employed in the analysis of different paints on the surface of an ancient pottery sherd demonstrating the capabilities of the proposed hybrid diagnostic approach. Despite its instrumental simplicity and compact size, the spectrometer is capable of supporting analytical campaigns relevant to archaeological, historical or art historical investigations, particularly when quick data acquisition is required in the context of surveys of large numbers of objects and samples.

Iterative atmospheric correction scheme and the polarization color of alpine snow

NASA Astrophysics Data System (ADS)

Ottaviani, Matteo; Cairns, Brian; Ferrare, Rich; Rogers, Raymond

2012-07-01

Characterization of the Earth's surface is crucial to remote sensing, both to map geomorphological features and because subtracting this signal is essential during retrievals of the atmospheric constituents located between the surface and the sensor. Current operational algorithms model the surface total reflectance through a weighted linear combination of a few geometry-dependent kernels, each devised to describe a particular scattering mechanism. The information content of these measurements is overwhelmed by that of instruments with polarization capabilities: proposed models in this case are based on the Fresnel reflectance of an isotropic distribution of facets. Because of its remarkable lack of spectral contrast, the polarized reflectance of land surfaces in the shortwave infrared spectral region, where atmospheric scattering is minimal, can be used to model the surface also at shorter wavelengths, where aerosol retrievals are attempted based on well-established scattering theories.In radiative transfer simulations, straightforward separation of the surface and atmospheric contributions is not possible without approximations because of the coupling introduced by multiple reflections. Within a general inversion framework, the problem can be eliminated by linearizing the radiative transfer calculation, and making the Jacobian (i.e., the derivative expressing the sensitivity of the reflectance with respect to model parameters) available at output. We present a general methodology based on a Gauss-Newton iterative search, which automates this procedure and eliminates de facto the need of an ad hoc atmospheric correction.In this case study we analyze the color variations in the polarized reflectance measured by the NASA Goddard Institute of Space Studies Research Scanning Polarimeter during a survey of late-season snowfields in the High Sierra. This insofar unique dataset presents challenges linked to the rugged topography associated with the alpine environment and a likely high water content due to melting. The analysis benefits from ancillary information provided by the NASA Langley High Spectral Resolution Lidar deployed on the same aircraft.The results obtained from the iterative scheme are contrasted against the surface polarized reflectance obtained ignoring multiple reflections, via the simplistic subtraction of the atmospheric scattering contribution. Finally, the retrieved reflectance is modeled after the scattering properties of a dense collection of ice crystals at the surface. Confirming that the polarized reflectance of snow is spectrally flat would allow to extend the techniques already in use for polarimetric retrievals of aerosol properties over land to the large portion of snow-covered pixels plaguing orbital and suborbital observations.

Iterative Atmospheric Correction Scheme and the Polarization Color of Alpine Snow

NASA Technical Reports Server (NTRS)

Ottaviani, Matteo; Cairns, Brian; Ferrare, Rich; Rogers, Raymond

2012-01-01

Characterization of the Earth's surface is crucial to remote sensing, both to map geomorphological features and because subtracting this signal is essential during retrievals of the atmospheric constituents located between the surface and the sensor. Current operational algorithms model the surface total reflectance through a weighted linear combination of a few geometry-dependent kernels, each devised to describe a particular scattering mechanism. The information content of these measurements is overwhelmed by that of instruments with polarization capabilities: proposed models in this case are based on the Fresnel reflectance of an isotropic distribution of facets. Because of its remarkable lack of spectral contrast, the polarized reflectance of land surfaces in the shortwave infrared spectral region, where atmospheric scattering is minimal, can be used to model the surface also at shorter wavelengths, where aerosol retrievals are attempted based on well-established scattering theories. In radiative transfer simulations, straightforward separation of the surface and atmospheric contributions is not possible without approximations because of the coupling introduced by multiple reflections. Within a general inversion framework, the problem can be eliminated by linearizing the radiative transfer calculation, and making the Jacobian (i.e., the derivative expressing the sensitivity of the reflectance with respect to model parameters) available at output. We present a general methodology based on a Gauss-Newton iterative search, which automates this procedure and eliminates de facto the need of an ad hoc atmospheric correction. In this case study we analyze the color variations in the polarized reflectance measured by the NASA Goddard Institute of Space Studies Research Scanning Polarimeter during a survey of late-season snowfields in the High Sierra. This insofar unique dataset presents challenges linked to the rugged topography associated with the alpine environment and a likely high water content due to melting. The analysis benefits from ancillary information provided by the NASA Langley High Spectral Resolution Lidar deployed on the same aircraft. The results obtained from the iterative scheme are contrasted against the surface polarized reflectance obtained ignoring multiple reflections, via the simplistic subtraction of the atmospheric scattering contribution. Finally, the retrieved reflectance is modeled after the scattering properties of a dense collection of ice crystals at the surface. Confirming that the polarized reflectance of snow is spectrally flat would allow to extend the techniques already in use for polarimetric retrievals of aerosol properties over land to the large portion of snow-covered pixels plaguing orbital and suborbital observations.

Reconstructing the Surface Permittivity Distribution from Data Measured by the CONSERT Instrument aboard Rosetta: Method and Simulations

NASA Astrophysics Data System (ADS)

Plettemeier, D.; Statz, C.; Hegler, S.; Herique, A.; Kofman, W. W.

2014-12-01

One of the main scientific objectives of the Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) aboard Rosetta is to perform a dielectric characterization of comet 67P/Chuyurmov-Gerasimenko's nucleus by means of a bi-static sounding between the lander Philae launched onto the comet's surface and the orbiter Rosetta. For the sounding, the lander part of CONSERT will receive and process the radio signal emitted by the orbiter part of the instrument and transmit a signal to the orbiter to be received by CONSERT. CONSERT will also be operated as bi-static RADAR during the descent of the lander Philae onto the comet's surface. From data measured during the descent, we aim at reconstructing a surface permittivity map of the comet at the landing site and along the path below the descent trajectory. This surface permittivity map will give information on the bulk material right below and around the landing site and the surface roughness in areas covered by the instrument along the descent. The proposed method to estimate the surface permittivity distribution is based on a least-squares based inversion approach in frequency domain. The direct problem of simulating the wave-propagation between lander and orbiter at line-of-sight and the signal reflected on the comet's surface is modelled using a dielectric physical optics approximation. Restrictions on the measurement positions by the descent orbitography and limitations on the instrument dynamic range will be dealt with by application of a regularization technique where the surface permittivity distribution and the gradient with regard to the permittivity is projected in a domain defined by a viable model of the spatial material and roughness distribution. The least-squares optimization step of the reconstruction is performed in such domain on a reduced set of parameters yielding stable results. The viability of the proposed method is demonstrated by reconstruction results based on simulated data.

Using Landsat Surface Reflectance Data as a Reference Target for Multiswath Hyperspectral Data Collected Over Mixed Agricultural Rangeland Areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCann, Cooper; Repasky, Kevin S.; Morin, Mikindra

Low-cost flight-based hyperspectral imaging systems have the potential to provide important information for ecosystem and environmental studies as well as aide in land management. To realize this potential, methods must be developed to provide large-area surface reflectance data allowing for temporal data sets at the mesoscale. This paper describes a bootstrap method of producing a large-area, radiometrically referenced hyperspectral data set using the Landsat surface reflectance (LaSRC) data product as a reference target. The bootstrap method uses standard hyperspectral processing techniques that are extended to remove uneven illumination conditions between flight passes, allowing for radiometrically self-consistent data after mosaicking. Throughmore » selective spectral and spatial resampling, LaSRC data are used as a radiometric reference target. Advantages of the bootstrap method include the need for minimal site access, no ancillary instrumentation, and automated data processing. Data from two hyperspectral flights over the same managed agricultural and unmanaged range land covering approximately 5.8 km 2 acquired on June 21, 2014 and June 24, 2015 are presented. As a result, data from a flight over agricultural land collected on June 6, 2016 are compared with concurrently collected ground-based reflectance spectra as a means of validation.« less

Using Landsat Surface Reflectance Data as a Reference Target for Multiswath Hyperspectral Data Collected Over Mixed Agricultural Rangeland Areas

DOE PAGES

McCann, Cooper; Repasky, Kevin S.; Morin, Mikindra; ...

2017-07-25

Low-cost flight-based hyperspectral imaging systems have the potential to provide important information for ecosystem and environmental studies as well as aide in land management. To realize this potential, methods must be developed to provide large-area surface reflectance data allowing for temporal data sets at the mesoscale. This paper describes a bootstrap method of producing a large-area, radiometrically referenced hyperspectral data set using the Landsat surface reflectance (LaSRC) data product as a reference target. The bootstrap method uses standard hyperspectral processing techniques that are extended to remove uneven illumination conditions between flight passes, allowing for radiometrically self-consistent data after mosaicking. Throughmore » selective spectral and spatial resampling, LaSRC data are used as a radiometric reference target. Advantages of the bootstrap method include the need for minimal site access, no ancillary instrumentation, and automated data processing. Data from two hyperspectral flights over the same managed agricultural and unmanaged range land covering approximately 5.8 km 2 acquired on June 21, 2014 and June 24, 2015 are presented. As a result, data from a flight over agricultural land collected on June 6, 2016 are compared with concurrently collected ground-based reflectance spectra as a means of validation.« less

Measuring Snow Grain Size with the Near-Infrared Emitting Reflectance Dome (NERD)

NASA Astrophysics Data System (ADS)

Schneider, A. M.; Flanner, M.

2014-12-01

Because of its high visible albedo, snow plays a large role in Earth's surface energy balance. This role is a subject of intense study, but due to the wide range of snow albedo, variations in the characteristics of snow grains can introduce radiative feedbacks in a snow pack. Snow grain size, for example, is one property which directly affects a snow pack's absorption spectrum. Previous studies model and observe this spectrum, but potential feedbacks induced by these variations are largely unknown. Here, we implement a simple and inexpensive technique to measure snow grain size in an instrument we call the Near-infrared Emitting Reflectance Dome (NERD). A small black styrene dome (~17cm diameter), fitted with two narrowband light-emitting diodes (LEDs) centered around 1300nm and 1550nm and three near-infrared reverse-biased photodiodes, is placed over the snow surface enabling a multi-spectral measurement of the hemispheric directional reflectance factor (HDRF). We illuminate the snow at each wavelength, measure directional reflectance, and infer grain size from the difference in HDRFs measured on the same snow crystals at fixed viewing angles. We validate measurements from the NERD using two different reflectance standards, materials designed to be near perfect Lambertian reflectors, having known, constant reflectances (~99% and ~55%) across a wide range of wavelengths. Using a 3D Monte Carlo model simulating photon pathways through a pack of spherical snow grains, we calculate the difference in HDRFs at 1300nm and 1550nm to predict the calibration curve for a wide range of grain sizes. This theoretically derived curve gives a relationship between effective radius and the difference in HDRFs and allows us to approximate grain sizes using the NERD in just a few seconds. Further calibration requires knowledge of truth values attainable using a previously validated instrument or measurements from an inter-comparison workshop.

Skylab

NASA Image and Video Library

1973-09-01

This Earth Resource Experiment Package (EREP) photograph of the Uncompahgre area of Colorado was electronically acquired in September of 1973 by the Multi-spectral Scarner, Skylab Experiment S192. EREP images were used to analyze the vegetation conditions and landscape characteristic of this area. Skylab's Earth sensors played the dual roles of gathering information about the planet and perfecting instruments and techniques for future satellites and manned stations. An array of six fixed cameras, another for high resolution, and the astronauts' handheld cameras photographed surface features. Other instruments, recording on magnetic tape, measured the reflectivity of plants, soils, and water. Radar measured the altitude of land and water surfaces. The sensors' objectives were to survey croplands and forests, identify soils and rock types, map natural features and urban developments, detect sediments and the spread of pollutants, study clouds and the sea, and determine the extent of snow and ice cover.

Ultraviolet spectral reflectance of carbonaceous materials

NASA Astrophysics Data System (ADS)

Applin, Daniel M.; Izawa, Matthew R. M.; Cloutis, Edward A.; Gillis-Davis, Jeffrey J.; Pitman, Karly M.; Roush, Ted L.; Hendrix, Amanda R.; Lucey, Paul G.

2018-06-01

A number of planetary spacecraft missions have carried instruments with sensors covering the ultraviolet (UV) wavelength range. However, there exists a general lack of relevant UV reflectance laboratory data to compare against these planetary surface remote sensing observations in order to make confident material identifications. To address this need, we have systematically analyzed reflectance spectra of carbonaceous materials in the 200-500 nm spectral range, and found spectral-compositional-structural relationships that suggest this wavelength region could distinguish between otherwise difficult-to-identify carbon phases. In particular (and by analogy with the infrared spectral region), large changes over short wavelength intervals in the refractive indices associated with the trigonal sp2π-π* transition of carbon can lead to Fresnel peaks and Christiansen-like features in reflectance. Previous studies extending to shorter wavelengths also show that anomalous dispersion caused by the σ-σ* transition associated with both the trigonal sp2 and tetrahedral sp3 sites causes these features below λ = 200 nm. The peak wavelength positions and shapes of π-π* and σ-σ* features contain information on sp3/sp2, structure, crystallinity, and powder grain size. A brief comparison with existing observational data indicates that the carbon fraction of the surface of Mercury is likely amorphous and submicroscopic, as is that on the surface of the martian satellites Phobos and Deimos, and possibly comet 67P/Churyumov-Gerasimenko, while further coordinated observations and laboratory experiments should refine these feature assignments and compositional hypotheses. The new laboratory diffuse reflectance data reported here provide an important new resource for interpreting UV reflectance measurements from planetary surfaces throughout the solar system, and confirm that the UV can be rich in important spectral information.

Surface contamination analysis technology team overview

NASA Astrophysics Data System (ADS)

Burns, H. Dewitt, Jr.

1996-11-01

The surface contamination analysis technology (SCAT) team was originated as a working roup of NASA civil service, Space Shuttle contractor, and university groups. Participating members of the SCAT Team have included personnel from NASA Marshall Space Flight Center's Materials and Processes Laboratory and Langley Research Center's Instrument Development Group; contractors-Thiokol Corporation's Inspection Technology Group, AC Engineering support contractor, Aerojet, SAIC, and Lockheed MArtin/Oak Ridge Y-12 support contractor and Shuttle External Tank prime contractor; and the University of Alabama in Huntsville's Center for Robotics and Automation. The goal of the SCAT team as originally defined was to develop and integrate a multi-purpose inspection head for robotic application to in-process inspection of contamination sensitive surfaces. One area of interest was replacement of ozone depleting solvents currently used for surface cleanliness verification. The team approach brought together the appropriate personnel to determine what surface inspection techniques were applicable to multi-program surface cleanliness inspection. Major substrates of interest were chosen to simulate space shuttle critical bonding surface or surfaces sensitive to contamination such as fuel system component surfaces. Inspection techniques evaluated include optically stimulated electron emission or photoelectron emission; Fourier transform infrared spectroscopy; near infrared fiber optic spectroscopy; and, ultraviolet fluorescence. Current plans are to demonstrate an integrated system in MSFC's Productivity Enhancement Complex within five years from initiation of this effort in 1992. Instrumentation specifications and designs developed under this effort include a portable diffuse reflectance FTIR system built by Surface Optics Corporation and a third generation optically stimulated electron emission system built by LaRC. This paper will discuss the evaluation of the various techniques on a number of substrate materials contaminated with hydrocarbons, silicones, and fluorocarbons. Discussion will also include standards development for instrument calibration and testing.

Emissive and reflective properties of curved displays in relation to image quality

NASA Astrophysics Data System (ADS)

Boher, Pierre; Leroux, Thierry; Bignon, Thibault; Collomb-Patton, Véronique; Blanc, Pierre; Sandré-Chardonnal, Etienne

2016-03-01

Different aspects of the characterization of curved displays are presented. The limit of validity of viewing angle measurements without angular distortion on such displays using goniometer or Fourier optics viewing angle instrument is given. If the condition cannot be fulfilled the measurement can be corrected using a general angular distortion formula as demonstrated experimentally using a Samsung Galaxy S6 edge phone display. The reflective properties of the display are characterized by measuring the spectral BRDF using a multispectral Fourier optics viewing angle system. The surface of a curved OLED TV has been measured. The BDRF patterns show a mirror like behavior with and additional strong diffraction along the pixels lines and columns that affect the quality of the display when observed with parasitic lighting. These diffraction effects are very common on OLED surfaces. We finally introduce a commercial ray tracing software that can use directly the measured emissive and reflective properties of the display to make realistic simulation under any lighting environment.

Impact of Spatial Sampling on Continuity of MODIS-VIIRS Land Surface Reflectance Products: A Simulation Approach

NASA Technical Reports Server (NTRS)

Pahlevan, Nima; Sarkar, Sudipta; Devadiga, Sadashiva; Wolfe, Robert E.; Roman, Miguel; Vermote, Eric; Lin, Guoqing; Xiong, Xiaoxiong

2016-01-01

With the increasing need to construct long-term climate-quality data records to understand, monitor, and predict climate variability and change, it is vital to continue systematic satellite measurements along with the development of new technology for more quantitative and accurate observations. The Suomi National Polar-orbiting Partnership mission provides continuity in monitoring the Earths surface and its atmosphere in a similar fashion as the heritage MODIS instruments onboard the National Aeronautics and Space Administrations Terra and Aqua satellites. In this paper, we aim at quantifying the consistency of Aqua MODIS and Suomi-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Reflectance (LSR) and NDVI products as related to their inherent spatial sampling characteristics. To avoid interferences from sources of measurement and/or processing errors other than spatial sampling, including calibration, atmospheric correction, and the effects of the bidirectional reflectance distribution function, the MODIS and VIIRSLSR products were simulated using the Landsat-8s Operational Land Imager (OLI) LSR products. The simulations were performed using the instruments point spread functions on a daily basis for various OLI scenes over a 16-day orbit cycle. It was found that the daily mean differences due to discrepancies in spatial sampling remain below 0.0015 (1) in absolute surface reflectance at subgranule scale (i.e., OLI scene size).We also found that the MODISVIIRS product intercomparisons appear to be minimally impacted when differences in the corresponding view zenith angles (VZAs) are within the range of -15deg to -35deg (VZA(sub v) - VZA(sub m)), where VIIRS and MODIS footprints resemble in size. In general, depending on the spatial heterogeneity of the OLI scene contents, per-grid-cell differences can reach up to 20.Further spatial analysis of the simulated NDVI and LSR products revealed that, depending on the user accuracy requirements for product intercomparisons, spatial aggregations may be used. It was found that if per-grid-cell differences on the order of 10(in LSR or NDVI) are tolerated, the product intercomparisons are expected to be immune from differences in spatial sampling.

Miniaturized Laser-Induced Breakdown Spectroscopy for the in-situ analysis of the Martian surface: Calibration and quantification

NASA Astrophysics Data System (ADS)

Rauschenbach, I.; Jessberger, E. K.; Pavlov, S. G.; Hübers, H.-W.

2010-08-01

We report on our ongoing studies to develop Laser-Induced Breakdown Spectroscopy (LIBS) for planetary surface missions to Mars and other planets and moons, like Jupiter's moon Europa or the Earth's moon. Since instruments for space missions are severely mass restricted, we are developing a light-weight miniaturized close-up LIBS instrument to be installed on a lander or rover for the in-situ geochemical analysis of planetary surface rocks and coarse fines. The total mass of the instrument will be ≈ 1 kg in flight configuration. Here we report on a systematic performance study of a LIBS instrument equipped with a prototype laser of 216 g total mass and an energy of 1.8 mJ. The LIBS measurements with the prototype laser and the comparative measurements with a regular 40 mJ laboratory laser were both performed under Martian atmospheric conditions. We calibrated 14 major and minor elements by analyzing 18 natural samples of certified composition. The calibration curves define the limits of detection that are > 5 ppm for the lab laser and > 400 ppm for the prototype laser, reflecting the different analyzed sample masses of ≈ 20 µg and ≈ 2 µg, respectively. To test the accuracy we compared the LIBS compositions, determined with both lasers, of Mars analogue rocks with certified or independently measured compositions and found agreements typically within 10-20%. In addition we verified that dust coverage is effectively removed from rock surfaces by the laser blast. Our study clearly demonstrates that a close-up LIBS instrument (spot size ≈ 50 µm) will decisively enhance the scientific output of planetary lander missions by providing a very large number of microscopic elemental analyses.

Elliptical varied line-space (EVLS) gratings

NASA Astrophysics Data System (ADS)

Thomas, Roger J.

2004-10-01

Imaging spectroscopy at wavelengths below 2000 Å offers an especially powerful method for studying many extended high-temperature astronomical objects, like the Sun and its outer layers. But the technology to make such measurements is also especially challenging, because of the poor reflectance of all standard materials at these wavelengths, and because the observation must be made from above the absorbing effects of the Earth's atmosphere. To solve these problems, single-reflection stigmatic spectrographs for XUV wavelengths have bee flown on several space missions based on designs with toroidal uniform line-space (TULS) or spherical varied line-space (SVLS) gratings that operate at near normal-incidence. More recently, three solar EUV/UV instruments have been selected that use toroidal varied line-space (TVLS) gratings; these are SUMI and RAISE, both sounding rocket payloads, and NEXUS, a SMEX satellite-mission. The next logical extension to such designs is the use of elliptical surfaces for varied line-space (EVLS) rulings. In fact, EVLS designs are found to provide superior imaging even at very large spectrograph magnifications and beam-speeds, permitting extremely high-quality performance in remarkably compact instrument packages. In some cases, such designs may be optimized even further by using a hyperbolic surface for the feeding telescope. The optical characteristics of two solar EUV spectrometers based on these concepts are described: EUS and EUI, both being developed as possible instruments for ESA's Solar Orbiter mission by consortia led by RAL and by MSSL, respectively.

Towards a first ground-based validation of aerosol optical depths from Sentinel-2 over the complex topography of the Alps

NASA Astrophysics Data System (ADS)

Marinelli, Valerio; Cremonese, Edoardo; Diémoz, Henri; Siani, Anna Maria

2017-04-01

The European Space Agency (ESA) is spending notable effort to put in operation a new generation of advanced Earth-observation satellites, the Sentinel constellation. In particular, the Sentinel-2 host an instrumental payload mainly consisting in a MultiSpectral Instrument (MSI) imaging sensor, capable of acquiring high-resolution imagery of the Earth surface and atmospheric reflectance at selected spectral bands, hence providing complementary measurements to ground-based radiometric stations. The latter can provide reference data for validating the estimates from spaceborne instruments such as Sentinel-2A (operating since October 2015), whose aerosol optical thickness (AOT) values, can be obtained from correcting SWIR (2190 nm) reflectance with an improved dense dark vegetation (DDV) algorithm. In the Northwestern European Alps (Saint-Christophe, 45.74°N, 7.36°E) a Prede POM-02 sun/sky aerosol photometer has been operating for several years within the EuroSkyRad network by the Environmental Protection Agency of Aosta Valley (ARPA Valle d'Aosta), gathering direct sun and diffuse sky radiance for retrieving columnar aerosol optical properties. This aerosol optical depth (AOD) dataset represents an optimal ground-truth for the corresponding Sentinel-2 estimates obtained with the Sen2cor processor in the challenging environment of the Alps (complex topography, snow-covered surfaces). We show the deviations between the two measurement series and propose some corrections to enhance the overall accuracy of satellite estimates.

ASTER VNIR 15 years growth to the standard imaging radiometer in remote sensing

NASA Astrophysics Data System (ADS)

Hiramatsu, Masaru; Inada, Hitomi; Kikuchi, Masakuni; Sakuma, Fumihiro

2015-10-01

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Visible and Near Infrared Radiometer (VNIR) is the remote sensing equipment which has 3 spectral bands and one along-track stereoscopic band radiometer. ASTER VNIR's planned long life design (more than 5 years) is successfully achieved. ASTER VNIR has been imaging the World-wide Earth surface multiband images and the Global Digital Elevation Model (GDEM). VNIR data create detailed world-wide maps and change-detection of the earth surface as utilization transitions and topographical changes. ASTER VNIR's geometric resolution is 15 meters; it is the highest spatial resolution instrument on NASA's Terra spacecraft. Then, ASTER VNIR was planned for the geometrical basis map makers in Terra instruments. After 15-years VNIR growth to the standard map-maker for space remote-sensing. This paper presents VNIR's feature items during 15-year operation as change-detection images , DEM and calibration result. VNIR observed the World-wide Earth images for biological, climatological, geological, and hydrological study, those successful work shows a way on space remote sensing instruments. Still more, VNIR 15 years observation data trend and onboard calibration trend data show several guide or support to follow-on instruments.

Evaluation of Long-term Aerosol Data Records from SeaWiFS over Land and Ocean

NASA Astrophysics Data System (ADS)

Bettenhausen, C.; Hsu, C.; Jeong, M.; Huang, J.

2010-12-01

Deserts around the globe produce mineral dust aerosols that may then be transported over cities, across continents, or even oceans. These aerosols affect the Earth’s energy balance through direct and indirect interactions with incoming solar radiation. They also have a biogeochemical effect as they deliver scarce nutrients to remote ecosystems. Large dust storms regularly disrupt air traffic and are a general nuisance to those living in transport regions. In the past, measuring dust aerosols has been incomplete at best. Satellite retrieval algorithms were limited to oceans or vegetated surfaces and typically neglected desert regions due to their high surface reflectivity in the mid-visible and near-infrared wavelengths, which have been typically used for aerosol retrievals. The Deep Blue aerosol retrieval algorithm was developed to resolve these shortcomings by utilizing the blue channels from instruments such as the Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) and the Moderate Resolution Imaging Spectroradiometer (MODIS) to infer aerosol properties over these highly reflective surfaces. The surface reflectivity of desert regions is much lower in the blue channels and thus it is easier to separate the aerosol and surface signals than at the longer wavelengths used in other algorithms. More recently, the Deep Blue algorithm has been expanded to retrieve over vegetated surfaces and oceans as well. A single algorithm can now follow dust from source to sink. In this work, we introduce the SeaWiFS instrument and the Deep Blue aerosol retrieval algorithm. We have produced global aerosol data records over land and ocean from 1997 through 2009 using the Deep Blue algorithm and SeaWiFS data. We describe these data records and validate them with data from the Aerosol Robotic Network (AERONET). We also show the relative performance compared to the current MODIS Deep Blue operational aerosol data in desert regions. The current results are encouraging and this dataset will be useful to future studies in understanding the effects of dust aerosols on global processes, long-term aerosol trends, quantifying dust emissions, transport, and inter-annual variability.

The Descent Imager/Spectral Radiometer (DISR) Experiment on the Huygens Entry Probe of Titan

NASA Astrophysics Data System (ADS)

Tomasko, M. G.; Buchhauser, D.; Bushroe, M.; Dafoe, L. E.; Doose, L. R.; Eibl, A.; Fellows, C.; Farlane, E. M.; Prout, G. M.; Pringle, M. J.; Rizk, B.; See, C.; Smith, P. H.; Tsetsenekos, K.

2002-07-01

The payload of the Huygens Probe into the atmosphere of Titan includes the Descent Imager/Spectral Radiometer (DISR). This instrument includes an integrated package of several optical instruments built around a silicon charge coupled device (CCD) detector, a pair of linear InGaAs array detectors, and several individual silicon detectors. Fiber optics are used extensively to feed these detectors with light collected from three frame imagers, an upward and downward-looking visible spectrometer, an upward and downward looking near-infrared spectrometer, upward and downward looking violet phtotometers, a four-channel solar aerole camera, and a sun sensor that determines the azimuth and zenith angle of the sun and measures the flux in the direct solar beam at 940 nm. An onboard optical calibration system uses a small lamp and fiber optics to track the relative sensitivity of the different optical instruments relative to each other during the seven year cruise to Titan. A 20 watt lamp and collimator are used to provide spectrally continuous illumination of the surface during the last 100 m of the descent for measurements of the reflection spectrum of the surface. The instrument contains software and hardware data compressors to permit measurements of upward and downward direct and diffuse solar flux between 350 and 1700 nm in some 330 spectral bands at approximately 2 km vertical resolution from an alititude of 160 km to the surface. The solar aureole camera measures the brightness of a 6° wide strip of the sky from 25 to 75° zenith angle near and opposite the azimuth of the sun in two passbands near 500 and 935 nm using vertical and horizontal polarizers in each spectral channel at a similar vertical resolution. The downward-looking spectrometers provide the reflection spectrum of the surface at a total of some 600 locations between 850 and 1700 nm and at more than 3000 locations between 480 and 960 nm. Some 500 individual images of the surface are expected which can be assembled into about a dozen panoramic mosaics covering nadir angles from 6° to 96° at all azimuths. The spatial resolution of the images varies from 300 m at 160 km altitude to some 20 cm in the last frames. The scientific objectives of the experiment fall into four areas including (1) measurement of the solar heating profile for studies of the thermal balance of Titan; (2) imaging and spectral reflection measurements of the surface for studies of the composition, topography, and physical processes which form the surface as well as for direct measurements of the wind profile during the descent; (3) measurements of the brightness and degree of linear polarization of scattered sunlight including the solar aureole together with measurements of the extinction optical depth of the aerosols as a function of wavelength and altitude to study the size, shape, vertical distribution, optical properties, sources and sinks of aerosols in Titan's atmosphere; and (4) measurements of the spectrum of downward solar flux to study the composition of the atmosphere, especially the mixing ratio profile of methane throughout the descent. We briefly outline the methods by which the flight instrument was calibrated for absolute response, relative spectral response, and field of view over a very wide temperature range. We also give several examples of data collected in the Earth's atmosphere using a spare instrument including images obtained from a helicopter flight program, reflection spectra of various types of terrain, solar aureole measurements including the determination of aerosol size, and measurements of the downward flux of violet, visible, and near infrared sunlight. The extinction optical depths measured as a function of wavelength are compared to models of the Earth's atmosphere and are divided into contributions from molecular scattering, aerosol extinction, and molecular absorption. The test observations during simulated descents with mountain and rooftop venues in the Earth's atmosphere are very important for driving out problems in the calibration and interpretion of the observations to permit rapid analysis of the observations after Titan entry.

Multi-angle Imaging SpectroRadiometer

NASA Technical Reports Server (NTRS)

Diner, David J. (Principal Investigator)

MISR views the sunlit Earth simultaneously at nine widely spaced angles and provides ongoing global coverage with high spatial detail. Its imagery is carefully calibrated to provide accurate measures of the brightness, contrast, and color of reflected sunlight. MISR provides new types of information for scientists studying Earth's climate, such as the regional and global distribution of different types of atmospheric particles and aerosols. The change in reflection at different view angles provides the means to distinguish aerosol types, cloud forms, and land surface cover. Combined with stereoscopic techniques, this enables construction of 3-D cloud models and estimation of the total amount of sunlight reflected by Earth's diverse environments. MISR was built for NASA by the Jet Propulsion Laboratory (JPL) in Pasadena, California. It is part of NASA's first Earth Observing System (EOS) spacecraft, the Terra spacecraft, which was launched into polar orbit from Vandenberg Air Force Base on December 18, 1999. MISR has been continuously providing data since February 24, 2000. [Mission Objectives] The MISR instrument acquires systematic multi-angle measurements for global monitoring of top-of-atmosphere and surface albedos and for measuring the shortwave radiative properties of aerosols, clouds, and surface scenes in order to characterize their impact on the Earth's climate. The Earth's climate is constantly changing -- as a consequence of both natural processes and human activities. Scientists care a great deal about even small changes in Earth's climate, since they can affect our comfort and well-being, and possibly our survival. A few years of below-average rainfall, an unusually cold winter, or a change in emissions from a coal-burning power plant, can influence the quality of life of people, plants, and animals in the region involved. The goal of NASA's Earth Observing System (EOS) is to increase our understanding of the climate changes that are occurring on our planet, and the reasons for these changes, so we are better equipped to anticipate and prepare for the future. The MISR instrument is a part of EOS. Its role is to measure the amount of sunlight scattered in different directions under natural conditions. These measurements will help quantify the amount of solar energy that heats the Earth's surface and atmosphere, and the changes that occur in them over the lifetime of the MISR instrument. From the MISR observations, we are also learning more about those components of the Earth's environment that scatter sunlight: particles in the atmosphere, the planet's surface, and clouds. MISR monitors changes in surface reflection properties, in atmospheric aerosol content and composition, and in cloudiness. Scientists use these data to study land use changes, air pollution, volcanic eruptions, as well as processes such as desertification, deforestation, and soil erosion. As part of the EOS program, computer models that predict future climate will be improved by the results of these studies. [Temporal_Coverage: Start_Date=2000-02-24; Stop_Date=] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180].

The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu

NASA Astrophysics Data System (ADS)

Reuter, D. C.; Simon, A. A.; Hair, J.; Lunsford, A.; Manthripragada, S.; Bly, V.; Bos, B.; Brambora, C.; Caldwell, E.; Casto, G.; Dolch, Z.; Finneran, P.; Jennings, D.; Jhabvala, M.; Matson, E.; McLelland, M.; Roher, W.; Sullivan, T.; Weigle, E.; Wen, Y.; Wilson, D.; Lauretta, D. S.

2018-03-01

The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm-1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.

Characterization of in Band Stray Light in SBUV-2 Instruments

NASA Technical Reports Server (NTRS)

Huang, L. K.; DeLand, M. T.; Taylor, S. L.; Flynn, L. E.

2014-01-01

Significant in-band stray light (IBSL) error at solar zenith angle (SZA) values larger than 77deg near sunset in 4 SBUV/2 (Solar Backscattered Ultraviolet) instruments, on board the NOAA-14, 17, 18 and 19 satellites, has been characterized. The IBSL error is caused by large surface reflection and scattering of the air-gapped depolarizer in front of the instrument's monochromator aperture. The source of the IBSL error is direct solar illumination of instrument components near the aperture rather than from earth shine. The IBSL contamination at 273 nm can reach 40% of earth radiance near sunset, which results in as much as a 50% error in the retrieved ozone from the upper stratosphere. We have analyzed SBUV/2 albedo measurements on both the dayside and nightside to develop an empirical model for the IBSL error. This error has been corrected in the V8.6 SBUV/2 ozone retrieval.

Instruments for Reading Direct-Marked Data-Matrix Symbols

NASA Technical Reports Server (NTRS)

Schramm, Harry F.; Corder, Eric L.

2006-01-01

Improved optoelectronic instruments (specially configured digital cameras) for reading direct-marked data-matrix symbols on the surfaces of optically reflective objects (including specularly reflective ones) are undergoing development. Data-matrix symbols are two-dimensional binary patterns that are used, like common bar codes, for automated identification of objects. The first data-matrix symbols were checkerboard-like patterns of black-and-white rectangles, typically existing in the forms of paint, ink, or detachable labels. The major advantage of direct marking (the marks are more durable than are painted or printed symbols or detachable labels) is offset by a major disadvantage (the marks generated by some marking methods do not provide sufficient contrast to be readable by optoelectronic instruments designed to read black-and-white data-matrix symbols). Heretofore, elaborate lighting, lensing, and software schemes have been tried in efforts to solve the contrast problem in direct-mark matrix- symbol readers. In comparison with prior readers based on those schemes, the readers now undergoing development are expected to be more effective while costing less. All of the prior direct-mark matrix-symbol readers are designed to be aimed perpendicularly to marked target surfaces, and they tolerate very little angular offset. However, the reader now undergoing development not only tolerates angular offset but depends on angular offset as a means of obtaining the needed contrast, as described below. The prototype reader (see Figure 1) includes an electronic camera in the form of a charge-coupled-device (CCD) image detector equipped with a telecentric lens. It also includes a source of collimated visible light and a source of collimated infrared light for illuminating a target. The visible and infrared illumination complement each other: the visible illumination is more useful for aiming the reader toward a target, while the infrared illumination is more useful for reading symbols on highly reflective surfaces. By use of beam splitters, the visible and infrared collimated lights are introduced along the optical path of the telecentric lens, so that the target is illuminated and viewed from the same direction.

Spectropolarimetric Imaging Observations

NASA Astrophysics Data System (ADS)

Bradley, Christine Lavella

The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms. The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces. An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.

Inspection of float glass using a novel retroreflective laser scanning system

NASA Astrophysics Data System (ADS)

Holmes, Jonathan D.

1997-07-01

Since 1988, Image Automation has marketed a float glass inspection system using a novel retro-reflective laser scanning system. The (patented) instrument scans a laser beam by use of a polygon through the glass onto a retro-reflective screen, and collects the retro-reflected light off the polygon, such that a stationary image of the moving spot on the screen is produced. The spot image is then analyzed for optical effects introduced by defects within the glass, which typically distort and attenuate the scanned laser beam, by use of suitable detectors. The inspection system processing provides output of defect size, shape and severity, to the factory network for use in rejection or sorting of glass plates to the end customer. This paper briefly describes the principles of operation, the system architecture, and limitations to sensitivity and measurement repeatability. New instruments based on the retro-reflective scanning method have recently been developed. The principles and implementation are described. They include: (1) Simultaneous detection of defects within the glass and defects in a mirror coating on the glass surface using polarized light. (2) A novel distortion detector for very dark glass. (3) Measurement of optical quality (flatness/refractive homogeneity) of the glass using a position sensitive detector.

Multiwalled carbon nanotubes for stray light suppression in space flight instruments

NASA Astrophysics Data System (ADS)

Hagopian, John G.; Getty, Stephanie A.; Quijada, Manuel; Tveekrem, June; Shiri, Ron; Roman, Patrick; Butler, James; Georgiev, Georgi; Livas, Jeff; Hunt, Cleophus; Maldonado, Alejandro; Talapatra, Saikat; Zhang, Xianfeng; Papadakis, Stergios J.; Monica, Andrew H.; Deglau, David

2010-08-01

Observations of the Earth are extremely challenging; its large angular extent floods scientific instruments with high flux within and adjacent to the desired field of view. This bright light diffracts from instrument structures, rattles around and invariably contaminates measurements. Astrophysical observations also are impacted by stray light that obscures very dim objects and degrades signal to noise in spectroscopic measurements. Stray light is controlled by utilizing low reflectance structural surface treatments and by using baffles and stops to limit this background noise. In 2007 GSFC researchers discovered that Multiwalled Carbon Nanotubes (MWCNTs) are exceptionally good absorbers, with potential to provide order-of-magnitude improvement over current surface treatments and a resulting factor of 10,000 reduction in stray light when applied to an entire optical train. Development of this technology will provide numerous benefits including: a.) simplification of instrument stray light controls to achieve equivalent performance, b.) increasing observational efficiencies by recovering currently unusable scenes in high contrast regions, and c.) enabling low-noise observations that are beyond current capabilities. Our objective was to develop and apply MWCNTs to instrument components to realize these benefits. We have addressed the technical challenges to advance the technology by tuning the MWCNT geometry using a variety of methods to provide a factor of 10 improvement over current surface treatments used in space flight hardware. Techniques are being developed to apply the optimized geometry to typical instrument components such as spiders, baffles and tubes. Application of the nanostructures to alternate materials (or by contact transfer) is also being investigated. In addition, candidate geometries have been tested and optimized for robustness to survive integration, testing, launch and operations associated with space flight hardware. The benefits of this technology extend to space science where observations of extremely dim objects require suppression of stray light.

New BRDF Model for Desert and Gobi Using Equivalent Mirror Plane Method, Establishment and Validation

NASA Astrophysics Data System (ADS)

Li, Y.; Rong, Z.

2017-12-01

The surface Bidirectional Reflectance Distribution Function (BRDF) is a key parameter that affects the vicarious calibration accuracy of visible channel remote sensing instrument. In the past 30 years, many studies have been made and a variety of models have been established. Among them, the Ross-li model was highly approved and widely used. Unfortunately, the model doesn't suitable for desert and Gobi quite well because of the scattering kernel it contained, needs the factors such as plant height and plant spacing. A new BRDF model for surface without vegetation, which is mainly used in remote sensing vicarious calibration, is established. That was called Equivalent Mirror Plane (EMP) BRDF. It is used to characterize the bidirectional reflectance of the near Lambertian surface. The accuracy of the EMP BRDF model is validated by the directional reflectance data measured on the Dunhuang Gobi and compared to the Ross-li model. Results show that the regression accuracy of the new model is 0.828, which is similar to the Ross-li model (0.825). Because of the simple form (contains only four polynomials) and simple principle (derived by the Fresnel reflection principle, don't include any vegetation parameters), it is more suitable for near Lambertian surface, such as Gobi, desert, Lunar and reference panel. Results also showed that the new model could also maintain a high accuracy and stability in sparse observation, which is very important for the retrieval requirements of daily updating BRDF remote sensing products.

In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

PubMed Central

Johnson, Grant E.; Gunaratne, K. Don Dasitha; Laskin, Julia

2014-01-01

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using conventional synthesis techniques. Coupling soft landing with in situ characterization using secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS) enables analysis of well-defined surfaces under clean vacuum conditions. The capabilities of three soft-landing instruments constructed in our laboratory are illustrated for the representative system of surface-bound organometallics prepared by soft landing of mass-selected ruthenium tris(bipyridine) dications, [Ru(bpy)3]2+ (bpy = bipyridine), onto carboxylic acid terminated self-assembled monolayer surfaces on gold (COOH-SAMs). In situ time-of-flight (TOF)-SIMS provides insight into the reactivity of the soft-landed ions. In addition, the kinetics of charge reduction, neutralization and desorption occurring on the COOH-SAM both during and after ion soft landing are studied using in situ Fourier transform ion cyclotron resonance (FT-ICR)-SIMS measurements. In situ IRRAS experiments provide insight into how the structure of organic ligands surrounding metal centers is perturbed through immobilization of organometallic ions on COOH-SAM surfaces by soft landing. Collectively, the three instruments provide complementary information about the chemical composition, reactivity and structure of well-defined species supported on surfaces. PMID:24961913

In Situ SIMS and IR Spectroscopy of Well-Defined Surfaces Prepared by Soft Landing of Mass-Selected Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Grant E.; Gunaratne, Kalupathirannehelage Don D.; Laskin, Julia

2014-06-16

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using conventional synthesis techniques. Coupling soft landing with in situ characterization using secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS) enables analysis of well-defined surfaces under clean vacuum conditions. The capabilities of three soft-landing instruments constructed in our laboratory are illustrated for the representative system of surface-bound organometallics prepared by soft landing of mass-selected ruthenium tris(bipyridine) dications, [Ru(bpy)3]2+, onto carboxylic acid terminated self-assembled monolayer surfaces on gold (COOH-SAMs). In situ time-of-flight (TOF)-SIMS provides insight into the reactivitymore » of the soft-landed ions. In addition, the kinetics of charge reduction, neutralization and desorption occurring on the COOH-SAM both during and after ion soft landing are studied using in situ Fourier transform ion cyclotron resonance (FT-ICR)-SIMS measurements. In situ IRRAS experiments provide insight into how the structure of organic ligands surrounding metal centers is perturbed through immobilization of organometallic ions on COOH-SAM surfaces by soft landing. Collectively, the three instruments provide complementary information about the chemical composition, reactivity and structure of well-defined species supported on surfaces.« less

Ground truth data for test sites (SL-4). [thermal radiation brightness temperature and solar radiation measurments

NASA Technical Reports Server (NTRS)

1974-01-01

Field measurements performed simultaneous with Skylab overpass in order to provide comparative calibration and performance evaluation measurements for the EREP sensors are presented. Wavelength region covered include: solar radiation (400 to 1300 nanometer), and thermal radiation (8 to 14 micrometer). Measurements consisted of general conditions and near surface meteorology, atmospheric temperature and humidity vs altitude, the thermal brightness temperature, total and diffuse solar radiation, direct solar radiation (subsequently analyzed for optical depth/transmittance), and target reflectivity/radiance. The particular instruments used are discussed along with analyses performed. Detailed instrument operation, calibrations, techniques, and errors are given.

Multi-Beam Surface Lidar for Lunar and Planetary Mapping

NASA Technical Reports Server (NTRS)

Bufton, Jack L.; Garvin, James B.

1998-01-01

Surface lidar techniques are now being demonstrated in low Earth orbit with a single beam of pulsed laser radiation at 1064 nm that profiles the vertical structure of Earth surface landforms along the nadir track of a spacecraft. In addition, a profiling laser altimeter, called MOLA, is operating in elliptical Martian orbit and returning surface topography data. These instruments form the basis for suggesting an improved lidar instrument that employs multiple beams for extension of sensor capabilities toward the goal of true, 3-dimensional mapping of the Moon or other similar planetary surfaces. In general the lidar waveform acquired with digitization of a laser echo can be used for laser distance measurement (i.e. range-to-the-surface) by time-of-flight measurement and for surface slope and shape measurements by examining the detailed lidar waveform. This is particularly effective when the intended target is the lunar surface or another planetary body free of any atmosphere. The width of the distorted return pulse is a first order measure of the surface incidence angle, a combination of surface slope and laser beam pointing. Assuming an independent and absolute (with respect to inertial space) measurement of laser beam pointing on the spacecraft, it is possible to derive a surface slope with-respect-to the mean planetary surface or its equipotential gravity surface. Higher-order laser pulse distortions can be interpreted in terms of the vertical relief of the surface or reflectivity variations within the area of the laser beam footprint on the surface.

MALIBU: A High Spatial Resolution Multi-Angle Imaging Unmanned Airborne System to Validate Satellite-derived BRDF/Albedo Products

NASA Astrophysics Data System (ADS)

Wang, Z.; Roman, M. O.; Pahlevan, N.; Stachura, M.; McCorkel, J.; Bland, G.; Schaaf, C.

2016-12-01

Albedo is a key climate forcing variable that governs the absorption of incoming solar radiation and its ultimate transfer to the atmosphere. Albedo contributes significant uncertainties in the simulation of climate changes; and as such, it is defined by the Global Climate Observing System (GCOS) as a terrestrial essential climate variable (ECV) required by global and regional climate and biogeochemical models. NASA's Goddard Space Flight Center's Multi AngLe Imaging Bidirectional Reflectance Distribution Function small-UAS (MALIBU) is part of a series of pathfinder missions to develop enhanced multi-angular remote sensing techniques using small Unmanned Aircraft Systems (sUAS). The MALIBU instrument package includes two multispectral imagers oriented at two different viewing geometries (i.e., port and starboard sides) capture vegetation optical properties and structural characteristics. This is achieved by analyzing the surface reflectance anisotropy signal (i.e., BRDF shape) obtained from the combination of surface reflectance from different view-illumination angles and spectral channels. Satellite measures of surface albedo from MODIS, VIIRS, and Landsat have been evaluated by comparison with spatially representative albedometer data from sparsely distributed flux towers at fixed heights. However, the mismatch between the footprint of ground measurements and the satellite footprint challenges efforts at validation, especially for heterogeneous landscapes. The BRDF (Bidirectional Reflectance Distribution Function) models of surface anisotropy have only been evaluated with airborne BRDF data over a very few locations. The MALIBU platform that acquires extremely high resolution sub-meter measures of surface anisotropy and surface albedo, can thus serve as an important source of reference data to enable global land product validation efforts, and resolve the errors and uncertainties in the various existing products generated by NASA and its national and international partners.

Influence of handling-relevant factors on the behaviour of a novel calculus-detection device.

PubMed

Meissner, Grit; Oehme, Bernd; Strackeljan, Jens; Kocher, Thomas

2005-03-01

The aim of periodontal therapy is always the complete debridement of root surfaces with the removal of calculus and without damaging cementum. We have recently demonstrated the feasibility of a surface recognition device that discriminates dental surfaces by mathematical analysis of reflected ultrasound waves. This principle should enable the construction of calculus detecting ultrasonic device. Pre-clinical test results are presented here. An impulse generator, coupled to a conventional piezo-driven ultrasonic scaler, sends signals to the cementum via the tip of an ultrasound device. The oscillation signal reflected from the surface contains the information necessary to analyse its characteristics. In order to discriminate different surfaces, learning sets were generated from 70 extracted teeth using standardized tip angle/lateral force combinations. The complete device was then used to classify root surfaces unknown to the system. About 80% of enamel and cementum was correctly identified in vivo (sensitivity: 75%, specificity: 82%). The surface discrimination method was not influenced by the application conditions examined. A new set of 200 tests on 10 teeth was correctly recognized in 82% of the cases (sensitivity: 87%, specificity: 76%). It was shown in vitro that the tooth surface recognition system is able to function correctly, independent of the lateral forces and the tip angle of the instrument. Copyright 2005 Blackwell Munksgaard.

Enhancements to NASA's Land Atmosphere Near real-time Capability for EOS (LANCE)

NASA Astrophysics Data System (ADS)

Michael, K.; Davies, D. K.; Schmaltz, J. E.; Boller, R. A.; Mauoka, E.; Ye, G.; Vermote, E.; Harrison, S.; Rinsland, P. L.; Protack, S.; Durbin, P. B.; Justice, C. O.

2016-12-01

NASA's Land, Atmosphere Near real-time Capability for EOS (LANCE) supports application users interested in monitoring a wide variety of natural and man-made phenomena. Near Real-Time (NRT) data and imagery from the AIRS, AMSR2, MISR, MLS, MODIS, OMI and VIIRS instruments are available much quicker than routine processing allows. Most data products are available within 3 hours from satellite observation. NRT imagery are generally available 3-5 hours after observation. This article describes LANCE and enhancements made to LANCE over the last year. These enhancements include: the addition of MISR L1 Georeferenced Radiance and L2 Cloud Motion Vector products, AMSR2 Unified L2B Half-Orbit 25 km EASE-Grid Surface Soil Moisture products and VIIRS VIIRS Day/Night Band, Land Surface Reflectance and Corrected Surface reflectance products. In addition, the selection of LANCE NRT imagery that can be interactively viewed through Worldview and the Global Imagery Browse Services (GIBS) has been expanded. LANCE is also working to ingest and process data from OMPS.

Wind Speed Measurement from Bistatically Scattered GPS Signals

NASA Technical Reports Server (NTRS)

Garrison, James L.; Komjathy, Attila; Zavorotny, Valery U.; Katzberg, Stephen J.

1999-01-01

Instrumentation and retrieval algorithms are described which use the forward, or bistatically scattered range-coded signals from the Global Positioning System (GPS) radio navigation system for the measurement of sea surface roughness. This roughness is known to be related directly to the surface wind speed. Experiments were conducted from aircraft along the TOPEX ground track, and over experimental surface truth buoys. These flights used a receiver capable of recording the cross correlation power in the reflected signal. The shape of this power distribution was then compared against analytical models derived from geometric optics. Two techniques for matching these functions were studied. The first recognized the most significant information content in the reflected signal is contained in the trailing edge slope of the waveform. The second attempted to match the complete shape of the waveform by approximating it as a series expansion and obtaining the nonlinear least squares estimate. Discussion is also presented on anomalies in the receiver operation and their identification and correction.

Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover.

PubMed

Korablev, Oleg I; Dobrolensky, Yurii; Evdokimova, Nadezhda; Fedorova, Anna A; Kuzmin, Ruslan O; Mantsevich, Sergei N; Cloutis, Edward A; Carter, John; Poulet, Francois; Flahaut, Jessica; Griffiths, Andrew; Gunn, Matthew; Schmitz, Nicole; Martín-Torres, Javier; Zorzano, Maria-Paz; Rodionov, Daniil S; Vago, Jorge L; Stepanov, Alexander V; Titov, Andrei Yu; Vyazovetsky, Nikita A; Trokhimovskiy, Alexander Yu; Sapgir, Alexander G; Kalinnikov, Yurii K; Ivanov, Yurii S; Shapkin, Alexei A; Ivanov, Andrei Yu

ISEM (Infrared Spectrometer for ExoMars) is a pencil-beam infrared spectrometer that will measure reflected solar radiation in the near infrared range for context assessment of the surface mineralogy in the vicinity of the ExoMars rover. The instrument will be accommodated on the mast of the rover and will be operated together with the panoramic camera (PanCam), high-resolution camera (HRC). ISEM will study the mineralogical and petrographic composition of the martian surface in the vicinity of the rover, and in combination with the other remote sensing instruments, it will aid in the selection of potential targets for close-up investigations and drilling sites. Of particular scientific interest are water-bearing minerals, such as phyllosilicates, sulfates, carbonates, and minerals indicative of astrobiological potential, such as borates, nitrates, and ammonium-bearing minerals. The instrument has an ∼1° field of view and covers the spectral range between 1.15 and 3.30 μm with a spectral resolution varying from 3.3 nm at 1.15 μm to 28 nm at 3.30 μm. The ISEM optical head is mounted on the mast, and its electronics box is located inside the rover's body. The spectrometer uses an acousto-optic tunable filter and a Peltier-cooled InAs detector. The mass of ISEM is 1.74 kg, including the electronics and harness. The science objectives of the experiment, the instrument design, and operational scenarios are described. Key Words: ExoMars-ISEM-Mars-Surface-Mineralogy-Spectroscopy-AOTF-Infrared. Astrobiology 17, 542-564.

Estimated Mid-Infrared (200-2000 cm-1) Optical Constants of Some Silica Polymorphs

NASA Astrophysics Data System (ADS)

Glotch, Timothy; Rossman, G. R.; Michalski, J. R.

2006-09-01

We use Lorentz-Lorenz dispersion analysis to model the mid-infrared (200-2000 cm-1) optical constants, of opal-A, opal-CT, and tridymite. These minerals, which are all polymorphs of silica (SiO2), are potentially important in the analysis of thermal emission spectra acquired by the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) and Mars Exploration Rover Mini-TES instruments in orbit and on the surface of Mars as well as emission spectra acquired by telescopes of planetary disks and dust and debris clouds in young solar systems. Mineral samples were crushed, washed, and sieved and emissivity spectra of the >100; μm size fraction were acquired at Arizona State University's emissivity spectroscopy laboratory. Therefore, the spectra and optical constants are representative of all crystal orientations. Ideally, emissivity or reflectance measurements of single polished crystals or fine powders pressed to compact disks are used for the determination of mid-infrared optical constants. Measurements of these types of surfaces eliminate or minimize multiple reflections, providing a specular surface. Our measurements, however, likely produce a reasonable approximation of specular emissivity or reflectance, as the minimum particle size is greater than the maximum wavelength of light measured. Future work will include measurement of pressed disks of powdered samples in emission and reflection, and when possible, small single crystals under an IR reflectance microscope, which will allow us to assess the variability of spectra and optical constants under different sample preparation and measurement conditions.

Land and cryosphere products from Suomi NPP VIIRS: Overview and status

PubMed Central

Justice, Christopher O; Román, Miguel O; Csiszar, Ivan; Vermote, Eric F; Wolfe, Robert E; Hook, Simon J; Friedl, Mark; Wang, Zhuosen; Schaaf, Crystal B; Miura, Tomoaki; Tschudi, Mark; Riggs, George; Hall, Dorothy K; Lyapustin, Alexei I; Devadiga, Sadashiva; Davidson, Carol; Masuoka, Edward J

2013-01-01

[1] The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument was launched in October 2011 as part of the Suomi National Polar-Orbiting Partnership (S-NPP). The VIIRS instrument was designed to improve upon the capabilities of the operational Advanced Very High Resolution Radiometer and provide observation continuity with NASA’s Earth Observing System’s Moderate Resolution Imaging Spectroradiometer (MODIS). Since the VIIRS first-light images were received in November 2011, NASA- and NOAA-funded scientists have been working to evaluate the instrument performance and generate land and cryosphere products to meet the needs of the NOAA operational users and the NASA science community. NOAA’s focus has been on refining a suite of operational products known as Environmental Data Records (EDRs), which were developed according to project specifications under the National Polar-Orbiting Environmental Satellite System. The NASA S-NPP Science Team has focused on evaluating the EDRs for science use, developing and testing additional products to meet science data needs, and providing MODIS data product continuity. This paper presents to-date findings of the NASA Science Team’s evaluation of the VIIRS land and cryosphere EDRs, specifically Surface Reflectance, Land Surface Temperature, Surface Albedo, Vegetation Indices, Surface Type, Active Fires, Snow Cover, Ice Surface Temperature, and Sea Ice Characterization. The study concludes that, for MODIS data product continuity and earth system science, an enhanced suite of land and cryosphere products and associated data system capabilities are needed beyond the EDRs currently available from the VIIRS. PMID:25821661

Land and cryosphere products from Suomi NPP VIIRS: Overview and status.

PubMed

Justice, Christopher O; Román, Miguel O; Csiszar, Ivan; Vermote, Eric F; Wolfe, Robert E; Hook, Simon J; Friedl, Mark; Wang, Zhuosen; Schaaf, Crystal B; Miura, Tomoaki; Tschudi, Mark; Riggs, George; Hall, Dorothy K; Lyapustin, Alexei I; Devadiga, Sadashiva; Davidson, Carol; Masuoka, Edward J

2013-09-16

[1] The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument was launched in October 2011 as part of the Suomi National Polar-Orbiting Partnership (S-NPP). The VIIRS instrument was designed to improve upon the capabilities of the operational Advanced Very High Resolution Radiometer and provide observation continuity with NASA's Earth Observing System's Moderate Resolution Imaging Spectroradiometer (MODIS). Since the VIIRS first-light images were received in November 2011, NASA- and NOAA-funded scientists have been working to evaluate the instrument performance and generate land and cryosphere products to meet the needs of the NOAA operational users and the NASA science community. NOAA's focus has been on refining a suite of operational products known as Environmental Data Records (EDRs), which were developed according to project specifications under the National Polar-Orbiting Environmental Satellite System. The NASA S-NPP Science Team has focused on evaluating the EDRs for science use, developing and testing additional products to meet science data needs, and providing MODIS data product continuity. This paper presents to-date findings of the NASA Science Team's evaluation of the VIIRS land and cryosphere EDRs, specifically Surface Reflectance, Land Surface Temperature, Surface Albedo, Vegetation Indices, Surface Type, Active Fires, Snow Cover, Ice Surface Temperature, and Sea Ice Characterization. The study concludes that, for MODIS data product continuity and earth system science, an enhanced suite of land and cryosphere products and associated data system capabilities are needed beyond the EDRs currently available from the VIIRS.

MAUVE/SWIPE: an imaging instrument concept with multi-angular, -spectral, and -polarized capability for remote sensing of aerosols, ocean color, clouds, and vegetation from space

NASA Astrophysics Data System (ADS)

Frouin, Robert; Deschamps, Pierre-Yves; Rothschild, Richard; Stephan, Edward; Leblanc, Philippe; Duttweiler, Fred; Ghaemi, Tony; Riedi, Jérôme

2006-12-01

The Monitoring Aerosols in the Ultraviolet Experiment (MAUVE) and the Short-Wave Infrared Polarimeter Experiment (SWIPE) instruments have been designed to collect, from a typical sun-synchronous polar orbit at 800 km altitude, global observations of the spectral, polarized, and directional radiance reflected by the earth-atmosphere system for a wide range of applications. Based on the heritage of the POLDER radiometer, the MAUVE/SWIPE instrument concept combines the merits of TOMS for observing in the ultra-violet, MISR for wide field-of-view range, MODIS, for multi-spectral aspects in the visible and near infrared, and the POLDER instrument for polarization. The instruments are camera systems with 2-dimensional detector arrays, allowing a 120-degree field-of-view with adequate ground resolution (i.e., 0.4 or 0.8 km at nadir) from satellite altitude. Multi-angle viewing is achieved by the along-track migration at spacecraft velocity of the 2-dimensional field-of-view. Between the cameras' optical assembly and detector array are two filter wheels, one carrying spectral filters, the other polarizing filters, allowing measurements of the first three Stokes parameters, I. Q, and V, of the incident radiation in 16 spectral bands optimally placed in the interval 350-2200 nm. The spectral range is 350-1050 nm for the MAUVE instrument and 1050-2200 nm for the SWIPE instrument. The radiometric requirements are defined to fully exploit the multi-angular, multi-spectral, and multi-polarized capability of the instruments. These include a wide dynamic range, a signal-to-noise ratio above 500 in all channels at maximum radiance level, i.e., when viewing a surface target of albedo equal to 1, and a noise-equivalent-differential reflectance better than 0.0005 at low signal level for a sun at zenith. To achieve daily global coverage, a pair of MAUVE and SWIPE instruments would be carried by each of two mini-satellites placed on interlaced orbits. The equator crossing time of the two satellites would be adjusted to allow simultaneous observations of the overlapping zone viewed from the two parallel orbits of the twin satellites. Using twin satellites instead of a single satellite would allow measurements in a more complete range of scattering angles. A MAUVE/SWIPE satellite mission would improve significantly the accuracy of ocean color observations from space, and will extend the retrieval of ocean optical properties to the ultra-violet, where they become very sensitive to detritus material and dissolved organic matter. It would also provide a complete description of the scattering and absorption properties of aerosol particles, as well as their size distribution and vertical distribution. Over land, the retrieved bidirectional reflectance function would allow a better classification of terrestrial vegetation and discrimination of surface types. The twin satellite concept, by providing stereoscopic capability, would offer the possibility to analyze the three-dimensional structure and radiative properties of cloud fields.

Anchorage, AK

NASA Technical Reports Server (NTRS)

2001-01-01

Anchorage, Alaska and Cook Inlet are seen in this 30 by 30 km (19 by 19 miles) sub-image, acquired May 12, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Orbiting at an altitude of 705 km (430 miles) on board NASA's Terra satellite, ASTER provides data at a resolution of 15 m (47 feet) and allows creation of this simulated natural color image. At the center of the image is the Ted Stevens Anchorage International Airport; in the upper right corner is Elmendorf Air Force Base. Dark green coniferous forests are seen in the northwest part of the image. A golf course, with its lush green fairways, is just south of the Air Force Base.

The image covers an area of 30 by 30 km, was acquired May 12, 2000, and is located at 61.2 degrees north latitude and 149.9 degrees west longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

Time-of-flight mass spectrometry of mineral volatilization: Toward direct composition analysis of shocked mineral vapor

NASA Astrophysics Data System (ADS)

Austin, Daniel E.; Shen, Andy H. T.; Beauchamp, J. L.; Ahrens, Thomas J.

2012-04-01

We have developed an orthogonal-acceleration time-of-flight mass spectrometer to study the volatiles produced when a mineral's shock-compressed state is isentropically released, as occurs when a shock wave, driven into the mineral by an impact, reflects upon reaching a free surface. The instrument is designed to use a gun or explosive-launched projectile as the source of the shock wave, impact onto a flange separating a poor vacuum and the high vacuum (10-7 Torr) interior of the mass spectrometer, and transmission of the shock wave through the flange to a mineral sample mounted on the high-vacuum side of the flange. The device extracts and analyzes the neutrals and ions produced from the shocked mineral prior to the possible occurrence of collateral instrument damage from the shock-inducing impact. The instrument has been tested using laser ablation of various mineral surfaces, and the resulting spectra are presented. Mass spectra are compared with theoretical distributions of molecular species, and with expected distributions from laser desorption.

Multibeam Laser Altimeter for Planetary Topographic Mapping

NASA Technical Reports Server (NTRS)

Garvin, J. B.; Bufton, J. L.; Harding, D. J.

1993-01-01

Laser altimetry provides an active, high-resolution, high-accuracy method for measurement of planetary and asteroid surface topography. The basis of the measurement is the timing of the roundtrip propagation of short-duration pulses of laser radiation between a spacecraft and the surface. Vertical, or elevation, resolution of the altimetry measurement is determined primarily by laser pulse width, surface-induced spreading in time of the reflected pulse, and the timing precision of the altimeter electronics. With conventional gain-switched pulses from solid-state lasers and nanosecond resolution timing electronics, submeter vertical range resolution is possible anywhere from orbital altitudes of approximately 1 km to altitudes of several hundred kilometers. Horizontal resolution is a function of laser beam footprint size at the surface and the spacing between successive laser pulses. Laser divergence angle and altimeter platform height above the surface determine the laser footprint size at the surface, while laser pulse repetition rate, laser transmitter beam configuration, and altimeter platform velocity determine the spacing between successive laser pulses. Multiple laser transmitters in a single laser altimeter instrument that is orbiting above a planetary or asteroid surface could provide across-track as well as along-track coverage that can be used to construct a range image (i.e., topographic map) of the surface. We are developing a pushbroom laser altimeter instrument concept that utilizes a linear array of laser transmitters to provide contiguous across-track and along-track data. The laser technology is based on the emerging monolithic combination of individual, 1-sq cm diode-pumped Nd:YAG laser pulse emitters. Details of the multi-emitter laser transmitter technology, the instrument configuration, and performance calculations for a realistic Discovery-class mission will be presented.

Updates from the MSL-RAD Experiment on the Mars Curiosity Rover

NASA Technical Reports Server (NTRS)

Zeitlin, Cary

2015-01-01

The MSL-RAD instrument continues to operate flawlessly on Mars. As of this writing, some 1040 sols (Martian days) of data have been successfully acquired. Several improvements have been made to the instrument's configuration, particularly aimed at enabling the analysis of neutral-particle data. The dose rate since MSL's landing in August 2012 has remained remarkably stable, reflecting the unusual and very weak solar maximum of Cycle 24. Only a few small SEP events have been observed by RAD, which is shielded by the Martian atmosphere. Gale Crater, where Curiosity landed, is 4.4 km below the mean surface of Mars, and the column depth of atmosphere above is approximately 20 g/sq cm, which provides significant attenuation of GCR heavy ions and SEPs. Recent analysis results will be presented, including updated estimates of the neutron contributions to dose and dose equivalent in cruise and on the surface of Mars.

General contamination criteria for optical surfaces. [instrument performance losses in spaceborne conditions

NASA Technical Reports Server (NTRS)

Bremer, J. C.

1982-01-01

Physical models are developed for establishing criteria to decide on the acceptable contamination level of optical devices in space-borne conditions. Optical systems can be degraded in terms of decreased throughput, i.e., transmissivity or reflectivity, or increases in the total integrated scatter (TIS). Performance losses can be caused by particulate accretion, molecular film accretion, and impact cratering. A quantitative relationship is defined for film thickness and loss of throughput. Formulas are also developed for cases where induced surface defects are larger than the desired viewing wavelengths, or smaller or of the same order of the observed wavelengths. The techniques are used to quantify the degradation of a VUV solar coronagraph, a VUV stellar telescope, and a solar cell due to TIS. Applications are projected for estimating the contamination sensitivity of specific instruments, assessing the contamination hazard from known particulates, or to define clean room standards.

Instrument for measurement of vacuum in sealed thin wall packets

DOEpatents

Kollie, T.G.; Thacker, L.H.; Fine, H.A.

1995-04-18

An instrument is disclosed for the measurement of vacuum within sealed packets, the packets having a wall that it can be deformed by the application of an external dynamic vacuum to an area thereof. The instrument has a detector head for placement against the deformable wall of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall with this deformation or lift monitored by the application of light as via a bifurcated light pipe. Retro-reflected light through the light pipe is monitored with a photo detector. A change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the dynamic vacuum applied through the head be to achieve this initiation of movement is equal to the vacuum within the packet. In a preferred embodiment a vacuum plate is placed beneath the packet to ensure that no deformation occurs on the reverse surface of the packet. A vacuum can be applied to a recess in this vacuum plate, the value of which can be used to calibrate the vacuum transducer in the detector head. 4 figs.

Instrument for measurement of vacuum in sealed thin wall packets

DOEpatents

Kollie, Thomas G.; Thacker, Louis H.; Fine, H. Alan

1995-01-01

An instrument for the measurement of vacuum within sealed packets 12, the packets 12 having a wall 14 that it can be deformed by the application of an external dynamic vacuum to an area thereof. The instrument has a detector head 18 for placement against the deformable wall 14 of the packet to apply the vacuum in a controlled manner to accomplish a limited deformation or lift of the wall 14, with this deformation or lift monitored by the application of light as via a bifurcated light pipe 20. Retro-reflected light through the light pipe is monitored with a photo detector 26. A change (e.g., a decrease) of retro-reflected light signals the wall movement such that the value of the dynamic vacuum applied through the head be to achieve this initiation of movement is equal to the vacuum within the packet 12. In a preferred embodiment a vacuum plate 44 is placed beneath the packet 12 to ensure that no deformation occurs on the reverse surface 16 of the packet. A vacuum can be applied to a recess in this vacuum plate, the value of which can be used to calibrate the vacuum transducer in the detector head.

A Manual Transportable Instrument Platform for Ground-Based Spectro-Directional Observations (ManTIS) and the Resultant Hyperspectral Field Goniometer System

PubMed Central

Buchhorn, Marcel; Petereit, Reinhold; Heim, Birgit

2013-01-01

This article presents and technically describes a new field spectro-goniometer system for the ground-based characterization of the surface reflectance anisotropy under natural illumination conditions developed at the Alfred Wegener Institute (AWI). The spectro-goniometer consists of a Manual Transportable Instrument platform for ground-based Spectro-directional observations (ManTIS), and a hyperspectral sensor system. The presented measurement strategy shows that the AWI ManTIS field spectro-goniometer can deliver high quality hemispherical conical reflectance factor (HCRF) measurements with a pointing accuracy of ±6 cm within the constant observation center. The sampling of a ManTIS hemisphere (up to 30° viewing zenith, 360° viewing azimuth) needs approx. 18 min. The developed data processing chain in combination with the software used for the semi-automatic control provides a reliable method to reduce temporal effects during the measurements. The presented visualization and analysis approaches of the HCRF data of an Arctic low growing vegetation showcase prove the high quality of spectro-goniometer measurements. The patented low-cost and lightweight ManTIS instrument platform can be customized for various research needs and is available for purchase.

Instrument pre-development activities for FLEX

NASA Astrophysics Data System (ADS)

Pettinato, L.; Fossati, E.; Coppo, P. M.; Taiti, A.; Labate, D.; Capanni, A.; Taccola, M.; Bézy, J. L.; Francois, M.; Meynart, R.; Erdmann, L.; Triebel, P.

2017-09-01

The FLuorescence Imaging Spectrometer (FLORIS) is the payload of the FLuorescence Explorer Mission (FLEX) of the European Space Agency. The mission objective is to perform quantitative measurements of the solar induced vegetation fluorescence to monitor photosynthetic activity. FLORIS works in a push-broom configuration and it is designed to acquire data in the 500-780 nm spectral range, with a sampling of 0.1 nm in the oxygen bands (759-769 nm and 686- 697 nm) and 0.5-2.0 nm in the red edge, chlorophyll absorption and Photochemical Reflectance Index bands. FLEX will fly in formation with Sentinel-3 to benefit of the measurements made by the Sentinel-3 instruments OLCI and SLSTR, particularly for cloud screening, proper characterization of the atmospheric state and determination of the surface temperature. The instrument concept is based on a common telescope and two modified Offner spectrometers with reflective concave gratings both for the High Resolution (HR) and Low Resolution (LR) spectrometers. In the frame of the instrument pre-development Leonardo Company (I) has built and tested an elegant breadboard of the instrument consisting of the telescope and the HR spectrometer. The development of the LR spectrometer is in charge of OHB System AG (D) and is currently in the manufacturing phase. The main objectives of the activity are: anticipate the development of the instrument and provide early risk retirement of critical components, evaluate the system performances such as imaging quality parameters, straylight, ghost, polarization sensitivity and environmental influences, verify the adequacy of critical tests such as spectral characterization and straylight, define and optimize instrument alignment procedures. Following a brief overview of the FLEX mission, the paper will cover the design and the development of the optics breadboard with emphasis on the results obtained during the tests and the lessons learned for the flight unit.

Ethylene glycol contamination effects on first surface aluminized mirrors

NASA Astrophysics Data System (ADS)

Dunlop, Patrick; Probst, Ronald G.; Evatt, Matthew; Reddell, Larry; Sprayberry, David

2016-07-01

The Dark Energy Spectroscopic Instrument (DESI) is under construction for installation on the Mayall 4 Meter telescope. The use of a liquid cooling system is proposed to maintain the DESI prime focus assembly temperature within ±1°C of ambient. Due to concerns of fluid deposition onto optical surfaces from possible leaks, systematic tests were performed of the effects on first surface aluminized mirrors of ethylene glycol and two other candidate coolants. Objective measurement of scattering and reflectivity was an important supplement to visual inspection. Rapid cleanup of a coolant spill followed by a hand wash of the mirror limited surface degradation to the equivalent of a few months of general environmental exposure. Prolonged exposure to corrosive coolants dissolved the aluminum, necesitating mirror recoating.

Evaluating lubricant performance by 3D profilometry of wear scars

NASA Astrophysics Data System (ADS)

Georgescu, C.; Deleanu, L.; Pirvu, C.

2016-08-01

Due to improvement in analysing surface texture and optical instruments for investigating the texture surface, the authors propose to evaluate the lubricant performance by analysing the change in several 3D parameters in comparison to an analysis on 2D profile. All the surface of the wear scar generated on the four ball machine is investigated and the conclusion is that from the tribological point of view, the 3D parameters reflect better the surface quality evolution after testing. Investigation was done on the wear scars generated on the three fixed balls, for five lubricants: a non-additivated transmission mineral oil (T90), two grades of rapeseed oil (coarse degummed and refined) and two grades of soybean oil (coarse and degummed).

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsioxane)-based phantoms

PubMed Central

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-01-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra. PMID:25983372

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsiloxane)-based phantoms

NASA Astrophysics Data System (ADS)

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-03-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra.

The Normalization of Surface Anisotropy Effects Present in SEVIRI Reflectances by Using the MODIS BRDF Method

NASA Technical Reports Server (NTRS)

Proud, Simon Richard; Zhang, Qingling; Schaaf, Crystal; Fensholt, Rasmus; Rasmussen, Mads Olander; Shisanya, Chris; Mutero, Wycliffe; Mbow, Cheikh; Anyamba, Assaf; Pak, Ed;

Petrology and Geochemistry of Mercury

NASA Astrophysics Data System (ADS)

Weider, Shoshana Z.

2018-04-01

Although having knowledge of a terrestrial planet's chemistry is fundamental to understanding the origin and composition of its rocks, until recently, the geochemistry of Mercury—the Solar System's innermost planet—was largely unconstrained. Without the availability of geological specimens from Mercury, studying the planet's surface and bulk composition relies on remote sensing techniques. Moreover, Mercury's proximity to the Sun makes it difficult to study with Earth/space-based telescopes, or with planetary probes. Indeed, to date, only NASA's Mariner 10 and MESSENGER missions have been sent to Mercury. The former made three "flyby" encounters of Mercury between 1974 and 1975, but did not carry any instrument to make geochemical or mineralogical measurements of the surface. Until the MESSENGER flyby and orbital campaigns (2008–2015), therefore, knowledge of Mercury's chemical composition was severely limited and consisted of only a few facts. For example, it has long been known that Mercury has the highest uncompressed density of all the terrestrial planets (and thus a disproportionately large iron core). In addition, Earth-based spectral reflectance observations indicated a dark surface, largely devoid of iron within silicate minerals. To improve understanding of Mercury's geochemistry, the MESSENGER payload included a suite of geochemical sensing instruments: namely the X-Ray Spectrometer, Gamma-Ray Spectrometer, and Neutron Spectrometer. Indeed, the datasets obtained from these instruments (as well as from other complementary instruments) during MESSENGER's 3.5-year orbital mission allow a much more complete picture of Mercury's geochemistry to be drawn, and quantitative abundance estimates for several major rock-forming elements in Mercury's crust are now available. Overall, the MESSENGER data reveal a surface that is rich in Mg, but poor in Al and Ca, compared with typical terrestrial and lunar crustal materials. Mercury's surface also contains high concentrations of the volatile elements Na, S, K, and Cl. Furthermore, the total surface Fe abundance is now known to be <2 wt%, and the planet's low reflectance is thought to be primarily caused by the presence of C (in graphite) at a level of >1 wt%. Such data are key to constraining models for Mercury's formation and early evolution. Large-scale spatial variations in the MESSENGER geochemical datasets have also led to the designation of several geochemical "terrains" across Mercury's surface, which do not always align to otherwise mapped geological regions. Based on the MESSENGER geochemical results, several recent petrological experiments and calculations have been, and continue to be, performed to study Mercury's surface mineralogy. The results show that there are substantial differences in the precise mineral compositions and abundances among the different terrains, but Mercury's surface appears to be dominated by Mg-rich olivines and pyroxenes, as well as plagioclase and sulphide phases. Depending on the classification scheme used, Mercury's ultramafic surface rocks can thus be described as similar in nature to terrestrial boninites, andesites, norites, or gabbros.

Depth Profilometry via Multiplexed Optical High-Coherence Interferometry

PubMed Central

Kazemzadeh, Farnoud; Wong, Alexander; Behr, Bradford B.; Hajian, Arsen R.

2015-01-01

Depth Profilometry involves the measurement of the depth profile of objects, and has significant potential for various industrial applications that benefit from non-destructive sub-surface profiling such as defect detection, corrosion assessment, and dental assessment to name a few. In this study, we investigate the feasibility of depth profilometry using an Multiplexed Optical High-coherence Interferometry MOHI instrument. The MOHI instrument utilizes the spatial coherence of a laser and the interferometric properties of light to probe the reflectivity as a function of depth of a sample. The axial and lateral resolutions, as well as imaging depth, are decoupled in the MOHI instrument. The MOHI instrument is capable of multiplexing interferometric measurements into 480 one-dimensional interferograms at a location on the sample and is built with axial and lateral resolutions of 40 μm at a maximum imaging depth of 700 μm. Preliminary results, where a piece of sand-blasted aluminum, an NBK7 glass piece, and an optical phantom were successfully probed using the MOHI instrument to produce depth profiles, demonstrate the feasibility of such an instrument for performing depth profilometry. PMID:25803289

Depth profilometry via multiplexed optical high-coherence interferometry.

PubMed

Kazemzadeh, Farnoud; Wong, Alexander; Behr, Bradford B; Hajian, Arsen R

2015-01-01

Depth Profilometry involves the measurement of the depth profile of objects, and has significant potential for various industrial applications that benefit from non-destructive sub-surface profiling such as defect detection, corrosion assessment, and dental assessment to name a few. In this study, we investigate the feasibility of depth profilometry using an Multiplexed Optical High-coherence Interferometry MOHI instrument. The MOHI instrument utilizes the spatial coherence of a laser and the interferometric properties of light to probe the reflectivity as a function of depth of a sample. The axial and lateral resolutions, as well as imaging depth, are decoupled in the MOHI instrument. The MOHI instrument is capable of multiplexing interferometric measurements into 480 one-dimensional interferograms at a location on the sample and is built with axial and lateral resolutions of 40 μm at a maximum imaging depth of 700 μm. Preliminary results, where a piece of sand-blasted aluminum, an NBK7 glass piece, and an optical phantom were successfully probed using the MOHI instrument to produce depth profiles, demonstrate the feasibility of such an instrument for performing depth profilometry.

X-Band Radar for Studies of Tropical Storms from High Altitude UAV Platform

NASA Technical Reports Server (NTRS)

Rodriquez, Shannon; Heymsfield, Gerald; Li, Lihua; Bradley, Damon

2007-01-01

The increased role of unmanned aerial vehicles (UAV) in NASA's suborbital program has created a strong interest in the development of instruments with new capabilities, more compact sizes and reduced weights than the instruments currently operated on manned aircrafts. There is a strong demand and tremendous potential for using high altitude UAV (HUAV) to carry weather radars for measurements of reflectivity and wind fields from tropical storms. Tropical storm genesis frequently occurs in ocean regions that are inaccessible to piloted aircraft due to the long off shore range and the required periods of time to gather significant data. Important factors of interest for the study of hurricane genesis include surface winds, profiled winds, sea surface temperatures, precipitation, and boundary layer conditions. Current satellite precipitation and surface wind sensors have resolutions that are too large and revisit times that are too infrequent to study this problem. Furthermore, none of the spaceborne sensors measure winds within the storm itself. A dual beam X-band Doppler radar, UAV Radar (URAD), is under development at the NASA Goddard Space Flight Center for the study of tropical storms from HUAV platforms, such as a Global Hawk. X-band is the most desirable frequency for airborne weather radars since these can be built in a relatively compact size using off-the-shelf components which cost significantly less than other higher frequency radars. Furthermore, X-band radars provide good sensitivity with tolerable attenuation in storms. The low-cost and light-weight URAD will provide new capabilities for studying hurricane genesis by analyzing the vertical structure of tropical cyclones as well as 3D reflectivity and wind fields in clouds. It will enable us to measure both the 3D precipitation structure and surface winds by using two antenna beams: fixed nadir and conical scanning each produced by its associated subsystem. The nadir subsystem is a magnetron based radar modified from a marine radar transceiver. It is capable of measuring vertical reflectivity and velocity profile while being a lower-cost, smaller size, and lighter weight version of the NASA ER-2 Doppler Radar (EDOP), which has flown during many NASA field campaigns and has provided valuable scientific information on hurricanes and weather phenomena. Unfortunately, EDOP is too large and heavy for most UAV platforms, but the experience gained with this instrument provided us with the heritage to build a new low-cost, light-weight, smaller system that will be capable of flying on UAVs. The scanning subsystem uses a TWT transmitter and provides measurements of 3D reflectivity/wind fields in-clouds. Conical scanning of the radar beam at a 35 deg. incidence angle will also provide information of surface wind speed and direction derived from the surface return over a single 360 deg. sweep. URAD data system will be Linux based with the capability of autonomous operation. It will utilize cutting edge digital receiver and FPGA technologies to carry out the data acquisition and processing tasks. High speed navigation data from the aircraft will also be captured and saved along with radar data for 3D measurement field reconstruction and aircraft motion correction. There is a tremendous potential for UAVs to carry down-looking weather radars for measurements of reflectivity, horizontal and vertical winds from tropical storms. With operation from HUAV platforms, the dual beam X-band radar under development promises to provide greatly needed information for tropical storm research.

INSTRUMENTS AND METHODS OF INVESTIGATION: Spectral and spectral-frequency methods of investigating atmosphereless bodies of the Solar system

NASA Astrophysics Data System (ADS)

Busarev, Vladimir V.; Prokof'eva-Mikhailovskaya, Valentina V.; Bochkov, Valerii V.

2007-06-01

A method of reflectance spectrophotometry of atmosphereless bodies of the Solar system, its specificity, and the means of eliminating basic spectral noise are considered. As a development, joining the method of reflectance spectrophotometry with the frequency analysis of observational data series is proposed. The combined spectral-frequency method allows identification of formations with distinctive spectral features, and estimations of their sizes and distribution on the surface of atmospherelss celestial bodies. As applied to investigations of asteroids 21 Lutetia and 4 Vesta, the spectral frequency method has given us the possibility of obtaining fundamentally new information about minor planets.

Surface Optical Property Measurements on Bark and Leaf Samples

DTIC Science & Technology

1990-12-31

individually positionable in sample measurement position. 100% Value Absolute, or in comparison to high-reflectance evaporated gold reference sample...evaporated gold on a smooth fused silica substrate. The absolute 100% measurement requires removing the sample from the measurement position and...choice is evaporated gold on a polished glass substrate. As- already noted, SOC uses two instruments to cover the full spectral region from 0.2 to 40.0

Satellite Validation: A Project to Create a Data-Logging System to Monitor Lake Tahoe

NASA Technical Reports Server (NTRS)

Roy, Rudy A.

2005-01-01

Flying aboard the satellite Terra, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an imaging instrument used to acquire detailed maps of Earth's surface temperature, elevation, emissivity, and reflectance. An automated site consisting of four buoys was established 6 years ago at Lake Tahoe for the validation of ASTERS thermal infrared data. Using Campbell CR23X Dataloggers, a replacement system to be deployed on a buoy was designed and constructed for the measurement of the lake's temperature profile, surrounding air temperature, humidity, wind direction and speed, net radiation, and surface skin temperature. Each Campbell Datalogger has been programmed to control, power, and monitor 14 different temperature sensors, a JPL-built radiometer, and an RM Young 32500 meteorological station. The logger communicates with the radiometer and meteorological station through a Campbell SDM-SIO4 RS232 serial interface, sending polling commands, and receiving filtered data back from the sensors. This data is then cataloged and sent back across a cellular modem network every hour to JPL. Each instrument is wired via a panel constructed with 18 individual plugs that allow for simple installation and expansion. Data sent back from the system are analyzed at JPL, where they are used to calibrate ASTER data.

Summary of the Results from the Lunar Orbiter Laser Altimeter after Seven Years in Lunar Orbit

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Mazarico, Erwan; Lemoine, Frank G.; Head, James W., III; Lucey, Paul G.; Aharonson, Oded; Robinson, Mark S.; Sun, Xiaoli;

High-resolution airborne imaging DOAS measurements of NO2 above Bucharest during AROMAT

NASA Astrophysics Data System (ADS)

Meier, Andreas Carlos; Schönhardt, Anja; Bösch, Tim; Richter, Andreas; Seyler, André; Ruhtz, Thomas; Constantin, Daniel-Eduard; Shaiganfar, Reza; Wagner, Thomas; Merlaud, Alexis; Van Roozendael, Michel; Belegante, Livio; Nicolae, Doina; Georgescu, Lucian; Burrows, John Philip

2017-05-01

In this study we report on airborne imaging DOAS measurements of NO2 from two flights performed in Bucharest during the AROMAT campaign (Airborne ROmanian Measurements of Aerosols and Trace gases) in September 2014. These measurements were performed with the Airborne imaging Differential Optical Absorption Spectroscopy (DOAS) instrument for Measurements of Atmospheric Pollution (AirMAP) and provide nearly gapless maps of column densities of NO2 below the aircraft with a high spatial resolution of better than 100 m. The air mass factors, which are needed to convert the measured differential slant column densities (dSCDs) to vertical column densities (VCDs), have a strong dependence on the surface reflectance, which has to be accounted for in the retrieval. This is especially important for measurements above urban areas, where the surface properties vary strongly. As the instrument is not radiometrically calibrated, we have developed a method to derive the surface reflectance from intensities measured by AirMAP. This method is based on radiative transfer calculation with SCIATRAN and a reference area for which the surface reflectance is known. While surface properties are clearly apparent in the NO2 dSCD results, this effect is successfully corrected for in the VCD results. Furthermore, we investigate the influence of aerosols on the retrieval for a variety of aerosol profiles that were measured in the context of the AROMAT campaigns. The results of two research flights are presented, which reveal distinct horizontal distribution patterns and strong spatial gradients of NO2 across the city. Pollution levels range from background values in the outskirts located upwind of the city to about 4 × 1016 molec cm-2 in the polluted city center. Validation against two co-located mobile car-DOAS measurements yields good agreement between the datasets, with correlation coefficients of R = 0.94 and R = 0.85, respectively. Estimations on the NOx emission rate of Bucharest for the two flights yield emission rates of 15.1 ± 9.4 and 13.6 ± 8.4 mol s-1, respectively.

Photometric properties of Titan's surface from Cassini VIMS: Relevance to titan's hemispherical albedo dichotomy and surface stability

USGS Publications Warehouse

Nelson, R.M.; Brown, R.H.; Hapke, B.W.; Smythe, W.D.; Kamp, L.; Boryta, M.D.; Leader, F.; Baines, K.H.; Bellucci, G.; Bibring, J.-P.; Buratti, B.J.; Capaccioni, F.; Cerroni, P.; Clark, R.N.; Combes, M.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Mennella, V.; Nicholson, P.D.; Sicardy, B.; Sotin, Christophe

2006-01-01

The Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini Saturn Orbiter returned spectral imaging data as the spacecraft undertook six close encounters with Titan beginning 7 July, 2004. Three of these flybys each produced overlapping coverage of two distinct regions of Titan's surface. Twenty-four points were selected on approximately opposite hemispheres to serve as photometric controls. Six points were selected in each of four reflectance classes. On one hemisphere each control point was observed at three distinct phase angles. From the derived phase coefficients, preliminary normal reflectances were derived for each reflectance class. The normal reflectance of Titan's surface units at 2.0178 ??m ranged from 0.079 to 0.185 for the most absorbing to the most reflective units assuming no contribution from absorbing haze. When a modest haze contribution of ??=0.1 is considered these numbers increase to 0.089-0.215. We find that the lowest three reflectance classes have comparable normal reflectance on either hemisphere. However, for the highest brightness class the normal reflectance is higher on the hemisphere encompassing longitude 14-65?? compared to the same high brightness class for the hemisphere encompassing 122-156?? longitude. We conclude that an albedo dichotomy observed in continental sized units on Titan is due not only to one unit having more areal coverage of reflective material than the other but the material on the brighter unit is intrinsically more reflective than the most reflective material on the other unit. This suggests that surface renewal processes are more widespread on Titan's more reflective units than on its less reflective units. We note that one of our photometric control points has increased in reflectance by 12% relative to the surrounding terrain from July of 2004 to April and May of 2005. Possible causes of this effect include atmospheric processes such as ground fog or orographic clouds; the suggestion of active volcanism cannot be ruled out. Several interesting circular features which resembled impact craters were identified on Titan's surface at the time of the initial Titan flyby in July of 2004. We traced photometric profiles through two of these candidate craters and attempted to fit these profiles to the photometric properties expected from model depressions. We find that the best-fit attempt to model these features as craters requires that they be unrealistically deep, approximately 70 km deep. We conclude that despite their appearance, these circular features are not craters, however, the possibility that they are palimpsests cannot be ruled out. We used two methods to test for the presence of vast expanses of liquids on Titan's surface that had been suggested to resemble oceans. Specular reflection of sunlight would be indicative of widespread liquids on the surface; we found no evidence of this. A large liquid body should also show uniformity in photometric profile; we found the profiles to be highly variable. The lack of specular reflection and the high photometric variability in the profiles across candidate oceans is inconsistent with the presence of vast expanses of flat-lying liquids on Titan's surface. While liquid accumulation may be present as small, sub-pixel-sized bodies, or in areas of the surface which still remain to be observed by VIMS, the presence of large ocean-sized accumulations of liquids can be ruled out. The Cassini orbital tour offers the opportunity for VIMS to image the same parts of Titan's surface repeatedly at many different illumination and observation geometries. This creates the possibility of understanding the properties of Titan's atmosphere and haze by iteratively adapting models to create a best fit to the surface reflectance properties. ?? 2006 Elsevier Ltd. All rights reserved.

NREL Solar Radiation Research Laboratory (SRRL): Baseline Measurement System (BMS); Golden, Colorado (Data)

DOE Data Explorer

Stoffel, T.; Andreas, A.

1981-07-15

The SRRL was established at the Solar Energy Research Institute (now NREL) in 1981 to provide continuous measurements of the solar resources, outdoor calibrations of pyranometers and pyrheliometers, and to characterize commercially available instrumentation. The SRRL is an outdoor laboratory located on South Table Mountain, a mesa providing excellent solar access throughout the year, overlooking Denver. Beginning with the basic measurements of global horizontal irradiance, direct normal irradiance and diffuse horizontal irradiance at 5-minute intervals, the SRRL Baseline Measurement System now produces more than 130 data elements at 1-min intervals that are available from the Measurement & Instrumentation Data Center Web site. Data sources include global horizontal, direct normal, diffuse horizontal (from shadowband and tracking disk), global on tilted surfaces, reflected solar irradiance, ultraviolet, infrared (upwelling and downwelling), photometric and spectral radiometers, sky imagery, and surface meteorological conditions (temperature, relative humidity, barometric pressure, precipitation, snow cover, wind speed and direction at multiple levels). Data quality control and assessment include daily instrument maintenance (M-F) with automated data quality control based on real-time examinations of redundant instrumentation and internal consistency checks using NREL's SERI-QC methodology. Operators are notified of equipment problems by automatic e-mail messages generated by the data acquisition and processing system. Radiometers are recalibrated at least annually with reference instruments traceable to the World Radiometric Reference (WRR).

The Lunar Regolith as a Remote Sensing Target for the Lunar Reconnaissance Orbiter (LRO)

NASA Technical Reports Server (NTRS)

Mendell, Wendell W.

2009-01-01

Of the 6 instruments and one technology demonstration aboard the LRO, only CRaTER does not measure some kind of interaction of particles with the lunar regolith. LEND detects neutron fluence that contains information about the number density of protons in the upper regolith. To infer the presence of protons, the PI must assume a model that characterizes the surface as a collection of atoms. Thus, LEND does not sense the regolith as a structure. LROC, LOLA, and LAMP sense reflected photons whose wavelength is much shorter than the median particle size in the regolith. The photons interact with electrons, either in atomic shells or in chemical bonds. These interactions occur within a nanometer or so of the surface of a particle. Thus, the particles are macroscopic objects and models of the reflection process invoke ray-tracing optics. DIVINER senses photons that have been emitted by surface particles through thermal phonon processes. The wavelengths detected by the instrument are of the same order as the median particle size, and the photons contain information on particle dimensions as well as the molecular bonds in the constituent compounds. The Mini-RF synthetic aperture radar generates and detects photons of a few centimeters wavelength that interact with the regolith as a dielectric, the dielectric properties of the particulate component being described through effective medium theory. However, the interaction with rocks (macroscopic objects of interest to geologists) can be characterized using Fresnel or Mie models of electromagnetic properties.

Retrieval of aerosol optical properties using MERIS observations: Algorithm and some first results.

PubMed

Mei, Linlu; Rozanov, Vladimir; Vountas, Marco; Burrows, John P; Levy, Robert C; Lotz, Wolfhardt

2017-08-01

The MEdium Resolution Imaging Spectrometer (MERIS) instrument on board ESA Envisat made measurements from 2002 to 2012. Although MERIS was limited in spectral coverage, accurate Aerosol Optical Thickness (AOT) from MERIS data are retrieved by using appropriate additional information. We introduce a new AOT retrieval algorithm for MERIS over land surfaces, referred to as eXtensible Bremen AErosol Retrieval (XBAER). XBAER is similar to the "dark-target" (DT) retrieval algorithm used for Moderate-resolution Imaging Spectroradiometer (MODIS), in that it uses a lookup table (LUT) to match to satellite-observed reflectance and derive the AOT. Instead of a global parameterization of surface spectral reflectance, XBAER uses a set of spectral coefficients to prescribe surface properties. In this manner, XBAER is not limited to dark surfaces (vegetation) and retrieves AOT over bright surface (desert, semiarid, and urban areas). Preliminary validation of the MERIS-derived AOT and the ground-based Aerosol Robotic Network (AERONET) measurements yield good agreement, the resulting regression equation is y = (0.92 × ± 0.07) + (0.05 ± 0.01) and Pearson correlation coefficient of R = 0.78. Global monthly means of AOT have been compared from XBAER, MODIS and other satellite-derived datasets.

Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) Data Products User's Guide

NASA Technical Reports Server (NTRS)

McPeters, Richard D.; Bhartia, P. K.; Krueger, Arlin J.; Herman, Jay R.; Schlesinger, Barry M.; Wellemeyer, Charles G.; Seftor, Colin J.; Jaross, Glen; Taylor, Steven L.; Swissler, Tom;

Delayed Shutters For Dual-Beam Molecular Epitaxy

NASA Technical Reports Server (NTRS)

Grunthaner, Frank J.; Liu, John L.; Hancock, Bruce

1989-01-01

System of shutters for dual-molecular-beam epitaxy apparatus delays start of one beam with respect to another. Used in pulsed-beam equipment for deposition of low-dislocation layers of InAs on GaAs substrates, system delays application of arsenic beam with respect to indium beam to assure proper stoichiometric proportions on newly forming InAs surface. Reflectance high-energy electron diffraction (RHEED) instrument used to monitor condition of evolving surface of deposit. RHEED signal used to time pulsing of molecular beams in way that minimizes density of defects and holds lattice constant of InAs to that of GaAs substrate.

Grape colour phenotyping: development of a method based on the reflectance spectrum.

PubMed

Rustioni, Laura; Basilico, Roberto; Fiori, Simone; Leoni, Alessandra; Maghradze, David; Failla, Osvaldo

2013-01-01

The colour of fruit is an important quality factor for cultivar classification and phenotyping techniques. Besides the subjective visual evaluation, new instruments and techniques can be used. This work aims at developping an objective, fast, easy and non-destructive method as a useful support for evaluating grapes' colour under different cultural and environmental conditions, as well as for breeding process and germplasm evaluation, supporting the plant characterization and the biodiversity preservation. Colours of 120 grape varieties were studied using reflectance spectra. The classification was realized using cluster and discriminant analysis. Reflectance of the whole berries surface was also compared with absorption properties of single skin extracts. A phenotyping method based on the reflectance spectra was developed, producing reliable colour classifications. A cultivar-independent index for pigment content evaluation has also been obtained. This work allowed the classification of the berry colour using an objective method. Copyright © 2013 John Wiley & Sons, Ltd.

Cryogenic Pupil Alignment Test Architecture for Aberrated Pupil Images

NASA Technical Reports Server (NTRS)

Bos, Brent; Kubalak, David A.; Antonille, Scott; Ohl, Raymond; Hagopian, John G.

2009-01-01

A document describes cryogenic test architecture for the James Webb Space Telescope (JWST) integrated science instrument module (ISIM). The ISIM element primarily consists of a mechanical metering structure, three science instruments, and a fine guidance sensor. One of the critical optomechanical alignments is the co-registration of the optical telescope element (OTE) exit pupil with the entrance pupils of the ISIM instruments. The test architecture has been developed to verify that the ISIM element will be properly aligned with the nominal OTE exit pupil when the two elements come together. The architecture measures three of the most critical pupil degrees-of-freedom during optical testing of the ISIM element. The pupil measurement scheme makes use of specularly reflective pupil alignment references located inside the JWST instruments, ground support equipment that contains a pupil imaging module, an OTE simulator, and pupil viewing channels in two of the JWST flight instruments. Pupil alignment references (PARs) are introduced into the instrument, and their reflections are checked using the instrument's mirrors. After the pupil imaging module (PIM) captures a reflected PAR image, the image will be analyzed to determine the relative alignment offset. The instrument pupil alignment preferences are specularly reflective mirrors with non-reflective fiducials, which makes the test architecture feasible. The instrument channels have fairly large fields of view, allowing PAR tip/tilt tolerances on the order of 0.5deg.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Overview

USGS Publications Warehouse

,

2008-01-01

The National Aeronautics and Space Administration (NASA) launched Terra, the Earth Observing System's (EOS) flagship satellite platform on December 18, 1999. The polar-orbiting Terra contains five remote sensing instruments, which enable the scientific study and analyses of global terrestrial processes and manifestations of global change. One of the five instruments is the multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), which is built in Japan by a consortium of government, industry, and research groups. It has three spectral bands in the visible near-infrared region (VNIR), six bands in the shortwave infrared region (SWIR), and five bands in the thermal infrared region (TIR), with 15-, 30-, and 90-meter ground resolutions, respectively. This combination of wide spectral coverage and high spatial resolution allows ASTER to discriminate among a wide variety of surface materials. The VNIR subsystem also has a backward-viewing telescope for high-resolution (15-meter) stereoscopic observation in the along-track direction, which facilitates the generation of digital elevation models (DEM).

Enhancing our Understanding of Snowfall Modes with Ground-Based Observations

NASA Astrophysics Data System (ADS)

Pettersen, C.; Kulie, M.; Petersen, W. A.; Bliven, L. F.; Wood, N.

2016-12-01

Snowfall can be broadly categorized into deep and shallow events based on the vertical distribution of the precipitating ice. Remotely sensed data refine these precipitation categories and aid in discerning the underlying macro- and microphysical mechanisms. The unique patterns in the remotely sensed instruments observations can potentially connect distinct modes of snowfall to specific processes. Though satellites can observe and recognize these patterns in snowfall, these measurements are limited - particularly in cases of shallow and light precipitation, as the snow may be too close to the surface or below the detection limits of the instrumentation. By enhancing satellite measurements with ground-based instrumentation, whether with limited-term field campaigns or long-term strategic sites, we can further our understanding and assumptions about different snowfall modes and how they are measured from spaceborne instruments. Presented are three years of data from a ground-based instrument suite consisting of a MicroRain Radar (MRR; optimized for snow events) and a Precipitation Imaging Package (PIP). These instruments are located at the Marquette, Michigan National Weather Service Weather Forecast Office to: a) use coincident meteorological measurements and observations to enhance our understanding of the thermodynamic drivers and b) showcase these instruments in an operational setting to enhance forecasts of shallow snow events. Three winters of MRR and PIP measurements are partitioned, based on meteorological surface observations, into two-dimensional histograms of reflectivity and particle size distribution data. These statistics improve our interpretation of deep versus shallow precipitation. Additionally, these statistical techniques are applied to similar datasets from Global Precipitation Measurement field campaigns for further insight into cloud and precipitation macro- and microphysical processes.

Synergistic Use of Spacecraft Telecom Links for Collection of Planetary Radar Science Data

NASA Astrophysics Data System (ADS)

Asmar, S.; Bell, D. J.; Chahat, N. E.; Decrossas, E.; Dobreva, T.; Duncan, C.; Ellliot, H.; Jin, C.; Lazio, J.; Miller, J.; Preston, R.

2017-12-01

On multiple solar system missions, radar instruments have been used to probe subsurface geomorphology and to infer chemical composition based on the dielectric signature derived from the reflected signal. Example spacecraft radar instruments are the 90 MHz CONSERT radar used to probe the interior of Comet 67P/Churyumov-Gerasimenko to a depth of 760m, the 20 MHz SHARAD instrument used to investigate Mars subsurface ice features from Mars orbit at depths of 300 to 3000 meters and the upcoming RIMFAX 150 MHz to 1200 MHz ground penetrating radar that will ride on the Mars 2020 rover investigating to a depth of 10m below the rover. In all of these applications, the radar frequency and signal structures were chosen to match science goals of desired depth of penetration and spatial resolution combined with the expected subsurface materials and structures below the surface. Recently, JPL investigators have proposed a new radar science paradigm, synergistic use of the telecom hardware and telecom links to collect bistatic or monostatic radar signatures. All JPL spacecraft employ telecom hardware that operates at UHF (400 MHz and 900 MHz), X-band (8 GHz) or Ka-band (32 GHz). Using existing open-loop record functions in these radios, the telecom hardware can be used to capture opportunistic radar signatures from telecom signals penetrating the surface and reflecting off of subsurface structures. This paper reports on telecom strategies, radar science applications and recent laboratory and field tests to demonstrate the effectiveness of telecom link based radar data collection.

Small business initiative -- Surface inspection machine infrared (SIMIR)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, G.L.; Beecroft, M.

This Cooperative Research and Development Agreement was a one year effort to make the surface inspection machine based on diffuse reflectance infrared spectroscopy (Surface Inspection Machine-Infrared, SIMIR), being developed by Surface Optics Corporation, perform to its highest potential as a practical, portable surface inspection machine. A secondary purpose was to evaluate applications that would serve both the private and the public sector. The design function of the SIMIR is to inspect sandblasted metal surfaces for cleanliness (stains). The system is also capable of evaluating graphite-resin systems for cure and heat damage, and for measuring the effects of moisture exposure onmore » lithium hydride, corrosion on uranium metal, and the constituents of and contamination on wood, paper, and fabrics. Surface Optics Corporation supplied LMES-Y12 with a prototype SOC-400 that was evaluated by LMES-Y12 and rebuilt by Surface Optics to achieve the desired performance. LMES-Y12 subsequently evaluated the instrument against numerous applications including determining part cleanliness at the Corpus Christi Army Depot, demonstrating the ability to detect plasticizers and other organic contaminants on metals to Pantex and LANL personnel, analyzed sandblasted metal contamination standards supplied by NASA-MSFC, and demonstrated to Lockheed Martin Tactical Aircraft, marietta, GA, for analyzing the paint applied to the F-22 Fighter. The instrument also demonstrated the analysis of yarn, fabric, and finish on the textiles.« less

Constraining the Global, Cloud-Free Reflected Solar Radiation Flux (RSRF) with Earth Observing System (EOS) Instruments

NASA Technical Reports Server (NTRS)

Kahn, Ralph

1999-01-01

Variations in the top-of-atmosphere reflected solar radiation flux, and in the factors that determine its value, are among the most important diagnostic indicators of changes in Earth's energy balance. Data from the MISR (Multi-angle Imaging SpectroRadiometer), MODIS (Moderate-resolution Imaging Spectroradiometer), SAGE-3 (Stratospheric Aerosol and Gas Experiment), and CERES (Clouds and Earth's Radiant Energy System), all of which are spacecraft instruments scheduled for launch in 1999, will each constrain pieces of the RSRF budget. Prior to launch, we are performing studies to determine the sensitivity of these instruments to key factors that influence the cloud-free RSRF: aerosol optical depth, aerosol scattering properties, and surface visible bidirectional reflectance distribution function (BRDF). We are also assessing the ability of the aggregate of instruments to constrain the overall RSRF budget under natural conditions over the globe. Consider the MISR retrieval of aerosols: according to simulations over cloud-free, calm ocean, for pure particles with natural ranges of optical depth, particle size, and indices of refraction, MISR can retrieve column aerosol optical depth for all but the darkest particles, to an uncertainty of at most 0.05 or 20%, whichever is larger, even if the particle properties are poorly known. For one common particle type, soot, constraints on the optical depth over dark ocean are very poor. The simulated measurements also allow us to distinguish spherical from non-spherical particles, to separate two to four compositional groups based on indices of refraction, and to identify three to four distinct size groups between 0. 1 and 2.0 microns characteristic radius at most latitudes. Based on these results, we expect to distinguish air masses containing different aerosol types, routinely and globally, with multiangle remote sensing data. Such results far exceed current satellite aerosol retrieval capabilities, which provide only total optical depth for assumed particle properties; the new information will complement in situ data, which give details about aerosol size and composition locally. In addition, our team is using climatologies that reflect the constraints each instrument is expected to provide, along with ERBE (Earth Radiation Budget Experiment) data and a radiative transfer code, to study overall sensitivity to RSRF, helping us prepare for similar studies with new data from the EOS-era instruments.

IR Spectropolarimeter Measurements of Planetary Materials

NASA Astrophysics Data System (ADS)

Brown, A. J.; Chenault, D. B.; Goldstein, D. H.

2006-12-01

The surfaces of rocky planetary bodies are chiefly ices and silicates. These materials have primary vibrational absorption bands at around 8-12 micons due to Si-O bending (silicates) and at around 3 microns due to H2O bending vibrations (water ices). These vibrations lie in the Thermal Infrared (TIR) region of the spectrum. This region is challenging for passive remote sensing methods due to the relatively low numbers of photons of this energy being reflected or emitted by cold planetary surfaces. We have tested an active reflectance and polarization sensor in the TIR region of the spectrum to determine the utility of an active sensing system for future rover missions to the Moon, asteroids, comets and airless satellites of the outer planets. Mars is also a possible target. A variety of samples were chosen in order to get an appreciation for the breadth of reseach required to characterize materials of different albedo, specularity and roughness. Two sulfate samples, gypsum and anhydrite, were chosen due to the strong possibility sulfates are present on Europa (Dalton, 2003) and the fact that gypsum and other sulfates have been detected on Mars (eg. Langevin, et. al 2005). The two other samples - labradorite and ilmenite, are known to be present on the Moon (Crown and Pieters, 1987, Raymond and Wenk, 1971). No ices were prepared for this study since the instrument was only able to operate in ambient conditions. The instrumental apparatus we used is capable of obtaining transmission or reflectance measurements and fully describing the complete polarization state of light reflected from a target surface (Goldstein and Chenault, 2002). We used the instrument to measure the reflectance of the samples, and obtained the polarization state in the form of a Mueller matrix as a function of wavelength. The results will be reported at this workshop and we will outline the direction of future investigations. We would like to acknowledge the assistance of Dr. Christian Grund at Ball Aerospace for his assistance on this project. References Crown, D.A. and Pieters, C.M. (1987) Spectral properties of plagioclase and pyroxene mixtures and the interpretation of lunar soil spectra, Icarus 72, 492-506 Dalton, J.B. (2003) Spectral Behavior of Hydrated Sulfate Salts: Implications for Europa Mission Spectrometer Design. Astrobiology 3(4) 771-784. Goldstein, D.H. and Chenault, D.B. (2002) Spectropolarimetric reflectometer, Optical Engineering, 41(5), 1013- 1020. Langevin, Y., et al. (2005) Sulfates in the North Polar Region of Mars Detected by OMEGA/Mars Express. Science, 307 (5715), 1584-1586. Raymond, K.N. and Wenk, H.R. (1971) Lunar ilmenite (Refinement of the crystal structure). Contributions to Mineralogy and Petrology 30(2) 135-140.

A low cost, simple, portable instrument for the measurement of infra-red reflectance of paints

NASA Astrophysics Data System (ADS)

Marson, F.

1982-05-01

The construction and design of a low cost, simple, portable infra-red reflectometer which can be used to estimate the reflectance of paint films in the 800 nm region is described. The infra-red reflectances of a range of lustreless, semigloss and gloss olive drab camouflage paints determined using this instrument are compared to those obtained using modified commercial equipment and to the reflectances measured at 800 nm using a Cary model 17 spectrophotometer. The new reflectometer was shown to be superior to the modified commercial instrument currently specified in Australian government paint specifications and to be capable of estimating the reflectance of olive drab paints to within about one per cent of the Cary derived reflectance values. The reflectance values for a range of 24 experimental coatings made with pigments of varying absorption in the infra-red region are used to illustrate the effect of the instrument's spectral response and the necessity of establishing a reliable working standard.

Validation of CERES/TERRA Data

NASA Technical Reports Server (NTRS)

Barkstrom, Bruce R.; Wieliski, Bruce A.; Smith, G. Louis; Lee, Robert B.; Priestley, Kory J.; Charlock, Thomas P.; Kratz, David P.

2000-01-01

There are 2 CERES scanning radiometer instruments aboard the TERRA spacecraft, one for mapping the solar radiation reflected from the Earth and the outgoing longwave radiation and the other for measuring the anisotropy of the radiation. Each CERES instrument has on-board calibration devices, which have demonstrated that from ground to orbit the broadband total and shortwave sensor responses maintained their ties to the International Temperature Scale of 1990 at precisions approaching radiances have been validated in orbit to +/- 0.3 % (0.3 W/sq m sr). Top of atmosphere fluxes are produced by use of the CERES data alone. By including data from other instruments, surface radiation fluxes and radiant fluxes within the atmosphere and at its top, shortwave and longwave, for both up and down components, are derived. Validation of these data products requires ground and aircraft measurements of fluxes and of cloud properties.

Classifying and monitoring water quality by use of satellite imagery

NASA Technical Reports Server (NTRS)

Scherz, J. P.; Crane, D. R.; Rogers, R. H.

1976-01-01

A technique is developed to eliminate the atmosphere and surface noise effects on Landsat signals of water bodies by manipulating the total signal from Landsat in such a way that only the volume reflectance is left as a residual. With the Landsat signal from a lake and the known volume reflectance for its clear water it is possible to eliminate the surface and atmospheric effects and have residual signals that are indicative only of the type and concentration of the material in other lakes. Laboratory values are more precise than field values because in the field one must contend with indirect skylight and wave action which can be removed in the laboratory. The volume reflectance of distilled water or a very clear lake approaching distilled water was determined in the laboratory by the use of the Bendix radiant power measuring instrument. The Bendix multispectral data analysis system provided a color categorized image of several hundred lakes in a Wisconsin area. These lakes were categorized for tannin and nontannin waters and for the degrees of algae, silt, weeds, and bottom effects present.

Processing of High Resolution, Multiparametric Radar Data for the Airborne Dual-Frequency Precipitation Radar APR-2

NASA Technical Reports Server (NTRS)

Tanelli, Simone; Meagher, Jonathan P.; Durden, Stephen L.; Im, Eastwood

2004-01-01

Following the successful Precipitation Radar (PR) of the Tropical Rainfall Measuring Mission, a new airborne, 14/35 GHz rain profiling radar, known as Airborne Precipitation Radar - 2 (APR-2), has been developed as a prototype for an advanced, dual-frequency spaceborne radar for a future spaceborne precipitation measurement mission. . This airborne instrument is capable of making simultaneous measurements of rainfall parameters, including co-pol and cross-pol rain reflectivities and vertical Doppler velocities, at 14 and 35 GHz. furthermore, it also features several advanced technologies for performance improvement, including real-time data processing, low-sidelobe dual-frequency pulse compression, and dual-frequency scanning antenna. Since August 2001, APR-2 has been deployed on the NASA P3 and DC8 aircrafts in four experiments including CAMEX-4 and the Wakasa Bay Experiment. Raw radar data are first processed to obtain reflectivity, LDR (linear depolarization ratio), and Doppler velocity measurements. The dataset is then processed iteratively to accurately estimate the true aircraft navigation parameters and to classify the surface return. These intermediate products are then used to refine reflectivity and LDR calibrations (by analyzing clear air ocean surface returns), and to correct Doppler measurements for the aircraft motion. Finally, the the melting layer of precipitation is detected and its boundaries and characteristics are identifIed at the APR-2 range resolution of 30m. The resulting 3D dataset will be used for validation of other airborne and spaceborne instruments, development of multiparametric rain/snow retrieval algorithms and melting layer characterization and statistics.

A hyperspectral imaging system for the evaluation of the human iris spectral reflectance

NASA Astrophysics Data System (ADS)

Di Cecilia, Luca; Marazzi, Francesco; Rovati, Luigi

2017-02-01

According to previous studies, the measurement of the human iris pigmentation can be exploited to detect certain eye pathological conditions in their early stage. In this paper, we propose an instrument and a method to perform hyperspectral quantitative measurements of the iris spectral reflectance. The system is based on a simple imaging setup, which includes a monochrome camera mounted on a standard ophthalmic microscope movement controller, a monochromator, and a flashing LED-based slit lamp. To assure quantitative measurements, the system is properly calibrated against a NIST reflectance standard. Iris reflectance images can be obtained in the spectral range 495-795 nm with a resolution of 25 nm. Each image consists of 1280 x 1024 pixels having a spatial resolution of 18 μm. Reflectance spectra can be calculated both from discrete areas of the iris and as the average of the whole iris surface. Preliminary results suggest that hyperspectral imaging of the iris can provide much more morphological and spectral information with respect to conventional qualitative colorimetric methods.

Are the Viking Lander sites representative of the surface of Mars?

NASA Technical Reports Server (NTRS)

Jakosky, B. M.; Christensen, P. R.

1986-01-01

Global remote sensing data of the Martian surface, collected by earth- and satellite-based instruments, are compared with data from the two Viking Landers to determine if the Lander data are representative of the Martian surface. The landing sites are boulder-strewn and feature abundant fine material and evidence of strong eolian forces. One site (VL-1) is in a plains-covered basin which is associated with volcanic activity; the VL-2 site is in the northern plains. Thermal IR, broadband albedo, color imaging and radar remote sensing has been carried out of the global Martian surface. The VL-1 data do not fit a general correlation observed between increases in 70-cm radar cross-sections and thermal inertia. A better fit is found with 12.5-cm cross sections, implying the presence of a thinner or discontinuous duricrust at the VL-1 site, compared to other higher-inertia regions. A thin dust layer is also present at the VL-2 site, based on the Lander reflectance data. The Lander sites are concluded to be among the three observed regions of anomalous reflectivity, which can be expected in low regions selected for the landings. Recommendations are furnished for landing sites of future surface probes in order to choose sites more typical of the global Martian surface.

Compact blackbody calibration sources for in-flight calibration of spaceborne infrared instruments

NASA Astrophysics Data System (ADS)

Scheiding, S.; Driescher, H.; Walter, I.; Hanbuch, K.; Paul, M.; Hartmann, M.; Scheiding, M.

2017-11-01

High-emissivity blackbodies are mandatory as calibration sources in infrared radiometers. Besides the requirements on the high spectral emissivity and low reflectance, constraints regarding energy consumption, installation space and mass must be considered during instrument design. Cavity radiators provide an outstanding spectral emissivity to the price of installation space and mass of the calibration source. Surface radiation sources are mainly limited by the spectral emissivity of the functional coating and the homogeneity of the temperature distribution. The effective emissivity of a "black" surface can be optimized, by structuring the substrate with the aim to enlarge the ratio of the surface to its projection. Based on the experiences of the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) calibration source MBB3, the results of the surface structuring on the effective emissivity are described analytically and compared to the experimental performance. Different geometries are analyzed and the production methods are discussed. The high-emissivity temperature calibration source features values of 0.99 for wavelength from 5 μm to 10 μm and emissivity larger than 0.95 for the spectral range from 10 μm to 40 μm.

Scanning imaging absorption spectrometer for atmospheric chartography

NASA Technical Reports Server (NTRS)

Burrows, John P.; Chance, Kelly V.

1991-01-01

The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY is an instrument which measures backscattered, reflected, and transmitted light from the earth's atmosphere and surface. SCIAMACHY has eight spectral channels which observe simultaneously the spectral region between 240 and 1700 nm and selected windows between 1940 and 2400 nm. Each spectral channel contains a grating and linear diode array detector. SCIAMACHY observes the atmosphere in nadir, limb, and solar and lunar occultation viewing geometries.

NIMBUS-7 CZCS. Coastal Zone Color Scanner Imagery for Selected Coastal Regions. North America - Europe. South America - Africa - Antarctica. Level 2 Photographic Product

NASA Technical Reports Server (NTRS)

1984-01-01

The Nimbus-7 Coastal Zone Color Scanner (CZCS) is the first spacecraft instrument devoted to the measurement of ocean color. Although instruments on other satellites have sensed ocean color, their spectral bands, spatial resolution, and dynamic range were optimized for geographical or meteorological use. In the CZCS, every parameter is optimized for use over water to the exclusion of any other type of sensing. The signal-to-noise ratios in the spectral channels sensing reflected solar radiance are higher than those required in the past. These ratios need to be high because the ocean is such a poor reflecting surface that the majority of the signal seen by the reflected energy channels at spacecraft altitudes is backscattered solar radiation from the atmosphere rather than reflected solar energy from the ocean. The CZCS is a conventional multichannel scanning radiometer utilizing a rotating plane mirror at a 45 deg angle to the optic axis of a Cassegrain telescope. The mirror scans 360 deg; however, only 80 deg of data centered on the spacecraft nadir is collected for ocean color measurements. Spatial resolution at spacecraft nadir is 825x825 m with some degradation at the edges of the scan swath. The useful swath width from a spacecraft altitude of 955 km is 1600 km.

Changes in Cloud and Aerosol Cover (1980-2006) from Reflectivity Time Series Using SeaWiFS, N7-TOMS, EP-TOMS, SBUV-2, and OMI Radiance Data

NASA Technical Reports Server (NTRS)

Herman, J. R.; Labow, G.; Hsu, N. C.; Larko, D.

2009-01-01

The amount of solar radiation reflected back to space or reaching the Earth's surface is primarily governed by the amount of cloud cover and, to a much lesser extent, by Rayleigh scatteri ng, aerosols, and various absorbing gases (e.g., O3, NO2, H2O). A useful measure of the effect of cloud plus aerosol cover is given by the amount that the 331 run Lambert Equivalent Reflectivity (LER) ofa scene exceeds the surfuce reflectivity for snow/ice-free scenes after Rayleigh scattering has been removed. Twenty-eight years of reflectivity data are available by overlapping data from several satellites: N7 (Nimbus 7, TOMS; 331 nm) from 1979 to 1992, SBUV-2 series (Solar Backscatter Ultraviolet, NOAA; 331 nm) 1985 to 2007, EP (Earth-Probe, TOMS; 331 nm) 1997 to 2006, SW (SeaWiFS; 412 nm) 1998 to 2006, and OMI (Ozone Measuring Instrument; 331 nm) 2004-2007. Only N7 and SW have a sufficiently long data record, Sun-synchronous orbits, and are adequately calibrated for long-term reflectivity trend estimation. Reflectivity data derived from these instruments and the SBUV-2 series are compared during the overlapping years. Key issues in determining long-term reflecti vity changes that have occurred during the N7 and SW operating periods are discussed. The largest reflectivity changes in the 412 nm SW LER and 331 nm EP LER are found to occur near the equator and are associated with a large EI Nino-Southern Oscillation event. Most other changes that have occurred are regional, such as the apparent cloud decrease over northern Europe since 1998. The fractional occurrence (fraction of days) of high reflectivity values over Hudson Bay, Canada (snow/ice and clouds) appears to have decreased when comparing reflectivity data from 1980 to 1992 to 1997-2006, suggesting shorter duration of ice in Hudson Bay since 1980.

Performance Assessment of the Mercury Laser Altimeter on MESSENGER from Mercury Orbit

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Cavanaugh, John F.; Neumann, Gregory A.; Mazarico, Edward M.

2009-01-01

The Mercury Laser Altimeter (MLA) is one of seven instruments on the MErcury Surface, Space ENvironment GEochemistry, and Ranging (MESSENGER) spacecraft,a mission in NASA's Discovery Program. MESSENGER was launched on August 3, 2004, and entered into orbit about Mercury on March 29, 2011. As of June 30, 2011 MLA started to collect science Measurements on March 29, 2011. As of June 30, 2011 MLA had accumulated about 3 million laser ranging measurements to the Mercury surface through one Mercury year, i.e ., one complete cycle of the spacecraft thermal environment. The average MLA laser output-pulse energy remained steady despite the harsh thermal environment, in which the laser bench temperature changed by as much as 15 C over a 35 min operating period . The laser beam-collimating telescope experienced a 30 C temperature swing over the same period, and the thermal cycling repeated every 12 hours. Nonetheless, MLA receiver optics appeared to be aligned and in focus throughout these temperature excursions. The maximum ranging distance of MLA was 1500 km at near-zero laser-beam incidence angle (and emission angle) and 600 km at 60 deg incidence angle. The MLA instrument performance in Mercury orbit has been consistent with the performance demonstrated during MESSENGER's Mercury flybys in January and October 2008 and during pre-launch testing. In addition to range measurements, MLA data are being used to estimate the surface reflectance of Mercury at 1064 nm wavelength, including regions of permanent shadow on the floors of polar craters. MLA also provides a measurement of the surface reflectance of sunlight at 1064 nm wavelength by its noise counters, for which output is a monotonic function of the background light.

Assessment of Satellite-Derived Surface Reflectances by NASA's CAR Airborne Radiometer over Railroad Valley, Nevada

NASA Technical Reports Server (NTRS)

Kharbouche, Said; Muller, Jan-Peter; Gatebe, Charles K.; Scanlon, Tracy; Banks, Andrew C.

2017-01-01

CAR (Cloud Absorption Radiometer) is a multi-angular and multi-spectral airborne radiometer instrument, whose radiometric and geometric characteristics are well calibrated and adjusted before and after each flight campaign. CAR was built by NASA (National Aeronautics and Space Administration) in 1984. On 16 May 2008, a CAR flight campaign took place over the well-known calibration and validation site of Railroad Valley in Nevada (38.504 deg N, 115.692 deg W).The campaign coincided with the overpasses of several key EO (Earth Observation) satellites such as Landsat-7, Envisat and Terra. Thus, there are nearly simultaneous measurements from these satellites and the CAR airborne sensor over the same calibration site. The CAR spectral bands are close to those of most EO satellites. CAR has the ability to cover the whole range of azimuth view angles and a variety of zenith angles depending on altitude and, as a consequence, the biases seen between satellite and CAR measurements due to both unmatched spectral bands and unmatched angles can be significantly reduced. A comparison is presented here between CARs land surface reflectance (BRF or Bidirectional Reflectance Factor) with those derived from Terra/MODIS (MOD09 and MAIAC), Terra/MISR, Envisat/MERIS and Landsat-7. In this study, we utilized CAR data from low altitude flights (approx. 180 m above the surface) in order to minimize the effects of the atmosphere on these measurements and then obtain a valuable ground-truth data set of surface reflectance. Furthermore, this study shows that differences between measurements caused by surface heterogeneity can be tolerated, thanks to the high homogeneity of the study site on the one hand, and on the other hand, to the spatial sampling and the large number of CAR samples. These results demonstrate that satellite BRF measurements over this site are in good agreement with CAR with variable biases across different spectral bands. This is most likely due to residual aerosol effects in the EO derived reflectances.

Unlocking the secrets of Venus surface mineralogy from orbit

NASA Astrophysics Data System (ADS)

Helbert, J.; Maturilli, A.; Ferrari, S.; Dyar, M. D.; Mueller, N. T.; Smrekar, S. E.; Koulen, J.

2016-12-01

The surface composition of a planet is a key to understand its interior and evolution. Proper interpretations of Venus surface observations in the near-infrared require a dedicated laboratory effort. The atmosphere of Venus dictates which spectral bands on the surface can be observed. This places severe constraints on the ability to identify rock-forming minerals. To complicate matters further, we cannot observe reflectance, as would be the standard at 1 mm. Observations are obtained on the night side where the thermal emission of the surface is measured directly. Finally, high surface temperatures are known to affect band positions of mineral spectra as expected from crystal field theory. Over the last year we have started at the Planetary Spectroscopy Laboratory (PSL) at DLR in Berlin, Germany to systematically build a spectral library for rocks and minerals under Venus thermal conditions. Using funding from the European Union as part of the EuroPlanet consortium we extended the spectral coverage for high temperature measurements down to 0.7 micron. The spectral library will be key in understanding and modeling differences in emissivity between ambient and Venus conditions, potentially enabling calibration transfer between datasets. We can show that the expected emissivity variation between felsic and mafic minerals would be observable even with the limited number of surface windows available. Furthermore the absolute emissivity derived from our laboratory measurements at Venus temperature match in situ reflectivity data from the Venera 9 and 10 landing sites in the same bands. Based on experience gained from using the VIRTIS instrument on Venus Express to observe the surface of Venus and the new high temperature laboratory experiments, we have developed the multi-spectral Venus Emissivity Mapper (VEM) to study the surface of Venus. VEM imposes minimal requirements on the spacecraft and mission design and can therefore be added to any future Venus mission. Ideally, the VEM instrument will be combined with a high-resolution radar mapper to provide accurate topographic information, as it will be the case for the proposed NASA Discovery VERITAS mission or the ESA EnVision M5 proposal.

Prototype Development and Evaluation of Self-Cleaning Concentrated Solar Power Collectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazumder, Malay K.; Horenstein, Mark N.; Joglekar, Nitin R.

The feasibility of integrating and retrofitting transparent electrodynamic screens (EDS) on the front surfaces of solar collectors was established as a means to provide active self-cleaning properties for parabolic trough and heliostat reflectors, solar panels, and Fresnel lenses. Prototype EDS-integrated solar collectors, including second-surface glass mirrors, metallized Acrylic-film mirrors, and dielectric mirrors, were produced and tested in environmental test chambers for removing the dust layer deposited on the front surface of the mirrors. The evaluation of the prototype EDS-integrated mirrors was conducted using dust and environmental conditions that simulate the field conditions of the Mojave Desert. Test results showed thatmore » the specular reflectivity of the mirrors could be maintained at over 90% over a wide range of dust loadings ranging from 0 to 10 g/m 2, with particle diameter varying from 1 to 50 μm. The measurement of specular reflectivity (SR) was performed using a D&S Reflectometer at wavelength 660 nm. A non-contact reflectometer was designed and constructed for rapid measurement of specular reflectivity at the same wavelength. The use of this new noncontact instrument allowed us to measure SR before and after EDS activation. Several EDS prototypes were constructed and evaluated with different electrode configurations, electrode materials, and encapsulating dielectric materials.« less

Ground-based automated radiometric calibration system in Baotou site, China

NASA Astrophysics Data System (ADS)

Wang, Ning; Li, Chuanrong; Ma, Lingling; Liu, Yaokai; Meng, Fanrong; Zhao, Yongguang; Pang, Bo; Qian, Yonggang; Li, Wei; Tang, Lingli; Wang, Dongjin

2017-10-01

Post-launch vicarious calibration method, as an important post launch method, not only can be used to evaluate the onboard calibrators but also can be allowed for a traceable knowledge of the absolute accuracy, although it has the drawbacks of low frequency data collections due expensive on personal and cost. To overcome the problems, CEOS Working Group on Calibration and Validation (WGCV) Infrared Visible Optical Sensors (IVOS) subgroup has proposed an Automated Radiative Calibration Network (RadCalNet) project. Baotou site is one of the four demonstration sites of RadCalNet. The superiority characteristics of Baotou site is the combination of various natural scenes and artificial targets. In each artificial target and desert, an automated spectrum measurement instrument is developed to obtain the surface reflected radiance spectra every 2 minutes with a spectrum resolution of 2nm. The aerosol optical thickness and column water vapour content are measured by an automatic sun photometer. To meet the requirement of RadCalNet, a surface reflectance spectrum retrieval method is used to generate the standard input files, with the support of surface and atmospheric measurements. Then the top of atmospheric reflectance spectra are derived from the input files. The results of the demonstration satellites, including Landsat 8, Sentinal-2A, show that there is a good agreement between observed and calculated results.

Descent imager/spectral radiometer (DISR) instrument aboard the Huygens probe of Titan

NASA Astrophysics Data System (ADS)

Tomasko, Martin G.; Doose, Lyn R.; Smith, Peter H.; Fellows, C.; Rizk, B.; See, C.; Bushroe, M.; McFarlane, E.; Wegryn, E.; Frans, E.; Clark, R.; Prout, M.; Clapp, S.

1996-10-01

The Huygen's probe of the atmosphere of Saturn's moon Titan includes one optical instrument sensitive to the wavelengths of solar radiation. The goals of this investigation fall into four broad areas: 1) the measurement of the profile of solar heating to support an improved understanding of the thermal balance of Titan and the role of the greenhouse effect in maintaining Titan's temperature structure; 2) the measurement of the size, vertical distribution, and optical properties of the aerosol and cloud particles in Titan's atmosphere to support studies of the origin, chemistry, life cycles, and role in the radiation balance of Titan played by these particles; 3) the composition of the atmosphere, particularly the vertical profile of the mixing ratio of methane, a condensable constituent in Titan's atmosphere; and 4) the physical state, composition, topography, and physical processes at work in determining the nature of the surface of Titan and its interaction with Titan's atmosphere. In order to accomplish these objectives, the Descent Imager/Spectral Radiometer (DISR) instrument makes extensive use of fiber optics to bring the light from several different sets of foreoptics to a silicon CCD detector, to a pair of InGaAs linear array detectors, and to three silicon photometers. Together these detectors permit DISR to make panoramic images of the clouds and surface of Titan, to measure the spectrum of upward and downward streaming sunlight from 350 to 1700 nm at a resolving power of about 200, to measure the reflection spectrum of >= 3000 locations on the surface, to measure the brightness and polarization of the solar aureole between 4 and 30 degrees from the sun at 500 and 935 nm, to separate the direct and diffuse downward solar flux at each wavelength measured, and to measure the continuous reflection spectrum of the ground between 850 and 1600 nm using an onboard lamp in the last 100 m of the descent.

Web-Enabled Optoelectronic Particle-Fallout Monitor

NASA Technical Reports Server (NTRS)

Lineberger, Lewis P.

2008-01-01

A Web-enabled optoelectronic particle- fallout monitor has been developed as a prototype of future such instruments that (l) would be installed in multiple locations for which assurance of cleanliness is required and (2) could be interrogated and controlled in nearly real time by multiple remote users. Like prior particle-fallout monitors, this instrument provides a measure of particles that accumulate on a surface as an indication of the quantity of airborne particulate contaminants. The design of this instrument reflects requirements to: Reduce the cost and complexity of its optoelectronic sensory subsystem relative to those of prior optoelectronic particle fallout monitors while maintaining or improving capabilities; Use existing network and office computers for distributed display and control; Derive electric power for the instrument from a computer network, a wall outlet, or a battery; Provide for Web-based retrieval and analysis of measurement data and of a file containing such ancillary data as a log of command attempts at remote units; and Use the User Datagram Protocol (UDP) for maximum performance and minimal network overhead.

Greenhouse Observations of the Stratosphere and Troposphere (GHOST): a novel shortwave infrared spectrometer developed for the Global Hawk unmanned aerial vehicle

NASA Astrophysics Data System (ADS)

Humpage, Neil; Boesch, Hartmut; Palmer, Paul; Parr-Burman, Phil; Vick, Andy; Bezawada, Naidu; Black, Martin; Born, Andy; Pearson, David; Strachan, Jonathan; Wells, Martyn

2014-05-01

The tropospheric distribution of greenhouse gases (GHGs) is dependent on surface flux variations, atmospheric chemistry and transport processes over a wide range of spatial and temporal scales. Errors in assumed atmospheric transport can adversely affect surface flux estimates inferred from surface, aircraft or satellite observations of greenhouse gas concentrations using inverse models. We present a novel, compact shortwave infrared spectrometer (GHOST) for installation on the NASA Global Hawk unmanned aerial vehicle to provide tropospheric column observations of CO2, CO, CH4, H2O and HDO over the ocean to address the need for large-scale, simultaneous, finely resolved measurements of key GHGs. These species cover a range of lifetimes and source processes, and measurements of their tropospheric columns will reflect the vertically integrated signal of their vertical and horizontal transport within the troposphere. The primary science objectives of GHOST are to: 1) provide observations which can be used to test atmospheric transport models; 2) validate satellite observations of GHG column observations over oceans, thus filling a critical gap in current validation capabilities; and 3) complement in-situ tropopause transition layer tracer observations from other instrumentation on board the Global Hawk to provide a link between upper and lower troposphere concentration measurements. The GHOST spectrometer system comprises a target acquisition module (TAM), a fibre slicer and feed system, and a multiple order spectrograph. The TAM design utilises a gimbal behind an optical dome, which is programmed to direct solar radiation reflected by the ocean surface into a fibre optic bundle. The fibre slicer and feed system then splits the light into the four spectral bands using order sorting filters. The fibres corresponding to each band are arranged with a small sideways offset to correctly centre each spectrum on the detector array. The spectrograph design is unique in that a single grating and detector is used for all four spectral bands. The whole instrument is housed within a liquid nitrogen cooled cryostat to ensure thermal stability. We summarise the GHOST project and its objectives, and will provide a detailed overview of the instrument concept, development, and proposed deployment on board the Global Hawk.

Towards GPS Surface Reflection Remote Sensing of Sea Ice Conditions

NASA Technical Reports Server (NTRS)

Komjathy, A.; Maslanik, J. A.; Zavorotny, V. U.; Axelrad, P.; Katzberg, S. J.

2000-01-01

This paper describes the research to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. The characteristics of the GPS signals and equipment afford the possibility of new measurements not possible with existing radar and passive microwave systems. In particular, the GPS receiving systems are small and light-weight, and as such are particularly well suited to be deployed on small aircraft or satellite platforms with minimal impact. Our preliminary models and experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and fresh-water ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska suggesting correlation between forward scattered GPS returns and RADARSAT backscattered signals.

Status of the Signals of Opportunity Airborne Demonstrator (SoOp-AD)

NASA Technical Reports Server (NTRS)

Garrison, Jim; Lin, Yao-Cheng; Piepmeier, Jeff; Knuble, Joe; Hersey, Ken; Du Toit, Cornelus; Joseph, Alicia; Deshpande, Manohar; Alikakos, George; O'Brien, Steve;

Development of a modified two-scale electromagnetic model simulating both active and passive microwave measurements: Comparison to data remotely sensed over the ocean

NASA Astrophysics Data System (ADS)

Boukabara, S. A.; Eymard, L.; Guillou, C.; Lemaire, D.; Sobieski, P.; Guissard, A.

2002-08-01

Spaceborne microwave remote sensing allows the determination of oceanic and atmospheric parameters. Operational payloads such as ERS-1 and ERS-2 and TOPEX/Poseidon as well as missions such as Jason (from NASA-Centre National d'Etudes) or Envisat (from the European Space Agency), have contained or contain paired microwave instruments looking at the nadir direction. This combination consists of microwave radiometers and a radar-altimeter. For the frequencies chosen in oceanographic satellite payloads, the active mode signal is mostly dependent on the surface state through its reflectivity and thus used for the near-surface wind speed retrieval. The active mode can also be attenuated by the atmosphere. On the other hand, the passive mode is related to the surface emissivity and the atmospheric radiation through the radiative transfer equation. Until now, the oceanic and atmospheric parameters have been retrieved separately, the latter being used to correct radar measurements. However, the reflectivity and the emissivity of a target are not independent quantities; hence the synergistic use of these two kinds of microwave measurements should allow one to improve the retrieval quality of the sea and atmosphere parameters. For this purpose, a unified model has been developed for the simulation of both the microwave backscattering coefficient σ° (active measurement) and the microwave emissivity, an important factor for the brightness temperature TB simulation, for every configuration (incidence angles, frequency, polarizations), taking into account the fact that the reflectivity and the emissivity are complementary to unity. The atmospheric absorption is computed following a widely used model from the literature. This paper gives a description and a first attempt of validation of this approach through a comparison with real data. The performance of the model is assessed by comparing the simulations to both brightness temperatures and backscattering coefficients from ERS-1 and TOPEX/Poseidon's instruments during the SEMAPHORE experiment, over a two-month period.

Field Geology/Processes

NASA Technical Reports Server (NTRS)

Allen, Carlton; Jakes, Petr; Jaumann, Ralf; Marshall, John; Moses, Stewart; Ryder, Graham; Saunders, Stephen; Singer, Robert

1996-01-01

The field geology/process group examined the basic operations of a terrestrial field geologist and the manner in which these operations could be transferred to a planetary lander. Four basic requirements for robotic field geology were determined: geologic content; surface vision; mobility; and manipulation. Geologic content requires a combination of orbital and descent imaging. Surface vision requirements include range, resolution, stereo, and multispectral imaging. The minimum mobility for useful field geology depends on the scale of orbital imagery. Manipulation requirements include exposing unweathered surfaces, screening samples, and bringing samples in contact with analytical instruments. To support these requirements, several advanced capabilities for future development are recommended. Capabilities include near-infrared reflectance spectroscopy, hyper-spectral imaging, multispectral microscopy, artificial intelligence in support of imaging, x ray diffraction, x ray fluorescence, and rock chipping.

Study of neutron shielding collimators for curved beamlines at the European Spallation Source

NASA Astrophysics Data System (ADS)

Santoro, V.; DiJulio, D. D.; Ansell, S.; Cherkashyna, N.; Muhrer, G.; Bentley, P. M.

2018-06-01

The European Spallation Source is being constructed in Lund, Sweden and is planned to be the world’s brightest pulsed spallation neutron source for cold and thermal neutron beams (≤ 1 eV). The facility uses a 2 GeV proton beam to produce neutrons from a tungsten target. The neutrons are then moderated in a moderator assembly consisting of both liquid hydrogen and water compartments. Surrounding the moderator are 22 beamports, which view the moderator’s outside surfaces. The beamports are connected to long neutron guides that transport the moderated neutrons to the sample position via reflections. As well as the desired moderated neutrons, fast neutrons coming directly from the target can find their way down the beamlines. These can create unwanted sources of background for the instruments. To mitigate such a kind of background, several instruments will use curved guides to lose direct line-of-sight (LoS) to the moderator and the target. In addition instruments can also use shielding collimators to reduce the amount of fast neutrons further traveling down the guide due to albedo reflections or streaming. Several different materials have been proposed for this purpose. We present the results of a study of different options for collimators and identify the optimal choices that balance cost, background and activation levels.

Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover

NASA Astrophysics Data System (ADS)

Korablev, Oleg I.; Dobrolensky, Yurii; Evdokimova, Nadezhda; Fedorova, Anna A.; Kuzmin, Ruslan O.; Mantsevich, Sergei N.; Cloutis, Edward A.; Carter, John; Poulet, Francois; Flahaut, Jessica; Griffiths, Andrew; Gunn, Matthew; Schmitz, Nicole; Martín-Torres, Javier; Zorzano, Maria-Paz; Rodionov, Daniil S.; Vago, Jorge L.; Stepanov, Alexander V.; Titov, Andrei Yu.; Vyazovetsky, Nikita A.; Trokhimovskiy, Alexander Yu.; Sapgir, Alexander G.; Kalinnikov, Yurii K.; Ivanov, Yurii S.; Shapkin, Alexei A.; Ivanov, Andrei Yu.

2017-07-01

ISEM (Infrared Spectrometer for ExoMars) is a pencil-beam infrared spectrometer that will measure reflected solar radiation in the near infrared range for context assessment of the surface mineralogy in the vicinity of the ExoMars rover. The instrument will be accommodated on the mast of the rover and will be operated together with the panoramic camera (PanCam), high-resolution camera (HRC). ISEM will study the mineralogical and petrographic composition of the martian surface in the vicinity of the rover, and in combination with the other remote sensing instruments, it will aid in the selection of potential targets for close-up investigations and drilling sites. Of particular scientific interest are water-bearing minerals, such as phyllosilicates, sulfates, carbonates, and minerals indicative of astrobiological potential, such as borates, nitrates, and ammonium-bearing minerals. The instrument has an ˜1° field of view and covers the spectral range between 1.15 and 3.30 μm with a spectral resolution varying from 3.3 nm at 1.15 μm to 28 nm at 3.30 μm. The ISEM optical head is mounted on the mast, and its electronics box is located inside the rover's body. The spectrometer uses an acousto-optic tunable filter and a Peltier-cooled InAs detector. The mass of ISEM is 1.74 kg, including the electronics and harness. The science objectives of the experiment, the instrument design, and operational scenarios are described.

Development and testing of the ultraviolet spectrometer for the Mariner Mars 1971 spacecraft

NASA Technical Reports Server (NTRS)

Farrar, J. W.

1972-01-01

The Mariner Mars 1971 ultraviolet spectrometer is an Ebert-Fastie type of the same basic design as the Mariner Mars 1969 instrument. Light enters the instrument and is split into component wavelengths by a scanning reflection diffraction grating. Two monochrometer exit slits allow the use of two independent photomultiplier tube sensors. Channel 1 has a spectral range of 1100 to 1692 A with a fixed gain, while Channel 2 has a spectral range of 1450 to 3528 A with an automatic step gain control, providing a dynamic range over the expected atmosphere and surface brightness of Mars. The scientific objectives, basic operation, design, testing, and calibration for the Mariner Mars 1971 ultraviolet spectrometer are described. The design discussion includes those modifications that were necessary to extend the lifetime of the instrument in order to accomplish the Mariner Mars 1971 mission objectives.

The spectroscopic, chemical, and photophysical properties of Martian soils and their analogs (MERC, phase 2)

NASA Technical Reports Server (NTRS)

Banin, Amos; Orenberg, James

1990-01-01

A series of variably proportioned iron/calcium smectite clays and iron loaded smectite clays containing iron up to the level found in the Martian soil were prepared from a typical montomorillonite clay using the Banin method. Evidence was obtained which supports the premise that these materials provide a unique and appropriate model soil system for the Martian surface in that they are consistent with the constraints imposed by the Viking surface elemental analysis, the reflectance data obtained by various spacecraft instruments and ground based telescopes, and the chemical reactivity measured by one of the Viking biology experiments, the Labeled Release (LR) experiment.

Dermoscopy-guided reflectance confocal microscopy of skin using high-NA objective lens with integrated wide-field color camera

NASA Astrophysics Data System (ADS)

Dickensheets, David L.; Kreitinger, Seth; Peterson, Gary; Heger, Michael; Rajadhyaksha, Milind

2016-02-01

Reflectance Confocal Microscopy, or RCM, is being increasingly used to guide diagnosis of skin lesions. The combination of widefield dermoscopy (WFD) with RCM is highly sensitive (~90%) and specific (~ 90%) for noninvasively detecting melanocytic and non-melanocytic skin lesions. The combined WFD and RCM approach is being implemented on patients to triage lesions into benign (with no biopsy) versus suspicious (followed by biopsy and pathology). Currently, however, WFD and RCM imaging are performed with separate instruments, while using an adhesive ring attached to the skin to sequentially image the same region and co-register the images. The latest small handheld RCM instruments offer no provision yet for a co-registered wide-field image. This paper describes an innovative solution that integrates an ultra-miniature dermoscopy camera into the RCM objective lens, providing simultaneous wide-field color images of the skin surface and RCM images of the subsurface cellular structure. The objective lens (0.9 NA) includes a hyperhemisphere lens and an ultra-miniature CMOS color camera, commanding a 4 mm wide dermoscopy view of the skin surface. The camera obscures the central portion of the aperture of the objective lens, but the resulting annular aperture provides excellent RCM optical sectioning and resolution. Preliminary testing on healthy volunteers showed the feasibility of combined WFD and RCM imaging to concurrently show the skin surface in wide-field and the underlying microscopic cellular-level detail. The paper describes this unique integrated dermoscopic WFD/RCM lens, and shows representative images. The potential for dermoscopy-guided RCM for skin cancer diagnosis is discussed.

Prime focus architectures for large space telescopes: reduce surfaces to save cost

NASA Astrophysics Data System (ADS)

Breckinridge, J. B.; Lillie, C. F.

2016-07-01

Conceptual architectures are now being developed to identify future directions for post JWST large space telescope systems to operate in the UV Optical and near IR regions of the spectrum. Here we show that the cost of optical surfaces within large aperture telescope/instrument systems can exceed $100M/reflection when expressed in terms of the aperture increase needed to over come internal absorption loss. We recommend a program in innovative optical design to minimize the number of surfaces by considering multiple functions for mirrors. An example is given using the Rowland circle imaging spectrometer systems for UV space science. With few exceptions, current space telescope architectures are based on systems optimized for ground-based astronomy. Both HST and JWST are classical "Cassegrain" telescopes derived from the ground-based tradition to co-locate the massive primary mirror and the instruments at the same end of the metrology structure. This requirement derives from the dual need to minimize observatory dome size and cost in the presence of the Earth's 1-g gravitational field. Space telescopes, however function in the zero gravity of space and the 1- g constraint is relieved to the advantage of astronomers. Here we suggest that a prime focus large aperture telescope system in space may have potentially have higher transmittance, better pointing, improved thermal and structural control, less internal polarization and broader wavelength coverage than Cassegrain telescopes. An example is given showing how UV astronomy telescopes use single optical elements for multiple functions and therefore have a minimum number of reflections.

A probabilistic approach to remote compositional analysis of planetary surfaces

USGS Publications Warehouse

Lapotre, Mathieu G.A.; Ehlmann, Bethany L.; Minson, Sarah E.

2017-01-01

Reflected light from planetary surfaces provides information, including mineral/ice compositions and grain sizes, by study of albedo and absorption features as a function of wavelength. However, deconvolving the compositional signal in spectra is complicated by the nonuniqueness of the inverse problem. Trade-offs between mineral abundances and grain sizes in setting reflectance, instrument noise, and systematic errors in the forward model are potential sources of uncertainty, which are often unquantified. Here we adopt a Bayesian implementation of the Hapke model to determine sets of acceptable-fit mineral assemblages, as opposed to single best fit solutions. We quantify errors and uncertainties in mineral abundances and grain sizes that arise from instrument noise, compositional end members, optical constants, and systematic forward model errors for two suites of ternary mixtures (olivine-enstatite-anorthite and olivine-nontronite-basaltic glass) in a series of six experiments in the visible-shortwave infrared (VSWIR) wavelength range. We show that grain sizes are generally poorly constrained from VSWIR spectroscopy. Abundance and grain size trade-offs lead to typical abundance errors of ≤1 wt % (occasionally up to ~5 wt %), while ~3% noise in the data increases errors by up to ~2 wt %. Systematic errors further increase inaccuracies by a factor of 4. Finally, phases with low spectral contrast or inaccurate optical constants can further increase errors. Overall, typical errors in abundance are <10%, but sometimes significantly increase for specific mixtures, prone to abundance/grain-size trade-offs that lead to high unmixing uncertainties. These results highlight the need for probabilistic approaches to remote determination of planetary surface composition.

Dermoscopy-guided reflectance confocal microscopy of skin using high-NA objective lens with integrated wide-field color camera.

PubMed

Dickensheets, David L; Kreitinger, Seth; Peterson, Gary; Heger, Michael; Rajadhyaksha, Milind

2016-02-01

Reflectance Confocal Microscopy, or RCM, is being increasingly used to guide diagnosis of skin lesions. The combination of widefield dermoscopy (WFD) with RCM is highly sensitive (~90%) and specific (~ 90%) for noninvasively detecting melanocytic and non-melanocytic skin lesions. The combined WFD and RCM approach is being implemented on patients to triage lesions into benign (with no biopsy) versus suspicious (followed by biopsy and pathology). Currently, however, WFD and RCM imaging are performed with separate instruments, while using an adhesive ring attached to the skin to sequentially image the same region and co-register the images. The latest small handheld RCM instruments offer no provision yet for a co-registered wide-field image. This paper describes an innovative solution that integrates an ultra-miniature dermoscopy camera into the RCM objective lens, providing simultaneous wide-field color images of the skin surface and RCM images of the subsurface cellular structure. The objective lens (0.9 NA) includes a hyperhemisphere lens and an ultra-miniature CMOS color camera, commanding a 4 mm wide dermoscopy view of the skin surface. The camera obscures the central portion of the aperture of the objective lens, but the resulting annular aperture provides excellent RCM optical sectioning and resolution. Preliminary testing on healthy volunteers showed the feasibility of combined WFD and RCM imaging to concurrently show the skin surface in wide-field and the underlying microscopic cellular-level detail. The paper describes this unique integrated dermoscopic WFD/RCM lens, and shows representative images. The potential for dermoscopy-guided RCM for skin cancer diagnosis is discussed.

The Expected Performance from the NASA OCO-2 Mission

NASA Astrophysics Data System (ADS)

Crisp, D.; Eldering, A.; Gunson, M. R.; Pollock, H.

2013-12-01

The NASA Orbiting Carbon Observatory-2 (OCO-2) will be launched from Vandenberg Air Force Base on a Delta-II 7320 launch vehicle as early as 1 July 2014. Once deployed in the 705-km Afternoon Constellation (A-Train), it will collect the measurements needed to estimate the column-averaged, atmospheric carbon dioxide (CO2) dry air mole fraction (XCO2) with improved precision, resolution, and coverage. The OCO-2 spacecraft carries and points a 3-channel, imaging, grating spectrometer that collects high resolution spectra of reflected sunlight in the 765 nm O2 A-band and in the CO2 bands centered near 1610 and 2060 nm. These spectral ranges overlap those used by the Japanese Greenhouse gases Observing SATellite (GOSAT) TANSO-FTS, the current standard in space-based XCO2 measurements. The OCO-2 instrument performance was extensively characterized during pre-launch testing, facilitating comparisons with the TANSO-FTS. OCO-2 has slightly lower spectral resolution, but the far wings of its instrument line shape functions decay more rapidly, such that it yields similar spectral contrast within O2 and CO2 bands. The instruments have similar continuum signal to noise ratios (SNR) for bright scenes, but the OCO-2 instrument has higher SNR at low light levels associated with absorption lines or dark surfaces. The OCO-2 spectrometers will collect 24 soundings per second, yielding up to a million soundings per day over the sunlit hemisphere. For routine operations, the OCO-2 instrument boresight will be pointed at the local nadir or at the 'glint spot,' where sunlight is specularly reflected from the surface. Nadir observations provide the best spatial resolution and are expected to yield more cloud-free soundings. Glint observations will have much better SNR over dark, ocean surfaces. The nominal plan is to alternate between glint and nadir observations on successive 16-day ground-track repeat cycles, so that the entire sunlit hemisphere is sampled in both modes at 32-day intervals. The instrument's rapid sampling, small (< 3 km2) sounding footprint, and high SNR, combined with the spacecraft's ability to point the instrument's aperture toward the glint spot over the entire sunlit hemisphere, are expected to provide more complete coverage of the ocean, cloudy regions, and high latitude continents. While the OCO-2 measurement capabilities provide opportunities to improve the XCO2 precision, resolution, and coverage, they also pose some formidable challenges for calibration, retrieval, and validation. To fully exploit this instrument's capabilities, the 24,000 spectral/spatial channels must be cross-calibrated to within a fraction of 1%. Substantial increases in algorithm speed and more efficient data screening techniques are needed to fully utilize the much larger data volume. Finally, a comprehensive validation program will be needed to ensure the accuracy of the retrieved XCO2 estimates. This presentation will summarize the OCO-2 measurement capabilities and observation strategies, and the methods adopted to address these challenges.

CLARREO Approach for Reference Intercalibration of Reflected Solar Sensors: On-Orbit Data Matching and Sampling

NASA Technical Reports Server (NTRS)

Roithmayr, Carlos; Lukashin, Constantine; Speth, Paul W.; Kopp, Gregg; Thome, Kurt; Wielicki, Bruce A.; Young, David F.

2014-01-01

The implementation of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission was recommended by the National Research Council in 2007 to provide an on-orbit intercalibration standard with accuracy of 0.3% (k = 2) for relevant Earth observing sensors. The goal of reference intercalibration, as established in the Decadal Survey, is to enable rigorous high-accuracy observations of critical climate change parameters, including reflected broadband radiation [Clouds and Earth's Radiant Energy System (CERES)], cloud properties [Visible Infrared Imaging Radiometer Suite (VIIRS)], and changes in surface albedo, including snow and ice albedo feedback. In this paper, we describe the CLARREO approach for performing intercalibration on orbit in the reflected solar (RS) wavelength domain. It is based on providing highly accurate spectral reflectance and reflected radiance measurements from the CLARREO Reflected Solar Spectrometer (RSS) to establish an on-orbit reference for existing sensors, namely, CERES and VIIRS on Joint Polar Satellite System satellites, Advanced Very High Resolution Radiometer and follow-on imagers on MetOp, Landsat imagers, and imagers on geostationary platforms. One of two fundamental CLARREO mission goals is to provide sufficient sampling of high-accuracy observations that are matched in time, space, and viewing angles with measurements made by existing instruments, to a degree that overcomes the random error sources from imperfect data matching and instrument noise. The data matching is achieved through CLARREO RSS pointing operations on orbit that align its line of sight with the intercalibrated sensor. These operations must be planned in advance; therefore, intercalibration events must be predicted by orbital modeling. If two competing opportunities are identified, one target sensor must be given priority over the other. The intercalibration method is to monitor changes in targeted sensor response function parameters: effective offset, gain, nonlinearity, optics spectral response, and sensitivity to polarization. In this paper, we use existing satellite data and orbital simulationmethods to determinemission requirements for CLARREO, its instrument pointing ability, methodology, and needed intercalibration sampling and data matching for accurate intercalibration of RS radiation sensors on orbit.

Phase-Shifted Laser Feedback Interferometry

NASA Technical Reports Server (NTRS)

Ovryn, Benjie

1999-01-01

Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.

GINA--a polarized neutron reflectometer at the Budapest Neutron Centre.

PubMed

Bottyán, L; Merkel, D G; Nagy, B; Füzi, J; Sajti, Sz; Deák, L; Endrőczi, G; Petrenko, A V; Major, J

2013-01-01

The setup, capabilities, and operation parameters of the neutron reflectometer GINA, the recently installed "Grazing Incidence Neutron Apparatus" at the Budapest Neutron Centre, are introduced. GINA, a dance-floor-type, constant-energy, angle-dispersive reflectometer is equipped with a 2D position-sensitive detector to study specular and off-specular scattering. Wavelength options between 3.2 and 5.7 Å are available for unpolarized and polarized neutrons. Spin polarization and analysis are achieved by magnetized transmission supermirrors and radio-frequency adiabatic spin flippers. As a result of vertical focusing by a five-element pyrolytic graphite monochromator, the reflected intensity from a 20 × 20 mm(2) sample has been doubled. GINA is dedicated to studies of magnetic films and heterostructures, but unpolarized options for non-magnetic films, membranes, and other surfaces are also provided. Shortly after its startup, reflectivity values as low as 3 × 10(-5) have been measured by the instrument. The instrument capabilities are demonstrated by a non-polarized and a polarized reflectivity experiment on a Si wafer and on a magnetic film of [(62)Ni/(nat)Ni](5) isotope-periodic layer composition. The facility is now open for the international user community. Its further development is underway establishing new sample environment options and spin analysis of off-specularly scattered radiation as well as further decreasing the background.

College Fjord, Prince Williams Sound

NASA Technical Reports Server (NTRS)

2000-01-01

The College Fjord with its glaciers was imaged by ASTER on June 24, 2000.

This image covers an area 20 kilometers (13 miles) wide and 24 kilometers (15 miles) long in three bands of the reflected visible and infrared wavelength region. College Fjord is located in Prince Williams Sound, east of Seward, Alaska. Vegetation is in red, and snow and ice are white and blue. Ice bergs calved off of the glaciers can be seen as white dots in the water. At the head of the fjord, Harvard Glacier (left) is one of the few advancing glaciers in the area; dark streaks on the glacier are medial moraines: rock and dirt that indicate the incorporated margins of merging glaciers. Yale Glacier to the right is retreating, exposing (now vegetated) bedrock where once there was ice. On the west edge of the fjord, several small glaciers enter the water. This fjord is a favorite stop for cruise ships plying Alaska's inland passage.

This image is located at 61.2 degrees north latitude and 147.7 degrees west longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

In situ NIR reflectance and LIBS measurements in lava tubes in preparation for future Mars missions

NASA Astrophysics Data System (ADS)

Leveille, R.; Sobron, P.

2017-12-01

The ATiLT (Astrobiology Training in Lava Tubes) program addresses Mars astrobiology exploration objectives by performing field work and instrumental analyses in lava tubes as high fidelity analog environments to putative lava tubes on Mars. The main field location for ATiLT is the Lava Beds National Monument (LABE) in Northern California. LABE is situated on the lower north flank of the Medicine Lake Volcano of the Cascade arc. This location features hundreds of caves, most of which are relatively shallow, typically well above the water table, reaching 20-45m below land surface at their maximum depth. Some LABE caves feature `cold sinks' where cold air sinks and becomes trapped in deeper cave passages, thus allowing perennial ice to accumulate despite above freezing surface temperatures. Several lava tube caves in LABE also contain seasonal or perennial ice accumulations, which makes them excellent analogs to Mars lava tubes where the presence of ice has been predicted. While lava tubes are very attractive systems to test hypotheses related to habitability and the possibility for life on Mars, at present there are no comprehensive in-situ instrument-driven characterizations of the mineralogy and geochemistry of lava tubes. ATiLT fills this gap by providing detailed, in-situ investigations with scientific instruments relevant to Mars exploration. Our aim is to help constrain future exploration targets on Mars and define future mission operations and requirements. For this purpose, in May 2017 we carried out a field campaign in several lava tubes at LABE. We deployed two miniature spectroscopic sensors suitable for dark, humid, cave conditions: NIR reflectance (1-5 μm) and LIBS (300-900 nm). The advantages of combining NIR reflectance and LIBS are evident: LIBS can reveal the relative concentration of major (and often trace) elements present in a bulk sample, whereas NIR reflectance yields information on the individual mineral species and their chemical and structural nature. We focused on secondary mineral precipitates and microbial mats, which are preserved in relatively stable physico-chemical conditions. This combination leads to formation and preservation of microbial biosignatures, or traces of life, in mineral deposits, which we detected and identified using our spectroscopic sensor suite.

VNIR spectroscopy of Mars Analogues with the ExoMars-Ma_Miss instrument .

NASA Astrophysics Data System (ADS)

De Angelis, S.; De Sanctis, M. C.; Ammannito, E.; Di Iorio, T.; Carli, C.; Frigeri, A.; Capria, M. T.; Federico, C.; Boccaccini, A.; Capaccioni, F.; Giardino, M.; Cerroni, P.; Palomba, E.; Piccioni, G.

The ExoMars 2018 mission will investigate the Martian surface environment with the aim of searching for eventual present or past signs of life, and to obtain a characterization of Martian soil and subsoil. The investigation of the near-surface environment and of the shallow subsurface with complementary techniques, will provide insights on the chemical and mineralogical composition, material grain size, the litotypes, the stratigraphy: these information will help us to understand the geologic processes that characterized the history of the Martian crust. The Ma_Miss (Mars Multispectral Imager for Subsurface Studies) instrument \\citep{coradini01} is a miniaturized visible and near-infrared spectrometer, integrated in the ExoMars Pasteur Rover Drill: it will acquire spectra of the borehole wall performed by the Drill, down to a depth up to two meters. Spectroscopic tests have been performed with the laboratory model (breadboard) on spectral targets and rock samples; furtherly, an activity of VNIR reflectance spectroscopy of Mars analogues has been begun with the breadboard to build a spectral library.

Characterization of a Low-Cost Multiparameter Sensor for Solar Resource Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habte, Aron M; Sengupta, Manajit; Andreas, Afshin M

Low-cost, multiparameter sensing and measurement devices enable cost-effective monitoring of the functional, operational reliability, efficiency, and resiliency of the electric grid. The National Renewable Research Laboratory (NREL) Solar Radiation Research Laboratory (SRRL), in collaboration with Arable Labs, Inc., deployed Arable Lab's Mark multiparameter sensor system. The device measures the downwelling and upwelling shortwave solar resource and longwave radiation, humidity, air temperature, and ground temperature. The system is also equipped with six downward-and upward-facing narrowband spectrometer channels that measure spectral radiation and surface spectral reflectance. This study describes the shortwave calibration, characterization, and validation of measurement accuracy of this instrument bymore » comparison with existing instruments that are part of NREL-SRRL's Baseline Measurement System.« less

Non-invasive identification of organic materials in historical stringed musical instruments by reflection infrared spectroscopy: a methodological approach.

PubMed

Invernizzi, Claudia; Daveri, Alessia; Vagnini, Manuela; Malagodi, Marco

2017-05-01

The analysis of historical musical instruments is becoming more relevant and the interest is increasingly moving toward the non-invasive reflection FTIR spectroscopy, especially for the analysis of varnishes. In this work, a specific infrared reflectance spectral library of organic compounds was created with the aim of identifying musical instrument materials in a totally non-invasive way. The analyses were carried out on pure organic compounds, as bulk samples and laboratory wooden models, to evaluate the diagnostic reflection mid-infrared (MIR) bands of proteins, polysaccharides, lipids, and resins by comparing reflection spectra before and after the KK correction. This methodological approach was applied to real case studies represented by four Stradivari violins and a Neapolitan mandolin.

Directional emissivity and reflectance: dependence on emergence angle

NASA Astrophysics Data System (ADS)

Maturilli, Alessandro; Helbert, Jörn

2017-04-01

Dependence of laboratory measured emissivity spectra from the emergence angle is a subject that still needs a lot of investigations to be fully understood. Most of the previous work is based on reflectance measurements in the VIS-NIR spectral region and on emissivity measurements of flat, solid surfaces (mainly metals), which are not directly applicable to the analysis of remote sensing data. Small bodies in particular (c.f. asteroids Itokawa and 1999JU3, the respective targets of JAXA Hayabusa and Hayabusa 2 missions) have a very irregular surface; hence the spectra from those rough surfaces are difficult to compare with laboratory spectra, where the observing geometry is always close to "nadir". At the Planetary Emissivity Laboratory (PEL) of the German Aerospace Center (DLR) we have set-up a series of spectral measurements to investigate this problem in the 1 - 16 µm spectral region. We measured the emissivity for two asteroid analog materials (meteorite Millbillillie and a synthetic enstatite) in vacuum and under purged air, at surface temperature of 100°C, for emergence angles of 0°, 5°, 10°, 20°, 30°, 40°, 50°, and 60°. Emissivity of a serpentinite slab, already used as calibration target for the MARA instrument on Hayabusa 2 MASCOT lander, and for the Thermal Infrared Imager (TIR) spectrometer on Hayabusa 2 orbiter was measured under the same conditions. Additionally a second basalt slab was measured. Both slabs were not measured at 5° inclination. Complementary reflectance measurements of the four samples were taken. For all the samples measured, we found that for calibrated emissivity, significant variations from values obtained at nadir (0° emergence angle) appear only for emergence angles ≥ 40°. Reflectance measurements confirmed this finding, showing the same trend of variations.

Photometric study of cometary analogs in the LOSSy laboratory at the University of Bern

NASA Astrophysics Data System (ADS)

Pommerol, A.; Thomas, N.; Jost, B.; Poch, O.

2014-07-01

We have set up the LOSSy laboratory (Laboratory for Outflow Studies of Sublimating Materials) to study the spectro-photometric properties of various analogs of planetary-object surfaces, with a special emphasis on icy samples and their evolution under simulated space conditions. This laboratory is currently equipped with two facilities: the PHIRE-2 radio-goniometer, designed to measure the bidirectional visible reflectance of samples under a wide range of geometries and the SCITEAS simulation chamber, designed to follow the evolution of icy samples subliming under low temperature and low pressure conditions by means of VIS-NIR hyperspectral imaging. We will report on the characterization of cometary analogs using both facilities. We produce these analogs by mixing in various proportions fine-grained ice, mineral and organic matter. Various preparation protocols have been defined to produce different textures of sample. Using the PHIRE-2 radio-goniometer, we are building a catalog of bidirectional reflectance data for various cometary analogs, varying by steps the different parameters susceptible to affect the reflectance phase function. In particular, we have recently upgraded the instrument to be able to characterize in detail the opposition effect by allowing measurements of the reflectance at very low phase angle. This laboratory dataset is intended to be used for the analysis of the data acquired by the OSIRIS imager onboard Rosetta. Using the SCITEAS simulation chamber, we have followed for 30 hours the evolution of a cometary analog placed under secondary vacuum (<10^{-6} mbar) and maintained at low temperature (170-200 K) for more than 30 hours. We analyzed the temporal evolution of the morphology and the photometry of the surface of the sample to identify which processes affect the surfaces of cometary nuclei during sublimation and how they affect their visible and near-infrared surface properties.

Coupled retrieval of aerosol properties and land surface reflection using the Airborne Multiangle SpectroPolarimetric Imager

NASA Astrophysics Data System (ADS)

Xu, Feng; van Harten, Gerard; Diner, David J.; Kalashnikova, Olga V.; Seidel, Felix C.; Bruegge, Carol J.; Dubovik, Oleg

2017-07-01

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) has been flying aboard the NASA ER-2 high-altitude aircraft since October 2010. In step-and-stare operation mode, AirMSPI acquires radiance and polarization data in bands centered at 355, 380, 445, 470*, 555, 660*, 865*, and 935 nm (* denotes polarimetric bands). The imaged area covers about 10 km by 11 km and is typically observed from nine viewing angles between ±66° off nadir. For a simultaneous retrieval of aerosol properties and surface reflection using AirMSPI, an efficient and flexible retrieval algorithm has been developed. It imposes multiple types of physical constraints on spectral and spatial variations of aerosol properties as well as spectral and temporal variations of surface reflection. Retrieval uncertainty is formulated by accounting for both instrumental errors and physical constraints. A hybrid Markov-chain/adding-doubling radiative transfer (RT) model is developed to combine the computational strengths of these two methods in modeling polarized RT in vertically inhomogeneous and homogeneous media, respectively. Our retrieval approach is tested using 27 AirMSPI data sets with low to moderately high aerosol loadings, acquired during four NASA field campaigns plus one AirMSPI preengineering test flight. The retrieval results including aerosol optical depth, single-scattering albedo, aerosol size and refractive index are compared with Aerosol Robotic Network reference data. We identify the best angular combinations for 2, 3, 5, and 7 angle observations from the retrieval quality assessment of various angular combinations. We also explore the benefits of polarimetric and multiangular measurements and target revisits in constraining aerosol property and surface reflection retrieval.

Comparison of narrow-band reflectance spectroscopy and tristimulus colorimetry for measurements of skin and hair color in persons of different biological ancestry.

PubMed

Shriver, M D; Parra, E J

2000-05-01

We have used two modern computerized handheld reflectometers, the Photovolt ColorWalk colorimeter (a tristimulus colorimeter; Photovolt, UMM Electronics, Indianapolis, IN) and the DermaSpectrometer (a specialized narrow-band reflectometer; Cortex Technology, Hadsund, Denmark), to compare two methods for the objective determination of skin and hair color. These instruments both determine color by measuring the intensity of reflected light of particular wavelengths. The Photovolt ColorWalk instrument does so by shining a white light and sensing the intensity of the reflected light with a linear photodiode array. The ColorWalk results can then be expressed in terms of several standard color systems, most importantly, the Commission International d'Eclairage (CIE) Lab system, in which any color can be described by three values: L*, the lightness; a*, the amount of green or red; and b*, the amount of yellow or blue. Instead of a white light and photodiodes, the DermaSpectrometer uses two light-emitting diodes (LEDs), one green and one red, to illuminate a surface, and then it records the intensity of the reflected light. The results of these readings are expressed in terms of erythema (E) and melanin (M) indices. We measured the unexposed skin of the inner upper arm, the exposed skin of the forehead, and the hair, of 80 persons using these two instruments. Since it is important for the application of these measures in anthropology that we understand their relationship across a number of different pigmentation levels, we sampled persons from several different groups, namely, European Americans (n = 55), African Americans (n = 9), South Asians (n = 7), and East Asians (n = 9). In these subjects, there is a very high correlation between L* and the M index for the inner arm (R(2) = 0.928, P < 0.001), the forehead (R(2) = 0.822, P < 0.001), and the hair (R(2) = 0.827, P < 0.001). The relationship between a* and the E index is complex and dependent on the pigmentation level. We conclude that while both types of instruments provide accurate estimates of pigment level in skin and hair, measurements using narrow-band instruments may be less affected by the greater redness of certain body sites due to increased vascularization. Copyright 2000 Wiley-Liss, Inc.

Tunable Reflective Spatial Heterodyne Spectrometer: A Technique for High Resolving Power, Wide Field Of View Observation Of Diffuse Emission Line Sources

NASA Astrophysics Data System (ADS)

Hosseini, Seyedeh Sona

The purpose of this dissertation is to discuss the need for new technology in broadband high-resolution spectroscopy based on the emerging technique of Spatial Heterodyne Spectroscopy (SHS) and to propose new solutions that should enhance and generalize this technology to other fields. Spectroscopy is a proven tool for determining compositional and other properties of remote objects. Narrow band imaging and low resolving spectroscopic measurements provide information about composition, photochemical evolution, energy distribution and density. The extension to high resolving power provides further access to temperature, velocity, isotopic ratios, separation of blended sources, and opacity effects. In current high resolving power devices, the drawback of high-resolution spectroscopy is bound to the instrumental limitations of lower throughput, the necessity of small entrance apertures, sensitivity, field of view, and large physical instrumental size. These limitations quickly become handicapping for observation of faint and/or extended targets and for spacecraft encounters. A technique with promise for the study of faint and extended sources at high resolving power is the reflective format of the Spatial Heterodyne Spectrometer (SHS). SHS instruments are compact and naturally tailored for both high etendue (defined in section 2.2.5) and high resolving power. In contrast, to achieve similar spectral grasp, grating spectrometers require large telescopes. For reference, SHS is a cyclical interferometer that produces Fizeau fringe pattern for all other wavelengths except the tuned wavelength. The large etendue obtained by SHS instruments makes them ideal for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables one to study the dynamical and physical properties described above. This document contains four chapters. Chapter 1, introduces a class of scientific targets that formerly have not been extensively observed due to absence of technical capabilities in current apparatus. We will introduce the concept of Special Heterodyne Spectrometers and address how it can fill the gap. Chapter 2 reports on the development of a new mathematical frame work for the Reflective SHS. Chapter 3 provides the details of the design and construction of a Tunable Reflective SHS at both UC Davis laboratory and Mt. Hamilton, Lick Observatory, CA. And chapter 4 contains an overview of the prospects of SHS instruments in future.

On-orbit solar calibrations using the Aqua Clouds and Earth's Radiant Energy System (CERES) in-flight calibration system

NASA Astrophysics Data System (ADS)

Wilson, Robert S.; Priestley, Kory J.; Thomas, Susan; Hess, Phillip

2009-08-01

The Clouds and the Earth's Radiant Energy System (CERES) spacecraft scanning thermistor bolometers were used to measure earth-reflected solar and earth-emitted longwave radiances, at satellite altitude. The bolometers measured the earth radiances in the broadband shortwave solar (0.3 - 5.0 micrometers) and total (0.3->100 micrometers) spectral bands as well as in the (8 - 12 micrometers) water vapor window spectral band over geographical footprints as small as 10 kilometers at nadir. In May 2002, the fourth and fifth sets of CERES bolometers were launched aboard the Aqua spacecraft. Ground vacuum calibrations defined the initial count conversion coefficients that were used to convert the bolometer output voltages into filtered earth radiances. The mirror attenuator mosaic (MAM), a solar diffuser plate, was built into the CERES instrument package calibration system in order to define in-orbit shifts or drifts in the sensor responses. The shortwave and total sensors are calibrated using the solar radiances reflected from the MAM's. Each MAM consists of baffle-solar diffuser plate systems, which guide incoming solar radiances into the instrument fields-of-view of the shortwave and total wave sensor units. The MAM diffuser reflecting type surface consists of an array of spherical aluminum mirror segments, which are separated by a Merck Black A absorbing surface, overcoated with silicon dioxide. Temperature sensors are located in each MAM plate and baffle. The CERES MAM wass designed to yield calibration precisions approaching .5 percent for the total and shortwave detectors. In this paper, the MAM solar calibration procedures are presented along with on-orbit results. Comparisons are also made between the Aqua,Terra and the Tropical Rainfall Measurement Mission (TRMM) CERES MAM solar calibrations.

Advances in Instrumental Techniques for Investigating Planetary Regolith Microstructure

NASA Astrophysics Data System (ADS)

Smythe, W. D.; Nelson, R. M.; Hapke, B. W.; Mannatt, K. S.; Eady, J.

2005-05-01

Introduction: The Opposition Effect (OE) is the non-linear increase in the intensity of light scattered from a surface as phase angle approaches 0o. It is seen in laboratory experiments and in remote sensing observations of planetary surfaces. Understanding the OE is a requirement to fitting photometric models which will produce meaningful results about regolith texture. Previously we have reported measurements from the JPL long arm goniometer and we have shown that this instrument enables us to distinguish between two distinct processes which create the opposition surges, Shadow Hiding (SHOE) and Coherent Backscattering (CBOE)(Hapke et al., 1993; Nelson, et al. 2000; 2002). SHOE arises because, as phase angle approaches zero, shadows cast by regolith grains on other grains become invisible to the observer. CBOE results from constructive interference between rays traveling the same path but in opposite directions. Our instrument was able to measure the phase curve using linearly and circularly polarized light which enabled us to distinguish between the singly and multiply scattered components in the reflected radiation. We were able to measure to angles as small at 0.05 degrees but our results were limited to maximum measurements of only 5 degrees. In the last year, we have extensively renovated the instrument so that measurements can be made from phase angles as small at 0.05 degrees to 20 degrees. This permits us to study the reflectance phase curve and the linear and circular polarization phase curves for phase angles at which important changes occur depending principally on the albedo, the particle size and the single scattering phase function of the material under investigation. We report the results from the first series of measurements of the refurbished instrument. The Experiment: We measured the angular scattering properties of 13 mixtures of Aluminum Oxide powders of the different particle size (0.1 to 30 microns). Along with the reflectance phase curve we measured the circular polarization ratio (CPR)-the ratio of the intensity of the light returned with the same helicity as the incident light to that with the opposite helicity. An increase in CPR with decreasing phase angle indicates increased multiple scattering and is consistent with CBOE (Hapke, 1993). Our results extended to a phase angle of 20 degrees are consistent with our earlier investigations which were limited to phase angles less than 5 degrees. We are also able to measure important parts of the linear and circular polarization phase curve which we had previously been unable to measure. Acknowledgement: This work was done at JPL and Pitt and was supported by NASA's PGG program. References: Hapke, 1993, Theory of Reflectance and Emittance Spectroscopy, Cambridge Hapke, B.W., R.M. Nelson, and W.D. Smythe, 1993, Science, 260, 509-511. Nelson, et al. 2000. Icarus, 147, 545-558. Nelson, et al., 2002, Planetary and Space Science, 50, 849-856.

The Effects of Reflective Activities on Skill Adaptation in a Work-Related Instrumental Learning Setting

ERIC Educational Resources Information Center

Roessger, Kevin M.

2014-01-01

In work-related instrumental learning contexts, the role of reflective activities is unclear. Kolb's experiential learning theory and Mezirow's transformative learning theory predict skill adaptation as an outcome. This prediction was tested by manipulating reflective activities and assessing participants' response and error rates during novel…

Investigating the Impact of Formal Reflective Activities on Skill Adaptation in a Work-Related Instrumental Learning Setting

ERIC Educational Resources Information Center

Roessger, Kevin M.

2013-01-01

In work-related, instrumental learning contexts the role of reflective activities is unclear. Kolb's (1985) experiential learning theory and Mezirow's transformative learning theory (2000) predict skill-adaptation as a possible outcome. This prediction was experimentally explored by manipulating reflective activities and assessing participants'…

Comprehensive Understanding for Vegetated Scene Radiance Relationships

NASA Technical Reports Server (NTRS)

Kimes, D. S.; Deering, D. W.

1984-01-01

The improvement of our fundamental understanding of the dynamics of directional scattering properties of vegetation canopies through analysis of field data and model simulation data is discussed. Directional reflectance distributions spanning the entire existance hemisphere were measured in two field studies; one using a Mark III 3-band radiometer and one using rapid scanning bidirectional field instrument called PARABOLA. Surfaces measured included corn, soybeans, bare soils, grass lawn, orchard grass, alfalfa, cotton row crops, plowed field, annual grassland, stipa grass, hard wheat, salt plain shrubland, and irrigated wheat. Some structural and optical measurements were taken. Field data show unique reflectance distributions ranging from bare soil to complete vegetation canopies. Physical mechanisms causing these trends are proposed based on scattering properties of soil and vegetation. Soil exhibited a strong backscattering peak toward the Sun. Complete vegetation exhibited a bowl distribution with the minimum reflectance near nadir. Incomplete vegetation canopies show shifting of the minimum reflectance off of nadir in the forward scattering direction because both the scattering properties or the vegetation and soil are observed.

The development and psychometrical evaluation of a set of instruments to evaluate the effectiveness of diabetes patient education.

PubMed

Duprez, Veerle; De Pover, Marleen; De Spiegelaere, Marc; Beeckman, Dimitri

2014-02-01

To develop a set of psychometrically sound instruments to assess knowledge, self-management and self-efficacy of diabetic patients. Furthermore, a survey to evaluate the satisfaction about diabetes education for patients was developed and tested. Treatment and secondary prevention of diabetes require a complex combination of care components. Patients' education has been accepted to improve diabetes knowledge, self-management and self-efficacy. Psychometrically sound instruments are needed to measure these patient-centred outcomes. Psychometric instrument validation. The first phase included a systematic literature review to develop the instruments. Content validity was evaluated using a two-round Delphi procedure involving diabetes experts. The content validity of the instruments was excellent. In a second phase, a convenience sample of 188 diabetic patients in two hospitals in one specific care region in Belgium participated in the psychometric evaluation. The criterion-related validity and internal consistency reliability were evaluated. The study produced a 21-item knowledge instrument, reflecting knowledge about 'glycemic control' and 'medico-social management aspects'. The self-management instrument included 32 statements, reflecting 'treatment and compliance' and 'general lifestyle'. The self-efficacy instrument included 30 items, reflecting 'nutrition', 'treatment' and 'regimen'. The patient satisfaction survey included 36 items, reflecting satisfaction about the relationship among the diabetes specialist, the diabetes educator, podiatrist and dietician. An instrument set with sound psychometric characteristics was developed to assess knowledge, self-management and self-efficacy of diabetic patients. Future studies should focus on the association between the instrument outcomes and clinical patient outcomes. The current instrument can support the design of educational interventions and training programmes and reduce inconsistencies in the information that patients receive. Furthermore, the instruments can be used for benchmarking the quality of diabetic patient education. © 2013 Blackwell Publishing Ltd.

VISdish: A new tool for canting and shape-measuring solar-dish facets.

PubMed

Montecchi, Marco; Cara, Giuseppe; Benedetti, Arcangelo

2017-06-01

Solar dishes allow us to obtain highly concentrated solar fluxes used to produce electricity or feed thermal processes/storage. For practical reasons, the reflecting surface is composed by a number of facets. After the dish assembly, facet-canting is an important task for improving the concentration of solar radiation around the focus-point, as well as the capture ratio at the receiver placed there. Finally, flux profile should be measured or evaluated to verify the concentration quality. All these tasks can be achieved by the new tool we developed at ENEA, named VISdish. The instrument is based on the visual inspection system (VIS) approach and can work in two functionalities: canting and shape-measurement. The shape data are entered in a simulation software for evaluating the flux profile and concentration quality. With respect to prior methods, VISdish offers several advantages: (i) simpler data processing, because light point-source and its reflections are univocally related, (ii) higher accuracy. The instrument functionality is illustrated through the preliminary experimental results obtained on the dish recently installed in ENEA-Casaccia in the framework of the E.U. project OMSoP.

Biooptical variability in the Greenland Sea observed with the Multispectral Airborne Radiometer System (MARS)

NASA Technical Reports Server (NTRS)

Mueller, James L.; Trees, Charles C.

1989-01-01

A site-specific ocean color remote sensing algorithm was developed and used to convert Multispectral Airborne Radiometer System (MARS) spectral radiance measurements to chlorophyll-a concentration profiles along aircraft tracklines in the Greenland Sea. The analysis is described and the results given in graphical or tabular form. Section 2 describes the salient characteristics and history of development of the MARS instrument. Section 3 describes the analyses of MARS flight segments over consolidated sea ice, resulting in a set of altitude dependent ratios used (over water) to estimate radiance reflected by the surface and atmosphere from total radiance measured. Section 4 presents optically weighted pigment concentrations calculated from profile data, and spectral reflectances measured in situ from the top meter of the water column; this data was analyzed to develop an algorithm relating chlorophyll-a concentrations to the ratio of radiance reflectances at 441 and 550 nm (with a selection of coefficients dependent upon whether significant gelvin presence is implied by a low ratio of reflectances at 410 and 550 nm). Section 5 describes the scaling adjustments which were derived to reconcile the MARS upwelled radiance ratios at 410:550 nm and 441:550 nm to in situ reflectance ratios measured simultaneously on the surface. Section 6 graphically presents the locations of MARS data tracklines and positions of the surface monitoring R/V. Section 7 presents stick-plots of MARS tracklines selected to illustrate two-dimensional spatial variability within the box covered by each day's flight. Section 8 presents curves of chlorophyll-a concentration profiles derived from MARS data along survey tracklines. Significant results are summarized in Section 1.

Archiving, processing, and disseminating ASTER products at the USGS EROS Data Center

USGS Publications Warehouse

Jones, B.; Tolk, B.; ,

2002-01-01

The U.S. Geological Survey EROS Data Center archives, processes, and disseminates Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data products. The ASTER instrument is one of five sensors onboard the Earth Observing System's Terra satellite launched December 18, 1999. ASTER collects broad spectral coverage with high spatial resolution at near infrared, shortwave infrared, and thermal infrared wavelengths with ground resolutions of 15, 30, and 90 meters, respectively. The ASTER data are used in many ways to understand local and regional earth-surface processes. Applications include land-surface climatology, volcanology, hazards monitoring, geology, agronomy, land cover change, and hydrology. The ASTER data are available for purchase from the ASTER Ground Data System in Japan and from the Land Processes Distributed Active Archive Center in the United States, which receives level 1A and level 1B data from Japan on a routine basis. These products are archived and made available to the public within 48 hours of receipt. The level 1A and level 1B data are used to generate higher level products that include routine and on-demand decorrelation stretch, brightness temperature at the sensor, emissivity, surface reflectance, surface kinetic temperature, surface radiance, polar surface and cloud classification, and digital elevation models. This paper describes the processes and procedures used to archive, process, and disseminate standard and on-demand higher level ASTER products at the Land Processes Distributed Active Archive Center.

Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces.

PubMed

Geminiani, Alessandro; Abdel-Azim, Tamer; Ercoli, Carlo; Feng, Changyong; Meirelles, Luiz; Massironi, Domenico

2014-07-01

Rotary and nonrotary cutting instruments are used to produce specific characteristics on the axial and marginal surfaces of teeth being prepared for fixed restorations. Oscillating instruments have been suggested for tooth preparation, but no comparative surface roughness data are available. To compare the surface roughness of simulated tooth preparations produced by oscillating instruments versus rotary cutting instruments with turbine and electric handpieces. Different grit rotary cutting instruments were used to prepare Macor specimens (n=36) with 2 handpieces. The surface roughness obtained with rotary cutting instruments was compared with that produced by oscillating cutting instruments. The instruments used were as follows: coarse, then fine-grit rotary cutting instruments with a turbine (group CFT) or an electric handpiece (group CFE); coarse, then medium-grit rotary cutting instruments with a turbine (group CMT) or an electric handpiece (group CME); coarse-grit rotary cutting instruments with a turbine handpiece and oscillating instruments at a low-power (group CSL) or high-power setting (group CSH). A custom testing apparatus was used to test all instruments. The average roughness was measured for each specimen with a 3-dimensional optical surface profiler and compared with 1-way ANOVA and the Tukey honestly significant difference post hoc test for multiple comparisons (α=.05). Oscillating cutting instruments produced surface roughness values similar to those produced by similar grit rotary cutting instruments with a turbine handpiece. The electric handpiece produced smoother surfaces than the turbine regardless of rotary cutting instrument grit. Rotary cutting instruments with electric handpieces produced the smoothest surface, whereas the same instruments used with a turbine and oscillating instruments achieved similar surface roughness. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Specular reflection on Titan: Liquids in Kraken Mare

USGS Publications Warehouse

Stephan, Katrin; Jaumann, Ralf; Brown, Robert H.; Soderblom, Jason M.; Soderblom, Laurence A.; Barnes, Jason W.; Sotin, Christophe; Griffith, Caitlin A.; Kirk, Randolph L.; Baines, Kevin H.; Buratti, Bonnie J.; Clark, Roger N.; Lytle, Dyer M.; Nelson, Robert M.; Nicholson, Phillip D.

2010-01-01

After more than 50 close flybys of Titan by the Cassini spacecraft, it has become evident that features similar in morphology to terrestrial lakes and seas exist in Titan's polar regions. As Titan progresses into northern spring, the much more numerous and larger lakes and seas in the north-polar region suggested by Cassini RADAR data, are becoming directly illuminated for the first time since the arrival of the Cassini spacecraft. This allows the Cassini optical instruments to search for specular reflections to provide further confirmation that liquids are present in these evident lakes. On July 8, 2009 Cassini VIMS detected a specular reflection in the north-polar region of Titan associated with Kraken Mare, one of Titan's large, presumed seas, indicating the lake's surface is smooth and free of scatterers with respect to the wavelength of 5 μm, where VIMS detected the specular signal, strongly suggesting it is liquid.

Vacuum deposition of iridium on large astronomical mirrors for use in the far UV

NASA Technical Reports Server (NTRS)

Herzig, H.; Spencer, R. S.

1982-01-01

An iridium coating has been deposited by electron-beam evaporation on a 0.91-m mirror which serves as the telescope primary of a sounding rocket instrument for far-UV spectrometry. The evaporation was carried out by applying 8 kV at 400 mA to the electron gun. Zone refined Ir of 99.99% purity was used, and the electron beam was electromagnetically swept over the surface of the evaporant. Under these conditions, deposition rates of 0.55 A/sec were achieved. The reflectance distribution achieved at a wavelength of 584 A was extremely uniform; the mean reflectance was 21.2% with a standard deviation of only 0.3%. This represents a substantial improvement over Al + MgF2 and Al + LiF coatings for applications involving multiple reflections and weak signals, as might be expected in a high-resolution spectrograph studying distant celestial objects.

Concorde sonic booms as an atmospheric probe.

PubMed

Balachandran, N K; Donn, W L; Rind, D H

1977-07-01

Infrasound generated by the sonic boom from the inbound Concorde supersonic transport is recorded at Palisades, New York (Lamont-Doherty Geological Observatory), as a series of impulses from distances varying from 165 to about 1000 kilometers. Refraction effects determined by temperature and wind conditions return the signal to the surface from both stratospheric (40 to 50 kilometers) and thermospheric (100 to 130 kilometers) levels. The frequency of the recorded signal is a function of the level of reflection; the frequency decreases from impulse stretching as the atmosphere becomes more rarified relative to the sound pressure. The horizontal trace velocity of the signal across the array of instruments is equal to the acoustic velocity at the reflection level. The sonic boom can thus be used to provide temperature-wind parameters at reflection levels estimated from the signal frequency. Daily observed signal variations have indicated significant variations in these parameters.

Finite element modelling of fibre Bragg grating strain sensors and experimental validation

NASA Astrophysics Data System (ADS)

Malik, Shoaib A.; Mahendran, Ramani S.; Harris, Dee; Paget, Mark; Pandita, Surya D.; Machavaram, Venkata R.; Collins, David; Burns, Jonathan M.; Wang, Liwei; Fernando, Gerard F.

2009-03-01

Fibre Bragg grating (FBG) sensors continue to be used extensively for monitoring strain and temperature in and on engineering materials and structures. Previous researchers have also developed analytical models to predict the loadtransfer characteristics of FBG sensors as a function of applied strain. The general properties of the coating or adhesive that is used to surface-bond the FBG sensor to the substrate has also been modelled using finite element analysis. In this current paper, a technique was developed to surface-mount FBG sensors with a known volume and thickness of adhesive. The substrates used were aluminium dog-bone tensile test specimens. The FBG sensors were tensile tested in a series of ramp-hold sequences until failure. The reflected FBG spectra were recorded using a commercial instrument. Finite element analysis was performed to model the response of the surface-mounted FBG sensors. In the first instance, the effect of the mechanical properties of the adhesive and substrate were modelled. This was followed by modelling the volume of adhesive used to bond the FBG sensor to the substrate. Finally, the predicted values obtained via finite element modelling were correlated to the experimental results. In addition to the FBG sensors, the tensile test specimens were instrumented with surface-mounted electrical resistance strain gauges.

Optical constants of electroplated gold from spectroscopic ellipsometry

NASA Astrophysics Data System (ADS)

Synowicki, R. A.; Herzinger, Craig M.; Hall, James T.; Malingowski, Andrew

2017-11-01

The optical constants of an opaque electroplated gold film (Laser Gold from Epner Technology Inc.), were determined by spectroscopic ellipsometry at room temperature over the spectral range from 0.142 μm in the vacuum ultraviolet to 36 μm in the infrared (photon energy range 0.034-8.75 eV). Data from two separate ellipsometer instruments covering different spectral ranges were analyzed simultaneously. The optical constants n&k or ε1&ε2 were determined by fitting an oscillator dispersion model combining Drude, Gaussian, and Sellmeier dispersion functions to the experimental Ψ and Δ data. The data were analyzed using both an ideal bulk substrate model and a simple overlayer model to account for surface roughness. Including the optical surface roughness layer improved ellipsometric data fits in the UV, and using a separate Drude function for the surface layer improved fits in the infrared. The surface roughness was also characterized using an Atomic Force Microscope. Using an oscillator dispersion model for the optical constants determined in this work allows for more realistic extrapolation to longer infrared wavelengths. Extending optical constants out to 50 μm and beyond is important for calibrating far-infrared reflectance measurements. Applications include understanding the thermal performance of cryogenic space-based instruments, such as the James Webb Space Telescope (JWST).

ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars

NASA Astrophysics Data System (ADS)

Johnson, Jeffrey R.; Bell, J. F.; Bender, S.; Blaney, D.; Cloutis, E.; DeFlores, L.; Ehlmann, B.; Gasnault, O.; Gondet, B.; Kinch, K.; Lemmon, M.; Le Mouélic, S.; Maurice, S.; Rice, M.; Wiens, R. C.

2015-03-01

The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400-840 nm) radiance from the martian surface. Using the onboard ChemCam calibration targets' housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65 mrad) and spectral sampling (<1 nm) visible/near-infrared reflectance spectra from a landed platform on Mars. Relative reflectance spectra of surface rocks and soils match those from orbital observations and multispectral data from the MSL Mastcam camera. Preliminary analyses of the band depths, spectral slopes, and reflectance ratios of the more than 2000 spectra taken during the first year of MSL operations demonstrate at least six spectral classes of materials distinguished by variations in ferrous and ferric components. Initial comparisons of ChemCam spectra to laboratory spectra of minerals and Mars analog materials demonstrate similarities with palagonitic soils and indications of orthopyroxene in some dark rocks. Magnesium-rich "raised ridges" tend to exhibit distinct near-infrared slopes. The ferric absorption downturn typically found for martian materials at <600 nm is greatly subdued in brushed rocks and drill tailings, consistent with their more ferrous nature. Calcium-sulfate veins exhibit the highest relative reflectances observed, but are still relatively red owing to the effects of residual dust. Such dust is overall less prominent on rocks sampled within the "blast zone" immediately surrounding the landing site. These samples were likely affected by the landing thrusters, which partially removed the ubiquitous dust coatings. Increased dust coatings on the calibration targets during the first year of the mission were documented by the ChemCam passive measurements as well. Ongoing efforts to model and correct for this dust component should improve calibration of the relative reflectance spectra. This will be useful as additional measurements are acquired during the rover's future examinations of hematite-, sulfate-, and phyllosilicate-bearing materials near the base of Mt. Sharp that are spectrally active in the 400-840 nm region.

Thermal-infrared spectral observations of geologic materials in emission

NASA Technical Reports Server (NTRS)

Christensen, Philip R.; Luth, Sharon J.

1987-01-01

The thermal-infrared spectra of geologic materials in emission were studied using the prototype Thermal Emission Spectrometer (TES). A variety of of processes and surface modifications that may influence or alter the spectra of primary rock materials were studied. It was confirmed that thermal emission spectra contain the same absorption features as those observed in transmission and reflection spectra. It was confirmed that the TES instrument can be used to obtain relevant spectra for analysis of rock and mineral composition.

Pluto's Far Ultraviolet Spectrum and Airglow Emissions

NASA Astrophysics Data System (ADS)

Steffl, A.; Schindhelm, E.; Kammer, J.; Gladstone, R.; Greathouse, T. K.; Parker, J. W.; Strobel, D. F.; Summers, M. E.; Versteeg, M. H.; Ennico Smith, K.; Hinson, D. P.; Linscott, I.; Olkin, C.; Parker, A. H.; Retherford, K. D.; Singer, K. N.; Tsang, C.; Tyler, G. L.; Weaver, H. A., Jr.; Woods, W. W.; Young, L. A.; Stern, A.

2015-12-01

The Alice far ultraviolet spectrograph on the New Horizons spacecraft is the second in a family of six instruments in flight on, or under development for, NASA and ESA missions. Here, we present initial results from the Alice observations of Pluto during the historic flyby. Pluto's far ultraviolet spectrum is dominated by sunlight reflected from the surface with absorption by atmospehric constituents. We tentatively identify C2H2 and C2H4 in Pluto's atmosphere. We also present evidence for weak airglow emissions.

Nickel-Phosphorous Development for Total Solar Irradiance Measurement

NASA Astrophysics Data System (ADS)

Carlesso, F.; Berni, L. A.; Vieira, L. E. A.; Savonov, G. S.; Nishimori, M.; Dal Lago, A.; Miranda, E.

2017-10-01

The development of an absolute radiometer instrument is currently a effort at INPE for TSI measurements. In this work, we describe the development of black Ni-P coatings for TSI radiometers absorptive cavities. We present a study of the surface blackening process and the relationships between morphological structure, chemical composition and coating absorption. Ni-P deposits with different phosphorous content were obtained by electroless techniques on aluminum substrates with a thin zincate layer. Appropriate phosphorus composition and etching parameters process produce low reflectance black coatings.

Spectrometer ISEM for ExoMars-2020 space mission

NASA Astrophysics Data System (ADS)

Dobrolenskiy, Y. S.; Korablev, O. I.; Fedorova, A. A.; Mantsevich, S. N.; Kalinnikov, Y. K.; Vyazovetskiy, N. A.; Titov, A. Y.; Stepanov, A. V.; Sapgir, A. G.; Alexandrov, K. V.; Evdokimova, N. A.; Kuzmin, R. O.

2017-09-01

Robust design, small dimensions and mass, the absence of moving parts in acousto-optic tunable filters (AOTFs) make them popular for space applications. Here we introduce a pencil-beam near-infrared AOTF-based spectrometer ISEM for context assessment of the surface mineralogy in the vicinity of a planetary probe or a rover analyzing the reflected solar radiation in the near infrared range. The ISEM (Infrared Spectrometer for ExoMars) instrument is to be deployed on the mast of ExoMars Rover planned for launch in 2020.

Payload Design for the Lunar Flashlight Mission

NASA Technical Reports Server (NTRS)

Cohen, B. A.; Hayne, P. O.; Greenhagen, B. T.; Paige, D. A.; Camacho, J. M.; Crabtree, K.; Paine, C.; Sellar, G.

2017-01-01

Recent reflectance data from LRO (Lunar Reconnaissance Orbiter) instruments suggest water ice and other volatiles may be present on the surface in lunar permanently shadowed regions, though the detection is not yet definitive. Understanding the composition, quantity, distribution, and form of water and other volatiles associated with lunar permanently shadowed regions (PSRs) is identified as a NASA Strategic Knowledge Gap (SKG). These polar volatile deposits are also scientifically interesting, having the potential to reveal important information about the delivery of water to the Earth-Moon system.

Lunar Flashlight: Illuminating the Lunar South Pole

NASA Technical Reports Server (NTRS)

Hayne, P. O.; Greenhagen,, B. T.; Paige, D. A.; Camacho, J. M.; Cohen, B. A.; Sellar, G.; Reiter, J.

2016-01-01

Recent reflectance data from LRO instruments suggest water ice and other volatiles may be present on the surface in lunar permanentlyshadowed regions, though the detection is not yet definitive. Understanding the composition, quantity, distribution, and form of water and other volatiles associated with lunar permanently shadowed regions (PSRs) is identified as a NASA Strategic Knowledge Gap (SKG) for Human Exploration. These polar volatile deposits are also scientifically interesting, having the potential to reveal important information about the delivery of water to the Earth- Moon system.

Lunar Flashlight: Illuminating the Moon's South Pole

NASA Technical Reports Server (NTRS)

Hayne, P. O.; Cohen, B. A.; Greenhagen, B. T.; Paige, D. A.; Camacho, J. M.; Sellar, R. G.; Reiter, J.

2016-01-01

Recent reflectance data from LRO instruments suggest water ice and other volatiles may be present on the surface in lunar permanently shadowed regions, though the detection is not yet definitive. Understanding the composition, quantity, distribution, and form of water and other volatiles associated with lunar permanently shadowed regions (PSRs) is identified as a NASA Strategic Knowledge Gap (SKG) for Human Exploration. These polar volatile deposits are also scientifically interesting, having the potential to reveal important information about the delivery of water to the Earth-Moon system.

Space Weathering: Laboratory Analyses and In-Situ Instrumentation

NASA Technical Reports Server (NTRS)

Bentley, M. S.; Ball, A. J.; Dyar, M. D.; Pieters, C. M.; Wright, I. P.; Zarnecki, J. C.

2005-01-01

Space weathering is now understood to be a key modifier of visible and near infrared reflectance spectra of airless bodies. Believed to be caused by vapour recondensation after either ion sputtering or impact vaporization, space weathering has been successfully simulated in the laboratory over the past few years. The optical changes caused by space weathering have been attributed to the accumulation of sub-microscopic iron on regolith grain surfaces. Such fine-grained metallic iron has distinctive magnetic properties that can be used to study it.

Spectroradiometric calibration of the thematic mapper and multispectral scanner system

NASA Technical Reports Server (NTRS)

Slater, P. N. (Principal Investigator); Palmer, J. M.

1983-01-01

The design of a spectroradiometer under construction for atmosheric and surface measurements at White Sands, New Mexico is described. The instrument's observation capability encompasses (1) measuring the solar radiance at a number of wavelengths as a function of air mass for Langley plot analysis in order to generate the optical depth; (2) measuring the ground radiance to determine the absolute ground reflectance; and (3) measuring the sky radiance as a method of checking the accuracy of the radiative transfer program.

Tunable liquid optics: electrowetting-controlled liquid mirrors based on self-assembled Janus tiles.

PubMed

Bucaro, Michael A; Kolodner, Paul R; Taylor, J Ashley; Sidorenko, Alex; Aizenberg, Joanna; Krupenkin, Tom N

2009-04-09

In this paper, we describe a tunable, high-reflectivity optofluidic device based on self-assembly of anisotropically functionalized hexagonal micromirrors (Janus tiles) on the surface of an oil droplet to create a concave liquid mirror. The liquid mirror is deposited on a patterned transparent electrode that allows the focal length and axial position to be electrically controlled. The mirror is mechanically robust and retains its integrity even at high levels of vibrational excitation of the interface. The use of reflection instead of refraction overcomes the limited available refractive-index contrast between pairs of density-matched liquids, allowing stronger focusing than is possible for a liquid lens of the same geometry. This approach is compatible with optical instruments that could provide novel functionality-for example, a dynamic 3D projector, i.e., a light source which can scan an image onto a moving, nonplanar focal surface. Janus tiles with complex optical properties can be manufactured using our approach, thus potentially enabling a wide range of novel optical elements.

Tunable liquid optics: electrowetting-controlled liquid mirrors based on self-assembled Janus tiles

NASA Astrophysics Data System (ADS)

Krupenkin, Tom; Bucaro, Mike; Kolodner, Paul; Taylor, Ashley; Sidorenko, Alex; Aizenberg, Joanna

2009-03-01

In this work we describe a tunable, high-reflectivity optofluidic device based on self-assembly of anisotropically-functionalized hexagonal micromirrors (Janus tiles) on the surface of an oil droplet to create a concave liquid mirror. The liquid mirror is deposited on a patterned transparent electrode that allows the focal length and axial position to be electrically controlled. The mirror is mechanically robust and retains its integrity even at high levels of vibrational excitation of the interface. The use of reflection instead of refraction overcomes the limited available refractive-index contrast between pairs of density-matched liquids, allowing stronger focusing than is possible for a liquid lens of the same geometry. This approach is compatible with optical instruments that could provide novel functionality - for example, a dynamic 3D projector; i.e., a light source which can scan an image onto a moving, non-planar focal surface. Janus tiles with complex optical properties can be manufactured using our approach, thus potentially enabling a wide range of novel optical elements.

Mars - Remote spectral identification of H2O frost and mineral hydrate

NASA Technical Reports Server (NTRS)

Huguenin, R. L.; Clark, R. N.; Mccord, T. B.

1978-01-01

A reflectance spectrum (0.62-2.6 microns) of Mars (integral disk) is obtained using a newly developed IR spectrometer at the 2.25 m telescope on Mauna Kea, Hawaii. Details of the instrument, observations, and data reduction are presented. Several distinct absorption features are evident that were apparently caused by H2O, but the positions and intensities of the features are quite unusual. In summary, the regolith is probably not as desiccated and dehydrated as the full disk reflectance spectrum and Viking soil analyses would suggest. The surface materials become desiccated and dehydrated as a result of solar UV effects and because of the relative adsorption and desorption rates during the strong diurnal cycling. There may be significant amounts of H2O at depth, and in the Solis Lacus region the H2O reservoir may extend to within a few centimeters of the surface. The Solis Lacus region may therefore be an important target for future Mars landing or sample return mission.

Geometry of illumination, luminance contrast, and gloss perception.

PubMed

Leloup, Frédéric B; Pointer, Michael R; Dutré, Philip; Hanselaer, Peter

2010-09-01

The influence of both the geometry of illumination and luminance contrast on gloss perception has been examined using the method of paired comparison. Six achromatic glass samples having different lightness were illuminated by two light sources. Only one of these light sources was visible in reflection by the observer. By separate adjustment of the intensity of both light sources, the luminance of both the reflected image and the adjacent off-specular surroundings could be individually varied. It was found that visual gloss appraisal did not correlate with instrumentally measured specular gloss; however, psychometric contrast seemed to be a much better correlate. It has become clear that not only the sample surface characteristics determine gloss perception: the illumination geometry could be an even more important factor.

Modular wide spectrum lighting system for diagnosis, conservation, and restoration

NASA Astrophysics Data System (ADS)

Miccoli, Matteo; Melis, Marcello

2013-05-01

In the framework of imaging, lighting systems have always played a key role due to the primary importance of both the uniformity of the illumination and the richness of the emitted spectra. Multispectral imaging, i.e. imaging systems working inside and outside the visible wavelength range, are even more demanding and require to pay further attention to a number of parameters characterizing the lighting system. A critical issue for lighting systems, even in the visible light, is the shape of the emitted spectra and (only in the visible range) the Color Rendering Index. The color we perceive from a surface is our eyes' interpretation of the linear spectral combination of the illuminant spectrum and the surface spectral reflectance. If there is a lack of energy in a portion of the visible spectrum, that portion will turn into black to our eyes (and to whatever instrument) regardless the actual reflectance of the surface. In other words a lack in the exciting energy hides part of the spectral reflectance of the observed subject. Furthermore, the wider is the investigated spectrum, the fewer are the sources of light able to cover such a range. In this paper we show how we solved both the problems of the not uniformity of the light beam, independently on the incident angle, and of the selection of a light source with energy rich and continuous enough emitted spectrum.

Computer screen photo-excited surface plasmon resonance imaging.

PubMed

Filippini, Daniel; Winquist, Fredrik; Lundström, Ingemar

2008-09-12

Angle and spectra resolved surface plasmon resonance (SPR) images of gold and silver thin films with protein deposits is demonstrated using a regular computer screen as light source and a web camera as detector. The screen provides multiple-angle illumination, p-polarized light and controlled spectral radiances to excite surface plasmons in a Kretchmann configuration. A model of the SPR reflectances incorporating the particularities of the source and detector explain the observed signals and the generation of distinctive SPR landscapes is demonstrated. The sensitivity and resolution of the method, determined in air and solution, are 0.145 nm pixel(-1), 0.523 nm, 5.13x10(-3) RIU degree(-1) and 6.014x10(-4) RIU, respectively, encouraging results at this proof of concept stage and considering the ubiquity of the instrumentation.

Becoming a Reflective Mathematics Teacher: A Guide for Observations and Self-Assessment. Studies in Mathematical Thinking and Learning Series.

ERIC Educational Resources Information Center

Artzt, Alice F.; Armour-Thomas, Eleanor

This activity-oriented book for preservice mathematics teachers who are taking methods courses or who have been student teaching offers a framework for teacher reflection and self- assessment. It supplies detailed observation instruments for observing other teachers, reflective activities, and guidelines and instruments for supervisors. There are…

3D View of Grand Canyon, Arizona

NASA Technical Reports Server (NTRS)

2000-01-01

The Grand Canyon is one of North America's most spectacular geologic features. Carved primarily by the Colorado River over the past six million years, the canyon sports vertical drops of 5,000 feet and spans a 445-kilometer-long stretch of Arizona desert. The strata along the steep walls of the canyon form a record of geologic time from the Paleozoic Era (250 million years ago) to the Precambrian (1.7 billion years ago).

The above view was acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument aboard the Terra spacecraft. Visible and near infrared data were combined to form an image that simulates the natural colors of water and vegetation. Rock colors, however, are not accurate. The image data were combined with elevation data to produce this perspective view, with no vertical exaggeration, looking from above the South Rim up Bright Angel Canyon towards the North Rim. The light lines on the plateau at lower right are the roads around the Canyon View Information Plaza. The Bright Angel Trail, which reaches the Colorado in 11.3 kilometers, can be seen dropping into the canyon over Plateau Point at bottom center. The blue and black areas on the North Rim indicate a forest fire that was smoldering as the data were acquired on May 12, 2000.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

There is no bidirectional hot-spot in Sentinel-2 data

NASA Astrophysics Data System (ADS)

Li, Z.; Roy, D. P.; Zhang, H.

2017-12-01

The Sentinel-2 multi-spectral instrument (MSI) acquires reflective wavelength observations with directional effects due to surface reflectance anisotropy, often described by the bidirectional reflectance distribution function (BRDF). Recently, we quantified Sentinel-2A (S2A) BRDF effects for 20° × 10° of southern Africa sensed in January and in April 2016 and found maximum BRDF effects for the January data and at the western scan edge, i.e., in the back-scatter direction (Roy et al. 2017). The hot-spot is the term used to describe the increased directional reflectance that occurs over most surfaces when the solar and viewing directions coincide, and has been observed in wide-field of view data such as MODIS. Recently, we observed that Landsat data will not have a hot-spot because the global annual minimum solar zenith angle is more than twice the maximum view zenith angle (Zhang et al. 2016). This presentation examines if there is a S2A hot-spot which may be possible as it has a wider field of view (20.6°) and higher orbit (786 km) than Landsat. We examined a global year of S2A metadata extracted using the Committee on Earth Observation Satellite Visualization Environment (COVE) tool, computed the solar zenith angles in the acquisition corners, and ranked the acquisitions by the solar zenith angle in the back-scatter direction. The available image data for the 10 acquisitions with the smallest solar zenith angle over the year were ordered from the ESA and their geometries examined in detail. The acquisition closest to the hot-spot had a maximum scattering angle of 173.61° on its western edge (view zenith angle 11.91°, solar zenith angle 17.97°) and was acquired over 60.80°W 24.37°N on June 2nd 2016. Given that hot-spots are only apparent when the scattering angle is close to 180° we conclude from this global annual analysis that there is no hot-spot in Sentinel-2 data. Roy, D.P, Li, J., Zhang, H.K., Yan, L., Huang, H., Li, Z., 2017, Examination of Sentinel-2A multi-spectral instrument (MSI) reflectance anisotropy and the suitability of a general method to normalize MSI reflectance to nadir BRDF adjusted reflectance, RSE. 199, 25-38. Zhang, H. K., Roy, D.P., Kovalskyy, V., 2016, Optimal solar geometry definition for global long term Landsat time series bi-directional reflectance normalization, IEEE TGRS. 54(3), 1410-1418.

ASTER Images San Francisco Bay Area

NASA Technical Reports Server (NTRS)

2000-01-01

These images of the San Francisco Bay region were acquired on March 3, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. Each covers an area 60 kilometers (37 miles) wide and 75 kilometers (47 miles) long. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image the Earth for the next 6 years to map and monitor the changing surface of our planet.

Upper Left: The color infrared composite uses bands in the visible and reflected infrared. Vegetation is red, urban areas are gray; sediment in the bays shows up as lighter shades of blue. Thanks to the 15 meter (50-foot) spatial resolution, shadows of the towers along the Bay Bridge can be seen.

Upper right: A composite of bands in the short wave infrared displays differences in soils and rocks in the mountainous areas. Even though these regions appear entirely vegetated in the visible, enough surface shows through openings in the vegetation to allow the ground to be imaged.

Lower left: This composite of multispectral thermal bands shows differences in urban materials in varying colors. Separation of materials is due to differences in thermal emission properties, analogous to colors in the visible.

Lower right: This is a color coded temperature image of water temperature, derived from the thermal bands. Warm waters are in white and yellow, colder waters are blue. Suisun Bay in the upper right is fed directly from the cold Sacramento River. As the water flows through San Pablo and San Francisco Bays on the way to the Pacific, the waters warm up.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

Improved Satellite Retrievals of NO2 and SO2 over the Canadian Oil Sands and Comparisons with Surface Measurements

NASA Technical Reports Server (NTRS)

McLinden, C. A.; Fioletov, V.; Boersma, K. F.; Kharol, S. K.; Krotkov, N.; Lamsal, L.; Makar, P. A.; Martin, R. V.; Veefkind, J. P.; Yang, K.

2014-01-01

Satellite remote sensing is increasingly being used to monitor air quality over localized sources such as the Canadian oil sands. Following an initial study, significantly low biases have been identified in current NO2 and SO2 retrieval products from the Ozone Monitoring Instrument (OMI) satellite sensor over this location resulting from a combination of its rapid development and small spatial scale. Air mass factors (AMFs) used to convert line-of-sight "slant" columns to vertical columns were re-calculated for this region based on updated and higher resolution input information including absorber profiles from a regional-scale (15 km × 15 km resolution) air quality model, higher spatial and temporal resolution surface reflectivity, and an improved treatment of snow. The overall impact of these new Environment Canada (EC) AMFs led to substantial increases in the peak NO2 and SO2 average vertical column density (VCD), occurring over an area of intensive surface mining, by factors of 2 and 1.4, respectively, relative to estimates made with previous AMFs. Comparisons are made with long-term averages of NO2 and SO2 (2005-2011) from in situ surface monitors by using the air quality model to map the OMI VCDs to surface concentrations. This new OMI-EC product is able to capture the spatial distribution of the in situ instruments (slopes of 0.65 to 1.0, correlation coefficients of greater than 0.9). The concentration absolute values from surface network observations were in reasonable agreement, with OMI-EC NO2 and SO2 biased low by roughly 30%. Several complications were addressed including correction for the interference effect in the surface NO2 instruments and smoothing and clear-sky biases in the OMI measurements. Overall these results highlight the importance of using input information that accounts for the spatial and temporal variability of the location of interest when performing retrievals.

Metrological issues related to BRDF measurements around the specular direction in the particular case of glossy surfaces

NASA Astrophysics Data System (ADS)

Obein, Gaël.; Audenaert, Jan; Ged, Guillaume; Leloup, Frédéric B.

2015-03-01

Among the complete bidirectional reflectance distribution function (BRDF), visual gloss is principally related to physical reflection characteristics located around the specular reflection direction. This particular part of the BRDF is usually referred to as the specular peak. A good starting point for the physical description of gloss could be to measure the reflection properties around this specular peak. Unfortunately, such a characterization is not trivial, since for glossy surfaces the width of the specular peak can become very narrow (typically a full width at half maximum inferior to 0.5° is encountered). In result, new BRDF measurement devices with a very small solid angle of detection are being introduced. Yet, differences in the optical design of BRDF measurement instruments engender different measurement results for the same specimen, complicating direct comparison of the measurement results. This issue is addressed in this paper. By way of example, BRDF measurement results of two samples, one being matte and the other one glossy, obtained by use of two high level goniospectrophotometers with a different optical design, are described. Important discrepancies in the results of the glossy sample are discussed. Finally, luminance maps obtained from renderings with the acquired BRDF data are presented, exemplifying the large visual differences that might be obtained. This stresses the metrological aspects that must be known for using BRDF data. Indeed, the comprehension of parameters affecting the measurement results is an inevitable step towards progress in the metrology of surface gloss, and thus towards a better metrology of appearance in general.

ROSAS: a robotic station for atmosphere and surface characterization dedicated to on-orbit calibration

NASA Astrophysics Data System (ADS)

Meygret, Aimé; Santer, Richard P.; Berthelot, Béatrice

2011-10-01

La Crau test site is used by CNES since 1987 for vicarious calibration of SPOT cameras. The former calibration activities were conducted during field campaigns devoted to the characterization of the atmosphere and the site reflectances. Since 1997, au automatic photometric station (ROSAS) was set up on the site on a 10m height pole. This station measures at different wavelengths, the solar extinction and the sky radiances to fully characterize the optical properties of the atmosphere. It also measures the upwelling radiance over the ground to fully characterize the surface reflectance properties. The photometer samples the spectrum from 380nm to 1600nm with 9 narrow bands. Every non cloudy days the photometer automatically and sequentially performs its measurements. Data are transmitted by GSM (Global System for Mobile communications) to CNES and processed. The photometer is calibrated in situ over the sun for irradiance and cross-band calibration, and over the Rayleigh scattering for the short wavelengths radiance calibration. The data are processed by an operational software which calibrates the photometer, estimates the atmosphere properties, computes the bidirectional reflectance distribution function of the site, then simulates the top of atmosphere radiance seen by any sensor over-passing the site and calibrates it. This paper describes the instrument, its measurement protocol and its calibration principle. Calibration results are discussed and compared to laboratory calibration. It details the surface reflectance characterization and presents SPOT4 calibration results deduced from the estimated TOA radiance. The results are compared to the official calibration.

Optimizing Waveform Maximum Determination for Specular Point Tracking in Airborne GNSS-R.

PubMed

Motte, Erwan; Zribi, Mehrez

2017-08-16

Airborne GNSS-R campaigns are crucial to the understanding of signal interactions with the Earth's surface. As a consequence of the specific geometric configurations arising during measurements from aircraft, the reflected signals can be difficult to interpret under certain conditions like over strongly attenuating media such as forests, or when the reflected signal is contaminated by the direct signal. For these reasons, there are many cases where the reflectivity is overestimated, or a portion of the dataset has to be flagged as unusable. In this study we present techniques that have been developed to optimize the processing of airborne GNSS-R data, with the goal of improving its accuracy and robustness under non-optimal conditions. This approach is based on the detailed analysis of data produced by the instrument GLORI, which was recorded during an airborne campaign in the south west of France in June 2015. Our technique relies on the improved determination of reflected waveform peaks in the delay dimension, which is related to the loci of the signals contributed by the zone surrounding the specular point. It is shown that when developing techniques for the correct localization of waveform maxima under conditions of surfaces of low reflectivity, and/or contamination from the direct signal, it is possible to correct and extract values corresponding to the real reflectivity of the zone in the neighborhood of the specular point. This algorithm was applied to a reanalysis of the complete campaign dataset, following which the accuracy and sensitivity improved, and the usability of the dataset was improved by 30%.

Characterizing energy budget variability at a Sahelian site: a test of NWP model behaviour

NASA Astrophysics Data System (ADS)

Mackie, Anna; Palmer, Paul I.; Brindley, Helen

2017-12-01

We use observations of surface and top-of-the-atmosphere (TOA) broadband radiation fluxes determined from the Atmospheric Radiation Measurement programme mobile facility, the Geostationary Earth Radiation Budget (GERB) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) instruments and a range of meteorological variables at a site in the Sahel to test the ability of the ECMWF Integrated Forecasting System cycle 43r1 to describe energy budget variability. The model has daily average biases of -12 and 18 W m-2 for outgoing longwave and reflected shortwave TOA radiation fluxes, respectively. At the surface, the daily average bias is 12(13) W m-2 for the longwave downwelling (upwelling) radiation flux and -21(-13) W m-2 for the shortwave downwelling (upwelling) radiation flux. Using multivariate linear models of observation-model differences, we attribute radiation flux discrepancies to physical processes, and link surface and TOA fluxes. We find that model biases in surface radiation fluxes are mainly due to a low bias in ice water path (IWP), poor description of surface albedo and model-observation differences in surface temperature. We also attribute observed discrepancies in the radiation fluxes, particularly during the dry season, to the misrepresentation of aerosol fields in the model from use of a climatology instead of a dynamic approach. At the TOA, the low IWP impacts the amount of reflected shortwave radiation while biases in outgoing longwave radiation are additionally coupled to discrepancies in the surface upwelling longwave flux and atmospheric humidity.

Thermal Infrared Spectrometer for Earth Science Remote Sensing Applications—Instrument Modifications and Measurement Procedures

PubMed Central

Hecker, Christoph; Hook, Simon; van der Meijde, Mark; Bakker, Wim; van der Werff, Harald; Wilbrink, Henk; van Ruitenbeek, Frank; de Smeth, Boudewijn; van der Meer, Freek

2011-01-01

In this article we describe a new instrumental setup at the University of Twente Faculty ITC with an optimized processing chain to measure absolute directional-hemispherical reflectance values of typical earth science samples in the 2.5 to 16 μm range. A Bruker Vertex 70 FTIR spectrometer was chosen as the base instrument. It was modified with an external integrating sphere with a 30 mm sampling port to allow measuring large, inhomogeneous samples and quantitatively compare the laboratory results to airborne and spaceborne remote sensing data. During the processing to directional-hemispherical reflectance values, a background radiation subtraction is performed, removing the effect of radiance not reflected from the sample itself on the detector. This provides more accurate reflectance values for low-reflecting samples. Repeat measurements taken over a 20 month period on a quartz sand standard show that the repeatability of the system is very high, with a standard deviation ranging between 0.001 and 0.006 reflectance units depending on wavelength. This high level of repeatability is achieved even after replacing optical components, re-aligning mirrors and placement of sample port reducers. Absolute reflectance values of measurements taken by the instrument here presented compare very favorably to measurements of other leading laboratories taken on identical sample standards. PMID:22346683

Thermal infrared spectrometer for Earth science remote sensing applications-instrument modifications and measurement procedures.

PubMed

Hecker, Christoph; Hook, Simon; van der Meijde, Mark; Bakker, Wim; van der Werff, Harald; Wilbrink, Henk; van Ruitenbeek, Frank; de Smeth, Boudewijn; van der Meer, Freek

2011-01-01

In this article we describe a new instrumental setup at the University of Twente Faculty ITC with an optimized processing chain to measure absolute directional-hemispherical reflectance values of typical earth science samples in the 2.5 to 16 μm range. A Bruker Vertex 70 FTIR spectrometer was chosen as the base instrument. It was modified with an external integrating sphere with a 30 mm sampling port to allow measuring large, inhomogeneous samples and quantitatively compare the laboratory results to airborne and spaceborne remote sensing data. During the processing to directional-hemispherical reflectance values, a background radiation subtraction is performed, removing the effect of radiance not reflected from the sample itself on the detector. This provides more accurate reflectance values for low-reflecting samples. Repeat measurements taken over a 20 month period on a quartz sand standard show that the repeatability of the system is very high, with a standard deviation ranging between 0.001 and 0.006 reflectance units depending on wavelength. This high level of repeatability is achieved even after replacing optical components, re-aligning mirrors and placement of sample port reducers. Absolute reflectance values of measurements taken by the instrument here presented compare very favorably to measurements of other leading laboratories taken on identical sample standards.

Fusion of intraoperative force sensoring, surface reconstruction and biomechanical modeling

NASA Astrophysics Data System (ADS)

Röhl, S.; Bodenstedt, S.; Küderle, C.; Suwelack, S.; Kenngott, H.; Müller-Stich, B. P.; Dillmann, R.; Speidel, S.

2012-02-01

Minimally invasive surgery is medically complex and can heavily benefit from computer assistance. One way to help the surgeon is to integrate preoperative planning data into the surgical workflow. This information can be represented as a customized preoperative model of the surgical site. To use it intraoperatively, it has to be updated during the intervention due to the constantly changing environment. Hence, intraoperative sensor data has to be acquired and registered with the preoperative model. Haptic information which could complement the visual sensor data is still not established. In addition, biomechanical modeling of the surgical site can help in reflecting the changes which cannot be captured by intraoperative sensors. We present a setting where a force sensor is integrated into a laparoscopic instrument. In a test scenario using a silicone liver phantom, we register the measured forces with a reconstructed surface model from stereo endoscopic images and a finite element model. The endoscope, the instrument and the liver phantom are tracked with a Polaris optical tracking system. By fusing this information, we can transfer the deformation onto the finite element model. The purpose of this setting is to demonstrate the principles needed and the methods developed for intraoperative sensor data fusion. One emphasis lies on the calibration of the force sensor with the instrument and first experiments with soft tissue. We also present our solution and first results concerning the integration of the force sensor as well as accuracy to the fusion of force measurements, surface reconstruction and biomechanical modeling.

The best of both worlds: automated CMP polishing of channel-cut monochromators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasman, Elina; Erdmann, Mark; Stoupin, Stanislav

2015-09-03

The use of a channel-cut monochromator is the most straightforward method to ensure that the two reflection surfaces maintain alignment between crystallographic planes without the need for complicated alignment mechanisms. Three basic characteristics that affect monochromator performance are: subsurface damage which contaminates spectral purity; surface roughness which reduces efficiency due to scattering; and surface figure error which imparts intensity structure and coherence distortion in the beam. Standard chemical-mechanical polishing processes and equipment are used when the diffracting surface is easily accessible, such as for single-bounce monochromators. Due to the inaccessibly of the surfaces inside a channel-cut monochromator for polishing, thesemore » optics are generally wet-etched for their final processing. This results in minimal subsurface damage, but very poor roughness and figure error. A new CMP channel polishing instrument design is presented which allows the internal diffracting surface quality of channel-cut crystals to approach that of conventional single-bounce monochromators« less

Estimations of the Global Distribution and Time Series of UV Noontime Irradiance (305, 310, 324, 380 nm, and Erythemal) from TOMS and SeaWiFS Data

NASA Technical Reports Server (NTRS)

Herman, J.

2004-01-01

The amount of UV irradiance reaching the Earth's surface is estimated from the measured cloud reflectivity, ozone, aerosol amounts, and surface reflectivity time series from 1980 to 1992 and 1997 to 2000 to estimate changes that have occurred over a 21-year period. Recent analysis of the TOMS data shows that there has been an apparent increase in reflectivity (decrease in W) in the Southern Hemisphere that is related to a calibration error in EP-TOMS. Data from the well-calibrated SeaWiFS satellite instrument have been used to correct the EP-TOMS reflectivity and UV time series. After correction, some of the local trend features seen in the N7 time series (1980 to 1992) have been continued in the combined time series, but the overall zonal average and global trends have changed. In addition to correcting the EP-TOMS radiance calibration, the use of SeaWiFS cloud data permits estimation of UV irradiance at higher spatial resolution (1 to 4 km) than is available from TOMS (100 km) under the assumption that ozone is slowly varying over a scale of 100 km. The key results include a continuing decrease in cloud cover over Europe and North America with a corresponding increase in UV and a decrease in UV irradiance near Antarctica.

Impact of aerosols present in Titan's atmosphere on The Cassini Radar experiment

NASA Astrophysics Data System (ADS)

Rodriguez, S.; Paillou, P.; Dobrijevic, M.; Ruffie, G.; Coll, P.; Bernard, J. M.; Encrenaz, P.

2002-09-01

One of the goals of the Cassini-Huygens mission, which will reach Saturn in 2004, is the study of the satellite Titan (its atmosphere and surface) by means of various remote sensing instruments on the orbiter and with the entry of the Huygens probe into Titan's atmosphere. In particular, the Cassini Radar experiment will use the high gain antenna at 13.78 GHz to "see" through Titan's atmosphere and map about 30 Two active modes (SAR and altimeter) and a passive mode (radiometer) will be used within the Radar experiment. The interpretation of future radar acquisitions will be conditioned by the electric properties of the atmospheric components the radar pulse will encounter, as well as the Titan's surface reflectivity. For this purpose, we made some dielectric constant measurements on synthetic analogs of Titan's aerosols, i.e. tholins. We found ǎrepsilon'=2-2.5 and a loss tangent between 5.10-2 and 10-3. These results were combined to scenarii of aerosol and rain formation in Titan's atmosphere into a simple simulation of the atmospheric transmission (Rayleigh and Mie scattering) in order to estimate the way aerosols and rain particles will affect the performance of the radar instrument, by attenuating the radar pulse before it reaches the surface. Results we obtained are surprisingly pessimistic for numbers of published atmospheric models, with computed attenuations that can be higher than 12 dB. Indeed, the occurrence of hydrocarbon rain in the low atmosphere could have a prejudicial effect on the radar pulses, since they could be partially attenuated, completely reflected, or distorted before reaching Titan's surface. We conclude on possible consequences that such atmospheric effects could have on the future analysis of Cassini Radar data. We also propose alternative ways to use combined altimeter and SAR data in order to decorrelate atmospheric and surface effects and then map the surface with less ambiguity, but also study the particles distribution in Titan's atmosphere. This work was supported by the French Programme National de Planétologie of the Institut National des Sciences de l'Univers, CNRS.

Gastroenterology-Urology Devices; Manual Gastroenterology-Urology Surgical Instruments and Accessories. Final rule; technical amendment.

PubMed

2017-03-01

The Food and Drug Administration (FDA) is amending the identification of manual gastroenterology-urology surgical instruments and accessories to reflect that the device does not include specialized surgical instrumentation for use with urogyencologic surgical mesh specifically intended for use as an aid in the insertion, placement, fixation, or anchoring of surgical mesh during urogynecologic procedures ("specialized surgical instrumentation for use with urogynecologic surgical mesh"). These amendments are being made to reflect changes made in the recently issued final reclassification order for specialized surgical instrumentation for use with urogynecologic surgical mesh.

Theoretical and Observational Determination of Global and Regional Radiation Budget, Forcing and Feedbacks at the Top-of-Atmosphere and Surface

NASA Technical Reports Server (NTRS)

Loeb, Norman G.

2004-01-01

Report consists of: 1. List of accomplishments 2. List of publications 3. Abstracts of published or submitted papers and 4. Subject invention disclosure. The accomplishments of the grant listed are: 1. Improved the third-order turbulence closure in cloud resolving models to remove the liquid water oscillation. 2. Used the University of California-Los Angeles (UCLA) large-eddy simulation (LES) model to provide data for radiation transfer testing. 3. Revised shortwave k-distribution models based on HITRAN 2000. 4. Developed a gamma-weighted two-stream radiative transfer model for radiation budget estimate applications. 5. Estimated the effect of spherical geometry to the earth radiation budget. 6. Estimated top-of-atmosphere irradiance over snow and sea ice surfaces. 7. Estimated the aerosol direct radiative effect at the top of the atmosphere. 8. Estimated the top-of-atmosphere reflectance of the clear-sky molecular atmosphere over ocean. 9. Developed and validated new set of Angular Distribution Models for the CERES TRMM satellite instrument (tropical) 10. Developed and validated new set of Angular Distribution Models for the CERES Terra satellite instrument (global) 11. Quantified the top-of-atmosphere direct radiative effect of aerosols over global oceans from merged CERES and MODIS observations 12 Clarified the definition of TOA flux reference level for radiation budget studies 13. Developed new algorithm for unfaltering CERES measured radiances 14. Used multiangle POLDER measurements to produce narrowband angular distribution models and examine the effect of scene identification errors on TOA albedo estimates 15. Developed and validated a novel algorithm called the Multidirectional Reflectance Matching (MRM) model for inferring TOA albedos from ice clouds using multi-angle satellite measurements. 16. Developed and validated a novel algorithm called the Multidirectional Polarized Reflectance Matching (MPRM) model for inferring particle shapes from ice clouds using multi-angle polarized satellite measurements. 17. Developed 4 advanced light scattering models including the three-dimensional (3D) uniaxial perfectly matched layer (UPML) finite-difference time-domain (FDTD) model. 18. Develop sunglint in situ measurement and study reflectance distribution in the sunglint area. 19. Lead a balloon-borne radiometer TOA albedo validation effort. 20. Developed a CERES surface UVB, UVA, and UV index product.

Soil Moisture Remote Sensing with GNSS-R at the Valencia Anchor Station. The SOMOSTA (Soil Moisture Station) Experiment

NASA Astrophysics Data System (ADS)

Lopez-Baeza, Ernesto

2016-07-01

In this paper, the SOMOSTA (Soil Moisture Monitoring Station) experiment on soil moisture monitoring byGlobal Navigation Satellite System Reflected signals(GNSS-R) at the Valencia Anchor Station is introduced. L-band microwaves have very good advantages in soil moisture remote sensing, for being unaffected by clouds and the atmosphere, and for the ability to penetrate vegetation. During this experimental campaign, the ESA GNSS-R Oceanpal antenna was installed on the same tower as the ESA ELBARA-II passive microwave radiometer, both measuring instruments having similar field of view. This experiment is fruitfully framed within the ESA - China Programme of Collaboration on GNSS-R. The GNSS-R instrument has an up-looking antenna for receiving direct signals from satellites, and two down-looking antennas for receiving LHCP (left-hand circular polarisation) and RHCP (right-hand circular polarisation) reflected signals from the soil surface. We could collect data from the three different antennas through the two channels of Oceanpal and, in addition, calibration could be performed to reduce the impact from the differing channels. Reflectivity was thus measured and soil moisture could be retrieved by the L- MEB (L-band Microwave Emission of the Biosphere) model considering the effect of vegetation optical thickness and soil roughness. By contrasting GNSS-R and ELBARA-II radiometer data, a negative correlation existed between reflectivity measured by GNSS-R and brightness temperature measured by the radiometer. The two parameters represent reflection and absorption of the soil. Soil moisture retrieved by both L-band remote sensing methods shows good agreement. In addition, correspondence with in-situ measurements and rainfall is also good.

Model Calculations of Solar Spectral Irradiance in the 3.7 Micron Band for Earth Remote Sensing Applications

NASA Technical Reports Server (NTRS)

Platnick, Steven; Fontenla, Juan M.

2006-01-01

Since the launch of the first Advanced Very High Resolution Radiometer (AVHRR) instrument aboard TIROS-N, measurements in the 3.7 micron atmospheric window have been exploited for use in cloud detection and screening, cloud thermodynamic phase and surface snow/ice discrimination, and quantitative cloud particle size retrievals. The utility of the band has led to the incorporation of similar channels on a number of existing satellite imagers and future operational imagers. Daytime observations in the band include both reflected solar and thermal emission energy. Since 3.7 micron channels are calibrated to a radiance scale (via onboard blackbodies), knowledge of the top-of-atmosphere solar irradiance in the spectral region is required to infer reflectance. Despite the ubiquity of 3.7 micron channels, absolute solar spectral irradiance data comes from either a single measurement campaign (Thekaekara et al. 1969) or synthetic spectra. In this study, we compare historical 3.7 micron band spectral irradiance data sets with the recent semi-empirical solar model of the quiet-Sun by Fontenla et al. (2006). The model has expected uncertainties of about 2 % in the 3.7 pm spectral region. We find that channel-averaged spectral irradiances using the observations reported by Thekaekara et al. are 3.2-4.1% greater than those derived from the Fontenla et al. model for MODIS and AVHRR instrument bandpasses; the Kurucz spectrum (1995) as included in the MODTRAN4 distribution, gives channel-averaged irradiances 1.2-1.5 % smaller than the Fontenla model. For the MODIS instrument, these solar irradiance uncertainties result in cloud microphysical retrievals uncertainties comparable with other fundamental reflectance error sources.

Characterization of sun and sky glint from wind ruffled sea surfaces for improved estimation of polarized remote sensing reflectance

NASA Astrophysics Data System (ADS)

Foster, Robert; Ibrahim, Amir; Gilerson, Alex; El-Habashi, Ahmed; Carrizo, Carlos; Ahmed, Sam

2015-09-01

During two cruises in 2014, the polarized radiance of the ocean and the sky were continuously acquired using a HyperSAS-POL system. The system consists of seven hyperspectral radiometric sensors, three of which (one unpolarized and two polarized) look at the water and similarly three at the sky. The system autonomously tracks the Sun position and the heading of the research vessel to which it is attached in order to maintain a fixed relative azimuth angle with respect to the Sun (i.e. 90°) and therefore avoid the specular reflection of the sunlight. For the duration of both cruises, (NASA Ship Aircraft Bio-Optical Research (SABOR), and NOAA VIIRS Validation/Calibration), in situ inherent optical properties (IOPs) were continuously acquired using a set of instrument packages modified for underway measurement, and hyperspectral radiometric measurements were taken manually at all stations. During SABOR, an underwater polarimeter was deployed when conditions permitted. All measurements were combined in an effort to first develop a glint (sky + Sun) correction scheme for the upwelling polarized signal from a wind driven ocean surface and compare with one assuming that the ocean surface is flat.

A diffuse radar scattering model from Martian surface rocks

NASA Technical Reports Server (NTRS)

Calvin, W. M.; Jakosky, B. M.; Christensen, P. R.

1987-01-01

Remote sensing of Mars has been done with a variety of instrumentation at various wavelengths. Many of these data sets can be reconciled with a surface model of bonded fines (or duricrust) which varies widely across the surface and a surface rock distribution which varies less so. A surface rock distribution map from -60 to +60 deg latitude has been generated by Christensen. Our objective is to model the diffuse component of radar reflection based on this surface distribution of rocks. The diffuse, rather than specular, scattering is modeled because the diffuse component arises due to scattering from rocks with sizes on the order of the wavelength of the radar beam. Scattering for radio waves of 12.5 cm is then indicative of the meter scale and smaller structure of the surface. The specular term is indicative of large scale surface undulations and should not be causally related to other surface physical properties. A simplified model of diffuse scattering is described along with two rock distribution models. The results of applying the models to a planet of uniform fractional rock coverage with values ranging from 5 to 20% are discussed.

Plasma surface reflectance spectroscopy for non-invasive and continuous monitoring of extracellular component of blood

NASA Astrophysics Data System (ADS)

Sakota, Daisuke; Takatani, Setsuo

2012-04-01

To achieve the quantitative optical non-invasive diagnosis of blood during extracorporeal circulation therapies, the instrumental technique to extract extracellular spectra from whole blood was developed. In the circuit, the continuous blood flow was generated by a centrifugal blood pump. The oxygen saturation was maintained 100% by an oxygenator. The developed glass optical flow cell was attached to the outlet tubing of the oxygenator. The halogen lamp including the light from 400 to 900 nm wavelength was used for the light source. The light was guided into an optical fiber. The light emitted by the fiber was collimated and emitted to the flow cell flat surface at the incident angle of 45 degrees. The light just reflected on the boundary between inner surface of the flow cell and plasma at 45 degrees was detected by the detection fiber. The detected light was analyzed by a spectral photometer. The obtained spectrum from 400 to 600nm wavelength was not changed with respect to the hematocrit. In contrast, the signal in the spectral range was changed when the plasma free hemoglobin increased. By using two spectral range, 505+/-5 nm and 542.5+/-2.5 nm, the differential spectrum was correlated with the free hemoglobin at R2=0.99. On the other hand, as for the hematocrit, the differential spectrum was not correlated at R2=0.01. Finally, the plasma free hemoglobin was quantified with the accuracy of 22+/-19mg/dL. The result shows that the developed plasma surface reflectance spectroscopy (PSRS) can extract the plasma spectrum from flowing whole blood.

Validation of OMI Measured Radiances Over Ice

NASA Astrophysics Data System (ADS)

Jaross, G.; Cebula, R. P.; Warner, J.

2005-12-01

The Ozone Monitoring Instrument (OMI) was launched aboard the EOS Aura satellite on 15 July, 2004 and has since performed quite well. Calibrated radiances in the form of Level 1 data products are produced regularly every orbit with minimal data loss. A total of 12 atmospheric constituent data products are currently planned for the OMI science data processing. All rely, to varying degrees, on the sun-normalized radiances of the OMI sensor. Retrievals of atmospheric trace constituents, such as NO{}_2, BrO, OCLO, and HCHO, rely upon spectroscopy and tend to be insensitive to errors in the absolute radiance levels. But column O{}_3 amount, aerosol properties, cloud heights, and UV surface radiation have significant sensitivities to changes in the sun-normalized radiances. In this presentation we discuss our evaluation of the OMI sun-normalized radiances between 330 nm and 500 nm. This covers most of the OMI spectral range where ozone absorption is small. Our technique involves a comparison of normalized radiances measured by OMI over the Antarctic continent with top-of-the-atmosphere (TOA) values computed with a radiative transfer model. In our model we assume a Rayleigh-scattering, aerosol-free, cloud-free atmosphere, and a mean surface reflectance derived from measurements on the ground. TOA radiances are sensitive to the bi-directional distribution of surface reflectance, especially at high solar zenith angles. We have developed a surface reflectance model to help correct these effects, but it still remains the largest source of uncertainty. We estimate the residual uncertainty at all wavelengths to be 2%.

Simultaneous determination of CRP and D-dimer in human blood plasma samples with White Light Reflectance Spectroscopy.

PubMed

Koukouvinos, Georgios; Petrou, Panagiota; Misiakos, Konstantinos; Drygiannakis, Dimitris; Raptis, Ioannis; Stefanitsis, Gerasimos; Martini, Spyridoula; Nikita, Dimitra; Goustouridis, Dimitrios; Moser, Isabella; Jobst, Gerhard; Kakabakos, Sotirios

2016-10-15

A dual-analyte assay for the simultaneous determination of C-reactive protein (CRP) and D-dimer in human blood plasma based on a white light interference spectroscopy sensing platform is presented. Measurement is accomplished in real-time by scanning the sensing surface, on which distinct antibody areas have been created, with a reflection probe used both for illumination of the surface and collection of the reflected interference spectrum. The composition of the transducer, the sensing surface chemical activation and biofunctionalization procedures were optimized with respect to signal magnitude and repeatability. The assay format involved direct detection of CRP whereas for D-dimer a two-site immunoassay employing a biotinylated reporter antibody and reaction with streptavidin was selected. The assays were sensitive with detection limits of 25ng/mL for both analytes, precise with intra- and inter-assay CV values ranging from 3.6% to 7.7%, and from 4.8% to 9.5%, respectively, for both assays, and accurate with recovery values ranging from 88.5% to 108% for both analytes. Moreover, the values determined for the two analytes in 35 human plasma samples were in excellent agreement with those received for the same samples by standard diagnostic laboratory instrumentation employing commercial kits. The excellent agreement of the results supported the validity of the proposed system for clinical application for the detection of multiple analytes since it was demonstrated that up to seven antibody areas can be created on the sensing surface and successfully interrogated with the developed optical set-up. Copyright © 2015. Published by Elsevier B.V.

An instrument for the geometric attributes of metallic appearance.

PubMed

Christie, J S

1969-09-01

With the use of a greater variety of metals and methods of finishing them, an increasing need to measure metallic appearance has developed in the automotive industry. A simple and easy to operate instrument has been designed to measure the geometric characteristics of reflectance related to metallic appearance. These are specular reflectance, distinctness of image, haze, and diffuseness. A series of selected aluminum and stainless steel specimens has been used to test the performance of the new instrument and of older devices with which it has been compared. Functionally, the new instrument combines features of the Distinctness of ReflectedImage (DORI)meter designed by Tingle, and the abridged goniophotometer designed by Tingle and George. The design and operation of the new instrument have been simplified by use of multiple receptor apertures with optical fiber light collectors. The measurement of a wide range of metal appearance characteristic has thus been achieved with mechanical and electrical circuit simplicity.

Range Imaging without Moving Parts

NASA Technical Reports Server (NTRS)

Blair, J. Bryan; Scott, V. Stanley, III; Ramos-Izquierdo, Luis

2008-01-01

Range-imaging instruments of a type now under development are intended to generate the equivalent of three-dimensional images from measurements of the round-trip times of flight of laser pulses along known directions. These instruments could also provide information on characteristics of targets, including roughnesses and reflectivities of surfaces and optical densities of such semi-solid objects as trees and clouds. Unlike in prior range-imaging instruments based on times of flight along known directions, there would be no moving parts; aiming of the laser beams along the known directions would not be accomplished by mechanical scanning of mirrors, prisms, or other optical components. Instead, aiming would be accomplished by using solid-state devices to switch input and output beams along different fiber-optic paths. Because of the lack of moving parts, these instruments could be extraordinarily reliable, rugged, and long-lasting. An instrument of this type would include an optical transmitter that would send out a laser pulse along a chosen direction to a target. An optical receiver coaligned with the transmitter would measure the temporally varying intensity of laser light reflected from the target to determine the distance and surface characteristics of the target. The transmitter would be a combination of devices for generating precise directional laser illumination. It would include a pulsed laser, the output of which would be coupled into a fiber-optic cable with a fan-out and solid-state optical switches that would enable switching of the laser beam onto one or more optical fibers terminated at known locations in an array on a face at the focal plane of a telescope. The array would be imaged by the telescope onto the target space. The receiver optical system could share the aforementioned telescope with the transmitter or could include a separate telescope aimed in the same direction as that of the transmitting telescope. In either case, light reflected from the target would be focused by the receiver optical system onto an array of optical fibers matching the array in the transmitter. These optical fibers would couple the received light to one or more photodetector( s). Optionally, the receiver could include solid-state optical switches for choosing which optical fiber(s) would couple light to the photodetector(s). This instrument architecture is flexible and can be optimized for a wide variety of applications and levels of performance. For example, it is scalable to any number of pixels and pixel resolutions and is compatible with a variety of ranging and photodetection methodologies, including, for example, ranging by use of modulated (including pulsed and encoded) light signals. The use of fixed arrays of optical fibers to generate controlled illumination patterns would eliminate the mechanical complexity and much of the bulk of optomechanical scanning assemblies. Furthermore, digital control of the selection of the fiber-optic pathways for the transmitted beams could afford capabilities not seen in previous three-dimensional range-imaging systems. Instruments of this type could be specialized for use as, for example, proximity detectors, three-dimensional robotic vision systems, airborne terrain-mapping systems, and inspection systems.

The effect of piezoelectric ultrasonic instrumentation on titanium discs: a microscopy and trace elemental analysis in vitro study.

PubMed

Tawse-Smith, A; Atieh, M A; Tompkins, G; Duncan, W J; Reid, M R; Stirling, C H

2016-08-01

To evaluate in vitro topographical and composition changes by piezoelectric ultrasonic instrumentation with metallic and plastic tips on machined and moderately roughened titanium surfaces. Twenty machined and moderately roughened laser-marked titanium discs were ultrasonically instrumented with metallic and plastic tips. Surface instrumentation was carried out with controlled pressure for 20 and 30 seconds at two power settings. For each time and power setting, instrumentation was repeated four times with one instrumentation per disc quadrant. Surface topography analysis was performed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Surface roughness measurements were compared between instrumented and non-instrumented surfaces. Surface element composition and rinsing solutions were evaluated using energy-dispersive spectroscopy (EDS) and trace elemental analysis using inductively coupled plasma mass spectrometry (ICPMS), respectively. SEM photomicrographs and CLSM 3D surface plot images of instrumented machined and moderately roughened surfaces demonstrated severe surface topographical alterations with metallic tips and mild to moderate changes for plastic tip instrumented sites. ICPMS analysis of the rinsing solutions identified titanium and other metal traces with the use of metallic tips, and mainly titanium and carbon when plastic tips were used. Surface EDS analysis showed elemental traces of the ultrasonic tips. Ultrasonic instrumentation with metallic or plastic tips created surface topographical and compositional changes. Different changes in surface topography were noted between the surfaces, as the roughness of the machined surfaces increased while the extent of roughness of the moderately roughened surfaces decreased. The clinical relevance of these changes is yet to be determined. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Spectral modeling of Ceres VIR data from Dawn: Method and Result

NASA Astrophysics Data System (ADS)

Raponi, Andrea; De Sanctis, M. C.; Ciarniello, M.; Carrozzo, F. G.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Frigeri, A.; Fonte, S.; Giardino, M.; Longobardo, A.; Magni, G.; Marchi, S.; Palomba, E.; Pieters, C. M.; Tosi, F.; Turrini, D.; Zambon, F.; Raymond, C. A.; Russell, C. T.

2015-11-01

The Dawn spacecraft [1] is at Ceres, the closest of the IAU-defined dwarf planets to the Sun. This work focuses on the interpretation of Ceres’ surface composition based on the data from the VIR instrument [2] onboard Dawn. The Visible InfraRed (VIR) mapping spectrometer combines high spectral and spatial resolution in the VIS (0.25-1mm) and IR (1-5mm) spectral ranges. VIR will provide a very good coverage of the surface during its orbital mission at Ceres.In order to model the measured spectra, we have utilized Hapke's radiative transfer model [3], which allows estimation of the mineral composition, the relative abundances of the spectral end-members, and the grain size. Optical constants of the spectral end-members are approximated by applying the methodology described in [4] to IR spectra reflectance obtained from the RELAB database.The observed spectra of Ceres surface are affected by a thermal emission component that prevents direct comparison with laboratory data at longer wavelengths. Thus to model the whole wavelength range measured by VIR, the thermal emission is modeled together with the reflectance. Calibrated spectra are first cleaned by removing artefacts. A best fit is obtained with a least square optimization algorithm. For further details on the method, see reference [5].The range 2.5 - 2.9 μm is severely hindered by Earth's atmosphere, but it contains a strong absorption band that dominates the IR Ceres’ spectrum. Thanks to the VIR instrument we can obtain a compositional model for the whole IR range [6]. We used several different combinations of materials hypothesized to be representative of the Ceres’ surface including phyllosilicates, ices, carbonaceous chondrites and salts. The results will be discussed.Acknowledgements This work is supported by the Italian Space Agencies and NASA. Enabling contributions from the Dawn Instrument, Operations, and Science Teams are gratefully acknowledged.Reference[1] Russell et al., Space Sci. Rev., 163, 3-23, 2011.[2] De Sanctis et al., Space Sci. Rev., 163, 329-369, 2011.[3] Hapke, Cambridge Univ. Press., 1993, 2012.[4] Carli et al., Icarus, 235, 207-219, 2014.[5] Raponi, PhD Thesis, arXiv:1503.08172, 2015.[6] De Sanctis et al., Nature submitted 2015.

Development of a Tip-Enhanced Near-Field Optical Microscope for Nanoscale Interrogation of Surface Chemistry and Plasmonic Phenomena

NASA Astrophysics Data System (ADS)

Heilman, Alexander Lee

Optical microscopy and spectroscopy are invaluable tools for the physical and chemical characterization of materials and surfaces in a wide range of scientific disciplines. However, the application of conventional optical methods in the study of nanomaterials is inherently limited by diffraction. Tip-enhanced near-field optical microscopy (TENOM) is a hybrid technique that marries optical spectroscopy with scanning probe microscopy to overcome the spatial resolution limit imposed by diffraction. By coupling optical energy into the plasmonic modes of a sharp metal probe tip, a strong, localized optical field is generated near the tip's apex and is used to enhance spectroscopic emissions within a sub-diffraction-limited volume. In this thesis, we describe the design, construction, validation, and application of a custom TENOM instrument with a unique attenuated total reflectance (ATR)-geometry excitation/detection system. The specific goals of this work were: (i) to develop a versatile TENOM instrument capable of investigating a variety of optical phenomena at the nanoscale, (ii) to use the instrument to demonstrate chemical interrogation of surfaces with sub-diffraction-limited spatial resolution (i.e., at super resolution), (iii) to apply the instrument to study plasmonic phenomena that influence spectroscopic enhancement in TENOM measurements, and (iv) to leverage resulting insights to develop systematic improvements that expand the ultimate capabilities of near-field optical interrogation techniques. The TENOM instrument described herein is comprised of three main components: an atomic force microscope (AFM), a side-on confocal Raman microscope, and a novel ATR excitation/detection system. The design of each component is discussed along with the results of relevant validation experiments, which were performed to rigorously assess each component's performance. Finite-difference time-domain (FDTD) optical simulations were also developed and used extensively to evaluate the results of validation studies and to optimize experimental design and instrument performance. By combining and synchronizing the operation of the instrument's three components, we perform a variety of near-field optical experiments that demonstrate the instrument's functionality and versatility. ATR illumination is combined with a plasmonic AFM tip to show that: (i) the tip can quantitatively transduce the optical near-field (evanescent waves) above the surface by scattering photons into the far-field, (ii) the ATR geometry enables excitation and characterization of surface plasmon polaritons (SPPs), whose associated optical fields are shown to enhance Raman scattering from a thin layer of copper phthalocyanine (CuPc), and (iii) SPPs can be used to plasmonically excite the tip for super-resolution chemical imaging of patterned CuPc via tip-enhanced Raman spectroscopy (TERS). ATR-illumination TERS is quantitatively compared with side-on illumination. In both cases, spatial resolution was better than 40 nm and tip-on/tip-off Raman enhancement factors were >6500. Furthermore, ATR illumination was shown to provide similar Raman signal levels at lower "effective'' pump powers due to additional optical energy delivered by SPPs to the active region in the tip-surface gap. We also investigate the sensitivity of the TENOM instrument to changes in the plasmonic properties of the tip-surface system in the strongly-coupled regime at small tip-surface separations. Specifically, we demonstrate detection of a resonant plasmonic tip-surface mode (a gap plasmon) that dramatically influences the optical response of the system, and we use experimental results and FDTD simulations to support a hypothesized mechanism. Moreover, we confirm that the gap plasmon resonance has a strong effect on the enhancement of both fluorescence and Raman scattering, and we propose that this phenomenon could ultimately be exploited to improve sensitivity in super-resolution chemical imaging measurements. Finally, we recommend a straightforward modification to the TENOM instrument that could enable future application of these gap-mode plasmon resonances to increase spectroscopic enhancements by an order of magnitude.

Big capabilities in small packages: hyperspectral imaging from a compact platform

NASA Astrophysics Data System (ADS)

Beasley, Matthew; Goldberg, Hannah; Voorhees, Christopher; Illsley, Peter

2016-09-01

We present the Compact Holographic Aberration-corrected Platform (CHAP) instrument, designed and developed at Planetary Resources Development Corporation. By combining a dispersive element with the secondary of a telescope, we are able to produce a relatively long focal length with moderate dispersion at the focal plane. This design enables us to build a capable hyperspectral imaging instrument within the size constraints of the Cubesat form-factor. The advantages of our design revolves around its simplicity: there are only two optical elements, producing both a white light and diffracted image. With the use of a replicated grating, we can produce a long focal length hyperspectral imager at a price point far below other spaceflight instruments. The design is scalable for larger platforms and since it has no transmitting optics and only two reflective surfaces could be designed to function at any desired wavelength. Our system will be capable of spectral imaging across the 400 to 900 nm spectral range for use in small body surveys.

Effects of electropolishing surface treatment on the cyclic fatigue resistance of BioRace nickel-titanium rotary instruments.

PubMed

Lopes, Hélio P; Elias, Carlos N; Vieira, Victor T L; Moreira, Edson J L; Marques, Raquel V L; de Oliveira, Julio C Machado; Debelian, Gilberto; Siqueira, José F

2010-10-01

This study evaluated the influence of electropolishing surface treatment on the number of cycles to fracture of BioRace rotary nickel-titanium endodontic instruments. BioRace size BR5C instruments with or without electropolishing surface treatment were used in an artificial curved canal under rotational speed of 300 rpm until fracture. Fractured surfaces and the helical shafts of fractured instruments were analyzed by scanning electron microscopy (SEM). Polished instruments displayed a significantly higher number of cycles to fracture when compared with nonpolished instruments (P < .001). Actually, the number of cycles to fracture of a polished BR5C instrument was 124% higher than that of a nonpolished instrument. SEM analysis showed that the fractured surface of both polished and nonpolished BR5C instruments had ductile morphologic characteristics. Evaluation of the separated fragments after cyclic fatigue testing showed the presence of microcracks near the fracture surface. Polished instruments exhibited fine cracks that assumed an irregular path (zigzag crack pattern), whereas nonpolished instruments showed cracks running along the machining grooves. Electropolishing surface treatment of BioRace endodontic instruments significantly increased the cyclic fatigue resistance. Copyright © 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Multifunctional ultra-high vacuum apparatus for studies of the interactions of chemical warfare agents on complex surfaces

NASA Astrophysics Data System (ADS)

Wilmsmeyer, Amanda R.; Gordon, Wesley O.; Davis, Erin Durke; Mantooth, Brent A.; Lalain, Teri A.; Morris, John R.

2014-01-01

A fundamental understanding of the surface chemistry of chemical warfare agents is needed to fully predict the interaction of these toxic molecules with militarily relevant materials, catalysts, and environmental surfaces. For example, rules for predicting the surface chemistry of agents can be applied to the creation of next generation decontaminants, reactive coatings, and protective materials for the warfighter. Here, we describe a multifunctional ultra-high vacuum instrument for conducting comprehensive studies of the adsorption, desorption, and surface chemistry of chemical warfare agents on model and militarily relevant surfaces. The system applies reflection-absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and mass spectrometry to study adsorption and surface reactions of chemical warfare agents. Several novel components have been developed to address the unique safety and sample exposure challenges that accompany the research of these toxic, often very low vapor pressure, compounds. While results of vacuum-based surface science techniques may not necessarily translate directly to environmental processes, learning about the fundamental chemistry will begin to inform scientists about the critical aspects that impact real-world applications.

Multifunctional ultra-high vacuum apparatus for studies of the interactions of chemical warfare agents on complex surfaces.

PubMed

Wilmsmeyer, Amanda R; Gordon, Wesley O; Davis, Erin Durke; Mantooth, Brent A; Lalain, Teri A; Morris, John R

2014-01-01

A fundamental understanding of the surface chemistry of chemical warfare agents is needed to fully predict the interaction of these toxic molecules with militarily relevant materials, catalysts, and environmental surfaces. For example, rules for predicting the surface chemistry of agents can be applied to the creation of next generation decontaminants, reactive coatings, and protective materials for the warfighter. Here, we describe a multifunctional ultra-high vacuum instrument for conducting comprehensive studies of the adsorption, desorption, and surface chemistry of chemical warfare agents on model and militarily relevant surfaces. The system applies reflection-absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and mass spectrometry to study adsorption and surface reactions of chemical warfare agents. Several novel components have been developed to address the unique safety and sample exposure challenges that accompany the research of these toxic, often very low vapor pressure, compounds. While results of vacuum-based surface science techniques may not necessarily translate directly to environmental processes, learning about the fundamental chemistry will begin to inform scientists about the critical aspects that impact real-world applications.

Multifunctional ultra-high vacuum apparatus for studies of the interactions of chemical warfare agents on complex surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilmsmeyer, Amanda R.; Morris, John R.; Gordon, Wesley O.

2014-01-15

A fundamental understanding of the surface chemistry of chemical warfare agents is needed to fully predict the interaction of these toxic molecules with militarily relevant materials, catalysts, and environmental surfaces. For example, rules for predicting the surface chemistry of agents can be applied to the creation of next generation decontaminants, reactive coatings, and protective materials for the warfighter. Here, we describe a multifunctional ultra-high vacuum instrument for conducting comprehensive studies of the adsorption, desorption, and surface chemistry of chemical warfare agents on model and militarily relevant surfaces. The system applies reflection-absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and mass spectrometry tomore » study adsorption and surface reactions of chemical warfare agents. Several novel components have been developed to address the unique safety and sample exposure challenges that accompany the research of these toxic, often very low vapor pressure, compounds. While results of vacuum-based surface science techniques may not necessarily translate directly to environmental processes, learning about the fundamental chemistry will begin to inform scientists about the critical aspects that impact real-world applications.« less

An X-Ray Diffractometer for Mineralogical Analysis of Exomars Mission

NASA Astrophysics Data System (ADS)

Marinangeli, L.; Baliva, A.; Critani, F.; Stevoli, A.; Scandelli, L.; Holland, A.; Hutchinson, I.; Nelms, N.; Delhez, R.

2006-12-01

The new results of the Mars Exploration Rovers and the Mars Express mission outline the importance of a correct assessment of the variety of geological contexts to understand the evolution of a habitable environment. The need of having complex scientific payload to perform a broad range of in situ measurements is a necessary step for a successful exobiological exploration. Furthermore, the compositional analysis of the surface samples is of fundamental importance to characterize the geological environments where life could have arisen and their evolution through time. In the last years, there has been a strong interest in Europe to develop a x-ray diffractometer (XRD) for mineralogical analyses of planetary surfaces. The identification of minerals using the diffraction technique is based on the x-ray interference with the geometrical parameters of the crystal lattice allowing an unequivocal recognition of different minerals. An US XRD instrument, CHEMIN, will flight for the first time in the NASA Mars Science Laboratory in 2009. An European XRD design has also been selected for the Pasteur Payload of the ESA ExoMars mission, planned for 2011. The proposed instrument is a miniaturised concept (1 kg) configured in a reflection geometry and will allow the identification of a large spectrum of minerals including those related to the presence of water, key element for the development of life. The complete mineralogical analysis will be performed on very small quantities of powder rock samples, thought analysis of pristine (no grinded) sample can also be achieved with the reflection configuration. Information on the elemental composition of the sample can be roughly estimated by the analysis of the x-ray fluorescence spectrum simultaneously acquired by the detection system. In order to demonstrate the instrument technological readiness for the ExoMars mission, the construction of a demonstrative prototype is on going with ESA funding. Preliminary result of the scientific evaluation of the prototype will be shown to assess the capability of the proposed concept in the identification of rock mineralogy. IRSPS and and Laben are respectively the team science coordinator and the engineering responsible for the instrument development. The detector assembly for the prototype has been developed by UK and discussion for the UK involvement on the future instrument development is on going. Delft is providing scientific contribution for the prototype evaluation.

Surface Reflectometry and Ionosphere Sounding from the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON)

NASA Astrophysics Data System (ADS)

Grima, C.; Blankenship, D. D.; Schroeder, D. M.; Moussessian, A.; Soderlund, K. M.; Gim, Y.; Plaut, J. J.; Greenbaum, J. S.; Lopez Garcia, E.; Campbell, B. A.; Putzig, N. E.; Patterson, G.

2015-12-01

The Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) has been selected for the scientific payload of a NASA's multiple flyby mission to explore the icy moon Europa. REASON is an active dual-frequency (9/60 MHz) instrument led by the University of Texas Institute for Geophysics (UTIG). It is designed to achieve multi-disciplinary measurements to investigate subsurface waters and the ice shell structure (Sounding), the surface elevation and tides (Altimetry), the surface physical properties (Reflectometry), and the ionospheric environment (Plasma/Particles). We will present the concepts behind the "Reflectometry" and "Plasma/Particles" measurements, demonstrate their efficiency with planetary analogs, and anticipate their capabilities for the exploration of Europa. We will also highlight the potential synergies with other instruments selected for the Europa mission payload.The "Reflectometry" compares the statistical behavior of the surface echo amplitudes with theoretical stochastic models to separate the reflected and scattered contributions to the signal. Once those two components are deduced they are used in a backscattering model to invert surface properties such as roughness, density, and/or impurity load. "Reflectometry" measurements will contribute to the statistical characterization of the surface over ~ 10-km-long areas with a ~ 10 m skin depth for geological investigation, near-surface brine detection, plume-deposited snow characterization, and landing site reconnaissance. The "Plasma/Particles" measurement relies on the dispersive signal delays induced by the ionospheric content integrated along the radio propagation path. Correction of this delay with existing techniques provides the total electron content below the spacecraft. "Plasma/Particles" measurements will constrain the ionosphere's shape and variability along the acquisition track and might detect transient plume-induced ionosphere when active.

The CZCS geolocation algorithms

NASA Technical Reports Server (NTRS)

Wilson, W. H.; Smith, R. C.; Nolten, J. W.

1981-01-01

The Coastal Zone Color Scanner (CZCS) on board the Nimbus 7 satellite was designed to measure surface radiance upwelled from the ocean in 6 spectral bands. The CZCS spectrometer obtains its information from a rotating mirror and is timed to collect data when the mirror views the Earth surface between ca. 40 degrees to the left and right of the subsatellite track. Each scan is divided into 1968 picture elements, pixels, of 0.04 degrees scan each. In order to avoid direct reflected Sun glint, the rotating mirror shaft can be tilted so that scans across the subsatellite track up to 20 degrees forward or aft of the point directed beneath the satellite. The CZCS is the first satellite borne instrument to have this tilted scan capability and therefore poses some new problems in locating the Earth surface position of viewed pixels.

Ice911 Research: A Reversible Localized Geo-Engineering Technique to Mitigate Climate Change Effects: Field Testing, Instrumentation and Climate Modeling Results

NASA Astrophysics Data System (ADS)

Field, L. A.; Sholtz, A.; Chetty, S.; Manzara, A.; Johnson, D.; Christodoulou, E.; Decca, R.; Walter, P.; Katuri, K.; Bhattacharyya, S.; Ivanova, D.; Mlaker, V.; Perovich, D. K.

2017-12-01

This work uses ecologically benign surface treatment of silica-based materials in carefully selected, limited areas to reduce polar ice melt by reflecting energy from summertime polar sun to attempt to slow ice loss due to the Ice-Albedo Feedback Effect. Application of Ice911's materials can be accomplished within a season, at a comparatively low cost, and with far less secondary environmental impact than many other proposed geo-engineering solutions. Field testing, instrumentation, safety testing, data-handling and modeling results will be presented. The albedo modification has been tested over a number of melt seasons with an evolving array of instrumentation, at multiple sites and on progressively larger scales, most recently in a small artificial pond in Minnesota and in a lake in Barrow, Alaska's BEO (Barrow Experimental Observatory) area. The test data show that the glass bubbles can provide an effective material for increasing albedo, significantly reducing the melting rate of ice. Using NCAR's CESM package the environmental impact of the approach of surface albedo modification was studied. During two separate runs, region-wide Arctic albedo modification as well as more targeted localized treatments were modeled and compared. The parameters of a surface snow layer are used as a proxy to simulate Ice911's high-albedo materials, and the modification is started in January over selected ice/snow regions in the Arctic. Preliminary results show promising possibilities of enhancements in surface albedo, sea ice area and sea-ice concentration, as well as temperature reductions of .5 to 3 degree Kelvin in the Arctic, and global average temperature reductions of .5 to 1 degrees.

Large area space qualified thermoelectrically (TE) cooled HgCdTe MW photovoltaic detectors for the Halogen Occultation Experiment (HALOE)

NASA Technical Reports Server (NTRS)

Norton, P. W.; Zimmermann, P. H.; Briggs, R. J.; Hartle, N. M.

1986-01-01

Large-area, HgCdTe MW photovoltaic detectors have been developed for the NASA-HALOE instrument scheduled for operation on the Upper Atmospheric Research Satellite. The photodiodes will be TE-cooled and were designed to operate in the 5.1-5.4 micron band at 185 K to measure nitric oxide concentrations in the atmosphere. The active area required 15 micron thick devices and a full backside common contact. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.

Measurement of atmospheric water vapor, leaf liquid water and reflectance with AVIRIS in the Boreal Ecosystem-Atmosphere Study: Initial results

NASA Technical Reports Server (NTRS)

Green, Robert O.; Conel, James E.; Roberts, Dar A.

1995-01-01

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) acquired data as part of the Boreal Ecosystem-Atmosphere Study (BOREAS) in 1994. Flights occurred over the northern study area (NSA) in the region of 56 degrees north latitude and 98.5 degrees west longitude and over the southern study area (SSA) at 54 degrees north latitude and 105 degrees west longitude. These data will be used to directly derive spectral properties of the surface and atmosphere and to provide supporting data for other instruments, models, and experiments in support of the BOREAS objectives. We present a preliminary evaluation of the AVIRIS data collected in BOREAS in terms of the AVIRIS-derived parameters: water vapor, leaf water, and apparent spectral reflectance.

Application of Phase Shifted, Laser Feedback Interferometry to Fluid Physics

NASA Technical Reports Server (NTRS)

Ovryn, Ben; Eppell, Steven J.; Andrews, James H.; Khaydarov, John

1996-01-01

We have combined the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce a new instrument that can measure both optical path length (OPL) changes and discern sample reflectivity variations. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. LFI can yield a high signal-to-noise ratio even for low reflectivity samples. By combining PSI and LFI, we have produced a robust instrument, based upon a HeNe laser, with high dynamic range that can be used to measure either static (dc) or oscillatory changes along the optical path. As with other forms of interferometry, large changes in OPL require phase unwrapping. Conversely, small phase changes are limited by the fraction of a fringe that can be measured. We introduce the phase shifts with an electro-optic modulator (EOM) and use either the Carre or Hariharan algorithms to determine the phase and visibility. We have determined the accuracy and precision of our technique by measuring both the bending of a cantilevered piezoelectric bimorph and linear ramps to the EOM. Using PSI, sub-nanometer displacements can be measured. We have combined our interferometer with a commercial microscope and scanning piezoelectric stage and have measured the variation in OPL and visibility for drops of PDMS (silicone oil) on coated single crystal silicon. Our measurement of the static contact angle agrees with the value of 68 deg stated in the literature.

Total Ozone Mapping Spectrometer (TOMS) Level-3 Data Products User's Guide

NASA Technical Reports Server (NTRS)

McPeters, Richard D.; Bhartia, P. K.; Krueger, Arlin J.; Herman, Jay R.; Wellemeyer, Charles G.; Seftor, Colin J.; Byerly, William; Celarier, Edward A.

2000-01-01

Data from the TOMS series of instruments span the time period from November 1978, through the present with about a one and a-half year gap from January 1994 through July 1996. A set of four parameters derived from the TOMS measurements have been archived in the form of daily global maps or Level-3 data products. These products are total column ozone, effective surface reflectivity, aerosol index, and erythermal ultraviolet estimated at the Earth surface. A common fixed grid of I degree latitude by 1.25 degree longitude cells over the entire globe is provided daily for each parameter. These data are archived at the Goddard Space Flight Center Distributed Active Archive Center (DAAQ in Hierarchical Data Format (HDF). They are also available in a character format through the TOMS web site at http://toms.gsfc.nasa.gov. The derivations of the parameters, the mapping algorithm, and the data formats are described. The trend uncertainty for individual TOMS instruments is about 1% decade, but additional uncertainty exists in the combined data record due to uncertainty in the relative calibrations of the various TOMS.

Development of low cost and accurate homemade sensor system based on Surface Plasmon Resonance (SPR)

NASA Astrophysics Data System (ADS)

Laksono, F. D.; Supardianningsih; Arifin, M.; Abraha, K.

2018-04-01

In this paper, we developed homemade and computerized sensor system based on Surface Plasmon Resonance (SPR). The developed systems consist of mechanical system instrument, laser power sensor, and user interface. The mechanical system development that uses anti-backlash gear design was successfully able to enhance the angular resolution angle of incidence laser up to 0.01°. In this system, the laser detector acquisition system and stepper motor controller utilizing Arduino Uno which is easy to program, flexible, and low cost, was used. Furthermore, we employed LabView’s user interface as the virtual instrument for facilitating the sample measurement and for transforming the data recording directly into the digital form. The test results using gold-deposited half-cylinder prism showed the Total Internal Reflection (TIR) angle of 41,34°± 0,01° and SPR angle of 44,20°± 0,01°, respectively. The result demonstrated that the developed system managed to reduce the measurement duration and data recording errors caused by human error. Also, the test results also concluded that the system’s measurement is repeatable and accurate.

Radiative transfer through terrestrial atmosphere and ocean: Software package SCIATRAN

NASA Astrophysics Data System (ADS)

Rozanov, V. V.; Rozanov, A. V.; Kokhanovsky, A. A.; Burrows, J. P.

2014-01-01

SCIATRAN is a comprehensive software package for the modeling of radiative transfer processes in the terrestrial atmosphere and ocean in the spectral range from the ultraviolet to the thermal infrared (0.18 - 40 μm) including multiple scattering processes, polarization, thermal emission and ocean-atmosphere coupling. The software is capable of modeling spectral and angular distributions of the intensity or the Stokes vector of the transmitted, scattered, reflected, and emitted radiation assuming either a plane-parallel or a spherical atmosphere. Simulations are done either in the scalar or in the vector mode (i.e. accounting for the polarization) for observations by space-, air-, ship- and balloon-borne, ground-based, and underwater instruments in various viewing geometries (nadir, off-nadir, limb, occultation, zenith-sky, off-axis). All significant radiative transfer processes are accounted for. These are, e.g. the Rayleigh scattering, scattering by aerosol and cloud particles, absorption by gaseous components, and bidirectional reflection by an underlying surface including Fresnel reflection from a flat or roughened ocean surface. The software package contains several radiative transfer solvers including finite difference and discrete-ordinate techniques, an extensive database, and a specific module for solving inverse problems. In contrast to many other radiative transfer codes, SCIATRAN incorporates an efficient approach to calculate the so-called Jacobians, i.e. derivatives of the intensity with respect to various atmospheric and surface parameters. In this paper we discuss numerical methods used in SCIATRAN to solve the scalar and vector radiative transfer equation, describe databases of atmospheric, oceanic, and surface parameters incorporated in SCIATRAN, and demonstrate how to solve some selected radiative transfer problems using the SCIATRAN package. During the last decades, a lot of studies have been published demonstrating that SCIATRAN is a valuable tool for a wide range of remote sensing applications. Here, we present some selected comparisons of SCIATRAN simulations to published benchmark results, independent radiative transfer models, and various measurements from satellite, ground-based, and ship instruments. Methods for solving inverse problems related to remote sensing of the Earth's atmosphere using the SCIATRAN software are outside the scope of this study and will be discussed in a follow-up paper. The SCIATRAN software package along with a detailed User's Guide is freely available for non-commercial use via the webpage of the Institute of Environmental Physics (IUP), University of Bremen: http://www.iup.physik.uni-bremen.de/sciatran.

An Evaluation of Sea Surface Temperature as Measured by the Nimbus 1 High Resolution Infrared Radiometer

NASA Technical Reports Server (NTRS)

Allison, Lewis J.; Kennedy, James S.

1967-01-01

An analysis of Nimbus I HRIR data over various parts of the world indicated limited success in deriving sea surface temperatures to within 3 to 6 K of aircraft radiation measurements (8- 13 microns) and synoptic-climatological ship sea surface temperature data. The areas studied included the east, west and Gulf coasts of the United States, West Greenland, Nova Scotia, southern Japan, the eastern Mediterranean Sea, Caspian Sea, Persian Gulf, and the Indian Ocean. At night, thin clouds which may fill the radiometer's field of view make it difficult to interpret the absolute values of derived sea surface temperature. During the daytime, the HRIR data is unusable for oceanographic temperature analysis because the contamination by reflected solar radiation mixes with the emitted radiation. Future satellite instrumentation, consisting of a HFUR radiometer (10-11 microns) when used in conjunction with television. data, will delineate cloud free ocean areas and permit the daily derivation of sea surface temperatures from approximately 10 to 30 Percent of the world's oceanic regions.

Reassessing biases and other uncertainties in sea surface temperature observations measured in situ since 1850: 2. Biases and homogenization

NASA Astrophysics Data System (ADS)

Kennedy, J. J.; Rayner, N. A.; Smith, R. O.; Parker, D. E.; Saunby, M.

2011-07-01

Changes in instrumentation and data availability have caused time-varying biases in estimates of global and regional average sea surface temperature. The size of the biases arising from these changes are estimated and their uncertainties evaluated. The estimated biases and their associated uncertainties are largest during the period immediately following the Second World War, reflecting the rapid and incompletely documented changes in shipping and data availability at the time. Adjustments have been applied to reduce these effects in gridded data sets of sea surface temperature and the results are presented as a set of interchangeable realizations. Uncertainties of estimated trends in global and regional average sea surface temperature due to bias adjustments since the Second World War are found to be larger than uncertainties arising from the choice of analysis technique, indicating that this is an important source of uncertainty in analyses of historical sea surface temperatures. Despite this, trends over the twentieth century remain qualitatively consistent.

Apparatus to measure adsorption of condensable solvents on technical surfaces by photothermal deflection

NASA Astrophysics Data System (ADS)

Plimmer, M. D.; du Colombier, D.; Iraqi Houssaini, N.; Silvestri, Z.; Pinot, P.; Hannachi, R.

2012-11-01

This article describes an instrument for the measurement of the mirage effect as a tool to determine the molar adsorption per unit surface area Y1 of condensable solvents in the presence of a non-condensable carrier gas. The present apparatus is a much improved version of previous prototypes developed in our laboratory and elsewhere with a higher surface bake-out temperature (150 °C rather than 40 °C), lower residual vacuum (3 Pa versus 100 Pa), greater sample surface (40 mm diameter instead of 10 mm), more powerful optical pump beam (150 W cf. 50 W), and larger saturated vapour preparation volume (4 L instead of 1 L). The new set-up also includes the in situ monitoring of the surface via a reflected HeNe laser beam for the real-time detection of the onset of condensation. Here, we give a detailed description of the various components, outline the experimental procedure, show typical results, and suggest some straightforward improvements.

Apparatus to measure adsorption of condensable solvents on technical surfaces by photothermal deflection.

PubMed

Plimmer, M D; du Colombier, D; Iraqi Houssaini, N; Silvestri, Z; Pinot, P; Hannachi, R

2012-11-01

This article describes an instrument for the measurement of the mirage effect as a tool to determine the molar adsorption per unit surface area Y(1) of condensable solvents in the presence of a non-condensable carrier gas. The present apparatus is a much improved version of previous prototypes developed in our laboratory and elsewhere with a higher surface bake-out temperature (150 °C rather than 40 °C), lower residual vacuum (3 Pa versus 100 Pa), greater sample surface (40 mm diameter instead of 10 mm), more powerful optical pump beam (150 W cf. 50 W), and larger saturated vapour preparation volume (4 L instead of 1 L). The new set-up also includes the in situ monitoring of the surface via a reflected HeNe laser beam for the real-time detection of the onset of condensation. Here, we give a detailed description of the various components, outline the experimental procedure, show typical results, and suggest some straightforward improvements.

Thermal removal from near-infrared imaging spectroscopy data of the Moon

USGS Publications Warehouse

Clark, R.N.; Pieters, C.M.; Green, R.O.; Boardman, J.W.; Petro, N.E.

2011-01-01

In the near-infrared from about 2 ??m to beyond 3 ??m, the light from the Moon is a combination of reflected sunlight and emitted thermal emission. There are multiple complexities in separating the two signals, including knowledge of the local solar incidence angle due to topography, phase angle dependencies, emissivity, and instrument calibration. Thermal emission adds to apparent reflectance, and because the emission's contribution increases over the reflected sunlight with increasing wavelength, absorption bands in the lunar reflectance spectra can be modified. In particular, the shape of the 2 ??m pyroxene band can be distorted by thermal emission, changing spectrally determined pyroxene composition and abundance. Because of the thermal emission contribution, water and hydroxyl absorptions are reduced in strength, lowering apparent abundances. It is important to quantify and remove the thermal emission for these reasons. We developed a method for deriving the temperature and emissivity from spectra of the lunar surface and removing the thermal emission in the near infrared. The method is fast enough that it can be applied to imaging spectroscopy data on the Moon. Copyright ?? 2011 by the American Geophysical Union.

Thermal removal from near-infrared imaging spectroscopy data of the Moon

USGS Publications Warehouse

Clark, Roger N.; Pieters, Carle M.; Green, Robert O.; Boardman, J.W.; Petro, Noah E.

2011-01-01

In the near-infrared from about 2 μm to beyond 3 μm, the light from the Moon is a combination of reflected sunlight and emitted thermal emission. There are multiple complexities in separating the two signals, including knowledge of the local solar incidence angle due to topography, phase angle dependencies, emissivity, and instrument calibration. Thermal emission adds to apparent reflectance, and because the emission's contribution increases over the reflected sunlight with increasing wavelength, absorption bands in the lunar reflectance spectra can be modified. In particular, the shape of the 2 μm pyroxene band can be distorted by thermal emission, changing spectrally determined pyroxene composition and abundance. Because of the thermal emission contribution, water and hydroxyl absorptions are reduced in strength, lowering apparent abundances. It is important to quantify and remove the thermal emission for these reasons. We developed a method for deriving the temperature and emissivity from spectra of the lunar surface and removing the thermal emission in the near infrared. The method is fast enough that it can be applied to imaging spectroscopy data on the Moon.

Recent advances and product enhancements in reflective cholesteric displays

NASA Astrophysics Data System (ADS)

Khan, Asad; Schneider, Tod; Miller, Nick; Marhefka, Duane; Ernst, Todd; Nicholson, Forrest; Doane, Joseph W.

2005-04-01

Bistable reflective cholesteric displays are a liquid crystal display technology developed to fill a market need for very low power displays on a low-cost, high resolution passive matrix. Their unique look, high reflectivity, bistability, and simple structure make them an ideal flat panel display choice for handheld or other portable devices where small lightweight batteries with long lifetimes are important. We discuss recent advances in cholesteric display technology at Kent Displays such as progress towards single layer black and white displays, standard products, lower cost display modules, and various interface options for cholesteric display applications. It will be shown that inclusion of radio frequency (rf) control options and serial peripheral interface (spi) can greatly enhance the cholesteric display module market penetration by enabling quick integration into end devices. Finally, some discussion will be on the progress of the development of flexible reflective cholesteric displays. These flexible displays can dramatically change industrial design methods by enabling curved surfaces with displays integrated in them. Additional discussion in the paper will include applications of various display modes including signs, hand held instrumentation, and the electronic book and reader.

Potential Long-Term Records of Surface Albedo at Fine Spatiotemporal Resolution from Landsat/Sentinle-2A Surface Reflectance and MODIS/VIIRS BRDF

NASA Astrophysics Data System (ADS)

Li, Z.; Schaaf, C.; Shuai, Y.; Liu, Y.; Sun, Q.; Erb, A.; Wang, Z.

2016-12-01

The land surface albedo products at fine spatial resolutions are generated by coupling surface reflectance (SR) from Landsat (30 m) or Sentinel-2A (20 m) with concurrent surface anisotropy information (the Bidirectional Reflectance Distribution Function - BRDF) at coarser spatial resolutions from sequential multi-angular observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) or its successor, the Visible Infrared Imaging Radiometer Suite (VIIRS). We assess the comparability of four types of fine-resolution albedo products (black-sky and white-sky albedos over the shortwave broad band) generated by coupling, (1) Landsat-8 Optical Land Imager (OLI) SR with MODIS BRDF; (2) OLI SR with VIIRS BRDF; (3) Sentinel-2A MultiSpectral Instrument (MSI) SR with MODIS BRDF; and (4) MSI SR with VIIRS BRDF. We evaluate the accuracy of these four types of fine-resolution albedo products using ground tower measurements of surface albedo over six SURFace RADiation Network (SURFRAD) sites in the United States. For comparison with the ground measurements, we estimate the actual (blue-sky) albedo values at the six sites by using the satellite-based retrievals of black-sky and white-sky albedos and taking into account the proportion of direct and diffuse solar radiation from the ground measurements at the sites. The coupling of the OLI and MSI SR with MODIS BRDF has already been shown to provide accurate fine-resolution albedo values. With demonstration of a high agreement in BRDF products from MODIS and VIIRS, we expect to see consistency between all four types of fine-resolution albedo products. This assurance of consistency between the couplings of both OLI and MSI with both MODIS and VIIRS guarantees the production of long-term records of surface albedo at fine spatial resolutions and an increased temporal resolution. Such products will be critical in studying land surface changes and associated surface energy balance over the dynamic and heterogeneous landscapes most susceptible to climate change (such as arctic, coastal, and high-elevation zones).

EXPERIMENTS - APOLLO 17

NASA Image and Video Library

1972-11-17

S72-53470 (November 1972) --- The Far-Ultraviolet Spectrometer, Experiment S-169, one of the lunar orbital science experiments which will be mounted in the SIM bay of the Apollo 17 Service Module. Controls for activating and deactivating the experiment and for opening and closing a protective cover are located in the Command Module. Atomic composition, density and scale height for several constituents of the lunar atmosphere will be measured by the far-ultraviolet spectrometer. Solar far-UV radiation reflected from the lunar surface as well as UV radiation emitted by galactic sources also will be detected by the instrument.

Feasibility of Using Remotely Sensed Data to Aid in Long-Term Monitoring of Biodiversity

NASA Technical Reports Server (NTRS)

Carroll, Mark L.; Brown, Molly E.; Elders, Akiko; Johnson, Kiersten

2014-01-01

Remote sensing is defined as making observations of an event or phenomena without physically sampling it. Typically this is done with instruments and sensors mounted on anything from poles extended over a cornfield,to airplanes,to satellites orbiting the Earth The sensors have characteristics that allow them to detect and record information regarding the emission and reflectance of electromagnetic energy from a surface or object. That information can then be represented visually on a screen or paper map or used in data analysis to inform decision-making.

Portable Infrared Reflectometer Designed and Manufactured for Evaluating Emittance in the Laboratory or in the Field

NASA Technical Reports Server (NTRS)

Jaworske, Donald A.

2000-01-01

The optical properties of materials play a key role in spacecraft thermal control. In space, radiant heat transfer is the only mode of heat transfer that can reject heat from a spacecraft. One of the key properties for defining radiant heat transfer is emittance, a measure of how efficiently a surface can reject heat in comparison to a perfect black body emitter. Heat rejection occurs in the infrared region of the spectrum, nominally in the range of 2 to 25 mm. To calculate emittance, one obtains the reflectance over this spectral range, calculates spectral absorptance by difference, and then uses Kirchhoff s Law and the Stefan-Boltzmann equation to calculate emittance. A new portable infrared reflectometer, the SOC 400t, was designed and manufactured to evaluate the emittance of surfaces and coatings in the laboratory or in the field. It was developed by Surface Optics Corporation under a contract with the NASA Glenn Research Center at Lewis Field to replace the Center s aging Gier-Dunkle DB-100 infrared reflectometer. The specifications for the new instrument include a wavelength range of 2 to 25 mm; reflectance repeatability of +/-1 percent; self-calibrating, near-normal spectral reflectance measurements; a full scan measurement time of 3.5 min, a sample size of 1.27 cm (0.5 in.); a spectral resolution selectable from 4, 8, 16, or 32/cm; and optical property characterization utilizing an automatic integration to calculate total emittance in a selectable temperature range.

Highly compact fiber Fabry-Perot interferometer: A new instrument design

NASA Astrophysics Data System (ADS)

Nowakowski, B. K.; Smith, D. T.; Smith, S. T.

2016-11-01

This paper presents the design, construction, and characterization of a new optical-fiber-based, low-finesse Fabry-Perot interferometer with a simple cavity formed by two reflecting surfaces (the end of a cleaved optical fiber and a plane, reflecting counter-surface), for the continuous measurement of displacements of several nanometers to several tens of millimeters. No beam collimation or focusing optics are required, resulting in a displacement sensor that is extremely compact (optical fiber diameter 125 μm), is surprisingly tolerant of misalignment (more than 5°), and can be used over a very wide range of temperatures and environmental conditions, including ultra-high-vacuum. The displacement measurement is derived from interferometric phase measurements using an infrared laser source whose wavelength is modulated sinusoidally at a frequency f. The phase signal is in turn derived from changes in the amplitudes of demodulated signals, at both the modulation frequency, f, and its harmonic at 2f, coming from a photodetector that is monitoring light intensity reflected back from the cavity as the cavity length changes. Simple quadrature detection results in phase errors corresponding to displacement errors of up to 25 nm, but by using compensation algorithms discussed in this paper, these inherent non-linearities can be reduced to below 3 nm. In addition, wavelength sweep capability enables measurement of the absolute surface separation. This experimental design creates a unique set of displacement measuring capabilities not previously combined in a single interferometer.

Upgrade of goniospectrophtometer GEFE for near-field scattering and fluorescence radiance measurements

NASA Astrophysics Data System (ADS)

Bernad, Berta; Ferrero, Alejandro; Pons, Alicia; Hernanz, M. L.; Campos, Joaquín.

2015-03-01

The goniospectrophotometer GEFE, designed and developed at IO-CSIC (Instituto de Optica, Agencia Estatal Consejo Superior de Investigaciones Cientificas), was conceived to measure the spectral Bidirectional Reflectance Distribution Function (BRDF) at any pair of irradiation and detection directions. Although the potential of this instrument has largely been proved, it still required to be upgraded to deal with some important scattering features for the assessment of the appearance. Since it was not provided with a detector with spatial resolution, it simply could not measure spectrophotometric quantities to characterize texture through the Bidirectional Texture Function (BTF) or translucency through the more complex Bidirectional Scattering-Surface Reflectance Distribution Function (BSSRDF). Another requirement in the GEFE upgrading was to provide it with the capability of measuring fluorescence at different geometries, since some of the new pigments used in industry are fluorescent, which can have a non-negligible impact in the color of the product. Then, spectral resolution at irradiation and detection had to be available in GEFE. This paper describes the upgrading of the goniospectrophotometer GEFE, and its new capabilities through the presentation of sparkle and goniofluorescence measurements. In addition, the potential of the instrument to evaluate translucency by the measurement of the BSSRDF is briefly discussed.

National Institute of Standards and Technology measurement service of the optical properties of biomedical phantoms: Current status.

PubMed

Lemaillet, Paul; Cooksey, Catherine C; Levine, Zachary H; Pintar, Adam L; Hwang, Jeeseong; Allen, David W

2016-03-24

The National Institute of Standards and Technology (NIST) has maintained scales for reflectance and transmittance over several decades. The scales are primarily intended for regular transmittance, mirrors, and solid surface scattering diffusers. The rapidly growing area of optical medical imaging needs a scale for volume scattering of diffuse materials that are used to mimic the optical properties of tissue. Such materials are used as phantoms to evaluate and validate instruments under development intended for clinical use. To address this need, a double-integrating sphere based instrument has been installed to measure the optical properties of tissue-mimicking phantoms. The basic system and methods have been described in previous papers. An important attribute in establishing a viable calibration service is the estimation of measurement uncertainties. The use of custom models and comparisons with other established scales enabled uncertainty measurements. Here, we describe the continuation of those efforts to advance the understanding of the uncertainties through two independent measurements: the bidirectional reflectance distribution function and the bidirectional transmittance distribution function of a commercially available solid biomedical phantom. A Monte Carlo-based model is used and the resulting optical properties are compared to the values provided by the phantom manufacturer.

Design VHF Antennas for Space Borne Receivers for SmallSats

NASA Technical Reports Server (NTRS)

Deshpande, Manohar

2017-01-01

Space borne microwave remote sensors at VHF/UHF frequencies are important instruments to observe reflective properties of land surfaces through thick and heavy forestation on a global scale. One of the most cost effective ways of measuring land reflectivity at VHF/UHF frequencies is to use signals transmitted by existing communication satellites (operating at VHF/UHF band) as a signal of opportunity (SoOp) signal and passive receivers integrated with airborne/space borne platforms operating in the Low Earth Orbit (LEO). One of the critical components of the passive receiver is two antennas (one to receive only direct signal and other to receive only reflected signal) which need to have ideally high (>30dB) isolation. However, because of small size of host platforms and broad beam width of dipole antennas, achieving adequate isolation between two channels is a challenging problem and need to be solved for successful implementation of space borne SoOp technology for remote sensing. In this presentation a novel enabling VHF antenna technology for Cubesat platforms is presented to receive direct as well as reflected signal with needed isolation. The novel scheme also allows enhancing the gain of individual channels by factor of 2 without use of reflecting ground plane.

Automated test-site radiometer for vicarious calibration

NASA Astrophysics Data System (ADS)

Li, Xin; Yin, Ya-peng; Liu, En-chao; Zhang, Yan-na; Xun, Li-na; Wei, Wei; Zhang, Zhi-peng; Qiu, Gang-gang; Zhang, Quan; Zheng, Xiao-bing

2014-11-01

In order to realize unmanned vicarious calibration, Automated Test-site Radiometer (ATR) was developed for surface reflectance measurements. ATR samples the spectrum from 400nm-1600 nm with 8 interference filters coupled with silicon and InGaAs detectors. The field of view each channel is 10 ° with parallel optical axis. One SWIR channel lies in the center and the other seven VNIR channels are on the circle of 4.8cm diameters which guarantee each channel to view nearly the same section of ground. The optical head as a whole is temperature controlled utilizing a TE cooler for greater stability and lower noise. ATR is powered by a solar panel and transmit its data through a BDS (China's BeiDou Navigation Satellite System) terminator for long-term measurements without personnel in site. ATR deployed in Dunhuang test site with ground field about 30-cm-diameter area for multi-spectral reflectance measurements. Other instruments at the site include a Cimel sunphotometer and a diffuser-to-globe irradiance meter for atmosphere observations. The methodology for band-averaged reflectance retrieval and hyperspectral reflectance fitting process are described. Then the hyperspectral reflectance and atmospheric parameters are put into 6s code to predict TOA radiance which compare with MODIS radiance.

FTIR reflectance of selected minerals and their mixtures: implications for ground temperature-sensor monitoring on Mars surface environment (NASA/MSL-Rover Environmental Monitoring Station).

PubMed

Martín-Redondo, M Paz; Martínez, Eduardo Sebastian; Sampedro, M Teresa Fernández; Armiens, Carlos; Gómez-Elvira, Javier; Martinez-Frias, Jesus

2009-07-01

The Rover Environmental Monitoring Station (REMS) is one of NASA/MSL's instruments, which has been designed for measuring ambient pressure, humidity, wind speed and direction, UV radiation, and air and ground temperature (GT). The GT-sensor is dedicated to measure the real temperature of the Martian surface, integrating the IR energy coming from the ground. The existing IR spectral data of Martian dust, rocks and sediments allow for comparing the Martian spectra with the spectra of different terrestrial minerals and lithologies, and those of their alteration and weathering products. The FTIR reflectance of a set of selected astrobiologically significant minerals (including oxides, oxi/hydroxides, sulfates, chlorides, opal and clays) and basalt (as the main and most widespread volcanic Martian rock) was measured, considering different mixing amounts, and covering the specific working wavelength range of the REMS' GT-sensor. The results obtained show important percentage increases or decreases of reflectance in the entire wavelength range (e.g. basalt-hematite vs. basalt-magnetite) and specific variations limited to some spectral bands (e.g. basalt-smectite vs. basalt-jasper). The basalt reflectance percentage increases or decreases, even up to 100%, depending on the mixing of the different minerals. This unequivocally confirms the need for considering the chemical-mineralogical assemblages (and their textures) for any investigation and interpretation of Mars surface environment. Some complementary applications of this research on our planet, either in relation to the specific performances and characteristics of the GT-sensor autonomous recalibration system, or those oriented to carrying out similar studies on different types of terrestrial environmental settings, are also described.

Using Ground Targets to Validate S-NPP VIIRS Day-Night Band Calibration

NASA Technical Reports Server (NTRS)

Chen, Xuexia; Wu, Aisheng; Xiong, Xiaoxiong; Lei, Ning; Wang, Zhipeng; Chiang, Kwofu

2016-01-01

In this study, the observations from S-NPP VIIRS Day-Night band (DNB) and Moderate resolution bands (M bands) of Libya 4 and Dome C over the first four years of the mission are used to assess the DNB low gain calibration stability. The Sensor Data Records produced by NASA Land Product Evaluation and Algorithm Testing Element (PEATE) are acquired from nearly nadir overpasses for Libya 4 desert and Dome C snow surfaces. A kernel-driven bidirectional reflectance distribution function (BRDF) correction model is used for both Libya 4 and Dome C sites to correct the surface BRDF influence. At both sites, the simulated top-of-atmosphere (TOA) DNB reflectances based on SCIAMACHY spectral data are compared with Land PEATE TOA reflectances based on modulated Relative Spectral Response (RSR). In the Libya 4 site, the results indicate a decrease of 1.03% in Land PEATE TOA reflectance and a decrease of 1.01% in SCIAMACHY derived TOA reflectance over the period from April 2012 to January 2016. In the Dome C site, the decreases are 0.29% and 0.14%, respectively. The consistency between SCIAMACHY and Land PEATE data trends is good. The small difference between SCIAMACHY and Land PEATE derived TOA reflectances could be caused by changes in the surface targets, atmosphere status, and on-orbit calibration. The reflectances and radiances of Land PEATE DNB are also compared with matching M bands and the integral M bands based on M4, M5, and M7. The fitting trends of the DNB to integral M bands ratios indicate a 0.75% decrease at the Libya 4 site and a 1.89% decrease at the Dome C site. Part of the difference is due to an insufficient number of sampled bands available within the DNB wavelength range. The above results indicate that the Land PEATE VIIRS DNB product is accurate and stable. The methods used in this study can be used on other satellite instruments to provide quantitative assessments for calibration stability.

Noncontact measurement of vibration using airborne ultrasound.

PubMed

Mater, O B; Remenieras, J P; Bruneel, C; Roncin, A; Patat, F

1998-01-01

A noncontact ultrasonic method for measuring the surface normal vibration of objects was studied. The instrument consists of a pair of 420 kHz ultrasonic air transducers. One is used to emit ultrasounds toward the moving surface, and the other receives the ultrasound reflected from the object under test. Two effects induce a phase modulation on the received signal. The first effect results from the variation of the round trip time interval tau required for the wavefront to go from the emitter to the moving surface and back to the receiver. This is the Doppler effect directly proportional to the surface displacement. The second effect results from the nonlinear parametric interactions of the ultrasonic beams (forward and backward) with the low frequency sound field emitted in the air by the vibrating surface. This latter phenomenon, which is a volume effect, is proportional to the velocity of the vibrating surface and increases with the distance between the transducers and the surface under test. The relative contribution of the Doppler and parametric effects are evaluated, and both have to be taken into account for ultrasonic interferometry in air.

ASTER Images the Island of Hawaii

NASA Technical Reports Server (NTRS)

2000-01-01

These images of the Island of Hawaii were acquired on March 19, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. Data are shown from the short wavelength and thermal infrared spectral regions, illustrating how different and complementary information is contained in different parts of the spectrum.

Left image: This false-color image covers an area 60 kilometers (37 miles) wide and 120 kilometers (75 miles) long in three bands of the short wavelength infrared region. While, much of the island was covered in clouds, the dominant central Mauna Loa volcano, rising to an altitude of 4115 meters (13,500 feet), is cloud-free. Lava flows can be seen radiating from the central crater in green and black tones. As they reach lower elevations, the flows become covered with vegetation, and their image color changes to yellow and orange. Mauna Kea volcano to the north of Mauna Loa has a thin cloud-cover, producing a bluish tone on the image. The ocean in the lower right appears brown due to the color processing.

Right image: This image is a false-color composite of three thermal infrared bands. The brightness of the colors is proportional to the temperature, and the hues display differences in rock composition. Clouds are black, because they are the coldest objects in the scene. The ocean and thick vegetation appear dark green because they are colder than bare rock surfaces, and have no thermal spectral features. Lava flows are shades of magenta, green, pink and yellow, reflecting chemical changes due to weathering and relative age differences.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

O-6 Optical Property Degradation of the Hubble Space Telescope's Wide Field Camera-2 Pick Off Mirror

NASA Technical Reports Server (NTRS)

McNamara, Karen M.; Hughes, D. W.; Lauer, H. V.; Burkett, P. J.; Reed, B. B.

2011-01-01

Degradation in the performance of optical components can be greatly affected by exposure to the space environment. Many factors can contribute to such degradation including surface contaminants; outgassing; vacuum, UV, and atomic oxygen exposure; temperature cycling; or combinations of parameters. In-situ observations give important clues to degradation processes, but there are relatively few opportunities to correlate those observations with post-flight ground analyses. The return of instruments from the Hubble Space Telescope (HST) after its final servicing mission in May 2009 provided such an opportunity. Among the instruments returned from HST was the Wide-Field Planetary Camera-2 (WFPC-2), which had been exposed to the space environment for 16 years. This work focuses on the identifying the sources of degradation in the performance of the Pick-off mirror (POM) from WFPC-2. Techniques including surface reflectivity measurements, spectroscopic ellipsometry, FTIR (and ATR-FTIR) analyses, SEM/EDS, X-ray photoelectron spectroscopy (XPS) with and without ion milling, and wet and dry physical surface sampling were performed. Destructive and contact analyses took place only after completion of the non-destructive measurements. Spectroscopic ellipsometry was then repeated to determine the extent of contaminant removal by the destructive techniques, providing insight into the nature and extent of polymerization of the contaminant layer.

Cross-calibration of MODIS with ETM+ and ALI sensors for long-term monitoring of land surface processes

USGS Publications Warehouse

Meyer, D.; Chander, G.

2006-01-01

Increasingly, data from multiple sensors are used to gain a more complete understanding of land surface processes at a variety of scales. Although higher-level products (e.g., vegetation cover, albedo, surface temperature) derived from different sensors can be validated independently, the degree to which these sensors and their products can be compared to one another is vastly improved if their relative spectroradiometric responses are known. Most often, sensors are directly calibrated to diffuse solar irradiation or vicariously to ground targets. However, space-based targets are not traceable to metrological standards, and vicarious calibrations are expensive and provide a poor sampling of a sensor's full dynamic range. Crosscalibration of two sensors can augment these methods if certain conditions can be met: (1) the spectral responses are similar, (2) the observations are reasonably concurrent (similar atmospheric & solar illumination conditions), (3) errors due to misregistrations of inhomogeneous surfaces can be minimized (including scale differences), and (4) the viewing geometry is similar (or, some reasonable knowledge of surface bi-directional reflectance distribution functions is available). This study explores the impacts of cross-calibrating sensors when such conditions are met to some degree but not perfectly. In order to constrain the range of conditions at some level, the analysis is limited to sensors where cross-calibration studies have been conducted (Enhanced Thematic Mapper Plus (ETM+) on Landsat-7 (L7), Advance Land Imager (ALI) and Hyperion on Earth Observer-1 (EO-1)) and including systems having somewhat dissimilar geometry, spatial resolution & spectral response characteristics but are still part of the so-called "A.M. constellation" (Moderate Resolution Imaging Spectrometer (MODIS) aboard the Terra platform). Measures for spectral response differences and methods for cross calibrating such sensors are provided in this study. These instruments are cross calibrated using the Railroad Valley playa in Nevada. Best fit linear coefficients (slope and offset) are provided for ALI-to-MODIS and ETM+-to-MODIS cross calibrations, and root-mean-squared errors (RMSEs) and correlation coefficients are provided to quantify the uncertainty in these relationships. In theory, the linear fits and uncertainties can be used to compare radiance and reflectance products derived from each instrument.

Cross-calibration of A.M. constellation sensors for long term monitoring of land surface processes

USGS Publications Warehouse

Meyer, D.; Chander, G.

2006-01-01

Data from multiple sensors must be used together to gain a more complete understanding of land surface processes at a variety of scales. Although higher-level products derived from different sensors (e.g., vegetation cover, albedo, surface temperature) can be validated independently, the degree to which these sensors and their products can be compared to one another is vastly improved if their relative spectro-radiometric responses are known. Most often, sensors are directly calibrated to diffuse solar irradiation or vicariously to ground targets. However, space-based targets are not traceable to metrological standards, and vicarious calibrations are expensive and provide a poor sampling of a sensor's full dynamic range. Cross-calibration of two sensors can augment these methods if certain conditions can be met: (1) the spectral responses are similar, (2) the observations are reasonably concurrent (similar atmospheric & solar illumination conditions), (3) errors due to misregistrations of inhomogeneous surfaces can be minimized (including scale differences), and (4) the viewing geometry is similar (or, some reasonable knowledge of surface bi-directional reflectance distribution functions is available). This study extends on a previous study of Terra/MODIS and Landsat/ETM+ cross calibration by including the Terra/ASTER and EO-1/ALI sensors, exploring the impacts of cross-calibrating sensors when conditions described above are met to some degree but not perfectly. Measures for spectral response differences and methods for cross calibrating such sensors are provided in this study. These instruments are cross calibrated using the Railroad Valley playa in Nevada. Best fit linear coefficients (slope and offset) are provided for ALI-to-MODIS and ETM+-to-MODIS cross calibrations, and root-mean-squared errors (RMSEs) and correlation coefficients are provided to quantify the uncertainty in these relationships. Due to problems with direct calibration of ASTER data, linear fits were developed between ASTER and ETM+ to assess the impacts of spectral bandpass differences between the two systems. In theory, the linear fits and uncertainties can be used to compare radiance and reflectance products derived from each instrument.

Assessment of GPS Reflectometry from TechDemoSat-1 for Scatterometry and Altimetry Applications

NASA Astrophysics Data System (ADS)

Shah, R.; Hajj, G. A.

2015-12-01

The value of GPS reflectometry for scatterometry and altimetry applications has been a topic of investigation for the past two decades. TechDemoSat-1 (TDS-1), a technology demonstration satellite launched in July of 2014, with an instrument to collect GPS reflections from 4 GPS satellites simultaneously, provide the first extensive data that allows for validation and evaluation of GPS reflectometry from space against more established techniques. TDS-1 uses a high gain (~13 dBi) L1 antenna pointing 6 degrees off nadir with a 60ohalf-beam width. Reflected GPS L1 signals are processed into Delay Doppler Maps (DDMs) inside the receiver and made available (through Level-1b) along with metadata describing the bistatic geometry, antenna gain, etc., on a second-by-second basis for each of the 4 GPS tracks recorded at any given time. In this paper we examine level-1b data from TDS-1 for thousands of tracks collected over the span of Jan.-Feb., 2015. This data corresponds to reflections from various types of surfaces throughout the globe including ice, deserts, forests, oceans, lakes, wetlands, etc. Our analysis will consider how the surface type manifests itself in the DDMs (e.g., coherence vs. non-coherence reflection) and derivable physical quantities. We will consider questions regarding footprint resolution, waveform rise time and corresponding bistatic range accuracy, and level of precision for altimetry (sea surface height) and scatterometry (significant wave height and sea surface wind). Tracks from TDS-1 that coincide with Jason-1 or 2 tracks will be analyzed, where the latter can be used as truth for comparison and validation. Where coincidences are found, vertical delay introduced by the media as measured by Jason will be mapped to bistatic propagation path to correct for neutral atmospheric and ionospheric delays.

Hemispherical Reflectance and Emittance Properties of Carbon Nanotubes Coatings at Far-Infrared Wavelengths

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; Hagopian, John G.; Getty, Stephanie; Kinzer, Raymond (Robin) E., Jr.; Wollack, Edward

2011-01-01

Recent visible wavelength observations of Multiwalled Carbon Nanotubes (MWCNT) coatings have revealed that they represent the blackest materials known in nature with a Total Hemispherical Reflectance (THR) less than .25%. This makes them as exceptionally good absorbers, with the potential to provide order-of-magnitude improvement in stray-light suppression over current black surface treatments when used in an optical system. Here we extend the characterization of this class of materials into the infrared spectral region to further evaluate their potential for use on instrument baffles for stray-light suppression and to manage spacecraft thermal properties to dissipate heat through radiant heat transfer process. These characterizations will include the wavelength-dependent Total Hemispherical Reflectance properties in the mid-IR and far-infrared spectral regions (2-100 micrometers). Determination of the temperature-dependent emittance will be investigated in the temperature range of 20 to 300 K. These results will be compared against other more conventional black coatings such as Acktar Fractal Black or Z-306 coatings among others.

Visible and near-infrared reflectance spectroscopy of planetary analog materials. Experimental facility at Laboratoire de Planetologie de Grenoble.

NASA Astrophysics Data System (ADS)

Pommerol, A.; Brissaud, O.; Schmitt, B.; Quirico, E.; Doute, S.

2007-08-01

We have developed an original experimental facility designed to measure the bidirectional reflectance spectra of planetary analog materials. These measurements are helpful to interpret the observations of the spectrometers on board space probes in orbit around various Solar System bodies. The central part of the facility is the LPG spectrogonio- radiometer (Brissaud et al., 2004). This instrument provides measurements of samples BRDF (Bidirectional Reflectance Distribution Function) with high photometric and spectrometric accuracy in the spectral range of visible and near-infrared (0.3 - 4.8 microns). Measurements can be made at any value of incidence and emergence angle up to 80°. Azimuth angle is allowed to vary between 0 and 180°. The instrument was recently installed in a cold room allowing ambient temperatures as low as -20°C. This makes possible the measurements on different kinds of water ice samples (slab ice, frost, snow...) and mixtures of minerals and water ice with unprecedented accuracy. We also have designed and built a simulation chamber to measure spectra of samples (water ice and/or minerals) under an atmosphere with perfectly controlled temperature, pressure and composition. The main objective of this last improvement is the study of water exchange between planetary regolith analogs and atmosphere (adsorption/ desorption, condensation/sublimation). Experimental results will mainly apply to Martian water cycle and hydrated mineralogy. This simulation chamber also provides an efficient way to obtain bidirectional reflectance spectra of dry materials (removal of adsorbed water) with implications for planetary bodies without atmospheric or surface water (Titan, asteroids...). The reflectance spectroscopy facility is part of a large panel of instruments and techniques available at Laboratoire de Planetologie de Grenoble that provide complementary measurements on the same samples: infrared transmission spectroscopy of thin ice films, thick liquid and solid samples and samples diluted in KBr pellets, infrared imaging microscope, numerical modeling of bidirectional reflectance spectra using laboratory-measured optical constants. We will present different examples of experimental results obtained on the reflectance spectroscopy facility: - Effects of particle size, mixtures between samples with different albedo and measurement geometries on the water-of-hydration near-infrared absorption signatures with implications for the Martian regolith water content. - BRDF of regolith analogs and natural snow. - Hydration and dehydration of planetary analogs. - Spectra of different kinds of mixtures between water ice and minerals. We will briefly discuss the planetary implications of each of these measurements and detail the future investigations that will be undertaken on our experimental facility.

Characterization and Discrimination of Selected Vegetation Canopies from Field Observations of Bidirectional Reflectances. M.S. Thesis

NASA Technical Reports Server (NTRS)

Donovan, Sheila

1985-01-01

A full evaluation of the bidirectional reflectance properties of different vegetated surfaces was limited in past studies by instrumental inadequacies. With the development of the PARABOLA, it is now possible to sample reflectances from a large number of view angles in a short period of time, maintaining an almost constant solar zenith angle. PARABOLA data collected over five different canopies in Texas are analyzed. The objective of this investigation was to evaluate the intercanopy and intracanopy differences in bidirectional reflectance patterns. Particular attention was given to the separability of canopy types using different view angles for the red and the near infrared (NIR) spectral bands. Comparisons were repeated for different solar zenith angles. Statistical and other quantitative techniques were used to assess these differences. For the canopies investigated, the greatest reflectances were found in the backscatter direction for both bands. Canopy discrimination was found to vary with both view angle and the spectral reflectance band considered, the forward scatter view angles being most suited to observations in the NIR and backscatter view angles giving better results in the red band. Because of different leaf angle distribution characteristics, discrimination was found to be better at small solar zenith angles in both spectral bands.

Airborne Spectral BRDF of Various Surface Types (Ocean, Vegetation, Snow, Desert, Wetlands, Cloud Decks, Smoke Layers) for Remote Sensing Applications

NASA Technical Reports Server (NTRS)

Gatebe, Charles K.; King, Michael D.

2016-01-01

In this paper we describe measurements of the bidirectional reflectance-distribution function (BRDF) acquired over a 30-year period (1984-2014) by the National Aeronautics and Space Administration's (NASA's) Cloud Absorption Radiometer (CAR). Our BRDF database encompasses various natural surfaces that are representative of many land cover or ecosystem types found throughout the world. CAR's unique measurement geometry allows a comparison of measurements acquired from different satellite instruments with various geometrical configurations, none of which are capable of obtaining such a complete and nearly instantaneous BRDF. This database is therefore of great value in validating many satellite sensors and assessing corrections of reflectances for angular effects. These data can also be used to evaluate the ability of analytical models to reproduce the observed directional signatures, to develop BRDF models that are suitable for sub-kilometer-scale satellite observations over both homogeneous and heterogeneous landscape types, and to test future spaceborne sensors. All of these BRDF data are publicly available and accessible in hierarchical data format (http:car.gsfc.nasa.gov/).

The Moon observed in Energetic Neutral Atoms: Review of the Scientific Findings from SARA/CENA on board Chandrayaan-1

NASA Astrophysics Data System (ADS)

Vorburger, Audrey; Wurz, Peter; Barabash, Stas; Wieser, Martin; Futaana, Yoshifumi; Bhardwaj, Anil; Dhanya, Mb; Asamura, Kazushi

2017-04-01

The Sub-keV Atom Reflecting Analyzer (SARA) instrument on board Chandrayaan-1 was exceptionally successful. The instrument not only achieved all its set science goals but also revealed several hitherto unknown and unexpected properties of the solar wind interaction with the lunar surface. SARA's scientific findings can be divided into two groups based on the nature of the particles detected: The first group contains findings gained from ion measurements (from SWIM, SARA's ion sensor) whereas the second group contains findings gained from energetic neutral atom (ENA) measurements (from CENA, SARA's ENA sensor). Here, we present a review of all scientific findings based on ENA measurements. Since the Moon is constantly bombarded by solar wind ions. Until recently, it was tacitly assumed that the ions that impinge onto the lunar surface are almost completely absorbed, with less than 1% reflection, (e.g. Crider and Vondrak, Adv. Space Res., 2002; Feldman et al., JGR, 2000). However, recent observations conducted showed that on average 16% of the impinging solar wind ions are reflected as ENAs (e.g. McComas et al., GRL, 2009; Wieser et al., PSS, 2009; Vorburger et al., JGR, 2013). The energy spectrum of the reflected ENAs is broader than the spectrum of the incident solar wind protons (Futaana et al., JGR, 2012; Harada et al., JGR, 2014), and the characteristic energy is < 50% of the incident solar wind characteristic energy. This hints at multiple scattering processes taking place on the lunar surface. Determination of the ENA angular backscatter function showed that, contrary to expectations, as the solar zenith angle (SZA) increases, particles scatter more toward the sunward direction than in the anti-sunward direction (Vorburger et al., GRL, 2011; Lue et al., JGR, 2016). The ENA reflection ratio is rather featureless over the lunar surface (Vorburger et al., JGR., 2013), showing only strong variations at local crustal magnetic fields due to the interaction of the plasma with so-called mini-magnetospheres (e.g., Wieser et al., GRL, 2010; Vorburger et al., JGR, 2012; Vorburger et al., JGR, 2013). CENA measurements were also used to derive the electric potential above a lunar magnetic anomaly (Futaana et al., GRL, 2012, Järvinen et al. GRL, 2014). Electrical potentials are of scientific interest because they can influence the local plasma and dust environment near the magnetic anomaly. CENA also presented the first-ever measurements of sputtered lunar oxygen (Vorburger et al., JGR., 2012) as well as the first-ever observations of backscattered solar wind helium (Vorburger et al., JGR., 2012). With the backscattered proton signal being unexpectedly large, these signals are small in comparison, but persistent nevertheless. Finally, recent CENA data analyses showed that a significant fraction of the solar wind plasma is able to reach far into the lunar nightside surface: CENA measured a 30 deg broad ENA ring parallel to the terminator, with a total flux equal to 1.5% of the total dayside flux (Vorburger et al., GR., 2016). These measurements shed light onto the expansion of plasma into voids as they occur in planetary wakes.

Transmission versus reflectance spectroscopy for quantitation.

PubMed

Gardner, Craig M

2018-01-01

The objective of this work was to compare the accuracy of analyte concentration estimation when using transmission versus diffuse reflectance spectroscopy of a scattering medium. Monte Carlo ray tracing of light through the medium was used in conjunction with pure component absorption spectra and Beer-Lambert absorption along each ray's pathlength to generate matched sets of pseudoabsorbance spectra, containing water and six analytes present in skin. PLS regression models revealed an improvement in accuracy when using transmission compared to reflectance for a range of medium thicknesses and instrument noise levels. An analytical expression revealed the source of the accuracy degradation with reflectance was due both to the reduced collection efficiency for a fixed instrument etendue and to the broad pathlength distribution that detected light travels in the medium before exiting from the incident side. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Nyiragonga Volcano

NASA Technical Reports Server (NTRS)

2001-01-01

This image of the Nyiragonga volcano eruption in the Congo was acquired on January 28, 2002 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters about 50 to 300 feet ), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

Image: A river of molten rock poured from the Nyiragongo volcano in the Congo on January 18, 2002, a day after it erupted, killing dozens, swallowing buildings and forcing hundreds of thousands to flee the town of Goma. The flow continued into Lake Kivu. The lave flows are depicted in red on the image indicating they are still hot. Two of them flowed south form the volcano's summit and went through the town of Goma. Another flow can be seen at the top of the image, flowing towards the northwest. One of Africa's most notable volcanoes, Nyiragongo contained an active lava lake in its deep summit crater that drained catastrophically through its outer flanks in 1977. Extremely fluid, fast-moving lava flows draining from the summit lava lake in 1977 killed 50 to 100 people, and several villages were destroyed. The image covers an area of 21 x 24 km and combines a thermal band in red, and two infrared bands in green and blue.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

JOVE

NASA Technical Reports Server (NTRS)

Schiller, Stephen

1997-01-01

The focus of our JOVE research has been to develop a field instrument that provides high quality data for atmospheric corrections and in-flight calibration of airborne and satellite remote sensing imaging systems. The instrument package is known as the Portable Ground-based Atmospheric Monitoring System or PGAMS. PGAMS collects a comprehensive set of spectroscopic/radiometric observations that describe the optical properties of the atmosphere and reflectance of a target area on the earth's surface at the time of the aircraft or satellite overpass. To date, the PGAMS instrument system and control software has been completed and used for data collection in several NASA field experiments across the continental US and Puerto Rico. Where do you see your JOVE research going after the initial JOVE Funding Expires? Our JOVE initiated research will continue to be very active in supporting validation and calibration activities in remote sensing involving NASA, DOE, DOD, NSF, and possibly commercial supported programs. Future effort will focus on projects related to NASA's Mission to Planet Earth. This will include field work using PGAMS and data analysis that evaluates sensor calibration and atmospheric effects in images recorded by ASTER, MODIS, and MISR instruments aboard the AM-1 platform.

Mineralogical In-situ Investigation of Acid-Sulfate Samples from the Rio Tinto River, Spain, with a Portable XRD/XRF Instrument

NASA Technical Reports Server (NTRS)

Sarrazin, P.; Ming, D. W.; Morris, R. V.; Fernandez-Remolar, D.; Amils, R.; Arvidson, R. E.; Blake, D.; Bish, D. L.

2007-01-01

A field campaign was organized in September 2006 by Centro de Astobiologica (Spain) and Washington University (St Louis, USA) for the geological study of the Rio Tinto river bed sediments using a suite of in-situ instruments comprising an ASD reflectance spectrometer, an emission spectrometer, panoramic and close-up color imaging cameras, a life detection system and NASA's CheMin 4 XRD/XRF prototype. The primary objectives of the field campaign were to study the geology of the site and test the potential of the instrument suite in an astrobiological investigation context for future Mars surface robotic missions. The results of the overall campaign will be presented elsewhere. This paper focuses on the results of the XRD/XRF instrument deployment. The specific objectives of the CheMin 4 prototype in Rio Tinto were to 1) characterize the mineralogy of efflorescent salts in their native environments; 2) analyze the mineralogy of salts and oxides from the modern environment to terraces formed earlier as part of the Rio Tinto evaporative system; and 3) map the transition from hematite-dominated terraces to the mixed goethite/salt-bearing terraces where biosignatures are best preserved.

Effect of finishing instrumentation using NiTi hand files on volume, surface area and uninstrumented surfaces in C-shaped root canal systems.

PubMed

Amoroso-Silva, P; Alcalde, M P; Hungaro Duarte, M A; De-Deus, G; Ordinola-Zapata, R; Freire, L G; Cavenago, B C; De Moraes, I G

2017-06-01

To assess the effect of 90°-oscillatory instrumentation with hand files on several morphological parameters (volume, surface area and uninstrumented surface) in C-shaped root canals after instrumentation using a single-file reciprocation system (Reciproc; VDW, Munich, Germany) and a Self-Adjusting File System (SAF; ReDent Nova, Ra'anana, Israel). Twenty mandibular second molars with C-shaped canals and C1 canal configurations were divided into two groups (n = 10) and instrumented with Reciproc and SAF instruments. A size 30 NiTi hand K-file attached to a 90°-oscillatory motion handpiece was used as final instrumentation in both groups. The specimens were scanned using micro-computed tomography after all procedures. Volume, surface area increase and uninstrumented root canal surface were analysed using CTAn software (Bruker-microCT, Kontich, Belgium). Also, the uninstrumented root canal surface was calculated for each canal third. All values were compared between groups using the Mann-Whitney test and within groups using the Wilcoxon's signed-rank test. Instrumentation with Reciproc significantly increased canal volume compared with instrumentation with SAF. Additionally, the canal volumes were significantly increased after 90°-oscillatory instrumentation (between and within group comparison; (P < 0.05)). Regarding the increase in surface area after all instrumentation protocols, statistical analysis only revealed significant differences in the within groups comparison (P < 0.05). Reciproc and SAF instrumentation yielded an uninstrumented root canal surface of 28% and 34%, respectively, which was not significantly different (P > 0.05). Final oscillatory instrumentation significantly reduced the uninstrumented root canal surface from 28% to 9% (Reciproc) and from 34% to 15% (SAF; P < 0.05). The apical and middle thirds exhibited larger uninstrumented root canal surfaces after the first instrumentation that was significantly reduced after oscillatory instrumentation (P < 0.05). The Reciproc and SAF system were associated with similar morphological parameters after instrumentation of mandibular second molars with C-shaped canals except for a higher canal volume increase in the Reciproc group compared to the SAF. Furthermore, the final use of 90°-oscillatory instrumentation using NiTi hand files significantly decreased the uninstrumented canal walls that remained after Reciproc and SAF instrumentation. © 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Modeling of forest canopy BRDF using DIRSIG

NASA Astrophysics Data System (ADS)

Rengarajan, Rajagopalan; Schott, John R.

2016-05-01

The characterization and temporal analysis of multispectral and hyperspectral data to extract the biophysical information of the Earth's surface can be significantly improved by understanding its aniosotropic reflectance properties, which are best described by a Bi-directional Reflectance Distribution Function (BRDF). The advancements in the field of remote sensing techniques and instrumentation have made hyperspectral BRDF measurements in the field possible using sophisticated goniometers. However, natural surfaces such as forest canopies impose limitations on both the data collection techniques, as well as, the range of illumination angles that can be collected from the field. These limitations can be mitigated by measuring BRDF in a virtual environment. This paper presents an approach to model the spectral BRDF of a forest canopy using the Digital Image and Remote Sensing Image Generation (DIRSIG) model. A synthetic forest canopy scene is constructed by modeling the 3D geometries of different tree species using OnyxTree software. The field collected spectra from the Harvard forest is used to represent the optical properties of the tree elements. The canopy radiative transfer is estimated using the DIRSIG model for specific view and illumination angles to generate BRDF measurements. A full hemispherical BRDF is generated by fitting the measured BRDF to a semi-empirical BRDF model. The results from fitting the model to the measurement indicates a root mean square error of less than 5% (2 reflectance units) relative to the forest's reflectance in the VIS-NIR-SWIR region. The process can be easily extended to generate a spectral BRDF library for various biomes.

Improved ocean-color remote sensing in the Arctic using the POLYMER algorithm

NASA Astrophysics Data System (ADS)

Frouin, Robert; Deschamps, Pierre-Yves; Ramon, Didier; Steinmetz, François

2012-10-01

Atmospheric correction of ocean-color imagery in the Arctic brings some specific challenges that the standard atmospheric correction algorithm does not address, namely low solar elevation, high cloud frequency, multi-layered polar clouds, presence of ice in the field-of-view, and adjacency effects from highly reflecting surfaces covered by snow and ice and from clouds. The challenges may be addressed using a flexible atmospheric correction algorithm, referred to as POLYMER (Steinmetz and al., 2011). This algorithm does not use a specific aerosol model, but fits the atmospheric reflectance by a polynomial with a non spectral term that accounts for any non spectral scattering (clouds, coarse aerosol mode) or reflection (glitter, whitecaps, small ice surfaces within the instrument field of view), a spectral term with a law in wavelength to the power -1 (fine aerosol mode), and a spectral term with a law in wavelength to the power -4 (molecular scattering, adjacency effects from clouds and white surfaces). Tests are performed on selected MERIS imagery acquired over Arctic Seas. The derived ocean properties, i.e., marine reflectance and chlorophyll concentration, are compared with those obtained with the standard MEGS algorithm. The POLYMER estimates are more realistic in regions affected by the ice environment, e.g., chlorophyll concentration is higher near the ice edge, and spatial coverage is substantially increased. Good retrievals are obtained in the presence of thin clouds, with ocean-color features exhibiting spatial continuity from clear to cloudy regions. The POLYMER estimates of marine reflectance agree better with in situ measurements than the MEGS estimates. Biases are 0.001 or less in magnitude, except at 412 and 443 nm, where they reach 0.005 and 0.002, respectively, and root-mean-squared difference decreases from 0.006 at 412 nm to less than 0.001 at 620 and 665 nm. A first application to MODIS imagery is presented, revealing that the POLYMER algorithm is robust when pixels are contaminated by sea ice.

Oahu, Hawaii

NASA Technical Reports Server (NTRS)

2000-01-01

This 60 by 55 km ASTER scene shows almost the entire island of Oahu, Hawaii on June 3, 2000. The data were processed to produce a simulated natural color presentation. Oahu is the commercial center of Hawaii and is important to United States defense in the Pacific. Pearl Harbor naval base is situated here. The chief agricultural industries are the growing and processing of pineapples and sugarcane. Tourism also is important to the economy. Among the many popular beaches is the renowned Waikiki Beach, backed by the famous Diamond Head, an extinct volcano. The largest community, Honolulu, is the state capital.

The image is located at 21.5 degrees north latitude and 158 degrees west longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

Los Angeles from Space

NASA Technical Reports Server (NTRS)

2001-01-01

This ASTER image was acquired on July 23, 2001 and covers an area of 64 x 72 km. The data were processed to create a simulated natural color image. From its start as a sleepy Spanish pueblo in 1781, LA and its metropolitan area has grown to become an ethnically diverse, semitropical megalopolis, laying claim as the principal center of the western US and the nation's second largest urban area. The city's economy is based on international trade, aerospace, agriculture, tourism, and filmmaking. LA provides a glimpse of the typically cosmopolitan and global city of the future.

The image is located at 34.1 degrees north latitude and 118.2 degrees west longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

ASTER View of Sharm El Sheik, Egypt

NASA Technical Reports Server (NTRS)

2000-01-01

The Red Sea golf resort in Sharm El Sheik, Egypt, where President Clinton met with Israeli Prime Minister Ehud Barak and Palestinian Authority President Yasser Arafat, stands out against the desert landscape in this image acquired on August 25, 2000.

This image of the southern tip of the Sinai Peninsula shows an area about 30 by 40 kilometers (19 by 25 miles) in the visible and near infrared wavelength region. Vegetation appears in red. The blue areas in the water at the top and bottom of the image are coral reefs. The airport is visible just to the north of the golf resort.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

Training and Validation of the Fast PCRTM_Solar Model

NASA Astrophysics Data System (ADS)

Yang, Q.; Liu, X.; Wu, W.; Yang, P.; Wang, C.

2015-12-01

Fast and accurate radiative transfer model is the key for satellite data assimilation for remote sensing application. The simulation of the satellite remote sensing radiances is very complicated since many physical processes, such as absorption, emission, and scattering, are involved due to the interactions between electromagnetic radiation and earth surface, water vapor, clouds, aerosols, and gas molecules in the sky. The principal component-based radiative transfer model (PCRTM) has been developed for various passive IR and MW instruments. In this work, we extended PCRTM to including the contribution from solar radiation. The cloud/aerosol bidirectional reflectances have been carefully calculated using the well-known Discrete-Ordinate-Method Radiative Transfer (DISORT) model under over 10 millions of diverse conditions with varying cloud particle size, wavelength, satellite viewing direction, and solar angles. The obtained results were compressed significantly using principal component analysis and used in the mono domain radiance calculation. We used 1352 different atmosphere profiles, each of them has different surface skin temperatures and surface pressures in our training. Different surface emissivity spectra were derived from ASTER database and emissivity models. Some artificially generated emissivity spectra were also used to account for diverse surface types of the earth. Concentrations of sixteen trace gases were varied systematically in the training and the remaining trace gas contributions were accounted for as a fixed gas. Training was done in both clear and cloudy skies conditions. Finally the nonlocal thermal equilibrium (NLTE) induced radiance change was included for daytime conditions. We have updated the PCRTM model for instruments such as IASI, NASTI, CrIS, AIRS, and SHIS. The training results show that the PCRTM model can calculate thousands of channel radiances by computing only a few hundreds of mono radiances. This greatly increased the computation efficiency since we do not need to calculate the millions of mono radiances and do the convolution process. The results from fast PCRTM_Solar simulation were compared to the instrument observed data. The simulated results were excellently agreed with the observations.

Great Wall of China

NASA Technical Reports Server (NTRS)

2001-01-01

This ASTER sub-image covers a 12 x 12 km area in northern Shanxi Province, China, and was acquired January 9, 2001. The low sun angle, and light snow cover highlight a section of the Great Wall, visible as a black line running diagonally through the image from lower left to upper right. The Great Wall is over 2000 years old and was built over a period of 1000 years. Stretching 4500 miles from Korea to the Gobi Desert it was first built to protect China from marauders from the north.

This image is located at 40.2 degrees north latitude and 112.8 degrees east longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

Sulfur Dioxide Plume During the Continuing Eruption of Mt. Etna, Italy

NASA Technical Reports Server (NTRS)

2001-01-01

The current eruption of Mt. Etna started on July 17, and has continued to the present. This ASTER image was acquired on Sunday, July 29 and shows the sulfur dioxide plume (in purple) originating form the summit, drifting over the city of Catania, and continuing over the Ionian Sea. ASTER's unique combination of multiple thermal infrared channels and high spatial resolution allows the determination of the thickness and position of the SO2 plume. The image covers an area of 24 x 30 km.

The image is centered at 37.7 degrees north latitude, 15 degrees east longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats, potentially active volcanoes, thermal pollution, and coral reef degradation; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; mapping surface temperature of soils and geology; and measuring surface heat balance.

Patagonia Glacier, Chile

NASA Technical Reports Server (NTRS)

2000-01-01

This ASTER images was acquired on May 2, 2000 over the North Patagonia Ice Sheet, Chile near latitude 47 degrees south, longitude 73 degrees west. The image covers 36 x 30 km. The false color composite displays vegetation in red. The image dramatically shows a single large glacier, covered with crevasses. A semi-circular terminal moraine indicates that the glacier was once more extensive than at present. ASTER data are being acquired over hundreds of glaciers worldwide to measure their changes over time. Since glaciers are sensitive indicators of warming or cooling, this program can provide global data set critical to understand climate change.

This image is located at 46.5 degrees south latitude and 73.9 degrees west longitude.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

On the effect of emergence angle on emissivity spectra: application to small bodies

NASA Astrophysics Data System (ADS)

Maturilli, Alessandro; Helbert, Jörn; Ferrari, Sabrina; D'Amore, Mario

2016-05-01

Dependence of laboratory-measured emissivity spectra from the emergence angle is a subject that still needs a lot of investigations to be fully understood. Most of the previous work is based on reflectance measurements in the VIS-NIR spectral region and on emissivity measurements of flat, solid surfaces (mainly metals), which are not directly applicable to the analysis of remote sensing data. Small bodies in particular (c.f. asteroids Itokawa and 1999JU3, the respective targets of JAXA Hayabusa and Hayabusa 2 missions) have a very irregular surface; hence, the spectra from those rough surfaces are difficult to compare with laboratory spectra, where the observing geometry is always close to "nadir." At the Planetary Emissivity Laboratory of the German Aerospace Center (DLR), we have set up a series of spectral measurements to investigate this problem in the 1- to 16-µm spectral region. We measured the emissivity for two asteroid analogue materials (meteorite Millbillillie and a synthetic enstatite) in vacuum and under purged air, at surface temperature of 100 °C, for emergence angles of 0°, 5°, 10°, 20°, 30°, 40°, 50°, and 60°. Emissivity of a serpentinite slab, already used as calibration target for the MARA instrument on Hayabusa 2 MASCOT lander and for the thermal infrared imager spectrometer on Hayabusa 2 orbiter, was measured under the same conditions. Additionally, a second basalt slab was measured. Both slabs were not measured at 5° inclination. Complementary reflectance measurements of the four samples were taken. For all the samples measured, we found that for calibrated emissivity, significant variations from values obtained at nadir (0° emergence angle) appear only for emergence angles ≥40°. Reflectance measurements confirmed this finding, showing the same trend of variations.

Superimposing various biophysical and social scales in a rapidly changing rural area (SW Niger)

NASA Astrophysics Data System (ADS)

Leduc, Christian; Massuel, Sylvain; Favreau, Guillaume; Cappelaere, Bernard; Leblanc, Marc; Bachir, Salifou; Ousmane, Boureïma

2014-05-01

In SW Niger, close to Niamey, a detailed hydrological survey has been developed for the last 20 years (international experiments HAPEX-SAHEL and later AMMA), investigating the distribution of water in atmosphere, surface, soil and aquifers. It covers an area of about 10 000 km2, with a series of imbricated scales of instrumentation, in time and space. This dense long term field observation led to many major scientific results. Among them, one of the most original and paradoxical is the continuous rise of the water table, even during the severe droughts of the 1970s and 1980s (about 3 m in the last 30 years). In spite of a large apparent homogeneity of the biophysical environment throughout the region, numerous heterogeneities exist at different scales, complicating the hydrological analysis. On the surface, the hydrological system was, ~6000 years ago, a structured drainage network leading to the Niger River. It was later broken into much smaller elements by aeolian dunes deposited during arid episodes and the study area now appears as a juxtaposition of hundreds of small endorheic catchments (most often 1 to 20 km2) where the surface runoff finally ends in temporary ponds. During most violent rainy events, erosion can be locally very severe and modify durably the size of the catchment and the local hydrology. Conversely, during smaller rainy events, surface runoff may never reach the ponds because it infiltrates in more permeable zones at mid-slope. The actual surface area of the catchment contributing to the surface runoff thus varies considerably with time. Because of their great number, only a few catchments are instrumented and extrapolation of measurements to ungauged catchments is an additional difficulty. Most of water temporarily stored in ponds infiltrates and recharges groundwater. The Continental Terminal (CT) aquifer system is made of three independent layers, of which the upper one (CT3) is only considered here. The CT aquifer systems is a transboundary aquifer that extends far beyond the study area, over about 150 000 km2. It is also heterogeneous. Like surface flows, but at a different scale, groundwater flows are marked by a strong endorheism. For example the Dantiandou closed piezometric depression extends over about approximately 5000 km2. These natural closed depressions are explained only by evapotranspiration uptake, weak in absolute terms (a few mm.a-1) but with a very high impact on hydrodynamics because of poor permeability and porosity. Both density of observations and hydraulic continuity of the CT3 aquifer give a fine idea of groundwater changes in the whole area. Human activities, continuously adapting in this poor rural area, add another complexity to the hydrological diversity in surface and ground water. The replacement of the natural vegetation with millet fields and fallow increased the surface runoff, and consequently water accumulation in temporary pools and then CT3 recharge. In the SE part of the study area, the water table has risen up to outcropping in the lowest valley bottoms. These new permanent ponds reflect groundwater while temporary ponds still reflect surface dynamics. This new component of the hydrological landscape induces several consequences, in physical and human dimensions. Evaporation strongly affects the permanent water and increases its salinity while the natural mineralization of groundwater is very low. The easier access to water resources allows a significant development of local gardening, which modifies the social functioning of villages (e.g. land rights between villages and within a village, diversification of crops and sources of income, new sales channels). Different physically based models (for surface and ground water) were built, with a significant discrepancy between their respective quantification of water flows at the region scale. Extrapolation of surface fluxes from the few instrumented catchments to a much larger mosaic of non-instrumented catchments is only partially compatible with the geochemical and hydrodynamic calculations for the CT3 aquifer. This leads to many questions about the representativeness of instrumentation (in spite of dense observations), the heterogeneity of the landscape (perhaps even stronger than supposed, complementarities and differences between methods, etc.). Similarly, the diversity and evolution of human behaviours facing new situations (population growth, environmental changes) are essential elements to take into account, not always easily accessible to hydrologists.

Broadband ultraviolet reflectance filters for space applications.

NASA Technical Reports Server (NTRS)

Osantowski, J. F.; Toft, A. R.

1973-01-01

It is shown that a simple metal-dielectric-metal filter for broadband ultraviolet (BUV) reflectance control can provide a stable and effective means for reducing stray visible radiation in UV reflective optical systems. The application of such a filter in a BUV instrument resulted in a reduction of scattered visible light by at least an order of magnitude. The instrument has been in orbit for 2.5 year without loss of sensitivity or an increase in scattered light background.-

Characterization of Silicon Moth-Eye Antireflection Coatings for Astronomical Applications in the Infrared

NASA Astrophysics Data System (ADS)

Jeram, Sarik; Ge, Jian; Jiang, Peng; Phillips, Blayne

2016-01-01

Silicon moth-eye antireflective structures have emerged to be an excellent approachfor reducing the amount of light that is lost upon incidence on a given surface of optics made of silicon. This property has been exploited for a wide variety of products ranging from eyeglasses and flat-panel displays to solar panels. These materials typically come in the form of coatings that are applied to an optical substrate such as glass. Moth-eye coatings, made of a periodic array of subwavelength pillars on silicon substrates or other substrates, can produce the desired antireflection (AR) performance for a broad wavelength range and over a wide range of incident angles. In the field of astronomy, every photon striking a detector is significant - and thus, losses from reflectivity at the various optical interfaces before a detector can have significant implications to the science at hand. Moth-eye AR coatings on these optical interfaces may minimize their reflection losses while maximizing light throughput for a multitude of different astronomical instruments. In addition, moth-eye AR coatings, which are patterned directly on silicon surfaces, can significantly enhance the coating durability. At the University of Florida, we tested two moth-eye filters designed for use in the near-infrared regime at 1-8 microns by examining their optical properties, such as transmission, the scattered light, and wavefront quality, and testing the coatings at cryogenic temperatures to characterize their viability for use in both ground- and space-based infrared instruments. This presentation will report our lab evaluation results.

Standardization of Solar Mirror Reflectance Measurements - Round Robin Test: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meyen, S.; Lupfert, E.; Fernandez-Garcia, A.

2010-10-01

Within the SolarPaces Task III standardization activities, DLR, CIEMAT, and NREL have concentrated on optimizing the procedure to measure the reflectance of solar mirrors. From this work, the laboratories have developed a clear definition of the method and requirements needed of commercial instruments for reliable reflectance results. A round robin test was performed between the three laboratories with samples that represent all of the commercial solar mirrors currently available for concentrating solar power (CSP) applications. The results show surprisingly large differences in hemispherical reflectance (sh) of 0.007 and specular reflectance (ss) of 0.004 between the laboratories. These differences indicate themore » importance of minimum instrument requirements and standardized procedures. Based on these results, the optimal procedure will be formulated and validated with a new round robin test in which a better accuracy is expected. Improved instruments and reference standards are needed to reach the necessary accuracy for cost and efficiency calculations.« less

The Time Series Technique for Aerosol Retrievals over Land from MODIS: Algorithm MAIAC

NASA Technical Reports Server (NTRS)

Lyapustin, Alexei; Wang, Yujie

2008-01-01

Atmospheric aerosols interact with sun light by scattering and absorbing radiation. By changing irradiance of the Earth surface, modifying cloud fractional cover and microphysical properties and a number of other mechanisms, they affect the energy balance, hydrological cycle, and planetary climate [IPCC, 2007]. In many world regions there is a growing impact of aerosols on air quality and human health. The Earth Observing System [NASA, 1999] initiated high quality global Earth observations and operational aerosol retrievals over land. With the wide swath (2300 km) of MODIS instrument, the MODIS Dark Target algorithm [Kaufman et al., 1997; Remer et al., 2005; Levy et al., 2007] currently complemented with the Deep Blue method [Hsu et al., 2004] provides daily global view of planetary atmospheric aerosol. The MISR algorithm [Martonchik et al., 1998; Diner et al., 2005] makes high quality aerosol retrievals in 300 km swaths covering the globe in 8 days. With MODIS aerosol program being very successful, there are still several unresolved issues in the retrieval algorithms. The current processing is pixel-based and relies on a single-orbit data. Such an approach produces a single measurement for every pixel characterized by two main unknowns, aerosol optical thickness (AOT) and surface reflectance (SR). This lack of information constitutes a fundamental problem of the remote sensing which cannot be resolved without a priori information. For example, MODIS Dark Target algorithm makes spectral assumptions about surface reflectance, whereas the Deep Blue method uses ancillary global database of surface reflectance composed from minimal monthly measurements with Rayleigh correction. Both algorithms use Lambertian surface model. The surface-related assumptions in the aerosol retrievals may affect subsequent atmospheric correction in unintended way. For example, the Dark Target algorithm uses an empirical relationship to predict SR in the Blue (B3) and Red (B1) bands from the 2.1 m channel (B7) for the purpose of aerosol retrieval. Obviously, the subsequent atmospheric correction will produce the same SR in the red and blue bands as predicted, i.e. an empirical function of 2.1. In other words, the spectral, spatial and temporal variability of surface reflectance in the Blue and Red bands appears borrowed from band B7. This may have certain implications for the vegetation and global carbon analysis because the chlorophyll-sensing bands B1, B3 are effectively substituted in terms of variability by band B7, which is sensitive to the plant liquid water. This chapter describes a new recently developed generic aerosol-surface retrieval algorithm for MODIS. The Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm simultaneously retrieves AOT and surface bi-directional reflection factor (BRF) using the time series of MODIS measurements.

Temperature dependent BRDF facility

NASA Astrophysics Data System (ADS)

Airola, Marc B.; Brown, Andrea M.; Hahn, Daniel V.; Thomas, Michael E.; Congdon, Elizabeth A.; Mehoke, Douglas S.

2014-09-01

Applications involving space based instrumentation and aerodynamically heated surfaces often require knowledge of the bi-directional reflectance distribution function (BRDF) of an exposed surface at high temperature. Addressing this need, the Johns Hopkins University Applied Physics Laboratory (JHU/APL) developed a BRDF facility that features a multiple-port vacuum chamber, multiple laser sources covering the spectral range from the longwave infrared to the ultraviolet, imaging pyrometry and laser heated samples. Laser heating eliminates stray light that would otherwise be seen from a furnace and requires minimal sample support structure, allowing low thermal conduction loss to be obtained, which is especially important at high temperatures. The goal is to measure the BRDF of ceramic-coated surfaces at temperatures in excess of 1000°C in a low background environment. Most ceramic samples are near blackbody in the longwave infrared, thus pyrometry using a LWIR camera can be very effective and accurate.

Rover Touchdown on Martian Surface

NASA Image and Video Library

1997-07-06

This picture taken by the IMP (Imager for Mars Pathfinder) aboard the Mars Pathfinder spacecraft depicts the rover Sojourner's position after driving onto the Martian surface. Sojourner has become the first autonomous robot ever to traverse the surface of Mars. This image reflects the success of Pathfinder's principle objective -- to place a payload on Mars in a safe, operational configuration. The primary mission of Sojourner, scheduled to last seven days, will be to use its Alpha Proton X-ray Spectrometer (APXS) instrument to determine the elements that make up the rocks and soil on Mars. A full study using the APXS takes approximately ten hours, and can measure all elements except hydrogen at any time of the Martian day or night. The APXS will conduct its studies by bombarding rocks and soil samples with alpha particle radiation -- charged particles equivalent to the nucleus of a helium atom, consisting of two protons and two neutrons. http://photojournal.jpl.nasa.gov/catalog/PIA00623

Calibration aspects of the JEM-EUSO mission

NASA Astrophysics Data System (ADS)

Adams, J. H.; Ahmad, S.; Albert, J.-N.; Allard, D.; Anchordoqui, L.; Andreev, V.; Anzalone, A.; Arai, Y.; Asano, K.; Ave Pernas, M.; Baragatti, P.; Barrillon, P.; Batsch, T.; Bayer, J.; Bechini, R.; Belenguer, T.; Bellotti, R.; Belov, K.; Berlind, A. A.; Bertaina, M.; Biermann, P. L.; Biktemerova, S.; Blaksley, C.; Blanc, N.; Błȩcki, J.; Blin-Bondil, S.; Blümer, J.; Bobik, P.; Bogomilov, M.; Bonamente, M.; Briggs, M. S.; Briz, S.; Bruno, A.; Cafagna, F.; Campana, D.; Capdevielle, J.-N.; Caruso, R.; Casolino, M.; Cassardo, C.; Castellinic, G.; Catalano, C.; Catalano, G.; Cellino, A.; Chikawa, M.; Christl, M. J.; Cline, D.; Connaughton, V.; Conti, L.; Cordero, G.; Crawford, H. J.; Cremonini, R.; Csorna, S.; Dagoret-Campagne, S.; de Castro, A. J.; De Donato, C.; de la Taille, C.; De Santis, C.; del Peral, L.; Dell'Oro, A.; De Simone, N.; Di Martino, M.; Distratis, G.; Dulucq, F.; Dupieux, M.; Ebersoldt, A.; Ebisuzaki, T.; Engel, R.; Falk, S.; Fang, K.; Fenu, F.; Fernández-Gómez, I.; Ferrarese, S.; Finco, D.; Flamini, M.; Fornaro, C.; Franceschi, A.; Fujimoto, J.; Fukushima, M.; Galeotti, P.; Garipov, G.; Geary, J.; Gelmini, G.; Giraudo, G.; Gonchar, M.; González Alvarado, C.; Gorodetzky, P.; Guarino, F.; Guzmán, A.; Hachisu, Y.; Harlov, B.; Haungs, A.; Hernández Carretero, J.; Higashide, K.; Ikeda, D.; Ikeda, H.; Inoue, N.; Inoue, S.; Insolia, A.; Isgrò, F.; Itow, Y.; Joven, E.; Judd, E. G.; Jung, A.; Kajino, F.; Kajino, T.; Kaneko, I.; Karadzhov, Y.; Karczmarczyk, J.; Karus, M.; Katahira, K.; Kawai, K.; Kawasaki, Y.; Keilhauer, B.; Khrenov, B. A.; Kim, J.-S.; Kim, S.-W.; Kim, S.-W.; Kleifges, M.; Klimov, P. A.; Kolev, D.; Kreykenbohm, I.; Kudela, K.; Kurihara, Y.; Kusenko, A.; Kuznetsov, E.; Lacombe, M.; Lachaud, C.; Lee, J.; Licandro, J.; Lim, H.; López, F.; Maccarone, M. C.; Mannheim, K.; Maravilla, D.; Marcelli, L.; Marini, A.; Martinez, O.; Masciantonio, G.; Mase, K.; Matev, R.; Medina-Tanco, G.; Mernik, T.; Miyamoto, H.; Miyazaki, Y.; Mizumoto, Y.; Modestino, G.; Monaco, A.; Monnier-Ragaigne, D.; Morales de los Ríos, J. A.; Moretto, C.; Morozenko, V. S.; Mot, B.; Murakami, T.; Murakami, M. Nagano; Nagata, M.; Nagataki, S.; Nakamura, T.; Napolitano, T.; Naumov, D.; Nava, R.; Neronov, A.; Nomoto, K.; Nonaka, T.; Ogawa, T.; Ogio, S.; Ohmori, H.; Olinto, A. V.; Orleański, P.; Osteria, G.; Panasyuk, M. I.; Parizot, E.; Park, I. H.; Park, H. W.; Pastircak, B.; Patzak, T.; Paul, T.; Pennypacker, C.; Perez Cano, S.; Peter, T.; Picozza, P.; Pierog, T.; Piotrowski, L. W.; Piraino, S.; Plebaniak, Z.; Pollini, A.; Prat, P.; Prévôt, G.; Prieto, H.; Putis, M.; Reardon, P.; Reyes, M.; Ricci, M.; Rodríguez, I.; Rodríguez Frías, M. D.; Ronga, F.; Roth, M.; Rothkaehl, H.; Roudil, G.; Rusinov, I.; Rybczyński, M.; Sabau, M. D.; Sáez-Cano, G.; Sagawa, H.; Saito, A.; Sakaki, N.; Sakata, M.; Salazar, H.; Sánchez, S.; Santangelo, A.; Santiago Crúz, L.; Sanz Palomino, M.; Saprykin, O.; Sarazin, F.; Sato, H.; Sato, M.; Schanz, T.; Schieler, H.; Scotti, V.; Segreto, A.; Selmane, S.; Semikoz, D.; Serra, M.; Sharakin, S.; Shibata, T.; Shimizu, H. M.; Shinozaki, K.; Shirahama, T.; Siemieniec-Oziȩbło, G.; Silva López, H. H.; Sledd, J.; Słomińska, K.; Sobey, A.; Sugiyama, T.; Supanitsky, D.; Suzuki, M.; Szabelska, B.; Szabelski, J.; Tajima, F.; Tajima, N.; Tajima, T.; Takahashi, Y.; Takami, H.; Takeda, M.; Takizawa, Y.; Tenzer, C.; Tibolla, O.; Tkachev, L.; Tokuno, H.; Tomida, T.; Tone, N.; Toscano, S.; Trillaud, F.; Tsenov, R.; Tsunesada, Y.; Tsuno, K.; Tymieniecka, T.; Uchihori, Y.; Unger, M.; Vaduvescu, O.; Valdés-Galicia, J. F.; Vallania, P.; Valore, L.; Vankova, G.; Vigorito, C.; Villaseñor, L.; von Ballmoos, P.; Wada, S.; Watanabe, J.; Watanabe, S.; Watts, J.; Weber, M.; Weiler, T. J.; Wibig, T.; Wiencke, L.; Wille, M.; Wilms, J.; Włodarczyk, Z.; Yamamoto, T.; Yamamoto, Y.; Yang, J.; Yano, H.; Yashin, I. V.; Yonetoku, D.; Yoshida, K.; Yoshida, S.; Young, R.; Zotov, M. Yu.; Zuccaro Marchi, A.

2015-11-01

The JEM-EUSO telescope will be, after calibration, a very accurate instrument which yields the number of received photons from the number of measured photo-electrons. The project is in phase A (demonstration of the concept) including already operating prototype instruments, i.e. many parts of the instrument have been constructed and tested. Calibration is a crucial part of the instrument and its use. The focal surface (FS) of the JEM-EUSO telescope will consist of about 5000 photo-multiplier tubes (PMTs), which have to be well calibrated to reach the required accuracy in reconstructing the air-shower parameters. The optics system consists of 3 plastic Fresnel (double-sided) lenses of 2.5 m diameter. The aim of the calibration system is to measure the efficiencies (transmittances) of the optics and absolute efficiencies of the entire focal surface detector. The system consists of 3 main components: (i) Pre-flight calibration devices on ground, where the efficiency and gain of the PMTs will be measured absolutely and also the transmittance of the optics will be. (ii) On-board relative calibration system applying two methods: a) operating during the day when the JEM-EUSO lid will be closed with small light sources on board. b) operating during the night, together with data taking: the monitoring of the background rate over identical sites. (iii) Absolute in-flight calibration, again, applying two methods: a) measurement of the moon light, reflected on high altitude, high albedo clouds. b) measurements of calibrated flashes and tracks produced by the Global Light System (GLS). Some details of each calibration method will be described in this paper.

Capturing Career Reflections: Construction of an Instrument to Explore Careers and Career Development

ERIC Educational Resources Information Center

McDonald, Kimberly S.; Hite, Linda M.; Mansour-Cole, Dina

2006-01-01

This study describes the development and validation of an instrument to tap employee reflections on career interests, needs and career development opportunities. Item construction was based on issues identified in previous qualitative research and themes prevalent in recent HRD career development literature. Pilot data for an exploratory factor…

Using a New Learning Environment Questionnaire for Reflection in Teacher Action Research

ERIC Educational Resources Information Center

Aldridge, Jill M.; Fraser, Barry J.; Bell, Lisa; Dorman, Jeffrey

2012-01-01

This article reports the development, validation and use of an instrument designed to provide teachers with feedback information, based on students' perceptions, about their classroom environments. The instrument was developed to provide teachers with feedback that they could use to reflect on their teaching practices and, in turn, guide the…

Biosphere/atmosphere CO2 exchange in tundra ecosystems - Community characteristics and relationships with multispectral surface reflectance

NASA Technical Reports Server (NTRS)

Whiting, Gary J.; Bartlett, David S.; Fan, Song-Miao; Bakwin, Peter S.; Wofsy, Steven C.

1992-01-01

CO2 exchange rates were measured at selected tundra sites near Bethel, Alaska using portable, climate-controlled, instrumented enclosures. The empirically modeled exchange rate for a representative area of vegetated tundra was 1.2 +/- 1.2 g/sq m/d, compared to a tower-measured exchange over the same time period of 1.1 +.0- 1.2 g/sq m/d. Net exchange in response to varying light levels was compared to wet meadow and dry upland tundra, and to the net exchange measured by the micrometeoroidal tower technique. The multispectral reflectance properties of the sites were measured and related to exchange rates in order to provide a quantitative foundation for the use of satellite remote sensing to monitor biosphere/atmosphere CO2 exchange in the tundra biome.

Deformed ellipsoidal diffraction grating blank

NASA Technical Reports Server (NTRS)

Decew, Alan E., Jr.

1994-01-01

The Deformed Ellipsoidal Grating Blank (DEGB) is the primary component in an ultraviolet spectrometer. Since one of the major concerns for these instruments is throughput, significant efforts are made to reduce the number of components and subsequently reflections. Each reflection results in losses through absorption and scattering. It is these two sources of photon loss that dictated the requirements for the DEGB. The first goal is to shape the DEGB in such a way that the energy at the entrance slit is focused as well as possible on the exit slit. The second goal is to produce a surface smooth enough to minimize the photon loss due to scattering. The program was accomplished in three phases. The first phase was the fabrication planning. The second phase was the actual fabrication and initial testing. The last phase was the final testing of the completed DEGB.

VCSEL fault location apparatus and method

DOEpatents

Keeler, Gordon A [Albuquerque, NM; Serkland, Darwin K [Albuquerque, NM

2007-05-15

An apparatus for locating a fault within an optical fiber is disclosed. The apparatus, which can be formed as a part of a fiber-optic transmitter or as a stand-alone instrument, utilizes a vertical-cavity surface-emitting laser (VCSEL) to generate a test pulse of light which is coupled into an optical fiber under test. The VCSEL is subsequently reconfigured by changing a bias voltage thereto and is used as a resonant-cavity photodetector (RCPD) to detect a portion of the test light pulse which is reflected or scattered from any fault within the optical fiber. A time interval .DELTA.t between an instant in time when the test light pulse is generated and the time the reflected or scattered portion is detected can then be used to determine the location of the fault within the optical fiber.

Observing System Simulations for Small Satellite Formations Estimating Bidirectional Reflectance

NASA Technical Reports Server (NTRS)

Nag, Sreeja; Gatebe, Charles K.; de Weck, Olivier

2015-01-01

The bidirectional reflectance distribution function (BRDF) gives the reflectance of a target as a function of illumination geometry and viewing geometry, hence carries information about the anisotropy of the surface. BRDF is needed in remote sensing for the correction of view and illumination angle effects (for example in image standardization and mosaicing), for deriving albedo, for land cover classification, for cloud detection, for atmospheric correction, and other applications. However, current spaceborne instruments provide sparse angular sampling of BRDF and airborne instruments are limited in the spatial and temporal coverage. To fill the gaps in angular coverage within spatial, spectral and temporal requirements, we propose a new measurement technique: Use of small satellites in formation flight, each satellite with a VNIR (visible and near infrared) imaging spectrometer, to make multi-spectral, near-simultaneous measurements of every ground spot in the swath at multiple angles. This paper describes an observing system simulation experiment (OSSE) to evaluate the proposed concept and select the optimal formation architecture that minimizes BRDF uncertainties. The variables of the OSSE are identified; number of satellites, measurement spread in the view zenith and relative azimuth with respect to solar plane, solar zenith angle, BRDF models and wavelength of reflection. Analyzing the sensitivity of BRDF estimation errors to the variables allow simplification of the OSSE, to enable its use to rapidly evaluate formation architectures. A 6-satellite formation is shown to produce lower BRDF estimation errors, purely in terms of angular sampling as evaluated by the OSSE, than a single spacecraft with 9 forward-aft sensors. We demonstrate the ability to use OSSEs to design small satellite formations as complements to flagship mission data. The formations can fill angular sampling gaps and enable better BRDF products than currently possible.

Observing system simulations for small satellite formations estimating bidirectional reflectance

NASA Astrophysics Data System (ADS)

Nag, Sreeja; Gatebe, Charles K.; Weck, Olivier de

2015-12-01

The bidirectional reflectance distribution function (BRDF) gives the reflectance of a target as a function of illumination geometry and viewing geometry, hence carries information about the anisotropy of the surface. BRDF is needed in remote sensing for the correction of view and illumination angle effects (for example in image standardization and mosaicing), for deriving albedo, for land cover classification, for cloud detection, for atmospheric correction, and other applications. However, current spaceborne instruments provide sparse angular sampling of BRDF and airborne instruments are limited in the spatial and temporal coverage. To fill the gaps in angular coverage within spatial, spectral and temporal requirements, we propose a new measurement technique: use of small satellites in formation flight, each satellite with a VNIR (visible and near infrared) imaging spectrometer, to make multi-spectral, near-simultaneous measurements of every ground spot in the swath at multiple angles. This paper describes an observing system simulation experiment (OSSE) to evaluate the proposed concept and select the optimal formation architecture that minimizes BRDF uncertainties. The variables of the OSSE are identified; number of satellites, measurement spread in the view zenith and relative azimuth with respect to solar plane, solar zenith angle, BRDF models and wavelength of reflection. Analyzing the sensitivity of BRDF estimation errors to the variables allow simplification of the OSSE, to enable its use to rapidly evaluate formation architectures. A 6-satellite formation is shown to produce lower BRDF estimation errors, purely in terms of angular sampling as evaluated by the OSSE, than a single spacecraft with 9 forward-aft sensors. We demonstrate the ability to use OSSEs to design small satellite formations as complements to flagship mission data. The formations can fill angular sampling gaps and enable better BRDF products than currently possible.

Spatially Complete Surface Albedo Data Sets: Value-Added Products Derived from Terra MODIS Land Products

NASA Technical Reports Server (NTRS)

Moody, Eric G.; King, Michael D.; Platnick, Steven; Schaaf, Crystal B.; Gao, Feng

2004-01-01

Spectral land surface albedo is an important parameter for describing the radiative properties of the Earth. Accordingly it reflects the consequences of natural and human interactions, such as anthropogenic, meteorological, and phenological effects, on global and local climatological trends. Consequently, albedos are integral parts in a variety of research areas, such as general circulation models (GCMs), energy balance studies, modeling of land use and land use change, and biophysical, oceanographic, and meteorological studies. Recent observations of diffuse bihemispherical (white-sky) and direct beam directional hemispherical (black-sky ) land surface albedo included in the MOD43B3 product from MODIS instruments aboard NASA's Terra and Aqua satellite platforms have provided researchers with unprecedented spatial, spectral, and temporal characteristics. Cloud and seasonal snow cover, however, curtail retrievals to approximately half the global land surfaces on an annual equal-angle basis, precluding MOD43B3 albedo products from direct inclusion in some research projects and production environments.

Wide-Angle Polarimetric Camera for Korea Pathfinder Lunar Orbiter

NASA Astrophysics Data System (ADS)

Choi, Y. J.; Kim, S.; Kang, K. I.

2016-12-01

A polarimetry data contains valuable information about the lunar surface such as the grain size and porosity of the regolith. However, a polarimetry toward the Moon in its orbit has not been performed. We plan to perform the polarimetry in lunar orbit through Korea Pathfinder Lunar Orbiter (KPLO), which will be launched around 2018/2019 as the first Korean lunar mission. Wide-Angle Polarimetric Camera (PolCam) is selected as one of the onboard instrument for KPLO. The science objectives are ; (1) To obtain the polarization data of the whole lunar surface at wavelengths of 430nm and 650nm for phase angle range from 0° to 120° with a spatial resolution of 80 m. (2) To obtain the reflectance ratios at 320 nm and 430 nm for the whole lunar surface with a spatial resolution of 80m. We will summarize recent results of lunar surface from ground-based polarimetric observations and will briefly introduce the science rationals and operation concept of PolCam.

High-Speed Laser Scanner Maps a Surface in Three Dimensions

NASA Technical Reports Server (NTRS)

Lavelle, Joseph; Schuet, Stefan

2006-01-01

A scanning optoelectronic instrument generates the digital equivalent of a threedimensional (X,Y,Z) map of a surface that spans an area with resolution on the order of 0.005 in. ( 0.125mm). Originally intended for characterizing surface flaws (e.g., pits) on space-shuttle thermal-insulation tiles, the instrument could just as well be used for similar purposes in other settings in which there are requirements to inspect the surfaces of many objects. While many commercial instruments can perform this surface-inspection function, the present instrument offers a unique combination of capabilities not available in commercial instruments. This instrument utilizes a laser triangulation method that has been described previously in NASA Tech Briefs in connection with simpler related instruments used for different purposes. The instrument includes a sensor head comprising a monochrome electronic camera and two lasers. The camera is a high-resolution

Tunable All Reflective Spatial Heterodyne Spectroscopy, A Technique For High Resolving Power Observation OI Defused Emission Line Sources

NASA Astrophysics Data System (ADS)

Hosseini, Seyedeh Sona

The solar system presents a challenge to spectroscopic observers, because it is an astrophysically low energy environment populated with often angularly extended targets (e.g, interplanetary medium, comets, planetary upper atmospheres, and planet and satellite near space environments). Spectroscopy is a proven tool for determining compositional and other properties of remote objects. Narrow band imaging and low resolving spectroscopic measurements provide information about composition, photochemical evolution, energy distribution and density. The extension to high resolving power provides further access to temperature, velocity, isotopic ratios, separation of blended sources, and opacity effects. The drawback of high-resolution spectroscopy comes from the instrumental limitations of lower throughput, the necessity of small entrance apertures, sensitivity, field of view, and large physical instrumental size. These limitations quickly become definitive for faint and/or extended targets and for spacecraft encounters. An emerging technique with promise for the study of faint, extended sources at high resolving power is the all-reflective form of the Spatial Heterodyne Spectrometer (SHS). SHS instruments are compact and naturally possess both high etendue and high resolving power. To achieve similar spectral grasp, grating spectrometers require big telescopes. SHS is a common-path beam Fourier transform interferometer that produces Fizeau fringe pattern for all other wavelengths except the tuned wavelength. Compared to similar Fourier transform Spectrometers (FTS), SHS has considerably relaxed optical tolerances that make it easier to use in the visible and UV spectral ranges. The large etendue of SHS instruments makes them ideal for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables the study of the dynamical and spectral characteristics described above. SHS also combines very high (R >105) spectral resolution and large etendue in a small package that is compatible with space mission requirements that have not been met with any other SHS technologies to date. One limitation of current SHS designs is the lack of a broadband capability. To address this gap we are developing a form of the reflective SHS that is tunable over a wide range of wavelength (TSHS). In this work, we describe the primary TSHS concept in a mathematical approach, describe the variations under development, and discuss their scientific potential for the exploration of faint extended targets. An in-development laboratory prototype of a second generation TSHS in which we address several technical limitations noted in earlier studies is shown. This document contains three chapters. Chapter 1, is an overview of the scientific need for a new instrument that we are introducing here and it is an summery of previous papers. Chapter 2 contains new work developing the mathematical frame work for the all reflective SHS. The results presented in this chapter have not been reported in any related literature before and will be presented in an upcoming conference paper. Chapter 3 contains a laboratory report for construction of a tunable all reflective SHS.

Generic control software connecting astronomical instruments to the reflective memory data recording system of VLTI - bossvlti

NASA Astrophysics Data System (ADS)

Pozna, E.; Ramirez, A.; Mérand, A.; Mueller, A.; Abuter, R.; Frahm, R.; Morel, S.; Schmid, C.; Duc, T. Phan; Delplancke-Ströbele, F.

2014-07-01

The quality of data obtained by VLTI instruments may be refined by analyzing the continuous data supplied by the Reflective Memory Network (RMN). Based on 5 years experience providing VLTI instruments (PACMAN, AMBER, MIDI) with RMN data, the procedure has been generalized to make the synchronization with observation trouble-free. The present software interface saves not only months of efforts for each instrument but also provides the benefits of software frameworks. Recent applications (GRAVITY, MATISSE) supply feedback for the software to evolve. The paper highlights the way common features been identified to be able to offer reusable code in due course.

Near specular scatter analysis method with a new goniophotometer

NASA Astrophysics Data System (ADS)

Meyen, Stephanie; Sutter, Florian; Heller, Peter

2014-09-01

The challenge of improving component quality and reducing cost has focused the attention of the solar thermal power industry on reliable component characterization methods. Since the reflector plays a key role in the energy conversion chain, the analysis of its reflectance properties has become a lively discussed issue in recent years. State of the art measurement instruments for specular reflectance do not give satisfying results, because they do not resolve sufficiently the near specular scatter of possible low cost mirror material candidates. The measurement of the BRDF offers a better solution than the traditional approach of placing a detector in the specular reflected beam path. However, due to the requirement of high angular resolution in the range of 1 mrad (0.057°) or better and the challenge of measuring high dynamic differences between the specular peak and the scatter signal, typical commercial scanning goniophotometers capable of this are rare. These instruments also face the disadvantages of impractically long acquisition times and, to reach the high angular resolution, occupy a large space (several meters side length). We have taken on the appealing idea of a parallel imaging goniophotometer and designed a prototype based on this principle. A mirrored ellipsoid is used to redirect the reflected light coming from a sample towards a camera with a fisheye lens. This way the complete light distribution is captured simultaneously. A key feature allows the distinction of the high intensity specular peak and the low intensity scatter. In this article we explain the prototype design and demonstrate its functionality based on comparison measurements done with a commercial scanning goniophotometer. We identify limitations related in part to the concept and in part to the specific prototype and suggest improvements. Finally we conclude that the concept is well suitable for the analysis of near specular scatter of mirror materials, although less adequate for the analysis of rough surfaces that require a full 180° view angle. Results obtained with this instrument are useful to evaluate the performance of a reflector material for a specific concentrating solar collector design and also serve in other applications that require near specular scatter analysis like degradation and soiling research.

A Tracking Sun Photometer Without Moving Parts

NASA Technical Reports Server (NTRS)

Strawa, Anthony W.

2012-01-01

This innovation is small, lightweight, and consumes very little electricity as it measures the solar energy attenuated by gases and aerosol particles in the atmosphere. A Sun photometer is commonly used on the Earth's surface, as well as on aircraft, to determine the solar energy attenuated by aerosol particles in the atmosphere and their distribution of sizes. This information is used to determine the spatial and temporal distribution of gases and aerosols in the atmosphere, as well as their distribution sizes. The design for this Sun photometer uses a combination of unique optics and a charge coupled device (CCD) array to eliminate moving parts and make the instrument more reliable. It could be selfcalibrating throughout the year. Data products would be down-welling flux, the direct-diffuse flux ratio, column abundance of gas phase constituents, aerosol optical depth at multiple-wavelengths, phase functions, cloud statistics, and an estimate of the representative size of atmospheric particles. These measurements can be used to obtain an estimate of aerosol size distribution, refractive index, and particle shape. Incident light is received at a light-reflecting (inner) surface, which is a truncated paraboloid. Light arriving from a hemispheric field of view (solid angle 2 steradians) enters the reflecting optic at an entrance aperture at, or adjacent to, the focus of the paraboloid, and is captured by the optic. Most of this light is reflected from an inner surface. The light proceeds substantially parallel to the paraboloid axis, and is detected by an array detector located near an exit aperture. Each of the entrance and exit apertures is formed by the intersection of the paraboloid with a plane substantially perpendicular to the paraboloid axis. Incident (non-reflected) light from a source of limited extent (the Sun) illuminates a limited area on the detector array. Both direct and diffuse illumination may be reflected, or not reflected, before being received on the detector array. As the Sun traverses a path in the sky over some time interval, the track of the Sun can be traced on the detector array. A suitably modified Sun photometer might be used to study the dynamics of an environment on another planet or satellite with an atmosphere.

Preliminary results of BTDF calibration of transmissive solar diffusers for remote sensing

NASA Astrophysics Data System (ADS)

Georgiev, Georgi T.; Butler, James J.; Thome, Kurt; Cooksey, Catherine; Ding, Leibo

2016-09-01

Satellite instruments operating in the reflected solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers. As a result, numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons have been conducted between the National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons have been conducted between National Measurement Laboratories (NMLs) and other metrology laboratories. On the other hand, there is a growing interest in the use of transmissive diffusers in the calibration of satellite, air-borne, and ground-based remote sensing instruments. Current remote sensing instruments employing transmissive diffusers include the Ozone Mapping and Profiler Suite instrument (OMPS) Limb instrument on the Suomi-National Polar-orbiting Partnership (S-NPP) platform,, the Geostationary Ocean Color Imager (GOCI) on the Korea Aerospace Research Institute's (KARI) Communication, Ocean, and Meteorological Satellite (COMS), the Ozone Monitoring Instrument (OMI) on NASA's Earth Observing System (EOS) Aura platform, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument and the Geostationary Environmental Monitoring Spectrometer (GEMS).. This ensemble of instruments requires validated BTDF measurements of their onboard transmissive diffusers from the ultraviolet through the near infrared. This paper presents the preliminary results of a BTDF comparison between the NASA Diffuser Calibration Laboratory (DCL) and NIST on quartz and thin Spectralon samples.

Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woronowicz, M. S.

2011-05-20

The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm{sup 3}. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may bemore » possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.« less

Spectrally controlled interferometry for measurements of flat and spherical optics

NASA Astrophysics Data System (ADS)

Salsbury, Chase; Olszak, Artur G.

2017-10-01

Conventional interferometry is widely used to measure spherical and at surfaces with nanometer level precision but is plagued by back reflections. We describe a new method of isolating the measurement surface by controlling spectral properties of the source (Spectrally Controlled Interferometry - SCI). Using spectral modulation of the interferometer's source enables formation of localized fringes where the optical path difference is non-zero. As a consequence it becomes possible to form white-light like fringes in common path interferometers, such as the Fizeau. The proposed setup does not require mechanical phase shifting, resulting in simpler instruments and the ability to upgrade existing interferometers. Furthermore, it allows absolute measurement of distance, including radius of curvature of lenses in a single setup with possibility of improving the throughput and removing some modes of failure.

Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

NASA Technical Reports Server (NTRS)

Woronowicz, M. S.

2010-01-01

The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cu cm. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

The Effect of Hydrofluoric Acid Surface Treatment on the Cyclic Fatigue Resistance of K3 NiTi Instruments

PubMed Central

2017-01-01

The aim of this study was to investigate the effect of 50% hydrofluoric acid (HF) surface treatment on the cyclic fatigue resistance (CFR) of K3 NiTi instruments. Twenty as-received and twenty HF-treated K3 NiTi instruments were compared in CFR. The surface texture and fracture surface of two instrument groups were examined with a scanning electron microscope (SEM). Additionally, any change of Ni and Ti composition from both instrument groups was investigated using energy dispersive spectrometry. The results were analyzed with t-test. The HF-treated K3 group showed statistically higher cyclic fatigue resistance than as-received K3 group (P < 0.05). HF-treated K3 instruments showed smoother and rounded surface compared to as-received K3 under SEM observation. The fracture surfaces of both groups showed typical patterns of cyclic fatigue fracture. There was no difference in surface Ni and Ti composition between two groups. HF treatment of K3 instruments smoothed the file surface and increased the cyclic fatigue resistance, while it had no effect on surface ion composition and the file fracture pattern. PMID:28539854

Rough-surface model for surface temperature calculations on Vesta

NASA Astrophysics Data System (ADS)

Palmer, E.; Sykes, M.

2014-07-01

We model observations by the Dawn Visual and Infrared spectrometer (VIR) [1] to reproduce the observed surface temperature of Vesta. The VIR instrument has collected over 3,700 spectral cubes of Vesta out to 5.1 microns. The observed surface temperature is derived by matching the irradiance near 5 microns with a grey body, the Planck function after removing a reflected-light component per previous procedures [2--5] with similar results. We noted that the observed surface temperatures are significantly hotter than what simple theoretical models would predict [2]. To better understand this, we used a high-resolution topographic model of Vesta [6] that provided exact phase, incidence, and emission angles for every VIR pixel. We assume an emissivity of 0.9, Bond albedo of between 0.16 and 0.22 [5], and a variety of thermal inertia values for a low-contrast, highly degraded, homogenous crater. We have created a ''rough-surface'' thermal model that takes into account how irregular grains create sub-pixel variations in the thermal spectrum and describe the effect it has on the observed surface temperatures of Vesta. We have applied this method to the VIR observations of Vesta, which produced a high level of agreement with the observed surface temperatures.

ASTER Images San Francisco Bay Area

NASA Technical Reports Server (NTRS)

2000-01-01

This image of the San Francisco Bay region was acquired on March 3, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters about 50 to 300 feet ), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

Image: This image covers an area 60 kilometers (37 miles) wide and 75 kilometers (47 miles) long in three bands of the reflected visible and infrared wavelength region. The combination of bands portrays vegetation in red, and urban areas in gray. Sediment in the Suisun Bay, San Pablo Bay, San Francisco Bay, and the Pacific Ocean shows up as lighter shades of blue. Along the west coast of the San Francisco Peninsula, strong surf can be seen as a white fringe along the shoreline. A powerful rip tide is visible extending westward from Daly City into the Pacific Ocean. In the lower right corner, the wetlands of the South San Francisco Bay National Wildlife Refuge appear as large dark blue and brown polygons. The high spatial resolution of ASTER allows fine detail to be observed in the scene. The main bridges of the area (San Mateo, San Francisco-Oakland Bay, Golden Gate, Richmond-San Rafael, Benicia-Martinez, and Carquinez) are easily picked out, connecting the different communities in the Bay area. Shadows of the towers along the Bay Bridge can be seen over the adjacent bay water. With enlargement the entire road network can be easily mapped; individual buildings are visible, including the shadows of the high-rises in downtown San Francisco.

Inset: This enlargement of the San Francisco Airport highlights the high spatial resolution of ASTER. With further enlargement and careful examination, airplanes can be seen at the terminals.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

Control of the positional relationship between a sample collection instrument and a surface to be analyzed during a sampling procedure with image analysis

DOEpatents

Van Berkel, Gary J.; Kertesz, Vilmos

2011-08-09

A system and method utilizes an image analysis approach for controlling the collection instrument-to-surface distance in a sampling system for use, for example, with mass spectrometric detection. Such an approach involves the capturing of an image of the collection instrument or the shadow thereof cast across the surface and the utilization of line average brightness (LAB) techniques to determine the actual distance between the collection instrument and the surface. The actual distance is subsequently compared to a target distance for re-optimization, as necessary, of the collection instrument-to-surface during an automated surface sampling operation.

Fires Burning near Big Sur, California

NASA Technical Reports Server (NTRS)

2008-01-01

Fires near Big Sur, Calif., continued to burn unchecked when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite captured this image on Sunday, June 29. In Northern California alone, fires have consumed more than 346,000 acres.At least 18,000 people have deployed to attempt to extinguish or control the flames. Air quality as far away as San Francisco has been adversely impacted by the dense clouds of smoke and ash blowing towards the northwest. The satellite image combines a natural color portrayal of the landscape with thermal infrared data showing the active burning areas in red. The dark area in the lower right is a previous forest fire.

ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

Size: 35.4 by 57 kilometers (21.9 by 34.2 miles) Location: 36.1 degrees North latitude, 121.6 degrees West longitude Orientation: North at top Image Data: ASTER bands 3, 2, and 1 Original Data Resolution: 15 meters (49 feet) Dates Acquired: June 29, 2008

Lunar Observer Laser Altimeter observations for lunar base site selection

NASA Technical Reports Server (NTRS)

Garvin, James B.; Bufton, Jack L.

1992-01-01

One of the critical datasets for optimal selection of future lunar landing sites is local- to regional-scale topography. Lunar base site selection will require such data for both engineering and scientific operations purposes. The Lunar Geoscience Orbiter or Lunar Observer is the ideal precursory science mission from which to obtain this required information. We suggest that a simple laser altimeter instrument could be employed to measure local-scale slopes, heights, and depths of lunar surface features important to lunar base planning and design. For this reason, we have designed and are currently constructing a breadboard of a Lunar Observer Laser Altimeter (LOLA) instrument capable of acquiring contiguous-footprint topographic profiles with both 30-m and 300-m along-track resolution. This instrument meets all the severe weight, power, size, and data rate limitations imposed by Observer-class spacecraft. In addition, LOLA would be capable of measuring the within-footprint vertical roughness of the lunar surface, and the 1.06-micron relative surface reflectivity at normal incidence. We have used airborne laser altimeter data for a few representative lunar analog landforms to simulate and analyze LOLA performance in a 100-km lunar orbit. We demonstrate that this system in its highest resolution mode (30-m diameter footprints) would quantify the topography of all but the very smallest lunar landforms. At its global mapping resolution (300-m diameter footprints), LOLA would establish the topographic context for lunar landing site selection by providing the basis for constructing a 1-2 km spatial resolution global, geodetic topographic grid that would contain a high density of observations (e.g., approximately 1000 observations per each 1 deg by 1 deg cell at the lunar equator). The high spatial and vertical resolution measurements made with a LOLA-class instrument on a precursory Lunar Observer would be highly synergistic with high-resolution imaging datasets, and will allow for direct quantification of critical slopes, heights, and depths of features visible in images of potential lunar base sites.

Calibration of passive remote observing optical and microwave instrumentation; Proceedings of the Meeting, Orlando, FL, Apr. 3-5, 1991

NASA Technical Reports Server (NTRS)

Guenther, Bruce W. (Editor)

1991-01-01

Various papers on the calibration of passive remote observing optical and microwave instrumentation are presented. Individual topics addressed include: on-board calibration device for a wide field-of-view instrument, calibration for the medium-resolution imaging spectrometer, cryogenic radiometers and intensity-stabilized lasers for EOS radiometric calibrations, radiometric stability of the Shuttle-borne solar backscatter ultraviolet spectrometer, ratioing radiometer for use with a solar diffuser, requirements of a solar diffuser and measurements of some candidate materials, reflectance stability analysis of Spectralon diffuse calibration panels, stray light effects on calibrations using a solar diffuser, radiometric calibration of SPOT 23 HRVs, surface and aerosol models for use in radiative transfer codes. Also addressed are: calibrated intercepts for solar radiometers used in remote sensor calibration, radiometric calibration of an airborne multispectral scanner, in-flight calibration of a helicopter-mounted Daedalus multispectral scanner, technique for improving the calibration of large-area sphere sources, remote colorimetry and its applications, spatial sampling errors for a satellite-borne scanning radiometer, calibration of EOS multispectral imaging sensors and solar irradiance variability.

An overview of the laser ranging method of space laser altimeter

NASA Astrophysics Data System (ADS)

Zhou, Hui; Chen, Yuwei; Hyyppä, Juha; Li, Song

2017-11-01

Space laser altimeter is an active remote sensing instrument to measure topographic map of Earth, Moon and planetary. The space laser altimeter determines the range between the instrument and laser footprint by measuring round trip time of laser pulse. The return pulse reflected from ground surface is gathered by the receiver of space laser altimeter, the pulsewidth and amplitude of which are changeable with the variability of the ground relief. Meantime, several kinds of noise overlapped on the return pulse signal affect its signal-to-noise ratio. To eliminate the influence of these factors that cause range walk and range uncertainty, the reliable laser ranging methods need to be implemented to obtain high-precision range results. Based on typical space laser altimeters in the past few decades, various ranging methods are expounded in detail according to the operational principle of instruments and timing method. By illustrating the concrete procedure of determining time of flight of laser pulse, this overview provides the comparison of the employed technologies in previous and undergoing research programs and prospect innovative technology for space laser altimeters in future.

OCAPI: a multidirectional multichannel polarizing imager

NASA Astrophysics Data System (ADS)

Le Naour, C.; Eichen, G.; Léon, J. F.

2017-11-01

OCAPI (Optical Carbonaceous and anthropogenic Aerosols Pathfinder Instrument) is an imager dedicated to the observation of the spectral, directional and polarized signatures of the solar radiance reflected by the Earth-Atmosphere system. The measurements are used to study air quality and pollution by tracking aerosol quantity, types and circulation at various scales in the visible range. The main characteristics of OCAPI are a 110° along track and cross track field of view, eight polarized channels distributed between 320 and 2130 nm. The resolution is 4 x 4 km2 in the visible and the shortwave infrared (SWIR) range, and 10 x 10 km2 in the UV. The instrumental concept is derived from POLDER and PARASOL with additional channels in the UV and SWIR to better determine aerosol properties and constrain Earth surface and cloud contributions in the detected signal. It is based on three wide field-ofview telecentric optics (UV, Visible and SWIR), a rotating wheel bearing spectral and polarized filters and two dimensional detector arrays at the focal plane of the optics. The instrument requirements, concept and budgets are presented.

Aletsch Glacier, Switzerland

NASA Image and Video Library

2002-09-03

Aletsch Glacier, the largest glacier of Europe, covers more than 120 square kilometers (more than 45 square miles) in southern Switzerland. At its eastern extremity lies a glacierlake, Mdrjelensee (2,350 meters/7,711 feet above sea level). To the west rises Aletschhorn (4,195 meters/13,763 feet), which was first climbed in 1859. The Rhone River flows along the southern flank of the mountains. This image was acquired on July 23, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. http://photojournal.jpl.nasa.gov/catalog/PIA03857

Nimbus-7 TOMS Version 7 Calibration

NASA Technical Reports Server (NTRS)

Wellemeyer, C. G.; Taylor, S. L.; Jaross, G.; DeLand, M. T.; Seftor, C. J.; Labow, G.; Swissler, T. J.; Cebula, R. P.

1996-01-01

This report describes an improved instrument characterization used for the Version 7 processing of the Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) data record. An improved internal calibration technique referred to as spectral discrimination is used to provide long-term calibration precision of +/- 1%/decade in total column ozone amount. A revised wavelength scale results in a day one calibration that agrees with other satellite and ground-based measurements of total ozone, while a wavelength independent adjustment of the initial radiometric calibration constants provides good agreement with surface reflectivity measured by other satellite-borne ultraviolet measurements. The impact of other aspects of the Nimbus-7 TOMS instrument performance are also discussed. The Version 7 data should be used in all future studies involving the Nimbus-7 TOMS measurements of ozone. The data are available through the NASA Goddard Space Flight Center's Distributive Active Archive Center (DAAC).

Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy

DOE PAGES

Bluhm, Hendrik; Crumlin, Ethan J.

2016-05-03

The Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) was held at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA, from December 7-9, 2015. It brought together more than 100 participants from 17 countries. The workshop followed the inaugural meeting at the French synchrotron SOLEIL in December 2014, which was organized by François Rochet. The strong interest in these workshops reflects the growth of the APXPS community over the last decade, with instruments now operational at more than 12 synchrotrons around the world (see SRN, Vol. 27, No. 2, pp. 14–23 (2014)), and a steady increase in themore » number of laboratory instruments. Finally, APXPS has established itself as an important method for the investigation of surfaces and interfaces under in situ and operando conditions, including liquid/vapor and liquid/solid interfaces.« less

Use your head! Perception of action possibilities by means of an object attached to the head.

PubMed

Wagman, Jeffrey B; Hajnal, Alen

2016-03-01

Perceiving any environmental property requires spontaneously assembling a smart perceptual instrument-a task-specific measurement device assembled across potentially independent anatomical units. Previous research has shown that to a large degree, perception of a given environmental property is anatomically independent. We attempted to provide stronger evidence for this proposal by investigating perception by an organization of anatomical and inert components that likely requires the spontaneous assembly of a novel smart perceptual instrument-a rod attached to the head. Specifically, we compared cephalic and manual perception of whether an inclined surface affords standing on. In both conditions, perception reflected the action capabilities of the perceiver and not the appendage used to wield the rod. Such results provide stronger evidence for anatomical independence of perception within a given perceptual system and highlight that flexible task-specific detection units can be assembled across units that span the body and inert objects.

Fire near South Lake Tahoe, California

NASA Technical Reports Server (NTRS)

2007-01-01

A destructive forest fire that broke out June 24, 2007 near South Lake Tahoe, Calif., continued to burn June 27 when this image was acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer instrument on NASA's Terra satellite. As of June 28, the fire had destroyed about 230 residences and other buildings. In all, about 2,000 people were evacuated, according to South Lake Tahoe Police. The blaze has charred more than 3,100 acres -- about 4.8 square miles -- and was 60 percent contained on June 28. In this ASTER image, the burned area is in gray, a combination of burned forest and some smoke, between Fallen Leaf Lake and the Tahoe Airport.

With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra spacecraft. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

Size: 15 by 15 kilometers (9.3 by 9.3 miles) Location: 38.9 degrees North latitude, 120 degrees West longitude Orientation: North at top Image Data: ASTER Bands 3, 2, and 1 Original Data Resolution: ASTER 15 meters (49.2 feet) Date Acquired: June 27, 2007.

Homogenization of Tianjin monthly near-surface wind speed using RHtestsV4 for 1951-2014

NASA Astrophysics Data System (ADS)

Si, Peng; Luo, Chuanjun; Liang, Dongpo

2018-05-01

Historical Chinese surface meteorological records provided by the special fund for basic meteorological data from the National Meteorological Information Center (NMIC) were processed to produce accurate wind speed data. Monthly 2-min near-surface wind speeds from 13 observation stations in Tianjin covering 1951-2014 were homogenized using RHtestV4 combined with their metadata. Results indicate that 10 stations had significant breakpoints—77% of the Tianjin stations—suggesting that inhomogeneity was common in the Tianjin wind speed series. Instrument change accounted for most changes, based on the metadata, including changes in type and height, especially for the instrument type. Average positive quantile matching (QM) adjustments were more than negative adjustments at 10 stations; positive biases with a probability density of 0.2 or more were mainly concentrates in the range 0.2 m s-1 to 1.2 m s-1, while the corresponding negative biases were mainly in the range -0.1 to -1.2 m s-1. Here, changes in variances and trends in the monthly mean surface wind speed series at 10 stations before and after adjustment were compared. Climate characteristics of wind speed in Tianjin were more reasonably reflected by the adjusted data; inhomogeneity in wind speed series was largely corrected. Moreover, error analysis reveals that there was a high consistency between the two datasets here and that from the NMIC, with the latter as the reference. The adjusted monthly near-surface wind speed series shows a certain reliability for the period 1951-2014 in Tianjin.

Land, Cryosphere, and Nighttime Environmental Products from Suomi NPP VIIRS: Overview and Status

NASA Technical Reports Server (NTRS)

Roman, Miguel O.; Justice, Chris; Csiszar, Ivan

2014-01-01

The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument was launched in October 2011 as part of the Suomi National Polar-orbiting Partnership (S-NPP: http://npp.gsfc.nasa.gov/). VIIRS was designed to improve upon the capabilities of the operational Advanced Very High Resolution Radiometer (AVHRR) and provide observation continuity with NASA's Earth Observing System's (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS). Since the VIIRS first-light images were received in November 2011, NASA and NOAA funded scientists have been working to evaluate the instrument performance and derived products to meet the needs of the NOAA operational users and the NASA science community. NOAA's focus has been on refining a suite of operational products known as Environmental Data Records (EDRs), which were developed according to project specifications under the former National Polar-orbiting Environmental Satellite System (NPOESS). The NASA S-NPP Science Team has focused on evaluating the EDRs for science use, developing and testing additional products to meet science data needs and providing MODIS data product continuity. This paper will present to-date findings of the NASA Science Team's evaluation of the VIIRS Land and Cryosphere EDRs, specifically Surface Reflectance, Land Surface Temperature, Surface Albedo, Vegetation Indices, Surface Type, Active Fires, Snow Cover, Ice Surface Temperature, and Sea Ice Characterization (http://viirsland.gsfc.nasa.gov/index.html). The paper will also discuss new capabilities being developed at NASA's Land Product Evaluation and Test Element (http://landweb.nascom.nasa.gov/NPP_QA/); including downstream data and products derived from the VIIRS Day/Night Band (DNB).

Lambert Reflectance Albedo And Temperature Mapping Of Thermal Emission Spectrometer Data During The Mars Global Surveyor Aerobraking Phase

NASA Astrophysics Data System (ADS)

Badri, K. M.; Alqasim, A.; Altunaiji, E. S.; Edwards, C. S.; Smith, M. D.

2017-12-01

The goal of this work is to create multiple sets of maps using Thermal Emission Spectrometer (TES) data that encompass the aerobraking phase of the Mars Global Surveyor mission. This work will serve as a proof of concept for the upcoming Emirates Mars Mission, where the Emirates Mars Infrared Spectrometer (EMRIS) will generate data acquired in a similar manner to that acquired by TES during aerobraking. To generate maps of these data on a global scale, python will be used in combination with the Spacecraft Planet Instrument Camera Matrix and Event (SPICE) toolkit to determine the geometry of the pixels on the planet surface. TES is an instrument within the Mars Global Surveyor (MGS) spacecraft. It is a Fourier transform infrared spectrometer developed to study the surface and atmosphere of Mars using thermal infrared emission spectroscopy. TES consists of six detectors arranged in a 2x3 array with a nominal spot size of 3 × 6 km when in its nominal mapping orbit. Over the southern hemisphere during aerobraking the footprint is significantly larger (10s of km) due to the elliptical nature of the orbit during this phase of the mission. TES aerobraking spectra were taken between Mars Year 23, Ls=180° and Mars Year 24, Ls=30°. Here we map TES footprints to the surface during MGS aerobraking, binned by solar longitude to observe differences on the surface in both temperature and Lambert albedo.

Development of technology for lightweight Beryllium Cassegrain Telescope for space applications and lessons learnt

NASA Astrophysics Data System (ADS)

Greger, R.; Rugi, E.; Hausner, Th.; Jahnen, W.; Frei, S.; Pellaton, D.; Mueller, P.; Hollenbach, I.

2017-11-01

This paper gives an overview on the development of a light weighted Cassegrain telescope with a 200 mm optical aperture as one key element of the Laser Altimeter which will fly on the BepiColombo mission to Mercury (BELA).The Receiver Telescope (RTL) collects the light pulse transmitted to Mercury and reflected from the planet's surface. Mercury's challenging thermal environment, the thermo-mechanical stability of the telescope and the stringent instrument's mass budget require the implementation of an innovative design solution to achieve the requested optical performance over an extended temperature range.

Elucidating ultrafast electron dynamics at surfaces using extreme ultraviolet (XUV) reflection-absorption spectroscopy.

PubMed

Biswas, Somnath; Husek, Jakub; Baker, L Robert

2018-04-24

Here we review the recent development of extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy. This method combines the benefits of X-ray absorption spectroscopy, such as element, oxidation, and spin state specificity, with surface sensitivity and ultrafast time resolution, having a probe depth of only a few nm and an instrument response less than 100 fs. Using this technique we investigated the ultrafast electron dynamics at a hematite (α-Fe2O3) surface. Surface electron trapping and small polaron formation both occur in 660 fs following photoexcitation. These kinetics are independent of surface morphology indicating that electron trapping is not mediated by defects. Instead, small polaron formation is proposed as the likely driving force for surface electron trapping. We also show that in Fe2O3, Co3O4, and NiO, band gap excitation promotes electron transfer from O 2p valence band states to metal 3d conduction band states. In addition to detecting the photoexcited electron at the metal M2,3-edge, the valence band hole is directly observed as transient signal at the O L1-edge. The size of the resulting charge transfer exciton is on the order of a single metal-oxygen bond length. Spectral shifts at the O L1-edge correlate with metal-oxygen bond covalency, confirming the relationship between valence band hybridization and the overpotential for water oxidation. These examples demonstrate the unique ability to measure ultrafast electron dynamics with element and chemical state resolution using XUV-RA spectroscopy. Accordingly, this method is poised to play an important role to reveal chemical details of previously unseen surface electron dynamics.

Optical Coating Performance for Heat Reflectors of the JWST-ISIM Electronic Component

NASA Technical Reports Server (NTRS)

Rashford, Robert A.; Perrygo, Charles M.; Garrison, Matthew B.; White, Bryant K.; Threat, Felix T.; Quijada, Manuel A.; Jeans, James W.; Huber, Frank K.; Bousquet, Robert R.; Shaw, Dave

2011-01-01

A document discusses a thermal radiator design consisting of lightweight composite materials and low-emittance metal coatings for use on the James Webb Space Telescope (JWST) structure. The structure will have a Thermal Subsystem unit to provide passive cooling to the Integrated Science Instrument Module (ISIM) control electronics. The ISIM, in the JWST observatory, is the platform that provides the mounting surfaces for the instrument control electronics. Dissipating the control electronic generated-heat away from JWST is of paramount importance so that the spacecraft s own heat does not interfere with the infrared-light gathering of distant cosmic sources. The need to have lateral control in the emission direction of the IEC (ISIM Electronics Compartment) radiators led to the development of a directional baffle design that uses multiple curved mirrorlike surfaces. This concept started out from the so-called Winston non-imaging optical concentrators that use opposing parabolic reflector surfaces, where each parabola has its focus at the opposite edge of the exit aperture. For this reason they are often known as compound parabolic concentrators or CPCs. This radiator system with the circular section was chosen for the IEC reflectors because it offers two advantages over other designs. The first is that the area of the reflector strips for a given radiator area is less, which results in a lower mass baffle assembly. Secondly, the fraction of energy emitted by the radiator strips and subsequently reflected by the baffle is less. These fewer reflections reduced the amount of energy that is absorbed and eventually re-emitted, typically in a direction outside the design emission range angle. A baffle frame holds the mirrors in position above a radiator panel on the IEC. Together, these will direct the majority of the heat from the IEC above the sunshield away towards empty space.

Evolution of aerosol loading in Santiago de Chile between 1997 and 2014

NASA Astrophysics Data System (ADS)

Pistone, Kristina; Gallardo, Laura

2015-04-01

While aerosols produced by major cities are a significant component of anthropogenic climate forcing as well as an important factor in public health, many South American cities have not been a major focus of aerosol studies due in part to relatively few long-term observations in the region. Here we present a synthesis of the available data for the emerging megacity of Santiago, Chile. We report new results from a recent NASA AERONET (AErosol RObotic NETwork) site in the Santiago basin, combining these with previous AERONET observations in Santiago as well as with a new assessment of the 11-station air quality monitoring network currently administered by the Chilean Environment Ministry (MMA, Ministerio del Medio Ambiente) to assess changes in aerosol composition since 1997. While the average surface concentration of pollution components (specifically PM2.5 and PM10) has decreased, no significant change in total aerosol optical depth was observed. However, changes in aerosol size and composition are suggested by the proxy measurements. Previous studies have revealed limitations in purely satellite-based studies over Santiago due to biases from high surface reflection in the region, particularly in summer months (e.g. Escribano et al 2014). To overcome this difficulty and certain limitations in the air quality data, we next incorporate analysis of aerosol products from the Multi-angle Imaging SpectroRadiometer (MISR) instrument along with those from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, both on NASA's Terra satellite, to better quantify the high bias of MODIS. Thus incorporating these complementary datasets, we characterize the aerosol over Santiago over the period 1997 to 2014, including the evolution of aerosol properties over time and seasonal dependencies in the observed trends. References: Escribano et al (2014), "Satellite Retrievals of Aerosol Optical Depth over a Subtropical Urban Area: The Role of Stratification and Surface Reflectance," Aerosol and Air Quality Research, doi:10.4209/aaqr.2013.03.0082.

Optimally designed narrowband guided-mode resonance reflectance filters for mid-infrared spectroscopy

PubMed Central

Liu, Jui-Nung; Schulmerich, Matthew V.; Bhargava, Rohit; Cunningham, Brian T.

2011-01-01

An alternative to the well-established Fourier transform infrared (FT-IR) spectrometry, termed discrete frequency infrared (DFIR) spectrometry, has recently been proposed. This approach uses narrowband mid-infrared reflectance filters based on guided-mode resonance (GMR) in waveguide gratings, but filters designed and fabricated have not attained the spectral selectivity (≤ 32 cm−1) commonly employed for measurements of condensed matter using FT-IR spectroscopy. With the incorporation of dispersion and optical absorption of materials, we present here optimal design of double-layer surface-relief silicon nitride-based GMR filters in the mid-IR for various narrow bandwidths below 32 cm−1. Both shift of the filter resonance wavelengths arising from the dispersion effect and reduction of peak reflection efficiency and electric field enhancement due to the absorption effect show that the optical characteristics of materials must be taken into consideration rigorously for accurate design of narrowband GMR filters. By incorporating considerations for background reflections, the optimally designed GMR filters can have bandwidth narrower than the designed filter by the antireflection equivalence method based on the same index modulation magnitude, without sacrificing low sideband reflections near resonance. The reported work will enable use of GMR filters-based instrumentation for common measurements of condensed matter, including tissues and polymer samples. PMID:22109445

Recend advances of using VIIRS DNB for surface PM2.5 and fire monitoring

NASA Astrophysics Data System (ADS)

Wang, J.; Polivka, T. N.; Hyer, E. J.; Xu, X.; Ichoku, I.

2017-12-01

The launch of the Suomi National Polar-orbiting Partner- ship (S-NPP) satellite on 28 October 2011 has opened up unprecedented capabilities with the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. With a heritage extending back over 40 years to the Defense Meteorological Satel- lite Program (DMSP) Sensor Aerospace Vehicle Electronics Package (SAP), first launched in 1970, Advanced Very High Resolution Radiometer (AVHRR, first launched 1978), and Moderate Resolution Imaging Spectroradiometer (MODIS, first launched in 1999), VIIRS boasts improved spatial resolution and a higher signal-to-noise ratio than these legacy sensors. In particular, at the spatial resolution of 750 m, the VIIRS' day-and-night band (DNB) can monitor the visible light reflected by the Earth and atmsophere in all conditions, from strong reflection of sun light by cloud to weak reflection of moon light by desert at night. While several studies have looked into the potential use of DNB for mapping city lights and for retrieving aerosol optical depth at night, there are still lots of learn about DNB. Here, we will present our recent work of using DNB together with other VIIRS data to improve detection of smaller and cooler fires, to characterize the smoldering vs. flamming phase of fires , and to derive surface PM2.5 at night. Quantiitve understanding of visible light trasnfer from surface to the top of atmospehre will be presented, along with the study to undertand the radiation of fires from visible to infrared spectrum. Varous case studies will be shown in which 30% more fire pixels were detected as comapred to tradiational infrared-mehod only. Cross validation of DNB-based regression model shows that the estimated surface PM2.5 concentration has nearly no bias and a linear correlation coefficient (R) of 0.67 with respect to the corresponding hourly observed surface PM2.5 concentration.

Wavelength independent interferometer

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

1991-01-01

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Measurements of atmospheric dimethylsulfide, hydrogen sulfide, and carbon disulfide during GTE/CITE 3

NASA Technical Reports Server (NTRS)

Cooper, David J.; Saltzman, Eric S.

1993-01-01

Measurements of atmospheric dimethylsulfide (DMS), hydrogen sulfide (H2S), and carbon disulfide (CS2) were made over the North and South Atlantic Ocean as part of the Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 3) project. DMS and CS2 samples were collected and analyzed using an automated gas chromatography/flame photometric detection system with a sampling frequency of 10 min. H2S samples were collected using silver nitrate impregnated filters and analyzed by fluorescence quenching. The DMS data from both hemispheres have a bimodal distribution. Over the North Atlantic this reflects the difference between marine and continental air masses. Over the South Atlantic it may reflect differences in the sea surface source of DMS, corresponding to different air mass source regions. The median boundary layer H2S and CS2 levels were significantly higher in the northern hemisphere than the southern hemisphere, reflecting the higher frequency of samples influenced by pollutant and/or coastal emissions. Composite vertical profiles of DMS and H2S are similar to each other, are consistent with a sea surface source. Vertical profiles of CS2 have maxima in the free troposphere, implicating a continental source. The low levels of H2S and CS2 found in the southern hemisphere constrain the role of these compounds in global budgets to significantly less than previously estimated.

Advances in engineering nanometrology at the National Physical Laboratory

NASA Astrophysics Data System (ADS)

Leach, Richard K.; Claverley, James; Giusca, Claudiu; Jones, Christopher W.; Nimishakavi, Lakshmi; Sun, Wenjuan; Tedaldi, Matthew; Yacoot, Andrew

2012-07-01

The National Physical Laboratory, UK, has been active in the field of engineering nanometrology for a number of years. A summary of progress over the last five years is presented in this paper and the following research projects discussed in detail. (1) Development of an infrastructure for the calibration of instruments for measuring areal surface topography, along with the development of areal software measurement standards. This work comprises the use of the optical transfer function and a technique for the simultaneous measurement of topography and the phase change on reflection, allowing composite materials to be measured. (2) Development of a vibrating micro-CMM probe with isotropic probing reaction and the ability to operate in a non-contact mode. (3) A review of x-ray computed tomography and its use in dimensional metrology. (4) The further development of a metrology infrastructure for atomic force microscopy and the development of an instrument for the measurement of the effect of the probe-surface interaction. (5) Traceable measurement of displacement using optical and x-ray interferometry to picometre accuracy. (6) Development of an infrastructure for low-force metrology, including the development of appropriate transfer artefacts.

Uncertainty in multispectral lidar signals caused by incidence angle effects

PubMed Central

Nevalainen, Olli; Hakala, Teemu; Kaasalainen, Mikko

2018-01-01

Multispectral terrestrial laser scanning (TLS) is an emerging technology. Several manufacturers already offer commercial dual or three wavelength airborne laser scanners, while multispectral TLS is still carried out mainly with research instruments. Many of these research efforts have focused on the study of vegetation. The aim of this paper is to study the uncertainty of the measurement of spectral indices of vegetation with multispectral lidar. Using two spectral indices as examples, we find that the uncertainty is due to systematic errors caused by the wavelength dependency of laser incidence angle effects. This finding is empirical, and the error cannot be removed by modelling or instrument modification. The discovery and study of these effects has been enabled by hyperspectral and multispectral TLS, and it has become a subject of active research within the past few years. We summarize the most recent studies on multi-wavelength incidence angle effects and present new results on the effect of specular reflection from the leaf surface, and the surface structure, which have been suggested to play a key role. We also discuss the consequences to the measurement of spectral indices with multispectral TLS, and a possible correction scheme using a synthetic laser footprint. PMID:29503718

Towards a long-term Science Exploitation Plan for the Sea and Land Surface Temperature Radiometer on Sentinel-3 and the Along-Track Scanning Radiometers

NASA Astrophysics Data System (ADS)

Remedios, John J.; Llewellyn-Jones, David

2014-05-01

The Sea and Land Surface Temperature Radiometer (SLSTR) on Sentinel-3 is the latest satellite instrument in a series of dual-angle optical and thermal sensors, the Along-Track Scanning Radiometers (ATSRs). Operating on Sentinel-3, the SLSTR has a number of significant improvements compared to the original ATSRs including wider swaths for nadir and dual angles, emphasis on all surface temperature domains, dedicated fire channels and additional cloud channels. The SLSTR therefore provides some excellent opportunities to extend science undertaken with the ATSRs whilst also providing long-term data sets to investigate climate change. The European Space Agency, together with the Department of Energy and Climate Change, sponsored the production of an Exploitation Plan for the ATSRs. In the last year, this been extended to cover the SLSTR also. The plan enables UK and European member states to plan activities related to SLSTR in a long-term context. Covering climate change, oceanography, land surface, atmosphere and cryosphere science, particular attention is paid to the exploitation of long-term data sets. In the case of SLSTR, relevant products include sea, land, lake and ice surface temperatures; aerosols and clouds; fires and gas flares; land surface reflectances. In this presentation, the SLSTR and ATSR science Exploitation Plan will be outlined with emphasis on SLSTR science opportunities, on appropriate co-ordinating mechanisms and on example implementation plans. Particular attention will be paid to the challenges of linking ATSR records with SLSTR to provide consistent long-term data sets, and on the international context of such data sets. The exploitation plan approach to science may prove relevant and useful for other Sentinel instruments.

Results of the application of seismic-reflection and electromagnetic techniques for near-surface hydrogeologic and environmental investigations at Fort Bragg, North Carolina

USGS Publications Warehouse

Meyer, M.T.; Fine, J.M.

1997-01-01

As part of the U.S. Geological Survey's Resource Conservation and Recovery Act, Facilities Investigations at Fort Bragg, North Carolina, selected geophysical techniques were evaluated for their usefulness as assessment tools for determining subsurface geology, delineating the areal extent of potentially contaminated landfill sites, and locating buried objects and debris of potential environmental concern. Two shallow seismic-reflection techniques (compression and shear wave) and two electromagnetic techniques (ground-penetrating radar and terrain conductivity) were evaluated at several sites at the U.S. Army Base. The electromagnetic techniques also were tested for tolerance to cultural noise, such as nearby fences, vehicles, and power lines. For the terrain conductivity tests, two instruments were used--the EM31 and EM34, which have variable depths of exploration. The shallowest reflection event was 70 feet below land surface observed in common-depth point, stacked compression-wave data from 24- and 12-fold shallow-seismic-reflection surveys. Several reflection events consistent with clay-sand interfaces between 70 and 120 feet below land surface, along with basement-saprolite surfaces, were imaged in the 24-fold, common- depth-point stacked data. 12-fold, common-depth-point stacked data set contained considerably more noise than the 24-fold, common-depth-point data, due to reduced shot-to-receiver redundancy. Coherent stacked reflection events were not observed in the 24-fold, common-depth-point stacked shear-wave data because of the partial decoupling of the shear- wave generator from the ground. At one site, ground-penetrating radar effectively delineated a shallow, 2- to 5-foot thick sand unit bounded by thin (less than 1 foot) clay layers. The radar signal was completely attenuated where the overlying and underlying clay units thickened and the sand unit thinned. The pene- tration depth of the radar signal was less than 10 feet below land surface. A slight increase in electromagnetic conductivity across shallow sampling EM31 and EM34 profiles provided corroborative evidence of the shallow, thickening clay units. Plots of raw EM31 and EM34 data provided no direct interpretable information to delineate sand and clay units in the shallow subsurface. At two sites, the ground-penetrating radar effectively delineated the lateral continuity of surficial sand units 5 to 25 feet in thickness and the tops of their underlying clay units. The effective exploration depth of the ground-penetrating radar was limited by the proximity of clay units to the subsurface and their thickness. The ground-penetrating radar delineated the areal extent and depth of cover at a previously unrecognized extension of a trench-like landfill underlying a vehicle salvage yard. Attenuation of the radar signal beneath the landfill cover and the adjacent subsurface clays made these two mediums indistinguishable by ground-penetrating radar; however, EM31 data indicated that the electrical conductivity of the landfill was higher than the subsurface material adjacent to the landfill. The EM31 and EM34 conductivity surveys defined the areal extent of a landfill whose boundaries were inaccurately mapped, and also identified the locations of an old dumpsite and waste incinerator site at another landfill. A follow-up ground-penetrating radar survey of the abandoned dumpsite showed incongruities in some of the shallow radar reflections interpreted as buried refuse dispersed throughout the landfill. The ground-penetrating radar and EM31 effectively delineated a shallow buried fuel-oil tank. Of the three electromagnetic instruments, the ground-penetrating radar with the shielded 100-megahertz antenna was the least affected by cultural noise followed, in order, by the EM31 and EM34. The combination of terrain- conductivity and ground-penetrating radar for the site assessment of the landfill provided a powerful means to identify the areal extent of the landfill, potenti