Science.gov

Sample records for absolute radiometric calibrations

  1. Absolute Radiometric Calibration of EUNIS-06

    NASA Technical Reports Server (NTRS)

    Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

    2007-01-01

    The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

  2. Absolute Radiometric Calibration of KOMPSAT-3A

    NASA Astrophysics Data System (ADS)

    Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.

    2016-06-01

    This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.

  3. Landsat-5 TM reflective-band absolute radiometric calibration

    USGS Publications Warehouse

    Chander, G.; Helder, D.L.; Markham, B.L.; Dewald, J.D.; Kaita, E.; Thome, K.J.; Micijevic, E.; Ruggles, T.A.

    2004-01-01

    The Landsat-5 Thematic Mapper (TM) sensor provides the longest running continuous dataset of moderate spatial resolution remote sensing imagery, dating back to its launch in March 1984. Historically, the radiometric calibration procedure for this imagery used the instrument's response to the Internal Calibrator (IC) on a scene-by-scene basis to determine the gain and offset of each detector. Due to observed degradations in the IC, a new procedure was implemented for U.S.-processed data in May 2003. This new calibration procedure is based on a lifetime radiometric calibration model for the instrument's reflective bands (1-5 and 7) and is derived, in part, from the IC response without the related degradation effects and is tied to the cross calibration with the Landsat-7 Enhanced Thematic Mapper Plus. Reflective-band absolute radiometric accuracy of the instrument tends to be on the order of 7% to 10%, based on a variety of calibration methods.

  4. The importance and attainment of accurate absolute radiometric calibration

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1984-01-01

    The importance of accurate absolute radiometric calibration is discussed by reference to the needs of those wishing to validate or use models describing the interaction of electromagnetic radiation with the atmosphere and earth surface features. The in-flight calibration methods used for the Landsat Thematic Mapper (TM) and the Systeme Probatoire d'Observation de la Terre, Haute Resolution visible (SPOT/HRV) systems are described and their limitations discussed. The questionable stability of in-flight absolute calibration methods suggests the use of a radiative transfer program to predict the apparent radiance, at the entrance pupil of the sensor, of a ground site of measured reflectance imaged through a well characterized atmosphere. The uncertainties of such a method are discussed.

  5. Landsat-7 ETM+ radiometric stability and absolute calibration

    USGS Publications Warehouse

    Markham, B.L.; Barker, J.L.; Barsi, J.A.; Kaita, E.; Thome, K.J.; Helder, D.L.; Palluconi, Frank Don; Schott, J.R.; Scaramuzza, P.; ,

    2002-01-01

    Launched in April 1999, the Landsat-7 ETM+ instrument is in its fourth year of operation. The quality of the acquired calibrated imagery continues to be high, especially with respect to its three most important radiometric performance parameters: reflective band instrument stability to better than ??1%, reflective band absolute calibration to better than ??5%, and thermal band absolute calibration to better than ??0.6 K. The ETM+ instrument has been the most stable of any of the Landsat instruments, in both the reflective and thermal channels. To date, the best on-board calibration source for the reflective bands has been the Full Aperture Solar Calibrator, which has indicated changes of at most -1.8% to -2.0% (95% C.I.) change per year in the ETM+ gain (band 4). However, this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on ground observations, which bound the changes in gain in band 4 at -0.7% to +1.5%. Also, ETM+ stability is indicated by the monitoring of desert targets. These image-based results for four Saharan and Arabian sites, for a collection of 35 scenes over the three years since launch, bound the gain change at -0.7% to +0.5% in band 4. Thermal calibration from ground observations revealed an offset error of +0.31 W/m 2 sr um soon after launch. This offset was corrected within the U. S. ground processing system at EROS Data Center on 21-Dec-00, and since then, the band 6 on-board calibration has indicated changes of at most +0.02% to +0.04% (95% C.I.) per year. The latest ground observations have detected no remaining offset error with an RMS error of ??0.6 K. The stability and absolute calibration of the Landsat-7 ETM+ sensor make it an ideal candidate to be used as a reference source for radiometric cross-calibrating to other land remote sensing satellite systems.

  6. Active radiometric calorimeter for absolute calibration of radioactive sources

    SciTech Connect

    Stump, K.E.; DeWerd, L.A.; Rudman, D.A.; Schima, S.A.

    2005-03-01

    This report describes the design and initial noise floor measurements of a radiometric calorimeter designed to measure therapeutic medical radioactive sources. The instrument demonstrates a noise floor of approximately 2 nW. This low noise floor is achieved by using high temperature superconducting (HTS) transition edge sensor (TES) thermometers in a temperature-control feedback loop. This feedback loop will be used to provide absolute source calibrations based upon the electrical substitution method. Other unique features of the calorimeter are (a) its ability to change sources for calibration without disrupting the vacuum of the instrument, and (b) the ability to measure the emitted power of a source in addition to the total contained source power.

  7. Absolute radiometric calibration of advanced remote sensing systems

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1982-01-01

    The distinction between the uses of relative and absolute spectroradiometric calibration of remote sensing systems is discussed. The advantages of detector-based absolute calibration are described, and the categories of relative and absolute system calibrations are listed. The limitations and problems associated with three common methods used for the absolute calibration of remote sensing systems are addressed. Two methods are proposed for the in-flight absolute calibration of advanced multispectral linear array systems. One makes use of a sun-illuminated panel in front of the sensor, the radiance of which is monitored by a spectrally flat pyroelectric radiometer. The other uses a large, uniform, high-radiance reference ground surface. The ground and atmospheric measurements required as input to a radiative transfer program to predict the radiance level at the entrance pupil of the orbital sensor are discussed, and the ground instrumentation is described.

  8. [In-flight absolute radiometric calibration of UAV multispectral sensor].

    PubMed

    Chen, Wei; Yan, Lei; Gou, Zhi-Yang; Zhao, Hong-Ying; Liu, Da-Ping; Duan, Yi-Ni

    2012-12-01

    Based on the data of the scientific experiment in Urad Front Banner for UAV Remote Sensing Load Calibration Field project, with the help of 6 hyperspectral radiometric targets with good Lambertian property, the wide-view multispectral camera in UAV was calibrated adopting reflectance-based method. The result reveals that for green, red and infrared channel, whose images were successfully captured, the linear correlation coefficients between the DN and radiance are all larger than 99%. In final analysis, the comprehensive error is no more than 6%. The calibration results demonstrate that the hyperspectral targets equipped by the calibration field are well suitable for air-borne multispectral load in-flight calibration. The calibration result is reliable and could be used in the retrieval of geophysical parameters.

  9. Absolute radiometric calibration of Landsat using a pseudo invariant calibration site

    USGS Publications Warehouse

    Helder, D.; Thome, K.J.; Mishra, N.; Chander, G.; Xiong, Xiaoxiong; Angal, A.; Choi, Tae-young

    2013-01-01

    Pseudo invariant calibration sites (PICS) have been used for on-orbit radiometric trending of optical satellite systems for more than 15 years. This approach to vicarious calibration has demonstrated a high degree of reliability and repeatability at the level of 1-3% depending on the site, spectral channel, and imaging geometries. A variety of sensors have used this approach for trending because it is broadly applicable and easy to implement. Models to describe the surface reflectance properties, as well as the intervening atmosphere have also been developed to improve the precision of the method. However, one limiting factor of using PICS is that an absolute calibration capability has not yet been fully developed. Because of this, PICS are primarily limited to providing only long term trending information for individual sensors or cross-calibration opportunities between two sensors. This paper builds an argument that PICS can be used more extensively for absolute calibration. To illustrate this, a simple empirical model is developed for the well-known Libya 4 PICS based on observations by Terra MODIS and EO-1 Hyperion. The model is validated by comparing model predicted top-of-atmosphere reflectance values to actual measurements made by the Landsat ETM+ sensor reflective bands. Following this, an outline is presented to develop a more comprehensive and accurate PICS absolute calibration model that can be Système international d'unités (SI) traceable. These initial concepts suggest that absolute calibration using PICS is possible on a broad scale and can lead to improved on-orbit calibration capabilities for optical satellite sensors.

  10. Vicarious absolute radiometric calibration of GF-2 PMS2 sensor using permanent artificial targets in China

    NASA Astrophysics Data System (ADS)

    Liu, Yaokai; Li, Chuanrong; Ma, Lingling; Wang, Ning; Qian, Yonggang; Tang, Lingli

    2016-10-01

    GF-2, launched on August 19 2014, is one of the high-resolution land resource observing satellite of the China GF series satellites plan. The radiometric performance evaluation of the onboard optical pan and multispectral (PMS2) sensor of GF-2 satellite is very important for the further application of the data. And, the vicarious absolute radiometric calibration approach is one of the most useful way to monitor the radiometric performance of the onboard optical sensors. In this study, the traditional reflectance-based method is used to vicarious radiometrically calibrate the onboard PMS2 sensor of GF-2 satellite using three black, gray and white reflected permanent artificial targets located in the AOE Baotou site in China. Vicarious field calibration campaign were carried out in the AOE-Baotou calibration site on 22 April 2016. And, the absolute radiometric calibration coefficients were determined with in situ measured atmospheric parameters and surface reflectance of the permanent artificial calibration targets. The predicted TOA radiance of a selected desert area with our determined calibrated coefficients were compared with the official distributed calibration coefficients. Comparison results show a good consistent and the mean relative difference of the multispectral channels is less than 5%. Uncertainty analysis was also carried out and a total uncertainty with 3.87% is determined of the TOA radiance.

  11. Artifact correction and absolute radiometric calibration techniques employed in the Landsat 7 image assessment system

    USGS Publications Warehouse

    Boncyk, Wayne C.; Markham, Brian L.; Barker, John L.; Helder, Dennis

    1996-01-01

    The Landsat-7 Image Assessment System (IAS), part of the Landsat-7 Ground System, will calibrate and evaluate the radiometric and geometric performance of the Enhanced Thematic Mapper Plus (ETM +) instrument. The IAS incorporates new instrument radiometric artifact correction and absolute radiometric calibration techniques which overcome some limitations to calibration accuracy inherent in historical calibration methods. Knowledge of ETM + instrument characteristics gleaned from analysis of archival Thematic Mapper in-flight data and from ETM + prelaunch tests allow the determination and quantification of the sources of instrument artifacts. This a priori knowledge will be utilized in IAS algorithms designed to minimize the effects of the noise sources before calibration, in both ETM + image and calibration data.

  12. The absolute radiometric calibration of the advanced very high resolution radiometer

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Teillet, P. M.; Ding, Y.

    1988-01-01

    The need for independent, redundant absolute radiometric calibration methods is discussed with reference to the Thematic Mapper. Uncertainty requirements for absolute calibration of between 0.5 and 4 percent are defined based on the accuracy of reflectance retrievals at an agricultural site. It is shown that even very approximate atmospheric corrections can reduce the error in reflectance retrieval to 0.02 over the reflectance range 0 to 0.4.

  13. A liquid-helium-cooled absolute reference cold load for long-wavelength radiometric calibration

    NASA Technical Reports Server (NTRS)

    Bensadoun, Marc; Witebsky, Chris; Smoot, George; De Amici, Giovanni; Kogut, AL; Levin, Steve

    1992-01-01

    Design, radiometric and thermal performance, and operation of a large diameter (78 cm) liquid-helium-cooled blackbody absolute reference cold load (CL) for the calibration of microwave radiometers is described. CL provides an absolute calibration near the liquid-helium (LHe) boiling point, with total uncertainty in the radiometric temperature of less than 30 mK over the 2.5-23 cm wavelength operating range. CL was used at several wavelengths at the South Pole, Antarctica and the White Mountain Research Center, California. Results show that, for the instruments operated at 20-, 12-, 7.9-, and 4.0 cm wavelength at the South Pole, the total corrections to the LHe boiling-point temperature (about 3.8 K) were 48 +/-23, 18 +/-10, 10 +/-18, and 15 +/-mK.

  14. Prelaunch absolute radiometric calibration of the reflective bands on the LANDSAT-4 protoflight Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Barker, J. L.; Ball, D. L.; Leung, K. C.; Walker, J. A.

    1984-01-01

    The results of the absolute radiometric calibration of the LANDSAT 4 thematic mapper, as determined during pre-launch tests with a 122 cm integrating sphere, are presented. Detailed results for the best calibration of the protoflight TM are given, as well as summaries of other tests performed on the sensor. The dynamic range of the TM is within a few per cent of that required in all bands, except bands 1 and 3. Three detectors failed to pass the minimum SNR specified for their respective bands: band 5, channel 3 (dead), band 2, and channels 2 and 4 (noisy or slow response). Estimates of the absolute calibration accuracy for the TM show that the detectors are typically calibrated to 5% absolute error for the reflective bands; 10% full-scale accuracy was specified. Ten tests performed to transfer the detector absolute calibration to the internal calibrator show a 5% range at full scale in the transfer calibration; however, in two cases band 5 showed a 10% and a 7% difference.

  15. The absolute radiometric calibration of the Landsat 8 Operational Land Imager using the reflectance-based approach and the Radiometric Calibration Test Site (RadCaTS)

    NASA Astrophysics Data System (ADS)

    Czapla-Myers, Jeffrey; Anderson, Nikolaus; Thome, Kurtis; Biggar, Stuart

    2014-10-01

    Landsat 8 was launched on 11 February 2013 as the newest platform in the Landsat program. It contains two Earthobserving instruments, one of which is the Operational Land Imager (OLI). OLI includes an onboard radiometric calibration system that is used to monitor changes in its responsivity throughout the mission lifetime, and it consists of Spectralon solar diffuser panels as well as tungsten lamp assemblies. External techniques are used to monitor both OLI and its calibration system, and they include lunar views, side slither maneuvers of the satellite, and ground-based vicarious calibration. This work presents the absolute radiometric calibration results for Landsat 8 OLI that were obtained using two ground-based measurement techniques. The first is the reflectance-based approach, where measurements of atmospheric and surface properties are made during a Landsat 8 overpass, and it requires personnel to be on site during the time of measurement. The second uses the Radiometric Calibration Test Site (RadCaTS), which was developed by the Remote Sensing Group in the College of Optical Sciences at the University of Arizona so that radiometric calibration data can be collected without the requirement of on-site personnel. It allows more data to be collected annually, which increases the temporal sampling of trending results.

  16. A Liquid-Helium-Cooled Absolute Reference Cold Load forLong-Wavelength Radiometric Calibration

    SciTech Connect

    Bensadoun, M.; Witebsky, C.; Smoot, George F.; De Amici,Giovanni; Kogut, A.; Levin, S.

    1990-05-01

    We describe a large (78-cm) diameter liquid-helium-cooled black-body absolute reference cold load for the calibration of microwave radiometers. The load provides an absolute calibration near the liquid helium (LHe) boiling point, accurate to better than 30 mK for wavelengths from 2.5 to 25 cm (12-1.2 GHz). The emission (from non-LHe temperature parts of the cold load) and reflection are small and well determined. Total corrections to the LHe boiling point temperature are {le} 50 mK over the operating range. This cold load has been used at several wavelengths at the South Pole and at the White Mountain Research Station. In operation, the average LHe loss rate was {le} 4.4 l/hr. Design considerations, radiometric and thermal performance and operational aspects are discussed. A comparison with other LHe-cooled reference loads including the predecessor of this cold load is given.

  17. Radiometric absolute noise-temperature measurement system features improved accuracy and calibration ease

    NASA Technical Reports Server (NTRS)

    Brown, W.; Ewen, H.; Haroules, G.

    1970-01-01

    Radiometric receiver system, which measures noise temperatures in degrees Kelvin, does not require cryogenic noise sources for routine operation. It eliminates radiometer calibration errors associated with RF attenuation measurements. Calibrated noise source is required only for laboratory adjustment and calibration.

  18. [In-flight absolute radiometric calibration of UAV hyperspectral camera and its validation analysis].

    PubMed

    Gou, Zhi-yang; Yan, Lei; Chen, Wei; Jing, Xin; Yin, Zhong-yi; Duan, Yi-ni

    2012-02-01

    With the data in Urad Front Banner, Inner Mongolia on November 14th, 2010, hyper-spectral camera on UAV was calibrated adopting reflectance-based method. During the in-flight absolute radiometric calibration, 6 hyper-spectral radiometric gray-scale targets were arranged in the validation field. These targets' reflectances are 4.5%, 20%, 30%, 40%, 50% and 60% separately. To validate the calibration result, four extra hyper-spectral targets with sharp-edge spectrum were arranged to simulate the reflection and absorption peaks in natural objectives. With these peaks, the apparent radiance calculated by radiation transfer model and that calculated through calibration coefficients are much different. The result shows that in the first 15 bands (blue bands), errors are somewhat huge due to the noises of equipment. In the rest bands with quite even spectrum, the errors are small, most of which are less than 10%. For those bands with sharp changes in spectral curves, the errors are quite considerable, varying from 10% to 25%.

  19. Field Measurement of Sand Dune Bidirectional Reflectance Characteristics for Absolute Radiometric Calibration of Optical Remote Sensing Data.

    NASA Astrophysics Data System (ADS)

    Coburn, C. A.; Logie, G.; Beaver, J.; Helder, D.

    2015-12-01

    The use of Pseudo Invariant Calibration Sites (PICS) for establishing the radiometric trending of optical remote sensing systems has a long history of successful implementation. Past studies have shown that the PICS method is useful for evaluating the trend of sensors over time or cross-calibration of sensors but was not considered until recently for deriving absolute calibration. Current interest in using this approach to establish absolute radiometric calibration stems from recent research that indicates that with empirically derived models of the surface properties and careful atmospheric characterisation Top of Atmosphere (TOA) reflectance values can be predicted and used for absolute sensor radiometric calibration. Critical to the continued development of this approach is the accurate characterization of the Bidirectional Reflectance Distribution Function (BRDF) of PICS sites. This paper presents the field data collected by a high-performance portable goniometer system in order to develop a BRDF model for the Algodones Dunes in California. These BRDF data are part of a larger study that is seeking to evaluate and quantify all aspects of this dune system (from regional effects to the micro scale optical properties of the sand) in order to provide an absolute radiometric calibration PICS. This paper presents the results of a dense temporal measurement sequence (several measurements per hour with high angular resolution), to yield detailed information on the nature of the surface reflectance properties. The BRDF data were collected covering typical view geometry of space borne sensors and will be used to close the loop on the calibration to create an absolute calibration target for optical satellite absolute radiometric calibration.

  20. Absolute Radiometric Calibration of ALS Intensity Data: Effects on Accuracy and Target Classification

    PubMed Central

    Kaasalainen, Sanna; Pyysalo, Ulla; Krooks, Anssi; Vain, Ants; Kukko, Antero; Hyyppä, Juha; Kaasalainen, Mikko

    2011-01-01

    Radiometric calibration of airborne laser scanning (ALS) intensity data aims at retrieving a value related to the target scattering properties, which is independent on the instrument or flight parameters. The aim of a calibration procedure is also to be able to compare results from different flights and instruments, but practical applications are sparsely available, and the performance of calibration methods for this purpose needs to be further assessed. We have studied the radiometric calibration with data from three separate flights and two different instruments using external calibration targets. We find that the intensity data from different flights and instruments can be compared to each other only after a radiometric calibration process using separate calibration targets carefully selected for each flight. The calibration is also necessary for target classification purposes, such as separating vegetation from sand using intensity data from different flights. The classification results are meaningful only for calibrated intensity data. PMID:22346660

  1. The absolute radiometric calibration of the advanced very high resolution radiometer

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Teillet, P. M.; Mao, Y.

    1987-01-01

    The early results of an absolute radiometric calibration of the NOAA-9 AVHRR sensor indicate significant degradations in the response of bands 1 and 2 compared to prelaunch values. The results are currently in the process of being verified and it may be that refinements of the methodology will be in order as additional data sets are analyzed. The LANDSAT TM calibration used in this approach is known to be very precise and the Herman radiative transfer code, supplemented by the 5-S code for gaseous transmission, is reliable as well. The extent to which other steps in the analysis procedure give rise to uncertainties in the results is currently under investigation. Particular attention is being given to the geometric matching of the AVHRR and TM imagery, as well as to the spectral redistribution procedure. By taking advantage of a reasonably precise calibration of TM imagery acquired on the same day as the AVHRR data at White Sands, a promising approach to the in-orbit calibration of AVHRR sensors is being developed. Current efforts involve primarily the examination of additional test cases and the investigation of possible simplifications in the procedure through judicious use of atmospheric models.

  2. Temporal dynamics of sand dune bidirectional reflectance characteristics for absolute radiometric calibration of optical remote sensing data

    NASA Astrophysics Data System (ADS)

    Coburn, Craig A.; Logie, Gordon; Beaver, Jason

    2016-09-01

    The use of Pseudo Invariant Calibration Sites (PICS) for establishing the radiometric trending of optical remote sensing systems has a long history of successful implementation. Past studies have shown that the PICS method is useful for evaluating the trend of sensors over time or cross-calibration of sensors but was not considered until recently for deriving absolute calibration. Current interest in using this approach to establish absolute radiometric calibration stems from recent research that indicates that with empirically derived models of the surface properties and careful atmospheric characterisation Top of Atmosphere (TOA) reflectance values can be predicted and used for absolute sensor radiometric calibration. Critical to the continued development of this approach is the accurate characterization of the Bidirectional Reflectance Distribution Function (BRDF) of PICS sites. This paper presents BRDF data collected by a high-performance portable goniometer system in order to develop a temporal BRDF model for the Algodones Dunes in California. The results demonstrated that the BRDF of a reasonably simple sand surface was complex with changes in anisotropy taking place in response to changing solar zenith angles. The nature of these complex interactions would present challenges to future model development.

  3. Exploring a Black Body Source as an Absolute Radiometric Calibration Standard and Comparison with a NIST Traced Lamp Standard

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Chrien, Thomas; Sarture, Chuck

    2001-01-01

    Radiometric calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is required for the scientific research and application objectives pursued with the spectroscopic measurements. Specifically calibration is required for: inter-comparison of AVIRIS data measured at different locations and at different times; analysis of AVIRIS data with data measured by other instruments; and analysis of AVIRIS data in conjunction with computer models. The primary effect of radiometric calibration is conversion of AVIRIS instrument response values (digitized numbers, or DN) to units of absolute radiance. For example, a figure shows the instrument response spectrum measured by AVIRIS over a portion of Rogers Dry Lake, California, and another figure shows the same spectrum calibrated to radiance. Only the calibrated spectrum may be quantitatively analyzed for science research and application objectives. Since the initial development of the AVIRIS instrument-radiometric calibration has been based upon a 1000-W irradiance lamp with a calibration traced to the National Institute of Standards and Technology (NIST). There are several advantages to this irradiance-lamp calibration approach. First, the considerable effort of NIST backs up the calibration. Second, by changing the distance to the lamp, the output can closely span the radiance levels measured by AVIRIS. Third, this type of standard is widely used. Fourth, these calibrated lamps are comparatively inexpensive. Conversely, there are several disadvantages to this approach as well. First, the lamp is not a primary standard. Second, the lamp output characteristics may change in an unknown manner through time. Third, it is difficult to assess, constrain, or improve the calibration uncertainty delivered with the lamp. In an attempt to explore the effect and potentially address some of these disadvantages a set of analyses and measurements comparing an irradiance lamp with a black-body source have been completed

  4. The Importance of Post-Launch, On-Orbit Absolute Radiometric Calibration for Remote Sensing Applications

    NASA Astrophysics Data System (ADS)

    Kuester, M. A.

    2015-12-01

    Remote sensing is a powerful tool for monitoring changes on the surface of the Earth at a local or global scale. The use of data sets from different sensors across many platforms, or even a single sensor over time, can bring a wealth of information when exploring anthropogenic changes to the environment. For example, variations in crop yield and health for a specific region can be detected by observing changes in the spectral signature of the particular species under study. However, changes in the atmosphere, sun illumination and viewing geometries during image capture can result in inconsistent image data, hindering automated information extraction. Additionally, an incorrect spectral radiometric calibration will lead to false or misleading results. It is therefore critical that the data being used are normalized and calibrated on a regular basis to ensure that physically derived variables are as close to truth as is possible. Although most earth observing sensors are well-calibrated in a laboratory prior to launch, a change in the radiometric response of the system is inevitable due to thermal, mechanical or electrical effects caused during the rigors of launch or by the space environment itself. Outgassing and exposure to ultra-violet radiation will also have an effect on the sensor's filter responses. Pre-launch lamps and other laboratory calibration systems can also fall short in representing the actual output of the Sun. A presentation of the differences in the results of some example cases (e.g. geology, agriculture) derived for science variables using pre- and post-launch calibration will be presented using DigitalGlobe's WorldView-3 super spectral sensor, with bands in the visible and near infrared, as well as in the shortwave infrared. Important defects caused by an incomplete (i.e. pre-launch only) calibration will be discussed using validation data where available. In addition, the benefits of using a well-validated surface reflectance product will be

  5. Landsat-7 ETM+ on-orbit reflective-band radiometric stability and absolute calibration

    USGS Publications Warehouse

    Markham, B.L.; Thome, K.J.; Barsi, J.A.; Kaita, E.; Helder, Dennis L.; Barker, J. L.; Scaramuzza, Pat

    2004-01-01

    Launched in April 1999, the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) instrument is in its sixth year of operation. The ETM+ instrument has been the most stable of any of the Landsat instruments. To date, the best onboard calibration source for the reflective bands has been the Full Aperture Solar Calibrator, a solar-diffuser-based system, which has indicated changes of between 1% to 2% per year in the ETM+ gain for bands 1-4 and 8 and less than 0.5%/year for bands 5 and 7. However, most of this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on vicarious calibrations and observations of "invariant sites", hyperarid sites of the Sahara and Arabia. Weighted average slopes determined from these datasets suggest changes of 0.0% to 0.4% per year for bands 1-4 and 8 and 0.4% to 0.5% per year for bands 5 and 7. Absolute calibration of the reflective bands of the ETM+ is consistent with vicarious observations and other sensors generally at the 5% level, though there appear to be some systematic differences.

  6. Absolute Radiometric Calibration of Narrow-Swath Imaging Sensors with Reference to Non-Coincident Wide-Swath Sensors

    NASA Technical Reports Server (NTRS)

    McCorkel, Joel; Thome, Kurtis; Lockwood, Ronald

    2012-01-01

    An inter-calibration method is developed to provide absolute radiometric calibration of narrow-swath imaging sensors with reference to non-coincident wide-swath sensors. The method predicts at-sensor radiance using non-coincident imagery from the reference sensor and knowledge of spectral reflectance of the test site. The imagery of the reference sensor is restricted to acquisitions that provide similar view and solar illumination geometry to reduce uncertainties due to directional reflectance effects. Spectral reflectance of the test site is found with a simple iterative radiative transfer method using radiance values of a well-understood wide-swath sensor and spectral shape information based on historical ground-based measurements. At-sensor radiance is calculated for the narrow-swath sensor using this spectral reflectance and atmospheric parameters that are also based on historical in situ measurements. Results of the inter-calibration method show agreement on the 2 5 percent level in most spectral regions with the vicarious calibration technique relying on coincident ground-based measurements referred to as the reflectance-based approach. While the variability of the inter-calibration method based on non-coincident image pairs is significantly larger, results are consistent with techniques relying on in situ measurements. The method is also insensitive to spectral differences between the sensors by transferring to surface spectral reflectance prior to prediction of at-sensor radiance. The utility of this inter-calibration method is made clear by its flexibility to utilize image pairings with acquisition dates differing in excess of 30 days allowing frequent absolute calibration comparisons between wide- and narrow-swath sensors.

  7. 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.

  8. The absolute radiometric calibration of the advanced very high resolution radiometer

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Teillet, P. M.; Ding, Y.

    1989-01-01

    The measurement conditions are described for an intensive field campaign at White Sands Missile Range for the calibration of the AVHRRs on NOAA-9, NOAA-10 and NOAA-11, LANDSAT-4 TM and SPOT. Three different methods for calibration of AVHRRs by reference to a ground surface site are reported, and results from these methods are compared. Significant degradations in NOAA-9 and NOAA-10 AVHRR responsivities occurred since prelaunch calibrations were completed. As of February 1988, degradations in NOAA-9 AVHRR responsivities were on the order of 37 percent in channel and 41 percent in channel 2, and for the NOAA-10 AVHRR these degradations were 42 and 59 percent in channels 1 and 2, respectively.

  9. Simplified Vicarious Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Stanley, Thomas; Ryan, Robert; Holekamp, Kara; Pagnutti, Mary

    2010-01-01

    A measurement-based radiance estimation approach for vicarious radiometric calibration of spaceborne multispectral remote sensing systems has been developed. This simplified process eliminates the use of radiative transfer codes and reduces the number of atmospheric assumptions required to perform sensor calibrations. Like prior approaches, the simplified method involves the collection of ground truth data coincident with the overpass of the remote sensing system being calibrated, but this approach differs from the prior techniques in both the nature of the data collected and the manner in which the data are processed. In traditional vicarious radiometric calibration, ground truth data are gathered using ground-viewing spectroradiometers and one or more sun photometer( s), among other instruments, located at a ground target area. The measured data from the ground-based instruments are used in radiative transfer models to estimate the top-of-atmosphere (TOA) target radiances at the time of satellite overpass. These TOA radiances are compared with the satellite sensor readings to radiometrically calibrate the sensor. Traditional vicarious radiometric calibration methods require that an atmospheric model be defined such that the ground-based observations of solar transmission and diffuse-to-global ratios are in close agreement with the radiative transfer code estimation of these parameters. This process is labor-intensive and complex, and can be prone to errors. The errors can be compounded because of approximations in the model and inaccurate assumptions about the radiative coupling between the atmosphere and the terrain. The errors can increase the uncertainty of the TOA radiance estimates used to perform the radiometric calibration. In comparison, the simplified approach does not use atmospheric radiative transfer models and involves fewer assumptions concerning the radiative transfer properties of the atmosphere. This new technique uses two neighboring uniform

  10. Radiometric calibration updates to the Landsat collection

    NASA Astrophysics Data System (ADS)

    Micijevic, Esad; Haque, Md. Obaidul; Mishra, Nischal

    2016-09-01

    The Landsat Project is planning to implement a new collection management strategy for Landsat products generated at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center. The goal of the initiative is to identify a collection of consistently geolocated and radiometrically calibrated images across the entire Landsat archive that is readily suitable for time-series analyses. In order to perform an accurate land change analysis, the data from all Landsat sensors must be on the same radiometric scale. Landsat 7 Enhanced Thematic Mapper Plus (ETM+) is calibrated to a radiance standard and all previous sensors are cross-calibrated to its radiometric scale. Landsat 8 Operational Land Imager (OLI) is calibrated to both radiance and reflectance standards independently. The Landsat 8 OLI reflectance calibration is considered to be most accurate. To improve radiometric calibration accuracy of historical data, Landsat 1-7 sensors also need to be cross-calibrated to the OLI reflectance scale. Results of that effort, as well as other calibration updates including the absolute and relative radiometric calibration and saturated pixel replacement for Landsat 8 OLI and absolute calibration for Landsat 4 and 5 Thematic Mappers (TM), will be implemented into Landsat products during the archive reprocessing campaign planned within the new collection management strategy. This paper reports on the planned radiometric calibration updates to the solar reflective bands of the new Landsat collection.

  11. [Laser-based radiometric calibration].

    PubMed

    Li, Zhi-gang; Zheng, Yu-quan

    2014-12-01

    Increasingly higher demands are put forward to spectral radiometric calibration accuracy and the development of new tunable laser based spectral radiometric calibration technology is promoted, along with the development of studies of terrestrial remote sensing, aeronautical and astronautical remote sensing, plasma physics, quantitative spectroscopy, etc. Internationally a number of national metrology scientific research institutes have built tunable laser based spectral radiometric calibration facilities in succession, which are traceable to cryogenic radiometers and have low uncertainties for spectral responsivity calibration and characterization of detectors and remote sensing instruments in the UK, the USA, Germany, etc. Among them, the facility for spectral irradiance and radiance responsivity calibrations using uniform sources (SIRCCUS) at the National Institute of Standards and Technology (NIST) in the USA and the Tunable Lasers in Photometry (TULIP) facility at the Physikalisch-Technische Bundesanstalt (PTB) in Germany have more representatives. Compared with lamp-monochromator systems, laser based spectral radiometric calibrations have many advantages, such as narrow spectral bandwidth, high wavelength accuracy, low calibration uncertainty and so on for radiometric calibration applications. In this paper, the development of laser-based spectral radiometric calibration and structures and performances of laser-based radiometric calibration facilities represented by the National Physical Laboratory (NPL) in the UK, NIST and PTB are presented, technical advantages of laser-based spectral radiometric calibration are analyzed, and applications of this technology are further discussed. Laser-based spectral radiometric calibration facilities can be widely used in important system-level radiometric calibration measurements with high accuracy, including radiance temperature, radiance and irradiance calibrations for space remote sensing instruments, and promote the

  12. Absolute Radiometric Calibration of the GÖKTÜRK-2 Satellite Sensor Using Tuz GÖLÜ (landnet Site) from Ndvi Perspective

    NASA Astrophysics Data System (ADS)

    Sakarya, Ufuk; Hakkı Demirhan, İsmail; Seda Deveci, Hüsne; Teke, Mustafa; Demirkesen, Can; Küpçü, Ramazan; Feray Öztoprak, A.; Efendioğlu, Mehmet; Fehmi Şimşek, F.; Berke, Erdinç; Zübeyde Gürbüz, Sevgi

    2016-06-01

    TÜBİTAK UZAY has conducted a research study on the use of space-based satellite resources for several aspects of agriculture. Especially, there are two precision agriculture related projects: HASSAS (Widespread application of sustainable precision agriculture practices in Southeastern Anatolia Project Region (GAP) Project) and AKTAR (Smart Agriculture Feasibility Project). The HASSAS project aims to study development of precision agriculture practice in GAP region. Multi-spectral satellite imagery and aerial hyperspectral data along with ground measurements was collected to analyze data in an information system. AKTAR aims to develop models for irrigation, fertilization and spectral signatures of crops in Inner Anatolia. By the end of the project precision agriculture practices to control irrigation, fertilization, pesticide and estimation of crop yield will be developed. Analyzing the phenology of crops using NDVI is critical for the projects. For this reason, absolute radiometric calibration of the Red and NIR bands in space-based satellite sensors is an important issue. The Göktürk-2 satellite is an earth observation satellite which was designed and built in Turkey and was launched in 2012. The Göktürk-2 satellite sensor has a resolution 2.5 meters in panchromatic and 5 meters in R/G/B/NIR bands. The absolute radiometric calibration of the Göktürk-2 satellite sensor was performed via the ground-based measurements - spectra-radiometer, sun photometer, and meteorological station- in Tuz Gölü cal/val site in 2015. In this paper, the first ground-based absolute radiometric calibration results of the Göktürk-2 satellite sensor using Tuz Gölü is demonstrated. The absolute radiometric calibration results of this paper are compared with the published cross-calibration results of the Göktürk-2 satellite sensor utilizing Landsat 8 imagery. According to the experimental comparison results, the Göktürk-2 satellite sensor coefficients for red and NIR bands

  13. OLI Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Markham, Brian; Morfitt, Ron; Kvaran, Geir; Biggar, Stuart; Leisso, Nathan; Czapla-Myers, Jeff

    2011-01-01

    Goals: (1) Present an overview of the pre-launch radiance, reflectance & uniformity calibration of the Operational Land Imager (OLI) (1a) Transfer to orbit/heliostat (1b) Linearity (2) Discuss on-orbit plans for radiance, reflectance and uniformity calibration of the OLI

  14. Compact radiometric microwave calibrator

    SciTech Connect

    Fixsen, D. J.; Wollack, E. J.; Kogut, A.; Limon, M.; Mirel, P.; Singal, J.; Fixsen, S. M.

    2006-06-15

    The calibration methods for the ARCADE II instrument are described and the accuracy estimated. The Steelcast coated aluminum cones which comprise the calibrator have a low reflection while maintaining 94% of the absorber volume within 5 mK of the base temperature (modeled). The calibrator demonstrates an absorber with the active part less than one wavelength thick and only marginally larger than the mouth of the largest horn and yet black (less than -40 dB or 0.01% reflection) over five octaves in frequency.

  15. Preliminary Evaluation of the Radiometric Calibration of LANDSAT-4 Thematic Mapper Data by the Canada Centre for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Murphy, J.; Park, W.; Fitzgerald, A.

    1985-01-01

    The radiometric characteristics of the LANDSAT-4 TM sensor are being studied with a view to developing absolute and relative radiometric calibration procedures. Preliminary results from several different approaches to the relative correction of all detectors within each band are reported. Topics covered include: the radiometric correction method; absolute calibration; the relative radiometric calibration algorithm; relative gain and offset calibration; relative gain and offset observations; and residual radiometric stripping.

  16. Visible/infrared radiometric calibration station

    SciTech Connect

    Byrd, D.A.; Maier, W.B. II; Bender, S.C.; Holland, R.F.; Michaud, F.D.; Luettgen, A.L.; Christensen, R.W.; O`Brian, T.R.

    1994-07-01

    We have begun construction of a visible/infrared radiometric calibration station that will allow for absolute calibration of optical and IR remote sensing instruments with clear apertures less than 16 inches in diameter in a vacuum environment. The calibration station broadband sources will be calibrated at the National Institute of Standards and Technology (NIST) and allow for traceable absolute radiometric calibration to within {plus_minus}3% in the visible and near IR (0.4--2.5 {mu}m), and less than {plus_minus}1% in the infrared, up to 12 {mu}m. Capabilities for placing diffraction limited images or for sensor full-field flooding will exist. The facility will also include the calibration of polarization and spectral effects, spatial resolution, field of view performance, and wavefront characterization. The configuration of the vacuum calibration station consists of an off-axis 21 inch, f/3.2, parabolic collimator with a scanning fold flat in collimated space. The sources are placed, via mechanisms to be described, at the focal plane of the off-axis parabola. Vacuum system pressure will be in the 10{sup {minus}6} Torr range. The broadband white-light source is a custom design by LANL with guidance from Labsphere Inc. The continuous operating radiance of the integrating sphere will be from 0.0--0.006 W/cm{sup 2}/Sr/{mu}m (upper level quoted for {approximately}500 nm wavelength). The blackbody source is also custom designed at LANL with guidance from NIST. The blackbody temperature will be controllable between 250--350{degrees}K. Both of the above sources have 4.1 inch apertures with estimated radiometric instability at less than 1%. The designs of each of these units will be described. The monochromator and interferometer light sources are outside the vacuum, but all optical relay and beam shaping optics are enclosed within the vacuum calibration station. These sources are described, as well as the methodology for alignment and characterization.

  17. AIRS radiometric calibration validation for climate research

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Pagano, Thomas S.; Elliott, Denis; Gaiser, Steve; Gregorich, Dave; Broberg, Steve

    2005-01-01

    Climate research using data from satellite based radiometers makes extreme demands on the traceability and stability of the radiometric calibration. The selection of a cooled grating array spectrometer for the Atmospheric Infrared Sounder, AIRS, is key, but does not ensured that AIRS data will be of climate quality. Additional design features, plus additional pre-launch testing, and extensive on-orbit calibration subsystem monitoring beyond what would suffice for application of the data to weather forecasting were required to ensure the radiometric data quality required for climate research. Validation that climate data quality are being generated makes use of the sea surface skin temperatures (SST and (obs-calc).

  18. A Non-Radiative Transfer Approach to Radiometric Vicarious Calibration

    NASA Technical Reports Server (NTRS)

    Ryan, Robert; Holekamp, Kara; Pagnutti, Mary; Stanley, Thomas

    2007-01-01

    TOA (top-of-atmosphere) radiance from high-spatial-resolution satellite imagery systems is important for a wide variety of research and applications. Many research initiatives require data with absolute radiometric accuracy better than a few percent. The conversion of satellite digital numbers to radiance depends on accurate radiometric calibration. A common method for determining and validating radiometric calibrations is to rely upon vicarious calibration approaches. Historically, vicarious calibration methods use radiative transfer codes with ground-based atmosphere and surface reflectance or radiance inputs for estimating TOA radiance values. These TOA radiance values are compared against the satellite digital numbers to determine the radiometric calibration. However, the radiative transfer codes used depend on many assumptions about the aerosol properties and the atmospheric point spread function. A measurement-based atmospheric radiance estimation approach for high-spatial-resolution, multispectral, visible/near-infrared sensors is presented that eliminates the use of radiative transfer codes and many of the underlying assumptions. A comparison between the radiative transfer and non-radiative transfer approaches is made.

  19. Revised landsat-5 thematic mapper radiometric calibration

    USGS Publications Warehouse

    Chander, G.; Markham, B.L.; Barsi, J.A.

    2007-01-01

    Effective April 2, 2007, the radiometric calibration of Landsat-5 (L5) Thematic Mapper (TM) data that are processed and distributed by the U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) will be updated. The lifetime gain model that was implemented on May 5, 2003, for the reflective bands (1-5, 7) will be replaced by a new lifetime radiometric-calibration curve that is derived from the instrument's response to pseudoinvariant desert sites and from cross calibration with the Landsat-7 (L7) Enhanced TM Plus (ETM+). Although this calibration update applies to all archived and future L5 TM data, the principal improvements in the calibration are for the data acquired during the first eight years of the mission (1984-1991), where the changes in the instrument-gain values are as much as 15%. The radiometric scaling coefficients for bands 1 and 2 for approximately the first eight years of the mission have also been changed. Users will need to apply these new coefficients to convert the calibrated data product digital numbers to radiance. The scaling coefficients for the other bands have not changed. ?? 2007 IEEE.

  20. Radiometric calibration of the Landsat MSS sensor series

    USGS Publications Warehouse

    Helder, Dennis L.; Karki, Sadhana; Bhatt, Rajendra; Micijevik, Esad; Aaron, David; Jasinski, Benjamin

    2012-01-01

    Multispectral remote sensing of the Earth using Landsat sensors was ushered on July 23, 1972, with the launch of Landsat-1. Following that success, four more Landsat satellites were launched, and each of these carried the Multispectral Scanner System (MSS). These five sensors provided the only consistent multispectral space-based imagery of the Earth's surface from 1972 to 1982. This work focuses on developing both a consistent and absolute radiometric calibration of this sensor system. Cross-calibration of the MSS was performed through the use of pseudoinvariant calibration sites (PICSs). Since these sites have been shown to be stable for long periods of time, changes in MSS observations of these sites were attributed to changes in the sensors themselves. In addition, simultaneous data collections were available for some MSS sensor pairs, and these were also used for cross-calibration. Results indicated substantial differences existed between instruments, up to 16%, and these were reduced to 5% or less across all MSS sensors and bands. Lastly, this paper takes the calibration through the final step and places the MSS sensors on an absolute radiometric scale. The methodology used to achieve this was based on simultaneous data collections by the Landsat-5 MSS and Thematic Mapper (TM) instruments. Through analysis of image data from a PICS location and through compensating for the spectral differences between the two instruments, the Landsat-5 MSS sensor was placed on an absolute radiometric scale based on the Landsat-5 TM sensor. Uncertainties associated with this calibration are considered to be less than 5%.

  1. GIFTS SM EDU Radiometric and Spectral Calibrations

    NASA Technical Reports Server (NTRS)

    Tian, J.; Reisse, R. a.; Johnson, D. G.; Gazarik, J. J.

    2007-01-01

    The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Sensor Module (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiance using a Fourier transform spectrometer (FTS). The GIFTS instrument gathers measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes the processing algorithms involved in the calibration. The calibration procedures can be subdivided into three categories: the pre-calibration stage, the calibration stage, and finally, the post-calibration stage. Detailed derivations for each stage are presented in this paper.

  2. Landsat-7 ETM+ radiometric calibration status

    NASA Astrophysics Data System (ADS)

    Barsi, Julia A.; Markham, Brian L.; Czapla-Myers, Jeffrey S.; Helder, Dennis L.; Hook, Simon J.; Schott, John R.; Haque, Md. Obaidul

    2016-09-01

    Now in its 17th year of operation, the Enhanced Thematic Mapper + (ETM+), on board the Landsat-7 satellite, continues to systematically acquire imagery of the Earth to add to the 40+ year archive of Landsat data. Characterization of the ETM+ on-orbit radiometric performance has been on-going since its launch in 1999. The radiometric calibration of the reflective bands is still monitored using on-board calibration devices, though the Pseudo-Invariant Calibration Sites (PICS) method has proven to be an effective tool as well. The calibration gains were updated in April 2013 based primarily on PICS results, which corrected for a change of as much as -0.2%/year degradation in the worst case bands. A new comparison with the SADE database of PICS results indicates no additional degradation in the updated calibration. PICS data are still being tracked though the recent trends are not well understood. The thermal band calibration was updated last in October 2013 based on a continued calibration effort by NASA/Jet Propulsion Lab and Rochester Institute of Technology. The update accounted for a 0.036 W/m2 sr μm or 0.26K at 300K bias error. The updated lifetime trend is now stable to within +/- 0.4K.

  3. Radiometric Calibration Assessment of Commercial High Spatial Resolution Multispectral Image Products

    NASA Technical Reports Server (NTRS)

    Holekamp, Kara; Aaron, David; Thome, Kurtis

    2006-01-01

    Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities can better understand their properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other systems. To address this calibration need, satellite at-sensor radiance values were compared to those estimated by each independent team member to determine the sensor's radiometric accuracy. The combined results of this evaluation provide the user community with an independent assessment of these commercially available high spatial resolution sensors' absolute calibration values.

  4. Estimation of Radiometric Calibration Coefficients of EGYPTSAT-1 Sensor

    NASA Astrophysics Data System (ADS)

    Nasr, A. H.; El Leithy, B. M.; Badr, H. S.; Centeno, J.

    2012-07-01

    Sensors usually must be calibrated as part of a measurement system. Calibration may include the procedure of correcting the transfer of the sensor, using the reference measurements, in such a way that a specific input-output relation can be guaranteed with a certain accuracy and under certain conditions. It is necessary to perform a calibration to relate the output signal precisely to the physical input signal (e.g., the output Digital Numbers (DNs) to the absolute units of at-sensor spectral radiance). Generic calibration data associated with Egyptsat-1 sensor are not provided by the manufacturer. Therefore, this study was conducted to estimate Egyptsat-1 sensor specific calibration data and tabulates the necessary constants for its different multispectral bands. We focused our attention on the relative calibration between Egyptsat-1 and Spot-4 sensors for their great spectral similarity. The key idea is to use concurrent correlation of signals received at both sensors in the same day (i.e., sensors are observing the same phenomenon). Calibration formula constructed from Spot-4 sensor is used to derive the calibration coefficients for Egyptsat-1. A brief overview of the radiometric calibration coefficients retrieval procedures is presented. A reasonable estimate of the overall calibration coefficient is obtained. They have been used to calibrate reflectances of Egyptsat-1 sensor. Further updates to evaluate and improve the retrieved calibration data are being investigated.

  5. Site characterization for calibration of radiometric sensors using vicarious method

    NASA Astrophysics Data System (ADS)

    Parihar, Shailesh; Rathore, L. S.; Mohapatra, M.; Sharma, A. K.; Mitra, A. K.; Bhatla, R.; Singh, R. S.; Desai, Yogdeep; Srivastava, Shailendra S.

    2016-05-01

    Radiometric performances of earth observation satellite/sensors vary from ground pre-launch calibration campaign to post launch period extended to lifetime of the satellite due to launching vibrations. Therefore calibration is carried out worldwide through various methods throughout satellite lifetime. In India Indian Space Research Organization (ISRO) calibrates the sensor of Resourcesat-2 satellite by vicarious method. One of these vicarious calibration methods is the reflectance-based approach that is applied in this study for radiometric calibration of sensors on-board Resouresat-2 satellite. The results of ground-based measurement of atmospheric conditions and surface reflectance are made at Bap, Rajasthan Calibration/Validation (Cal/Val) site. Cal/Val observations at site were carried out with hyper-spectral Spectroradiometer covering spectral range of 350nm- 2500nm for radiometric characterization of the site. The Sunphotometer/Ozonometer for measuring the atmospheric parameters has also been used. The calibrated radiance is converted to absolute at-sensor spectral reflectance and Top-Of-Atmosphere (TOA) radiance. TOA radiance was computed using radiative transfer model `Second simulation of the satellite signal in the solar spectrum' (6S), which can accurately simulate the problems introduced by the presence of the atmosphere along the path from Sun to target (surface) to Sensor. The methodology for band averaged reflectance retrieval and spectral reflectance fitting process are described. Then the spectral reflectance and atmospheric parameters are put into 6S code to predict TOA radiance which compare with Resourcesat-2 radiance. Spectral signature and its reflectance ratio indicate the uniformity of the site. Thus the study proves that the selected site is suitable for vicarious calibration of sensor of Resourcesat-2. Further the study demonstrates the procedure for similar exercise for site selection for Cal/Val analysis of other satellite over India

  6. Principal Component Noise Filtering for NAST-I Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Tian, Jialin; Smith, William L., Sr.

    2011-01-01

    The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed- Interferometer (NAST-I) instrument is a high-resolution scanning interferometer that measures emitted thermal radiation between 3.3 and 18 microns. The NAST-I radiometric calibration is achieved using internal blackbody calibration references at ambient and hot temperatures. In this paper, we introduce a refined calibration technique that utilizes a principal component (PC) noise filter to compensate for instrument distortions and artifacts, therefore, further improve the absolute radiometric calibration accuracy. To test the procedure and estimate the PC filter noise performance, we form dependent and independent test samples using odd and even sets of blackbody spectra. To determine the optimal number of eigenvectors, the PC filter algorithm is applied to both dependent and independent blackbody spectra with a varying number of eigenvectors. The optimal number of PCs is selected so that the total root-mean-square (RMS) error is minimized. To estimate the filter noise performance, we examine four different scenarios: apply PC filtering to both dependent and independent datasets, apply PC filtering to dependent calibration data only, apply PC filtering to independent data only, and no PC filters. The independent blackbody radiances are predicted for each case and comparisons are made. The results show significant reduction in noise in the final calibrated radiances with the implementation of the PC filtering algorithm.

  7. Branching Ratios for The Radiometric Calibration of EUNIS-2012

    NASA Technical Reports Server (NTRS)

    Daw, Adrian N.; Bhatia, A. K.; Rabin, Douglas M.

    2012-01-01

    The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument is a two-channel imaging spectrograph that observes the solar corona and transition region with high spectral resolution and a rapid cadence made possible by unprecedented sensitivity. The upcoming flight will incorporate a new wavelength channel covering the range 524-630 Angstroms, the previously-flown 300-370 Angstroms channel, and the first flight demonstration of cooled active pixel sensor (APS) arrays. The new 524-630 Angstrom channel incorporates a Toroidal Varied Line Space (TVLS) grating coated with B4C/Ir, providing broad spectral coverage and a wide temperature range of 0.025 to 10 MK. Absolute radiometric calibration of the two channels is being performed using a hollow cathode discharge lamp and NIST-calibrated AXUV-100G photodiode. Laboratory observations of He I 584 Angstroms and He II 304 Angstroms provide absolute radiometric calibrations of the two channels at those two respective wavelengths by using the AXUV photodiode as a transfer standard. The spectral responsivity is being determined by observing line pairs with a common upper state in the spectra of Ne I-III and Ar II-III. Calculations of A-values for the observed branching ratios are in progress.

  8. Intra-annual NDVI validation of the Landsat 5 TM radiometric calibration

    USGS Publications Warehouse

    Chander, G.; Groeneveld, D.P.

    2009-01-01

    Multispectral data from the Landsat 5 (L5) Thematic Mapper (TM) sensor provide the backbone of the extensive archive of moderate‐resolution Earth imagery. Even after more than 24 years of service, the L5 TM is still operational. Given the longevity of the satellite, the detectors have aged and the sensor's radiometric characteristics have changed since launch. The calibration procedures and parameters in the National Land Archive Production System (NLAPS) have also changed with time. Revised radiometric calibrations in 2003 and 2007 have improved the radiometric accuracy of recently processed data. This letter uses the Normalized Difference Vegetation Index (NDVI) as a metric to evaluate the radiometric calibration. The calibration change has improved absolute calibration accuracy, consistency over time, and consistency with Landsat 7 (L7) Enhanced Thematic radiometry and will provide the basis for continued long‐term studies of the Earth's land surfaces.

  9. Calibrated infrared ground/air radiometric spectrometer

    NASA Astrophysics Data System (ADS)

    Silk, J. K.; Schildkraut, Elliot Robert; Bauldree, Russell S.; Goodrich, Shawn M.

    1996-06-01

    The calibrated infrared ground/air radiometric spectrometer (CIGARS) is a new high performance, multi-purpose, multi- platform Fourier transform spectrometer (FPS) sensor. It covers the waveband from 0.2 to 12 micrometer, has spectral resolution as fine as 0.3 cm-1, and records over 100 spectra per second. Two CIGARS units are being used for observations of target signatures in the air or on the ground from fixed or moving platforms, including high performance jet aircraft. In this paper we describe the characteristics and capabilities of the CIGARS sensor, which uses four interchangeable detector modules (Si, InGaAs, InSb, and HgCdTe) and two optics modules, with internal calibration. The data recording electronics support observations of transient events, even without precise information on the timing of the event. We present test and calibration data on the sensitivity, spectral resolution, stability, and spectral rate of CIGARS, and examples of in- flight observations of real targets. We also discuss plans for adapting CIGARS for imaging spectroscopy observations, with simultaneous spectral and spatial data, by replacing the existing detectors with a focal plane array (FPA).

  10. Correction to Method of Establishing the Absolute Radiometric Accuracy of Remote Sensing Systems While On-orbit Using Characterized Stellar Sources

    NASA Technical Reports Server (NTRS)

    Bowen, Howard S.; Cunningham, Douglas M.

    2007-01-01

    The contents include: 1) Brief history of related events; 2) Overview of original method used to establish absolute radiometric accuracy of remote sensing instruments using stellar sources; and 3) Considerations to improve the stellar calibration approach.

  11. Relative radiometric calibration of LANDSAT TM reflective bands

    NASA Technical Reports Server (NTRS)

    Barker, J. L.

    1984-01-01

    Raw thematic mapper (TM) calibration data from pre-launch tests and in-orbit acquisitions from LANDSAT 4 and 5 satellites are analyzed to assess the radiometric characteristics of the TM sensor. A software program called TM radiometric and algorithmic performance program (TRAPP) was used for the majority of analyses. Radiometric uncertainty in the final TM image originates from: (1) scene variability (solar irradiance and atmospheric scattering); (2) optical and electrical variability of the sensor; and (3) variability introduced during image processing.

  12. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  13. NASA IKONOS Multispectral Radiometric Calibration and 3-Year Temporal Stability Assessment

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Carver, David; Holekamp, Kara; Ryan, Robert; Zanoni, Vicki; Thome, Kurtis; Schiller, Stephen; Aaran, David

    2003-01-01

    Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities can place confidence in the imagery they use and can fully understand its properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other system. In addition, the user community has little or no insight into the design and operation of commercial sensors or into the methods involved in generating commercial products. To address this calibration need, the NASA Stennis Space Center (SSC) Earth Science Applications (ESA) Directorate established a commercial satellite imaging radiometric calibration team consisting of three independent groups: NASA, SSC,ESA, the University of Arizona Remote Sensing Group, and South Dacota State University. Each group determined the absolute radiometric calibration coefficients of the Space Imaging IKONOS 4-band, 4 m multispectral product covering the visible through near-infrared spectral region. For a three year period beginning in 2000, each team employed some variant of a reflectance-based vicarious calibration approach, requiring ground-based measurements coincident with IKONOS image acquisitions and radiative transfer calculations. Several study sites throughout the United States were employed that covered nearly the entire dynamic range of the IKONOS sensor. IKONOS at-sensor radiance values were compared to those estimated by each independent group to determine the IKONOS sensor's radiometric accuracy and stability. Over 10 individual vicariously determined at-sensor radiance estimates were used each year. When combined, these estimates provided a high-precision radiometric gain calibration coefficient. No significant calibration offset was observed. The results of this evaluation provide the scientific community with an independent assessment of the IKONOS sensor's absolute calibration and temporal stability over the 3

  14. Evaluation of computational radiometric and spectral sensor calibration techniques

    NASA Astrophysics Data System (ADS)

    Manakov, Alkhazur

    2016-04-01

    Radiometric and spectral calibration are essential for enabling the use of digital sensors for measurement purposes. Traditional optical calibration techniques require expensive equipment such as specialized light sources, monochromators, tunable filters, calibrated photo-diodes, etc. The trade-offs between computational and physics-based characterization schemes are, however, not well understood. In this paper we perform an analysis of existing computational calibration schemes and elucidate their weak points. We highlight the limitations by comparing against ground truth measurements performed in an optical characterization laboratory (EMVA 1288 standard). Based on our analysis, we present accurate and affordable methods for the radiometric and spectral calibration of a camera.

  15. Radiometric Calibration of the Earth Observing System's Imaging Sensors

    NASA Technical Reports Server (NTRS)

    Slater, Philip N. (Principal Investigator)

    1997-01-01

    The work on the grant was mainly directed towards developing new, accurate, redundant methods for the in-flight, absolute radiometric calibration of satellite multispectral imaging systems and refining the accuracy of methods already in use. Initially the work was in preparation for the calibration of MODIS and HIRIS (before the development of that sensor was canceled), with the realization it would be applicable to most imaging multi- or hyper-spectral sensors provided their spatial or spectral resolutions were not too coarse. The work on the grant involved three different ground-based, in-flight calibration methods reflectance-based radiance-based and diffuse-to-global irradiance ratio used with the reflectance-based method. This continuing research had the dual advantage of: (1) developing several independent methods to create the redundancy that is essential for the identification and hopefully the elimination of systematic errors; and (2) refining the measurement techniques and algorithms that can be used not only for improving calibration accuracy but also for the reverse process of retrieving ground reflectances from calibrated remote-sensing data. The grant also provided the support necessary for us to embark on other projects such as the ratioing radiometer approach to on-board calibration (this has been further developed by SBRS as the 'solar diffuser stability monitor' and is incorporated into the most important on-board calibration system for MODIS)- another example of the work, which was a spin-off from the grant funding, was a study of solar diffuser materials. Journal citations, titles and abstracts of publications authored by faculty, staff, and students are also attached.

  16. MODIS Radiometric Calibration and Uncertainty Assessment

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Chiang, Vincent; Sun, Junqiang; Wu, Aisheng

    2011-01-01

    Since launch, Terra and Aqua MODIS have collected more than II and 9 years of datasets for comprehensive studies of the Earth's land, ocean, and atmospheric properties. MODIS observations are made in 36 spectral bands: 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). Compared to its heritage sensors, MODIS was developed with very stringent calibration and uncertainty requirements. As a result, MODIS was designed and built with a set of state of the art on-board calibrators (OBC), which allow key sensor performance parameters and on-orbit calibration coefficients to be monitored and updated if necessary. In terms of its calibration traceability, MODIS RSB calibration is reflectance based using an on-board solar diffuser (SD) and the TEB calibration is radiance based using an on-board blackbody (BB). In addition to on-orbit calibration coefficients derived from its OBC, calibration parameters determined from sensor pre-launch calibration and characterization are used in both the RSB and TEB calibration and retrieval algorithms. This paper provides a brief description of MODIS calibration methodologies and discusses details of its on-orbit calibration uncertainties. It assesses uncertainty contributions from individual components and differences between Terra and Aqua MODIS due to their design characteristics and on-orbit periormance. Also discussed in this paper is the use of MODIS LIB uncertainty index CUI) product.

  17. Using AIRS and IASI Data to Evaluate Absolute Radiometric Accuracy and Stability for Climate Applications

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Pagano, Thomas S.

    2008-01-01

    The creation of multi-decadal data sets for climate research requires better than 100 mK absolute calibration accuracy for the full range of spectral temperatures encountered under global conditions. Validation that this accuracy is achieved by the operational hyperspectral sounders from polar orbit is facilitated by comparing data from two instruments. Extreme radiometric calibration stability is critical to allow a long time series of noisy, but presumably long-term accurate truth measurements to be used for the validation of absolute accuracy at the 100 mK level. We use the RTGSST in the tropical oceans as ground truth. The difference between the AIRS derived sst2616 and the RTGSST based on six years of data shows a systematic cold bias of about 250 mK, but better than 4 mK/year stability. The double difference between AIRS and the RTGSST and IASI and the RTGSST with less than one year of data already allows statements at the 100 mK absolute level. It shows a 60 mK difference between the AIRS and the IASI calibration at 2616 cm-(sup 1) and 300 K, with a statistically insignificant 20 mK shift in six months.

  18. MODIS Radiometric Calibration Program, Methods and Results

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Guenther, Bruce; Angal, Amit; Barnes, William; Salomonson, Vincent; Sun, Junqiang; Wenny, Brian

    2012-01-01

    As a key instrument for NASA s Earth Observing System (EOS), the Moderate Resolution Imaging Spectroradiometer (MODIS) has made significant contributions to the remote sensing community with its unprecedented amount of data products continuously generated from its observations and freely distributed to users worldwide. MODIS observations, covering spectral regions from visible (VIS) to long-wave infrared (LWIR), have enabled a broad range of research activities and applications for studies of the earth s interactive system of land, oceans, and atmosphere. In addition to extensive pre-launch measurements, developed to characterize sensor performance, MODIS carries a set of on-board calibrators (OBC) that can be used to track on-orbit changes of various sensor characteristics. Most importantly, dedicated and continuous calibration efforts have been made to maintain sensor data quality. This paper provides an overview of the MODIS calibration program, on-orbit calibration activities, methods, and performance. Key calibration results and lessons learned from the MODIS calibration effort are also presented in this paper.

  19. Networks of Absolute Calibration Stars for SST, AKARI, and WISE

    NASA Astrophysics Data System (ADS)

    Cohen, M.

    2007-04-01

    I describe the Cohen-Walker-Witteborn (CWW) network of absolute calibration stars built to support ground-based, airborne, and space-based sensors, and how they are used to calibrate instruments on the SPITZER Space Telescope (SST and Japan's AKARI (formerly ASTRO-F), and to support NASA's planned MidEx WISE (the Wide-field Infrared Survey Explorer). All missions using this common calibration share a self-consistent framework embracing photometry and low-resolution spectroscopy. CWW also underpins COBE/DIRBE several instruments used on the Kuiper Airborne Observatory ({KAO}), the joint Japan-USA ``IR Telescope in Space" (IRTS) Near-IR and Mid-IR spectrometers, the European Space Agency's IR Space Observatory (ISO), and the US Department of Defense's Midcourse Space eXperiment (MSX). This calibration now spans the far-UV to mid-infrared range with Sirius (one specific Kurucz synthetic spectrum) as basis, and zero magnitude defined from another Kurucz spectrum intended to represent an ideal Vega (not the actual star with its pole-on orientation and mid-infrared dust excess emission). Precision 4-29 μm radiometric measurements on MSX validate CWW's absolute Kurucz spectrum of Sirius, the primary, and a set of bright K/MIII secondary standards. Sirius is measured to be 1.0% higher than predicted. CWW's definitions of IR zero magnitudes lie within 1.1% absolute of MSX measurements. The US Air Force Research Laboratory's independent analysis of on-orbit {MSX} stellar observations compared with emissive reference spheres show CWW primary and empirical secondary spectra lie well within the ±1.45% absolute uncertainty associated with this 15-year effort. Our associated absolute calibration for the InfraRed Array Camera (IRAC) on the SST lies within ˜2% of the recent extension of the calibration of the Hubble Space Telescope's STIS instrument to NICMOS (Bohlin, these Proceedings), showing the closeness of these two independent approaches to calibration.

  20. Characterization of radiometric calibration of LANDSAT-4 TM reflective bands

    NASA Technical Reports Server (NTRS)

    Barker, J. L.; Abrams, R. B.; Ball, D. L.; Leung, K. C.

    1984-01-01

    Prelaunch and postlaunch internal calibrator, image, and background data is to characterize the radiometric performance of the LANDSAT-4 TM and to recommend improved procedures for radiometric calibration. All but two channels (band 2, channel 4; band 5, channel 3) behave normally. Gain changes relative to a postlaunch reference for channels within a band vary within 0.5 percent as a group. Instrument gain for channels in the cold focal plane oscillates. Noise in background and image data ranges from 0.5 to 1.7 counts. Average differences in forward and reverse image data indicate a need for separate calibration processing of forward and reverse scans. Precision is improved by increasing the pulse integration width from 31 to 41 minor frames, depending on the band.

  1. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  2. Operational Land Imager relative radiometric calibration

    NASA Astrophysics Data System (ADS)

    Barsi, Julia A.; Markham, Brian L.

    2015-09-01

    The Operational Land Imager (OLI), on board the Landsat-8 satellite, is a pushbroom sensor with nearly 7000 detectors per band, divided between 14 separate modules. While rigorously characterized prior to launch, the shear number of individual detectors presents a challenge to maintaining the on-orbit relative calibration, such that stripes, bands and other artifacts are minimized in the final image products. On-orbit relative calibration of the OLI is primarily monitored and corrected by observing an on-board primary solar diffuser panel. The panel is the most uniform target available to the OLI, though as observed but the OLI, it has a slope across the field of view due to view angle effects. Just after launch, parameters were derived using the solar diffuser data, to correct for the angular effects across the 14 modules. The residual discontinuities between arrays and the detector-to-detector uniformity continue to be monitored on a weekly basis. The observed variations in the responses to the diffuser panel since launch are thought to be due to real instrument changes. Since launch, the Coastal/Aerosol (CA) and Blue bands have shown the most variation in relative calibration of the VNIR bands, with as much as 0.14% change (3-sigma) between consecutive relative gain estimates. The other VNIR bands (Green, Red and NIR) initially had detectors showing a slow drift of about 0.2% per year, though this stopped after an instrument power cycle about seven months after launch. The SWIR bands also exhibit variability between collects (0.11% 3-sigma) but the larger changes have been where individual detectors' responses change suddenly by as much as 1.5%. The mechanisms behind these changes are not well understood but in order to minimize impact to the users, the OLI relative calibration is updated on a quarterly basis in order to capture changes over time.

  3. Radiometric cross-calibration of KOMPSAT-3 with Landsat-8

    NASA Astrophysics Data System (ADS)

    Shin, Dongyoon; Jin, Cheonggil; Ahn, Hoyong; Choi, Chuluong

    2015-10-01

    This paper presents a radiometric cross calibration of KOMPSAT-3 AEISS based on Landsat-8 OLI. Cross calibration between the two sensors using simultaneous image pairs, acquired during an underfly event over the Libya 4 pseudo invariant calibration site (PICS) site. The spectral profile of the target comes from the near-simultaneous EO-1 Hyperion data over these sites for apply Spectral Band Adjustment Factor (SBAF). The results indicate that the Top Of Atmosphere (TOA) reflectance measurements for KOMPSAT-3 agree with Landsat-8 to within 5% after the application of SBAF. To validate radiometric coefficient, comparison TOA reflectance executed in north Virginia, USA. The difference in TOA reflectance was calculated to within a maximum ±1.55%. There was a huge improvement when the standard deviation altered from 0.1 to 0.01, when applying the SBAF. The result of radiometric coefficient presented here appear to be a good standard for maintaining the optical quality of the KOMPSAT-3, for which prelaunch, onboard, and vicarious calibration data are lacking.

  4. Dynamic noise corrected hyperspectral radiometric calibration in the SWIR range using a supercontinuum laser

    NASA Astrophysics Data System (ADS)

    Keresztes, Janos C.; Aernouts, Ben; Koshel, R. J.; Saeys, Wouter

    2015-09-01

    As line scanning short wave infrared (SWIR) hyperspectral imaging (HSI) is a growing field in the food industry, it is important to select efficient illumination designs to image contaminants with high contrast and low noise. Illumination systems can efficiently be compared and optimized through the use of ray tracing simulations. However, these simulations provide illumination patterns in absolute radiometric units while HSI systems typically provide relative measurements. To bridge this gap, a supercontinuum laser and monochromator setup was used in this study to calibrate a SWIR HSI imager in spectral radiometric units. For the radiometric calibration, an integrating sphere (IS) was illuminated with the monochromatic laser light, while both a high sensitivity photodiode and the hyperspectral camera were positioned at different ports of the IS to measure the diffuse light synchronously. For each spectral band, the radiance observed by the imager corresponding to a line was detected using image analysis, while the remainder of the image was used to sample the noise of the sensor. Laser power fluctuations were monitored using a power meter coupled with a thermal sensor, allowing for their correction. As these measurements were time consuming, while InGaAs based sensors are very sensitive to thermal drift, the dark current was sampled frequently to avoid noise time drifts. This approach allowed correcting for 6% of temporal noise fluctuations. A per-pixel linear radiometric model was fitted with an R2 of 0:94+/-0:3 and used to transfer the measured light distribution of a halogen spot with and without a diffuser into absolute radiometric units. This allowed comparing measurements with the results of ray tracing.

  5. Radiometric calibration of Landsat Thematic Mapper multispectral images

    USGS Publications Warehouse

    Chavez, P.S.

    1989-01-01

    A main problem encountered in radiometric calibration of satellite image data is correcting for atmospheric effects. Without this correction, an image digital number (DN) cannot be converted to a surface reflectance value. In this paper the accuracy of a calibration procedure, which includes a correction for atmospheric scattering, is tested. Two simple methods, a stand-alone and an in situ sky radiance measurement technique, were used to derive the HAZE DN values for each of the six reflectance Thematic Mapper (TM) bands. The DNs of two Landsat TM images of Phoenix, Arizona were converted to surface reflectances. -from Author

  6. Spectrally and Radiometrically Stable, Wideband, Onboard Calibration Source

    NASA Technical Reports Server (NTRS)

    Coles, James B.; Richardson, Brandon S.; Eastwood, Michael L.; Sarture, Charles M.; Quetin, Gregory R.; Porter, Michael D.; Green, Robert O.; Nolte, Scott H.; Hernandez, Marco A.; Knoll, Linley A.

    2013-01-01

    The Onboard Calibration (OBC) source incorporates a medical/scientific-grade halogen source with a precisely designed fiber coupling system, and a fiber-based intensity-monitoring feedback loop that results in radiometric and spectral stabilities to within less than 0.3 percent over a 15-hour period. The airborne imaging spectrometer systems developed at the Jet Propulsion Laboratory incorporate OBC sources to provide auxiliary in-use system calibration data. The use of the OBC source will provide a significant increase in the quantitative accuracy, reliability, and resulting utility of the spectral data collected from current and future imaging spectrometer instruments.

  7. Radiometric calibration and SNR calculation of a SWIR imaging telescope

    SciTech Connect

    Yilmaz, Ozgur; Turk, Fethi; Selimoglu, Ozgur

    2012-09-06

    Radiometric calibration of an imaging telescope is usually made using a uniform illumination sphere in a laboratory. In this study, we used the open-sky images taken during bright day conditions to calibrate our telescope. We found a dark signal offset value and a linear response coefficient value for each pixel by using three different algorithms. Then we applied these coefficients to the taken images, and considerably lowered the image non-uniformity. Calibration can be repeated during the operation of telescope with an object that has better uniformity than open-sky. Also SNR (Signal to Noise Ratio) of each pixel was calculated from the open-sky images using the temporal mean and standard deviations. It is found that SNR is greater than 80 for all pixels even at low light levels.

  8. Radiometric calibration of SPOT 2 HRV - A comparison of three methods

    NASA Technical Reports Server (NTRS)

    Biggar, Stuart F.; Dinguirard, Magdeleine C.; Gellman, David I.; Henry, Patrice; Jackson, Ray D.; Moran, M. S.; Slater, Philip N.

    1991-01-01

    Three methods for determining an absolute radiometric calibration of a spacecraft optical sensor are compared. They are the well-known reflectance-based and radiance-based methods and a new method based on measurements of the ratio of diffuse-to-global irradiance at the ground. The latter will be described in detail and the comparison of the three approaches will be made with reference to the SPOT-2 HRV cameras for a field campaign 1990-06-19 through 1990-06-24 at the White Sands Missile Range in New Mexico.

  9. a Comparison of LIDAR Reflectance and Radiometrically Calibrated Hyperspectral Imagery

    NASA Astrophysics Data System (ADS)

    Roncat, A.; Briese, C.; Pfeifer, N.

    2016-06-01

    In order to retrieve results comparable under different flight parameters and among different flight campaigns, passive remote sensing data such as hyperspectral imagery need to undergo a radiometric calibration. While this calibration, aiming at the derivation of physically meaningful surface attributes such as a reflectance value, is quite cumbersome for passively sensed data and relies on a number of external parameters, the situation is by far less complicated for active remote sensing techniques such as lidar. This fact motivates the investigation of the suitability of full-waveform lidar as a "single-wavelength reflectometer" to support radiometric calibration of hyperspectral imagery. In this paper, this suitability was investigated by means of an airborne hyperspectral imagery campaign and an airborne lidar campaign recorded over the same area. Criteria are given to assess diffuse reflectance behaviour; the distribution of reflectance derived by the two techniques were found comparable in four test areas where these criteria were met. This is a promising result especially in the context of current developments of multi-spectral lidar systems.

  10. Preliminary radiometric calibration assessment of ALOS AVNIR-2

    USGS Publications Warehouse

    Bouvet, M.; Goryl, P.; Chander, G.; Santer, R.; Saunier, S.

    2008-01-01

    This paper summarizes the activities carried out in the frame of the data quality activities of the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) sensor onboard the Advanced Land Observing Satellite (ALOS). Assessment of the radiometric calibration of the AVNIR-2 multi-spectral imager is achieved via three intercomparisons to currently flying sensors over the Libyan desert, during the first year of operation. AU three methodologies indicate a slight underestimation of AVNIR-2 in band 1 by 4 to 7% with respect to other sensors radiometric scale. Band 2 does not show any obvious bias. Results for band 3 are affected by saturation due to inappropriate gain setting. Two methodologies indicate no significant bias in band 4. Preliminary results indicate possible degradations of the AVNIR-2 channels, which, when modeled as an exponentially decreasing functions, have time constants of respectively 13.2 %.year-1, 8.8%.year-1 and 0.1%.year-1 in band 1, 2 and 4 (with respect to the radiometric scale of the MEdium Resolution Imaging Spectrometer, MERIS). Longer time series of AVNIR-2 data are needed to draw final conclusions. ?? 2007 IEEE.

  11. Laboratory-Based BRDF Calibration of Radiometric Tarps

    NASA Technical Reports Server (NTRS)

    Georgiev, Georgi T.; Butler, James J.

    2007-01-01

    The current study provides the remote sensing community with important high accuracy laboratory-based BRDF calibration of radiometric tarps. The results illustrate the dependence of tarps' weft and warp threads orientation on BRDF. The study was done at incident angles of 0deg, 10deg, and 30deg; scatter zenith angles from 0deg to 60deg, and scatter azimuth angles of 0deg, 45deg, 90deg, 135deg, and 180deg. The wavelengths were 485nm, 550nm, 633nm and 800nm. The dependence is well defined at all measurement geometries and wavelengths. It can be as high as 8% at 0deg incident angle and 2% at 30deg incident angle. The fitted BRDF data show a very small discrepancy from the measured ones. New data on the forward and backscatter properties of radiometric tarps is reported. The backward scatter is well pronounced for the white samples. The black sample has well pronounced forward scatter. The BRDF characterization of radiometric tarps can be successfully extended to other structured surface fabric samples. The results are NIST traceable.

  12. Galileo SSI/Gaspra Radiometrically Calibrated Images V1.0

    NASA Astrophysics Data System (ADS)

    Domingue, D. L.

    2015-05-01

    This data set includes Galileo Orbiter SSI radiometrically calibrated images of the asteroid 951 Gaspra, created using ISIS software and assuming nadir pointing. This is an original delivery of radiometrically calibrated files, not an update to existing files. All images archived include the the asteroid within the image frame. Calibration was performed in 2013-2014.

  13. Galileo SSI/Ida Radiometrically Calibrated Images V1.0

    NASA Astrophysics Data System (ADS)

    Domingue, D. L.

    2016-05-01

    This data set includes Galileo Orbiter SSI radiometrically calibrated images of the asteroid 243 Ida, created using ISIS software and assuming nadir pointing. This is an original delivery of radiometrically calibrated files, not an update to existing files. All images archived include the asteroid within the image frame. Calibration was performed in 2013-2014.

  14. High dynamic range infrared thermography by pixelwise radiometric self calibration

    NASA Astrophysics Data System (ADS)

    Ochs, M.; Schulz, A.; Bauer, H.-J.

    2010-03-01

    A procedure is described where the response function of each pixel of an InSb detector is determined by radiometric self-calibration. With the present approach no knowledge of the spectral characteristics of the IR system is required to recover a quantity which is linear with the incident irradiance of the object. The inherent detector non-uniformity is corrected on the basis of self-calibrated scaled irradiance. Compared to the standard two-point non-uniformity correction procedure - performed with the detector signal - only two NUC-tables are required for arbitrary integration times. Images obtained at various exposures are fused to a single high dynamic range image. The procedure is validated with synthetic data and its performance is demonstrated by measurements performed with a high resolution InSb FPA.

  15. Revised radiometric calibration technique for LANDSAT-4 Thematic Mapper data

    NASA Technical Reports Server (NTRS)

    Murphy, J.; Butlin, T.; Duff, P.; Fitzgerald, A.

    1984-01-01

    Depending on detector number, there are random fluctuations in the background level for spectral band 1 of magnitudes ranging from 2 to 3.5 digital numbers (DN). Similar variability is observed in all the other reflective bands, but with smaller magnitude in the range 0.5 to 2.5 DN. Observations of background reference levels show that line dependent variations in raw TM image data and in the associated calibration data can be measured and corrected within an operational environment by applying simple offset corrections on a line-by-line basis. The radiometric calibration procedure defined by the Canadian Center for Remote Sensing was revised accordingly in order to prevent striping in the output product.

  16. Radiometric calibration of Landsat Thematic Mapper Thermal Band

    NASA Technical Reports Server (NTRS)

    Wukelic, G. E.; Gibbons, D. E.; Martucci, L. M.; Foote, H. P.

    1989-01-01

    Radiometric calibration of satellite-acquired data is essential for quantitative scientific studies, as well as for a variety of image-processing applications. This paper describes a multiyear, on-orbit radiometric calibration of the Landsat Thematic Mapper (TM) Band 6 conducted at DOE's Pacific Northwest Laboratory. Numerous Landsat TM scenes acquired and analyzed included day and night coverages at several geographical locations over several seasons. Concurrent with Landsat overpasses, thermal field and local meteorological (surface and radiosonde) measurements were collected. At-satellite (uncorrected) radiances and temperatures for water and nonwater land cover were compared to ground truth (GT) measurements after making adjustments for atmospheric (using LOWTRAN), mixed-pixel, and emissivity effects. Results indicate that, for both water and nonwater features, TM Band 6 average corrected temperature determinations using local radiosonde data to adjust for atmospheric effects, and using appropriate emissivities, are within 1.0 C of GT temperature values. Temperatures of water pixels derived from uncorrected TM Band 6 data varied roughly between 1 and 3 C of ground truth values for water temperatures ranging between 4 and 24 C. Moreover, corrections using nonlocal and noncoincident radiosonde data resulted in errors as large as 12 C. Corrections using the U.S. Standard Atmosphere gave temperature values within 1 to 2 C of GT. The average uncertainty for field instruments was + or - 0.2 C; average uncertainty for Landsat TM corrected temperature determinations was + or - 0.4 C.

  17. Design, manufacture, and calibration of infrared radiometric blackbody sources

    SciTech Connect

    Byrd, D.A.; Michaud, F.D.; Bender, S.C.

    1996-04-01

    A Radiometric Calibration Station (RCS) is being assembled at the Los Alamos National Laboratories (LANL) which will allow for calibration of sensors with detector arrays having spectral capability from about 0.4-15 {mu}m. The configuration of the LANL RCS. Two blackbody sources have been designed to cover the spectral range from about 3-15 {mu}m, operating at temperatures ranging from about 180-350 K within a vacuum environment. The sources are designed to present a uniform spectral radiance over a large area to the sensor unit under test. The thermal uniformity requirement of the blackbody cavities has been one of the key factors of the design, requiring less than 50 mK variation over the entire blackbody surface to attain effective emissivity values of about 0.999. Once the two units are built and verified to the level of about 100 mK at LANL, they will be sent to the National Institute of Standards and Technology (NIST), where at least a factor of two improvement will be calibrated into the blackbody control system. The physical size of these assemblies will require modifications of the existing NIST Low Background Infrared (LBIR) Facility. LANL has constructed a bolt-on addition to the LBIR facility that will allow calibration of our large aperture sources. Methodology for attaining the two blackbody sources at calibrated levels of performance equivalent to present state of the art will be explained in the following.

  18. Thermal Infrared Radiometric Calibration of the Entire Landsat 4, 5, and 7 Archive (1982-2010)

    NASA Technical Reports Server (NTRS)

    Schott, John R.; Hook, Simon J.; Barsi, Julia A.; Markham, Brian L.; Miller, Jonathan; Padula, Francis P.; Raqueno, Nina G.

    2012-01-01

    Landsat's continuing record of the thermal state of the earth's surface represents the only long term (1982 to the present) global record with spatial scales appropriate for human scale studies (i.e., tens of meters). Temperature drives many of the physical and biological processes that impact the global and local environment. As our knowledge of, and interest in, the role of temperature on these processes have grown, the value of Landsat data to monitor trends and process has also grown. The value of the Landsat thermal data archive will continue to grow as we develop more effective ways to study the long term processes and trends affecting the planet. However, in order to take proper advantage of the thermal data, we need to be able to convert the data to surface temperatures. A critical step in this process is to have the entire archive completely and consistently calibrated into absolute radiance so that it can be atmospherically compensated to surface leaving radiance and then to surface radiometric temperature. This paper addresses the methods and procedures that have been used to perform the radiometric calibration of the earliest sizable thermal data set in the archive (Landsat 4 data). The completion of this effort along with the updated calibration of the earlier (1985 1999) Landsat 5 data, also reported here, concludes a comprehensive calibration of the Landsat thermal archive of data from 1982 to the present

  19. Radiometric calibration of the telescope and ultraviolet spectrometer SUMER on SOHO

    NASA Astrophysics Data System (ADS)

    Hollandt, Jörg; Schühle, Udo; Paustian, Wolfgang; Curdt, Werner; Kühne, Michael; Wende, Burkhard; Wilhelm, Klaus

    1996-09-01

    The prelaunch spectral-sensitivity calibration of the solar spectrometer SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is described. SUMER is part of the payload of the Solar and Heliospheric Observatory (SOHO), which begins its scientific mission in 1996. The instrument consists of a telescope and a spectrometer capable of taking spatially and spectrally highly resolved images of the Sun in a spectral range from 50 to 161 nm. The pointing capabilities, the dynamic range, and the sensitivity of the instrument allow measurements both on the solar disk and above the limb as great as two solar radii. To determine plasma temperatures and densities in the solar atmosphere, the instrument needs an absolute spectral-sensitivity calibration. Here we describe the prelaunch calibration of the full instrument, which utilizes a radiometric transfer-standard source. The transfer standard was based on a high-current hollow-cathode discharge source. It had been calibrated in the laboratory for vacuum UV radiometry of the Physikalisch-Technische Bundesanstalt by use of the calculable spectral photon flux of the Berlin electron storage ring for synchrotron radiation (BESSY)-a primary radiometric source standard.

  20. Landsat-8 Thermal Infrared Sensor (TIRS) Vicarious Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Barsi, Julia A.; Shott, John R.; Raqueno, Nina G.; Markham, Brian L.; Radocinski, Robert G.

    2014-01-01

    Launched in February 2013, the Landsat-8 carries on-board the Thermal Infrared Sensor (TIRS), a two-band thermal pushbroom imager, to maintain the thermal imaging capability of the Landsat program. The TIRS bands are centered at roughly 10.9 and 12 micrometers (Bands 10 and 11 respectively). They have 100 m spatial resolution and image coincidently with the Operational Land Imager (OLI), also on-board Landsat-8. The TIRS instrument has an internal calibration system consisting of a variable temperature blackbody and a special viewport with which it can see deep space; a two point calibration can be performed twice an orbit. Immediately after launch, a rigorous vicarious calibration program was started to validate the absolute calibration of the system. The two vicarious calibration teams, NASA/Jet Propulsion Laboratory (JPL) and the Rochester Institute of Technology (RIT), both make use of buoys deployed on large water bodies as the primary monitoring technique. RIT took advantage of cross-calibration opportunity soon after launch when Landsat-8 and Landsat-7 were imaging the same targets within a few minutes of each other to perform a validation of the absolute calibration. Terra MODIS is also being used for regular monitoring of the TIRS absolute calibration. The buoy initial results showed a large error in both bands, 0.29 and 0.51 W/sq m·sr·micrometers or -2.1 K and -4.4 K at 300 K in Band 10 and 11 respectively, where TIRS data was too hot. A calibration update was recommended for both bands to correct for a bias error and was implemented on 3 February 2014 in the USGS/EROS processing system, but the residual variability is still larger than desired for both bands (0.12 and 0.2 W/sq m·sr·micrometers or 0.87 and 1.67 K at 300 K). Additional work has uncovered the source of the calibration error: out-of-field stray light. While analysis continues to characterize the stray light contribution, the vicarious calibration work proceeds. The additional data have

  1. The Landsat Data Continuity Mission Operational Land Imager (OLI) Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Markham, Brian L.; Dabney, Philip W.; Murphy-Morris, Jeanine E.; Knight, Edward J.; Kvaran, Geir; Barsi, Julia A.

    2010-01-01

    The Operational Land Imager (OLI) on the Landsat Data Continuity Mission (LDCM) has a comprehensive radiometric characterization and calibration program beginning with the instrument design, and extending through integration and test, on-orbit operations and science data processing. Key instrument design features for radiometric calibration include dual solar diffusers and multi-lamped on-board calibrators. The radiometric calibration transfer procedure from NIST standards has multiple checks on the radiometric scale throughout the process and uses a heliostat as part of the transfer to orbit of the radiometric calibration. On-orbit lunar imaging will be used to track the instruments stability and side slither maneuvers will be used in addition to the solar diffuser to flat field across the thousands of detectors per band. A Calibration Validation Team is continuously involved in the process from design to operations. This team uses an Image Assessment System (IAS), part of the ground system to characterize and calibrate the on-orbit data.

  2. A definitive calibration record for the Landsat-5 thematic mapper anchored to the Landsat-7 radiometric scale

    USGS Publications Warehouse

    Teillet, P.M.; Helder, D.L.; Ruggles, T.A.; Landry, R.; Ahern, F.J.; Higgs, N.J.; Barsi, J.; Chander, G.; Markham, B.L.; Barker, J.L.; Thome, K.J.; Schott, J.R.; Palluconi, Frank Don

    2004-01-01

    A coordinated effort on the part of several agencies has led to the specification of a definitive radiometric calibration record for the Landsat-5 thematic mapper (TM) for its lifetime since launch in 1984. The time-dependent calibration record for Landsat-5 TM has been placed on the same radiometric scale as the Landsat-7 enhanced thematic mapper plus (ETM+). It has been implemented in the National Landsat Archive Production Systems (NLAPS) in use in North America. This paper documents the results of this collaborative effort and the specifications for the related calibration processing algorithms. The specifications include (i) anchoring of the Landsat-5 TM calibration record to the Landsat-7 ETM+ absolute radiometric calibration, (ii) new time-dependent calibration processing equations and procedures applicable to raw Landsat-5 TM data, and (iii) algorithms for recalibration computations applicable to some of the existing processed datasets in the North American context. The cross-calibration between Landsat-5 TM and Landsat-7 ETM+ was achieved using image pairs from the tandem-orbit configuration period that was programmed early in the Laridsat-7 mission. The time-dependent calibration for Landsat-5 TM is based on a detailed trend analysis of data from the on-board internal calibrator. The new lifetime radiometric calibration record for Landsat-5 will overcome problems with earlier product generation owing to inadequate maintenance and documentation of the calibration over time and will facilitate the quantitative examination of a continuous, near-global dataset at 30-m scale that spans almost two decades.

  3. Characterization of the Sonoran desert as a radiometric calibration target for Earth observing sensors

    USGS Publications Warehouse

    Angal, Amit; Chander, Gyanesh; Xiong, Xiaoxiong; Choi, Tae-young; Wu, Aisheng

    2011-01-01

    To provide highly accurate quantitative measurements of the Earth's surface, a comprehensive calibration and validation of the satellite sensors is required. The NASA Moderate Resolution Imaging Spectroradiometer (MODIS) Characterization Support Team, in collaboration with United States Geological Survey, Earth Resources Observation and Science Center, has previously demonstrated the use of African desert sites to monitor the long-term calibration stability of Terra MODIS and Landsat 7 (L7) Enhanced Thematic Mapper plus (ETM+). The current study focuses on evaluating the suitability of the Sonoran Desert test site for post-launch long-term radiometric calibration as well as cross-calibration purposes. Due to the lack of historical and on-going in situ ground measurements, the Sonoran Desert is not usually used for absolute calibration. An in-depth evaluation (spatial, temporal, and spectral stability) of this site using well calibrated L7 ETM+ measurements and local climatology data has been performed. The Sonoran Desert site produced spatial variability of about 3 to 5% in the reflective solar regions, and the temporal variations of the site after correction for view-geometry impacts were generally around 3%. The results demonstrate that, barring the impacts due to occasional precipitation, the Sonoran Desert site can be effectively used for cross-calibration and long-term stability monitoring of satellite sensors, thus, providing a good test site in the western hemisphere.

  4. 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.

  5. Removal of Topographic Effect on Radiometric Calibration Based on the Simulated SAR Image

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Zeng, Qiming; Jiao, Jian; Zhou, Xiao

    2013-01-01

    Topographic effects on radiometric calibration is significant in the region with large slope angle, and limit the absolute radiometric calibration accuracy of the general calibration algorithm to about 1dB, especially serious in the undulating hilly region. We propose a method to remove the effect of topography, including an effective area correction of a pixel in the low slope areas in the SAR image, and data fusion from the real image and the empirical scattering model based on DEM. During the overall processing, the simulated SAR image derived from the range- Doppler imaging model, DEM data and empirical scattering model plays an importance in the removal of topographic effect, including the geocoding process of SAR image and DEM data registration to the SAR image. A scene of ASAR IMS data in Bam, Iran is selected for this research because a little vegetation covered in this region. The experimental results show that the backscattering intensity in the low slope area decreased about from 0.4 to 0.6 dB, but the backscattering from mountain areas has much changed after introducing the simulated SAR image and empirical scattering model. The result showed that texture of the final result looks more reasonable and similar with the reality.

  6. A Review of LIDAR Radiometric Processing: From Ad Hoc Intensity Correction to Rigorous Radiometric Calibration.

    PubMed

    Kashani, Alireza G; Olsen, Michael J; Parrish, Christopher E; Wilson, Nicholas

    2015-11-06

    In addition to precise 3D coordinates, most light detection and ranging (LIDAR) systems also record "intensity", loosely defined as the strength of the backscattered echo for each measured point. To date, LIDAR intensity data have proven beneficial in a wide range of applications because they are related to surface parameters, such as reflectance. While numerous procedures have been introduced in the scientific literature, and even commercial software, to enhance the utility of intensity data through a variety of "normalization", "correction", or "calibration" techniques, the current situation is complicated by a lack of standardization, as well as confusing, inconsistent use of terminology. In this paper, we first provide an overview of basic principles of LIDAR intensity measurements and applications utilizing intensity information from terrestrial, airborne topographic, and airborne bathymetric LIDAR. Next, we review effective parameters on intensity measurements, basic theory, and current intensity processing methods. We define terminology adopted from the most commonly-used conventions based on a review of current literature. Finally, we identify topics in need of further research. Ultimately, the presented information helps lay the foundation for future standards and specifications for LIDAR radiometric calibration.

  7. On-orbit performance of the Landsat-7 ETM+ radiometric calibrators

    USGS Publications Warehouse

    Markham, Brian L; Barker, J. L.; Kaita, E.; Seiferth, J.; Morfitt, Ron

    2003-01-01

    The Landsat-7 Enhanced Thematic Mapper Plus (ETM+) incorporates two new devices to improve its absolute radiometric calibration: a Full Aperture Solar Calibrator (FASC) and a Partial Aperture Solar Calibrator (PASC). The FASC is a diffuser panel, typically deployed once per month. Initial FASC absolute calibration results were within 5% of the pre-launch calibrations. Over time, the responses of the ETM+ to the FASC have varied with the location viewed on the panel, suggesting a localized degradation or contamination of the panel. On the best part of the panel, the trends in response range from m 1.4% y m 1 (band 4) to +0.6% y m 1 (band 7), with band 5 showing the least change at m 0.4% y m 1 . Changes in the panel reflectance due to UV exposure are believed to be the origin of these trends. The PASC is a set of auxiliary optics that allows the ETM+ to image the Sun through reduced apertures. PASC data have normally been acquired on a daily basis. Unlike the FASC, the PASC has exhibited significant anomalies. During the first six months of operation, responses to the PASC increased up to 60%, sending bands 2, 3 and 8 into saturation (band 1 was saturated at launch). The short-wave infrared (SWIR) band individual detectors have shown variations up to - 20% in response to the PASC. The variation is different for each detector. After the first six months, the responses to the PASC have become more stable, with much of the variation related to the within-scan position of the solar image. Overall results to date for all calibrators and comparisons with vicarious calibrations indicate that most of the response variations have been due to the calibrators themselves and suggest that the instrument has been stable with changes in response of less than 0.5% y m 1 .

  8. Radiometric Cross-Calibration of the HJ-1B IRS in the Thermal Infrared Spectral Band

    NASA Astrophysics Data System (ADS)

    Sun, K.

    2012-12-01

    The natural calamities occur continually, environment pollution and destruction in a severe position on the earth presently, which restricts societal and economic development. The satellite remote sensing technology has an important effect on improving surveillance ability of environment pollution and natural calamities. The radiometric calibration is precondition of quantitative remote sensing; which accuracy decides quality of the retrieval parameters. Since the China Environment Satellite (HJ-1A/B) has been launched successfully on September 6th, 2008, it has made an important role in the economic development of China. The satellite has four infrared bands; and one of it is thermal infrared. With application fields of quantitative remote sensing in china, finding appropriate calibration method becomes more and more important. Many kinds of independent methods can be used to do the absolute radiometric calibration. In this paper, according to the characteristic of thermal infrared channel of HJ-1B thermal infrared multi-spectral camera, the thermal infrared spectral band of HJ-1B IRS was calibrated using cross-calibration methods based on MODIS data. Firstly, the corresponding bands of the two sensors were obtained. Secondly, the MONDTRAN was run to analyze the influences of different spectral response, satellite view zenith angle, atmosphere condition and temperature on the match factor. In the end, their band match factor was calculated in different temperature, considering the dissimilar band response of the match bands. Seven images of Lake Qinghai in different time were chosen as the calibration data. On the basis of radiance of MODIS and match factor, the IRS radiance was calculated. And then the calibration coefficients were obtained by linearly regressing the radiance and the DN value. We compared the result of this cross-calibration with that of the onboard blackbody calibration, which consistency was good.The maximum difference of brightness temperature

  9. Radiometric Measurement Comparisons Using Transfer Radiometers in Support of the Calibration of NASA's Earth Observing System (EOS) Sensors

    NASA Technical Reports Server (NTRS)

    Butler, James J.; Johnson, B. Carol; Brown, Steven W.; Yoon, Howard W.; Barnes, Robert A.; Markham, Brian L.; Biggar, Stuart F.; Zalewski, Edward F.; Spyak, Paul R.; Cooper, John W.; Sakuma, Fumihiro

    1999-01-01

    EOS satellite instruments operating in the visible through the shortwave infrared wavelength regions (from 0.4 micrometers to 2.5 micrometers) are calibrated prior to flight for radiance response using integrating spheres at a number of instrument builder facilities. The traceability of the radiance produced by these spheres with respect to international standards is the responsibility of the instrument builder, and different calibration techniques are employed by those builders. The National Aeronautics and Space Administration's (NASA's) Earth Observing System (EOS) Project Science Office, realizing the importance of preflight calibration and cross-calibration, has sponsored a number of radiometric measurement comparisons, the main purpose of which is to validate the radiometric scale assigned to the integrating spheres by the instrument builders. This paper describes the radiometric measurement comparisons, the use of stable transfer radiometers to perform the measurements, and the measurement approaches and protocols used to validate integrating sphere radiances. Stable transfer radiometers from the National Institute of Standards and Technology, the University of Arizona Optical Sciences Center Remote Sensing Group, NASA's Goddard Space Flight Center, and the National Research Laboratory of Metrology in Japan, have participated in these comparisons. The approaches used in the comparisons include the measurement of multiple integrating sphere lamp levels, repeat measurements of select lamp levels, the use of the stable radiometers as external sphere monitors, and the rapid reporting of measurement results. Results from several comparisons are presented. The absolute radiometric calibration standard uncertainties required by the EOS satellite instruments are typically in the +/- 3% to +/- 5% range. Preliminary results reported during eleven radiometric measurement comparisons held between February 1995 and May 1998 have shown the radiance of integrating spheres

  10. A Review of LIDAR Radiometric Processing: From Ad Hoc Intensity Correction to Rigorous Radiometric Calibration

    PubMed Central

    Kashani, Alireza G.; Olsen, Michael J.; Parrish, Christopher E.; Wilson, Nicholas

    2015-01-01

    In addition to precise 3D coordinates, most light detection and ranging (LIDAR) systems also record “intensity”, loosely defined as the strength of the backscattered echo for each measured point. To date, LIDAR intensity data have proven beneficial in a wide range of applications because they are related to surface parameters, such as reflectance. While numerous procedures have been introduced in the scientific literature, and even commercial software, to enhance the utility of intensity data through a variety of “normalization”, “correction”, or “calibration” techniques, the current situation is complicated by a lack of standardization, as well as confusing, inconsistent use of terminology. In this paper, we first provide an overview of basic principles of LIDAR intensity measurements and applications utilizing intensity information from terrestrial, airborne topographic, and airborne bathymetric LIDAR. Next, we review effective parameters on intensity measurements, basic theory, and current intensity processing methods. We define terminology adopted from the most commonly-used conventions based on a review of current literature. Finally, we identify topics in need of further research. Ultimately, the presented information helps lay the foundation for future standards and specifications for LIDAR radiometric calibration. PMID:26561813

  11. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  12. Landsat-7 ETM+ On-Orbit Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Markham, Brian L.; Kaita, Ed; Miller, Jeff; Barsi, Julia; Smith, David E. (Technical Monitor)

    2000-01-01

    percent in responsivity since launch and that the absolute calibration is good to the advertised five percent.

  13. Relative radiometric calibration of LANDSAT TM reflective bands

    NASA Technical Reports Server (NTRS)

    Barker, J. L.

    1984-01-01

    A common scientific methodology and terminology is outlined for characterizing the radiometry of both TM sensors. The magnitude of the most significant sources of radiometric variability are discussed and methods are recommended for achieving the exceptional potential inherent in the radiometric precision and accuracy of the TM sensors.

  14. Simultaneous Inflight Spectral and Radiometric Calibration Validation of AVRIS and HYDICE Over Lunar Lake, Nevada

    NASA Technical Reports Server (NTRS)

    Chrien, Thomas; Green, Robert; Chovit, Chris; Faust, Jessica; Johnson, Howell; Basedow, Robert; Zalewski, Edward; Colwell, John

    1995-01-01

    An experiment to check the spectral and radiometric calibration of two sensors--the airborne visible/infrared imaging spectromenter (AVRIS) and the Hyperspectral digital image collection experiment (HYDICE)--is described.

  15. In-flight UV and polarized-VL radiometric calibrations of the solar orbiter/METIS imaging coronagraph

    NASA Astrophysics Data System (ADS)

    Focardi, M.; Capobianco, G.; Andretta, V.; Sasso, C.; Romoli, M.; Landini, F.; Fineschi, S.; Pancrazzi, M.; Bemporad, A.; Nicolini, G.; Pucci, S.; Uslenghi, M.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Teriaca, L.; SchuÌhle, U. H.; Antonucci, E.

    2014-07-01

    METIS is an innovative inverted occulted solar coronagraph capable of obtaining for the first time simultaneous imaging of the full corona in linearly polarized visible-light (580-640 nm) and narrow-band (+/- 10 nm) ultraviolet H I Ly-α (121.6 nm). It has been selected to fly aboard the Solar Orbiter1 spacecraft, whose launch is foreseen in July 2017. Thanks to its own capabilities and exploiting the peculiar opportunities offered by the Solar Orbiter planned orbit, METIS will address some of the still open issues in understanding the physical processes in the corona and inner heliosphere. The Solar Orbiter Nominal Mission Phase (NMP) will be characterized by three scientific observing windows per orbit and METIS will perform at least one in-flight calibration per observing window. The two imaging channels of METIS will be calibrated on ground and periodically checked, verified and re-calibrated in-flight. In particular, radiometric calibration images will be needed to determine the absolute brightness of the solar corona. For UV radiometric calibration a set of targets is represented by continuum-emitting early type bright stars (e.g. A and B spectral types) whose photospheres produce a bright far-ultraviolet continuum spectrum stable over long timescales. These stars represent an important reference standard not only for METIS in-flight calibrations but also for other Solar Orbiter instruments and they will be crucial for instruments cross-calibrations as well. For VL radiometric calibration, a set of linearly polarized stars will be used. These targets shall have a minimum degree of linear polarization (DoLP > 5%) and a detectable magnitude, compatible with the instrument integration times constrained by the desired S/N ratio and the characteristics of the spacecraft orbit dynamics.

  16. Quantum Efficient Detectors for Use in Absolute Calibration

    NASA Technical Reports Server (NTRS)

    Faust, Jessica; Eastwood, Michael; Pavri, Betina; Raney, James

    1998-01-01

    The trap or quantum efficient detector has a quantum efficiency of greater than 0.98 for the region from 450 to 900 nm. The region of flattest response is from 600 to 900 nm. The QED consists of three windowless Hamamatsu silicon detectors. The QED was mounted below AVIRIS to monitor the Spectralon panel for changes in radiance during radiometric calibration. The next step is to permanently mount the detector to AVIRIS and monitor the overall radiance of scenes along with calibration.

  17. Absolute calorimetric calibration of low energy brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Stump, Kurt E.

    the current instrument to direct further work in this field. It has been found that for sources with powers above approximately 2 muW the instrument is able to determine the source power in agreement to within less than 7% of what is expected based upon the current source strength standard. For lower power sources, the agreement is still within the uncertainty of the power measurement, but the calorimeter noise dominates. Thus, to provide absolute calibration of lower power sources additional measures must be taken. The conclusion of this thesis describes these measures and how they will improve the factors that limit the current instrument. The results of the work presented in this thesis establish the methodology of active radiometric calorimetey for the absolute calibration of radioactive sources. The method is an improvement over previous techniques in that there is no reliance upon the thermal properties of the materials used or the heat flow pathways on the source measurements. The initial work presented here will help to shape future refinements of this technique to allow lower power sources to be calibrated with high precision and high accuracy.

  18. Transmittance Measurement of a Heliostat Facility used in the Preflight Radiometric Calibration of Earth-Observing Sensors

    NASA Technical Reports Server (NTRS)

    Czapla-Myers, J.; Thome, K.; Anderson, N.; McCorkel, J.; Leisso, N.; Good, W.; Collins, S.

    2009-01-01

    Ball Aerospace and Technologies Corporation in Boulder, Colorado, has developed a heliostat facility that will be used to determine the preflight radiometric calibration of Earth-observing sensors that operate in the solar-reflective regime. While automatically tracking the Sun, the heliostat directs the solar beam inside a thermal vacuum chamber, where the sensor under test resides. The main advantage to using the Sun as the illumination source for preflight radiometric calibration is because it will also be the source of illumination when the sensor is in flight. This minimizes errors in the pre- and post-launch calibration due to spectral mismatches. It also allows the instrument under test to operate at irradiance values similar to those on orbit. The Remote Sensing Group at the University of Arizona measured the transmittance of the heliostat facility using three methods, the first of which is a relative measurement made using a hyperspectral portable spectroradiometer and well-calibrated reference panel. The second method is also a relative measurement, and uses a 12-channel automated solar radiometer. The final method is an absolute measurement using a hyperspectral spectroradiometer and reference panel combination, where the spectroradiometer is calibrated on site using a solar-radiation-based calibration.

  19. Transmittance measurement of a heliostat facility used in the preflight radiometric calibration of Earth-observing sensors

    NASA Astrophysics Data System (ADS)

    Czapla-Myers, J.; Thome, K.; Anderson, N.; McCorkel, J.; Leisso, N.; Good, W.; Collins, S.

    2009-08-01

    Ball Aerospace and Technologies Corporation in Boulder, Colorado, has developed a heliostat facility that will be used to determine the preflight radiometric calibration of Earth-observing sensors that operate in the solar-reflective regime. While automatically tracking the Sun, the heliostat directs the solar beam inside a thermal vacuum chamber, where the sensor under test resides. The main advantage to using the Sun as the illumination source for preflight radiometric calibration is because it will also be the source of illumination when the sensor is in flight. This minimizes errors in the pre- and post-launch calibration due to spectral mismatches. It also allows the instrument under test to operate at irradiance values similar to those on orbit. The Remote Sensing Group at the University of Arizona measured the transmittance of the heliostat facility using three methods, the first of which is a relative measurement made using a hyperspectral portable spectroradiometer and well-calibrated reference panel. The second method is also a relative measurement, and uses a 12-channel automated solar radiometer. The final method is an absolute measurement using a hyperspectral spectroradiometer and reference panel combination, where the spectroradiometer is calibrated on site using a solar-radiation-based calibration.

  20. 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.

  1. Radiometric cross-calibration of Terra ASTER and MODIS

    NASA Astrophysics Data System (ADS)

    Yuan, Karen; Thome, Kurt; McCorkel, Joel

    2015-09-01

    Calibration and validation play an essential role during the acquisition and processing of satellite data for Earth Observing System satellites in addition to being an integral part of maintaining scientific values of archived satellite data. The Advanced Spaceborne Thermal Emission and Reflection and Radiometer (ASTER) and Moderate Resolution Imaging Spectroradiometer (MODIS) are two of five sensors onboard the Terra platform. ASTER has a swath width of 60 km with 8 spectral bands in the visible and near infrared (VNIR) and thermal infrared (TIR) spectral range with a spatial resolution of 15-m (bands 1-3) and 90-m (bands 10-14), respectively while MODIS has a swath width of 2300 km with 36 spectral bands from visible to infrared spectral range with a spatial resolution of 250 m (bands 1-2), 500 m (bands 3-7), and 1 km (bands 8-36). ASTER is the `zoom' lens and MODIS is the `keystone' instrument for Terra; they provide quantitative measurements of various earth system variables to the scientific and to the broader community. The simultaneous view of the sensors simplifies the intercomparison between them and the current work relies on the use of the Railroad Valley Playa test site to reduce uncertainties caused by spatial heterogeneity and spectral differences in the sensors. The fact that Railroad Valley is a calibration test site for ASTER ensures that ASTER was tasked at a higher rate over this area providing more scenes for an intercomparison. The study compares ASTER L1B data for the three VNIR bands reprocessed with recent calibration updates and MODIS 02 Collection 6 data products for the similar bands. No correction for geometry angle is needed and coincident 3-km by 3-km regions are used to reduce the impact of spatial heterogeneity. A correction for spectral differences between the sensors is applied based on seasonal averages of EO-1 Hyperion spectral range. Results indicate that the calibrated radiance products from the two sensors agree to within the

  2. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO

  3. Radiometric Calibration of the AWiFS Sensor and a Cross-calibration Enhanced Vicarious Calibration Technique

    NASA Technical Reports Server (NTRS)

    Aaron, David

    2007-01-01

    Using vicarious calibration validation of moderate resolution sensors such as AWiFS is complicated by requiring more land area to ensure proper registration and sufficient pixel numbers. A trial AWiFS calibration was performed on a grass site that consisted of two dramatically different grass heights. Ground truth data was collected over relatively small areas representing only a few pixels. The radiometric gain results for each of these areas will be reported. To enhance this analysis, since a near coincidence high resolution image was collected, the high resolution data was effectively resized to produce pixels comparable to AWiFS and the atmospheric model was used to produce a top of canopy radiance map. Multiple uniform vegetated areas of several radiances were then identified and subsequently propagated to the top of atmosphere viewpoint of the moderate resolution (AWiFS) satellite. The radiometric gain was then calculated based on the vendor high resolution satellite gains (for the 3 bands with comparable wavelengths). Band-to-band conversion was performed assuming a hyperspectral reflectance based on the standard vegetated site. The initial comparison produces AWiFS radiometric gain values that agree to better than 10% of the values measured using the standard vicarious gain technique.

  4. Radiometric Calibration of Mars HiRISE High Resolution Imagery Based on Fpga

    NASA Astrophysics Data System (ADS)

    Hou, Yifan; Geng, Xun; Xing, Shuai; Tang, Yonghe; Xu, Qing

    2016-06-01

    Due to the large data amount of HiRISE imagery, traditional radiometric calibration method is not able to meet the fast processing requirements. To solve this problem, a radiometric calibration system of HiRISE imagery based on field program gate array (FPGA) is designed. The montage gap between two channels caused by gray inconsistency is removed through histogram matching. The calibration system is composed of FPGA and DSP, which makes full use of the parallel processing ability of FPGA and fast computation as well as flexible control characteristic of DSP. Experimental results show that the designed system consumes less hardware resources and the real-time processing ability of radiometric calibration of HiRISE imagery is improved.

  5. Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor

    PubMed Central

    Ponzoni, Flávio Jorge; Albuquerque, Bráulio Fonseca Carneiro

    2008-01-01

    Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community. PMID:27873886

  6. Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor.

    PubMed

    Ponzoni, Flávio Jorge; Albuquerque, Bráulio Fonseca Carneiro

    2008-10-23

    Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community.

  7. System and method for calibrating a rotary absolute position sensor

    NASA Technical Reports Server (NTRS)

    Davis, Donald R. (Inventor); Permenter, Frank Noble (Inventor); Radford, Nicolaus A (Inventor)

    2012-01-01

    A system includes a rotary device, a rotary absolute position (RAP) sensor generating encoded pairs of voltage signals describing positional data of the rotary device, a host machine, and an algorithm. The algorithm calculates calibration parameters usable to determine an absolute position of the rotary device using the encoded pairs, and is adapted for linearly-mapping an ellipse defined by the encoded pairs to thereby calculate the calibration parameters. A method of calibrating the RAP sensor includes measuring the rotary position as encoded pairs of voltage signals, linearly-mapping an ellipse defined by the encoded pairs to thereby calculate the calibration parameters, and calculating an absolute position of the rotary device using the calibration parameters. The calibration parameters include a positive definite matrix (A) and a center point (q) of the ellipse. The voltage signals may include an encoded sine and cosine of a rotary angle of the rotary device.

  8. Absolute sensitivity calibration of extreme ultraviolet photoresists

    SciTech Connect

    Jones, Juanita; Naulleau, Patrick P.; Gullikson, Eric M.; Aquila, Andrew; George, Simi; Niakoula, Dimitra

    2008-05-16

    One of the major challenges facing the commercialization of extreme ultraviolet (EUV) lithography remains simultaneously achieving resist sensitivity, line-edge roughness, and resolution requirement. Sensitivity is of particular concern owing to its direct impact on source power requirements. Most current EUV exposure tools have been calibrated against a resist standard with the actual calibration of the standard resist dating back to EUV exposures at Sandia National Laboratories in the mid 1990s. Here they report on an independent sensitivity calibration of two baseline resists from the SEMATECH Berkeley MET tool performed at the Advanced Light Source Calibrations and Standards beamline. The results show the baseline resists to be approximately 1.9 times faster than previously thought based on calibration against the long standing resist standard.

  9. Absolute sensitivity calibration of extreme ultraviolet photoresists.

    PubMed

    Naulleau, Patrick P; Gullikson, Eric M; Aquila, Andrew; George, Simi; Niakoula, Dimitra

    2008-07-21

    One of the major challenges facing the commercialization of extreme ultraviolet (EUV) lithography remains simultaneously achieving resist sensitivity, line-edge roughness, and resolution requirement. Sensitivity is of particular concern owing to its direct impact on source power requirements. Most current EUV exposure tools have been calibrated against a resist standard with the actual calibration of the standard resist dating back to EUV exposures at Sandia National Laboratories in the mid 1990s. Here we report on an independent sensitivity calibration of two baseline resists from the SEMATECH Berkeley MET tool performed at the Advanced Light Source Calibrations and Standards beamline. The results show the baseline resists to be approximately 1.9 times faster than previously thought based on calibration against the long standing resist standard.

  10. On accuracy of radiometric calibration of hyperspectral visible/NIR satellite remote sensing instruments using test sites of different altitudes

    NASA Astrophysics Data System (ADS)

    Borovski, Alexander; Ivanov, Victor; Pankratova, Natalia; Postylyakov, Oleg

    2016-04-01

    To provide accurate data the regular on-board absolute radiometric calibration of a satellite hyperspectral instrument is required. Together with the internal calibration the external calibration using comparison of radiance measurements above special ground test sites and calculated radiances is performed. The top of the atmosphere radiances are calculated using a radiative transfer model basing on atmospheric and surface characteristics measured at the test sites. The paper presents preliminary results of the comparative theoretical analysis of the errors of a satellite hyperspectral instrument radiometric calibration using test sites located at 200 m.a.s.l. and 2000 m.a.s.l. with the atmospheric composition and surface reflectance measurements. The analysis is performed for an instrument with the spectral resolution of 1-8 nm which is typical for special regime of payload GSA of Russian satellite Resurs-P. The errors related with the atmospheric composition and albedo measurement errors and scenarios of the aerosol vertical distribution were theoretically examined. The error is less than 4% in all the cases at all the wavelengths between 400 nm and 1000 nm with the exception of the absorption bands of water vapor. In the absorption bands of water vapor about 720 nm and 820 nm the errors reach 5% at the mountain site and 10% at the downcountry site. In the absorption band of 950 nm the errors reach 15% in mountains and 35% in downcountry.

  11. Preparation of a new autonomous instrumented radiometric calibration site: Gobabeb, Namib Desert

    NASA Astrophysics Data System (ADS)

    Greenwell, Claire; Bialek, Agnieszka; Marks, Amelia; Woolliams, Emma; Berthelot, Béatrice; Meygret, Aimé; Marcq, Sébastien; Bouvet, Marc; Fox, Nigel

    2015-10-01

    A new permanently instrumented radiometric calibration site for high/medium resolution imaging satellite sensors is currently under development, focussing on the visible and near infra-red parts of the spectrum. The site will become a European contribution to the Committee on Earth Observation Satellites (CEOS) initiative RadCalNet (Radiometric Calibration Network). The exact location of the permanent monitoring instrumentation will be defined following the initial site characterisation. The new ESA/CNES RadCalNet site will have a robust uncertainty budget and its data fully SI traceable through detailed characterisation and calibration by NPL of the instruments and artefacts to be used on the site. This includes a CIMEL sun photometer (the permanent instrumentation) an ASD FieldSpec spectroradiometer, Gonio Radiometric Spectrometer System (GRASS), and reference reflectance standards.

  12. Absolute flux density calibrations: Receiver saturation effects

    NASA Technical Reports Server (NTRS)

    Freiley, A. J.; Ohlson, J. E.; Seidel, B. L.

    1978-01-01

    The effect of receiver saturation was examined for a total power radiometer which uses an ambient load for calibration. Extension to other calibration schemes is indicated. The analysis shows that a monotonic receiver saturation characteristic could cause either positive or negative measurement errors, with polarity depending upon operating conditions. A realistic model of the receiver was made by using a linear-cubic voltage transfer characteristic. The evaluation of measurement error for this model provided a means for correcting radio source measurements.

  13. Retinal vessel oximetry: toward absolute calibration

    NASA Astrophysics Data System (ADS)

    Smith, Matthew H.; Denninghoff, Kurt R.; Lompado, Arthur; Hillman, Lloyd W.

    2000-06-01

    Accurately measuring the oxygen saturation of blood within retinal arteries and veins has proven to be a deceptively difficult task. Despite the excellent optical accessibility of the vessels and a wide range of reported instrumentation, we are unaware of any measurement technique that has proven to be calibrated across wide ranges of vessel diameter and fundus pigmentation. We present an overview of our retinal oximetry technique, present the results of an in vitro calibration experiment, and present preliminary human data.

  14. Monochromator-Based Absolute Calibration of Radiation Thermometers

    NASA Astrophysics Data System (ADS)

    Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Hartmann, J.

    2011-08-01

    A monochromator integrating-sphere-based spectral comparator facility has been developed to calibrate standard radiation thermometers in terms of the absolute spectral radiance responsivity, traceable to the PTB cryogenic radiometer. The absolute responsivity calibration has been improved using a 75 W xenon lamp with a reflective mirror and imaging optics to a relative standard uncertainty at the peak wavelength of approximately 0.17 % ( k = 1). Via a relative measurement of the out-of-band responsivity, the spectral responsivity of radiation thermometers can be fully characterized. To verify the calibration accuracy, the absolutely calibrated radiation thermometer is used to measure Au and Cu freezing-point temperatures and then to compare the obtained results with the values obtained by absolute methods, resulting in T - T 90 values of +52 mK and -50 mK for the gold and copper fixed points, respectively.

  15. Establishing metrological traceability for radiometric calibration of earth observation sensor in Malaysia

    NASA Astrophysics Data System (ADS)

    Ng, S. W.; Zulkifli, A.

    2016-10-01

    The space borne earth observation (EO) sensor provides a continuous large spatial coverage over the earth at relatively low cost (cost-effective) and can be practically accessible worldwide. The daily synoptic view offered by instrument in earth orbit is tremendously useful in various applications, particularly long term global monitoring that needs multi-disciplinary, multi-temporal and multi-sensor data. Due to the indirect measurement nature of the EO sensor, calibration and validation (cal/val) are essentially required to establish the linkage between the acquired raw data and the actual target of interest. Ultimately, EO sensor provider must strive to deliver “the right information, at the right time, to the right people”. This paper is authored with the main aim to report the process of establishing metrological traceability for radiometric calibration of EO sensor at Optical Calibration Laboratory (OCL), National Space Agency of Malaysia (ANGKASA). The paper is structured into six sections. The first section introduces the context of EO and background of radiometric calibration. The next section discusses the requirements for metrological traceability in radiometric calibration while the following third section outlines ANGKASA efforts in setting up the metrological traceability laboratory in radiometric calibration. Meanwhile, the uncertainty estimation results is reported in the fourth section and the fifth section explains some of the continuous efforts made in order to improve the current metrological traceability set up. Lastly, the summary of this paper is provided in the last section.

  16. [VMTBB-Based Spectral Radiometric Calibration of NIR Fiber Coupled Spectrometer].

    PubMed

    Zheng, Feng; Liu, Li-ying; Liu, Xiao-xi; Li, Ye; Shi, Xiao-guang; Zhang, Guo-yu; Huan, Ke-wei

    2015-09-01

    The medium temperature black body (MTBB) is conventional high precision equipment used as spectral radiometric scale in infrared spectral region. However, in near-infrared (NIR) spectral region, there are few papers about spectral radiometric calibration by using MTBB, that is because NIR spectral region is the borderland of its effective spectral region. The main research of this paper is spectral radiometric calibration method by using MTBB in NIR spectral region. Accordingly, this paper is devoted mostly to a discussion of how the calibration precision could be affected by selecting different structural parameters of calibration model. The purpose of this paper is to present the results of research and provide technical reference for improving the traceability in NIR spectral radiometric calibration. In this paper, a NIR fiber coupled spectrometer, whose wavelength range covers from 950 to 1700 nm, has been calibrated by a MTBB with adjustable temperature range from 50 to 1050 °C. Concentrating on calibration process, two key points have been discussed. For one thing, the geometric factors of radiation transfer model of the calibration systems have been compared between traditional structure and fiber direct-coupled structure. Because the fiber direct-coupled model is simple and effective, it has been selected instead of traditional model based on the radiation transfer between two coaxial discs. So, it is an advantaged radiation transfer model for radiometric calibration of fiber coupled spectrometer. For another thing, the relation between calibration accuracy and structural parameters of calibration model has been analyzed intensively. The root cause is scale feature of attribute of calibration data itself, which is the nonlinear structure in scales of spectral data. So, the high precision calibration needs nonlinear calibration model, and the uniform sampling for scale feature is also very important. Selecting sample is an inevitable problem when the

  17. Calibration chain design based on integrating sphere transfer radiometer for SI-traceable on-orbit spectral radiometric calibration and its uncertainty analysis

    NASA Astrophysics Data System (ADS)

    Zhao, Wei-Ning; Fang, Wei; Sun, Li-Wei; Cui, Li-Hong; Wang, Yu-Peng

    2016-09-01

    In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors, a transfer chain consisting of a fiber coupling monochromator (FBM) and an integrating sphere transfer radiometer (ISTR) was designed in this paper. Depending on the Sun, this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band (RSB) covering 300-2500 nm with a spectral bandwidth of 0.5-6 nm. It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard. This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor, including the weak spectral signal measurement with uncertainty of 0.28%. According to the peculiar design and comprehensive uncertainty analysis, it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%. The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality. Project supported by the National Natural Science Foundation of China (Grant No. 41474161) and the National High-Technology Program of China (Grant No. 2015AA123703).

  18. “Once is Enough” in Radiometric Calibrations

    PubMed Central

    Fraser, Gerald T.; Gibson, Charles E.; Yoon, Howard W.; Parr, Albert C.

    2007-01-01

    The successful development of an Optical Technology Division quality system for optical radiation measurement services has provided the opportunity to reconsider the existing calibration procedures to improve quality and reduce costs. We have instituted procedures in our calibration programs to eliminate uninformative repetitive measurements by concentrating our efforts on controlling and understanding the measurement process. The first program in our calibration services to undergo these revisions is described in this paper. PMID:27110453

  19. Progress Report of CNES Activities Regarding the Absolute Calibration Method

    DTIC Science & Technology

    2010-11-01

    several receivers (Ashtech Z12-T, Septentrio PolaRx2, and Dicom GTR50) and a GNSS signal simulator (Spirent 4760) according to the temperature and...laboratories, Ashtech Z12- T, Septentrio PolaRx2, and Dicom GTR50, can be calibrated with the absolute method [6,8]. The last works concerned the...Ashtech, Septentrio, and Dicom receiver calibrations. Table 2. Uncertainty of the different receiver calibrations. Uncertainty Source

  20. A Study on Optimal Strategy in Relative Radiometric Calibration for Optical Sensors

    PubMed Central

    Yu, Kai; Liu, Suhong; Zhao, Yongchao

    2017-01-01

    Based on the analysis of three main factors involved in the relative radiometric calibration for optical sensors, namely: the number of radiance level; the number of measurements at each level; and the radiance level grouping method, an optimal strategy is presented in this paper for relative radiometric calibration. First, the maximization to the possible extent of either the number of the radiance level or the number of measurements at each level can improve the precision of the calibration results, where the recommended number of measurements is no less than 20. Second, when the number of the radiance level is divisible by four, dividing all the levels evenly into four groups by intensity gradient order and conducting averages for each group could achieve calibration results with the highest precision, which is higher than the result of no grouping or any other grouping method with the mean square error being 22Mn/IT (where Mn is the mean square error of noise in the calibration data, I is the number of the radiance level, and T is the number of measurements for each level. In this case, the first two factors had an equivalent effect and showed their strongest effect on the precision. Third, when the calibration data were not evenly divided, the number of measurements demonstrated a stronger effect than the number of the radiance level. These cognitions are helping to achieve more precise relative radiometric calibration of optical sensors. PMID:28257083

  1. Absolute Calibration Accuracy for Hyperspectral Imagers in the Solar Reflective

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis

    2009-01-01

    The characterization and calibration of hyperspectral imagers is a challenging one that is expected to become even more challenging as needs increase for highly-accurate radiometric data from such systems. The preflight calibration of the Advanced Responsive Tactically Effective Military Imaging Spectrometer (ARTEMIS) is used as an example of the difficulties to calibrate hyperspectrally. Results from a preflight solar radiation-based calibration are presented with a discussion of the uncertainties in such a method including the NISI-traceable and SItraceable aspects. Expansion on the concept of solar-based calibration is given with descriptions of methods that view the solar disk directly, illuminate a solar diffuser that is part of the sensor's inflight calibration, and illuminate an external diffuser that is imaged by the sensor. The results of error analysis show that it is feasible to achieve preflight calibration using the sun as a source at the same level of uncertainty as those of lamp-based approaches. The error analysis is evaluated and verified through the solar-radiation-based calibration of several of laboratory grade radiometers. Application of these approaches to NASA's upcoming CLARREO mission are discussed including proposed methods for significantly reducing the uncertainties to allow CLARREO data to be used for climate data records.

  2. Absolute calibration of 10Be AMS standards

    NASA Astrophysics Data System (ADS)

    Nishiizumi, Kunihiko; Imamura, Mineo; Caffee, Marc W.; Southon, John R.; Finkel, Robert C.; McAninch, Jeffrey

    2007-05-01

    The increased detection sensitivity offered by AMS has dramatically expanded the utility of 10Be. As these applications become more sophisticated attention has focused on the accuracy of the 10Be standards used to calibrate the AMS measurements. In recent years it has become apparent that there is a discrepancy between two of the most widely used 10Be AMS standards, the ICN 10Be standard and the NIST 10Be standard. The ICN (ICN Chemical & Radioisotope Division) 10Be AMS standard was calibrated by radioactive decay counting. Dilutions, ranging from 5 × 10 -13 to 3 × 10 -1110Be/Be, have been prepared and are extensively used in many AMS laboratories. The NIST 10Be standard, prepared at the National Institute of Standards and Technology (NIST), is calibrated by mass spectrometric isotope ratio measurements. To provide an independent calibration of the 10Be standards we implanted a known number of 10Be atoms in both Si detectors and Be foil targets. The 10Be concentrations in these targets were measured by AMS. The results were compared with both the ICN and NIST AMS standards. Our 10Be measurements indicate that the 10Be/ 9Be isotopic ratio of the ICN AMS standard, which is based on a 10Be half-life of 1.5 × 10 6 yr, is 1.106 ± 0.012 times lower than the nominal value. Since the decay rate of the ICN standard is well determined, the decrease in 10Be/ 9Be ratio requires that the 10Be half-life be reduced to (1.36 ± 0.07) × 10 6 yr. The quoted uncertainty includes a ±5% uncertainty in the activity measurement carried out by ICN. In a similar fashion, we determined that the value of the NIST 10Be standard (SRM4325) is (2.79 ± 0.03) × 10 -1110Be/ 9Be, within error of the certified value of (2.68 ± 0.14) × 10 -11. The Lawrence Livermore National Laboratory (LLNL) internal standards were also included in this study. We conclude that the 9Be(n, γ) neutron cross section is 7.8 ± 0.23 mb, without taking into account the uncertainty in the neutron irradiation.

  3. Investigation of Pre- and Post-Flight Radiometric Calibration Uncertainties from Surface Based Measurements

    SciTech Connect

    Heath, D.F.; Wei, Z.Y.; Ahman, Z.

    1997-06-01

    A new technique has been developed for inferring column ozone amounts and aerosol optical depths from zenith sky observations. A new radiometric calibration technique for large aperture remote sensing instruments observing the earth through space has been validated which subsequently increased the accuracy of remote sensing measurements of ozone and vertical profiles using measurements of back-scattered ultraviolet solar radiation.

  4. Radiometric calibration status of Landsat-7 and Landsat-5

    USGS Publications Warehouse

    Barsi, J.A.; Markham, B.L.; Helder, D.L.; Chander, G.

    2007-01-01

    Launched in April 1999, Landsat-7 ETM+ continues to acquire data globally. The Scan Line Corrector in failure in 2003 has affected ground coverage and the recent switch to Bumper Mode operations in April 2007 has degraded the internal geometric accuracy of the data, but the radiometry has been unaffected. The best of the three on-board calibrators for the reflective bands, the Full Aperture Solar Calibrator, has indicated slow changes in the ETM+, but this is believed to be due to contamination on the panel rather then instrument degradation. The Internal Calibrator lamp 2, though it has not been used regularly throughout the whole mission, indicates smaller changes than the FASC since 2003. The changes indicated by lamp 2 are only statistically significant in band 1, circa 0.3% per year, and may be lamp as opposed to instrument degradations. Regular observations of desert targets in the Saharan and Arabian deserts indicate the no change in the ETM+ reflective band response, though the uncertainty is larger and does not preclude the small changes indicated by lamp 2. The thermal band continues to be stable and well-calibrated since an offset error was corrected in late-2000. Launched in 1984, Landsat-5 TM also continues to acquire global data; though without the benefit of an on-board recorder, data can only be acquired where a ground station is within range. Historically, the calibration of the TM reflective bands has used an onboard calibration system with multiple lamps. The calibration procedure for the TM reflective bands was updated in 2003 based on the best estimate at the time, using only one of the three lamps and a cross-calibration with Landsat-7 ETM+. Since then, the Saharan desert sites have been used to validate this calibration model. Problems were found with the lamp based model of up to 13% in band 1. Using the Saharan data, a new model was developed and implemented in the US processing system in April 2007. The TM thermal band was found to have a

  5. Absolute flux calibration of optical spectrophotometric standard stars

    NASA Technical Reports Server (NTRS)

    Colina, Luis; Bohlin, Ralph C.

    1994-01-01

    A method based on Landolt photometry in B and V is developed to correct for a wavelength independent offset of the absolute flux level of optical spectrophotometric standards. The method is based on synthetic photometry techniques in B and V and is accurate to approximately 1%. The correction method is verified by Hubble Space Telescope Faint Object Spectrograph absolute fluxes for five calibration stars, which agree with Landolt photometry to 0.5% in B and V.

  6. Improving Ocean Color Data Products using a Purely Empirical Approach: Reducing the Requirement for Radiometric Calibration Accuracy

    NASA Technical Reports Server (NTRS)

    Gregg, Watson

    2008-01-01

    Radiometric calibration is the foundation upon which ocean color remote sensing is built. Quality derived geophysical products, such as chlorophyll, are assumed to be critically dependent upon the quality of the radiometric calibration. Unfortunately, the goals of radiometric calibration are not typically met in global and large-scale regional analyses, and are especially deficient in coastal regions. The consequences of the uncertainty in calibration are very large in terms of global and regional ocean chlorophyll estimates. In fact, stability in global chlorophyll requires calibration uncertainty much greater than the goals, and outside of modern capabilities. Using a purely empirical approach, we show that stable and consistent global chlorophyll values can be achieved over very wide ranges of uncertainty. Furthermore, the approach yields statistically improved comparisons with in situ data, suggesting improved quality. The results suggest that accuracy requirements for radiometric calibration cab be reduced if alternative empirical approaches are used.

  7. Radiometric cross-calibration of the Terra MODIS and Landsat 7 ETM+ using an invariant desert site

    NASA Astrophysics Data System (ADS)

    Choi, Taeyoung; Angal, Amit; Chander, Gyanesh; Xiong, Xiaoxiong

    2008-08-01

    A methodology for long-term radiometric cross-calibration between the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) sensors was developed. The approach involves calibration of near-simultaneous surface observations between 2000 and 2007. Fifty-seven cloudfree image pairs were carefully selected over the Libyan desert for this study. The Libyan desert site (+28.55°, +23.39°), located in northern Africa, is a high reflectance site with high spatial, spectral, and temporal uniformity. Because the test site covers about 12 kmx13 km, accurate geometric preprocessing is required to match the footprint size between the two sensors to avoid uncertainties due to residual image misregistration. MODIS Level 1B radiometrically corrected products were reprojected to the corresponding ETM+ image's Universal Transverse Mercator (UTM) grid projection. The 30 m pixels from the ETM+ images were aggregated to match the MODIS spatial resolution (250 m in Bands 1 and 2, or 500 m in Bands 3 to 7). The image data from both sensors were converted to absolute units of at-sensor radiance and top-of atmosphere (TOA) reflectance for the spectrally matching band pairs. For each band pair, a set of fitted coefficients (slope and offset) is provided to quantify the relationships between the testing sensors. This work focuses on long-term stability and correlation of the Terra MODIS and L7 ETM+ sensors using absolute calibration results over the entire mission of the two sensors. Possible uncertainties are also discussed such as spectral differences in matching band pairs, solar zenith angle change during a collection, and differences in solar irradiance models.

  8. Radiometric cross-calibration of the Terra MODIS and Landsat 7 ETM+ using an invariant desert site

    USGS Publications Warehouse

    Choi, T.; Angal, A.; Chander, G.; Xiong, X.

    2008-01-01

    A methodology for long-term radiometric cross-calibration between the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) sensors was developed. The approach involves calibration of near-simultaneous surface observations between 2000 and 2007. Fifty-seven cloud-free image pairs were carefully selected over the Libyan desert for this study. The Libyan desert site (+28.55??, +23.39??), located in northern Africa, is a high reflectance site with high spatial, spectral, and temporal uniformity. Because the test site covers about 12 kmx13 km, accurate geometric preprocessing is required to match the footprint size between the two sensors to avoid uncertainties due to residual image misregistration. MODIS Level IB radiometrically corrected products were reprojected to the corresponding ETM+ image's Universal Transverse Mercator (UTM) grid projection. The 30 m pixels from the ETM+ images were aggregated to match the MODIS spatial resolution (250 m in Bands 1 and 2, or 500 m in Bands 3 to 7). The image data from both sensors were converted to absolute units of at-sensor radiance and top-ofatmosphere (TOA) reflectance for the spectrally matching band pairs. For each band pair, a set of fitted coefficients (slope and offset) is provided to quantify the relationships between the testing sensors. This work focuses on long-term stability and correlation of the Terra MODIS and L7 ETM+ sensors using absolute calibration results over the entire mission of the two sensors. Possible uncertainties are also discussed such as spectral differences in matching band pairs, solar zenith angle change during a collection, and differences in solar irradiance models.

  9. Extreme Ultraviolet Variability Experiment (EVE) Multiple EUV Grating Spectrographs (MEGS): Radiometric Calibrations and Results

    NASA Technical Reports Server (NTRS)

    Hock, R. A.; Woods, T. N.; Crotser, D.; Eparvier, F. G.; Woodraska, D. L.; Chamberlin, P. C.; Woods, E. C.

    2010-01-01

    The NASA Solar Dynamics Observatory (SDO), scheduled for launch in early 2010, incorporates a suite of instruments including the Extreme Ultraviolet Variability Experiment (EVE). EVE has multiple instruments including the Multiple Extreme ultraviolet Grating Spectrographs (MEGS) A, B, and P instruments, the Solar Aspect Monitor (SAM), and the Extreme ultraviolet SpectroPhotometer (ESP). The radiometric calibration of EVE, necessary to convert the instrument counts to physical units, was performed at the National Institute of Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF III) located in Gaithersburg, Maryland. This paper presents the results and derived accuracy of this radiometric calibration for the MEGS A, B, P, and SAM instruments, while the calibration of the ESP instrument is addressed by Didkovsky et al. . In addition, solar measurements that were taken on 14 April 2008, during the NASA 36.240 sounding-rocket flight, are shown for the prototype EVE instruments.

  10. Absolute calibration and beam background of the Squid Polarimeter

    SciTech Connect

    Blaskiewicz, M.M.; Cameron, P.R.; Shea, T.J.

    1996-12-31

    The problem of beam background in Squid Polarimetry is not without residual benefits. The authors may deliberately generate beam background by gently kicking the beam at the spin tune frequency. This signal may be used to accomplish a simple and accurate absolute calibration of the polarimeter. The authors present details of beam background calculations and their application to polarimeter calibration, and suggest a simple proof-of-principle accelerator experiment.

  11. An absolute sensitivity calibration of the JET VUV SPRED spectrometer

    NASA Astrophysics Data System (ADS)

    Lawson, K. D.; Coffey, I. H.; Zacks, J.; Stamp, M. F.; contributors, JET-EFDA

    2009-04-01

    The determination of a good relative and absolute sensitivity calibration for wideband VUV spectrometers is challenging. On JET, the possible T and Be contamination of the VUV spectrometer precludes its removal to a synchrotron source and, consequently, a range of alternative in situ techniques have been investigated in depth. This has resulted in a reliable calibration for the complete spectral range, the relative calibration at short wavelengths being particularly accurate. At these wavelengths, a novel approach is used, in which the calibration is extended using a number of Na- and Li-like metal doublets. At longer wavelengths, the Li-like doublets of Ar and Ne have been used in conjunction with CII, CIII and CIV line intensity ratios. Unexplained discrepancies between the measured and modelled C results have meant that the exceptional short wavelength accuracy has not be repeated at these longer wavelengths. The absolute sensitivity has been determined from branching ratios to an absolutely calibrated visible spectrometer. The long term stability of the calibration is discussed.

  12. Emissivity Model Sensitivity on Radiometric Inter-calibration between the GMI and Its Constellation Imager Radiometers

    NASA Astrophysics Data System (ADS)

    Chen, R.

    2015-12-01

    The inter-satellite radiometric calibration technique (also known as XCAL) has been applied with great success between the TRMM Microwave Imager (TMI) -calibration transfer standard- and its constellation imagers, namely, WindSat, AMSR2 and SSMIS. However, while the TRMM mission has now ended, it is now time to change the radiometric transfer standard from the previous TMI to the GPM Microwave Imager (GMI). In this paper, we conduct the inter-calibration between GMI and other imager instruments in its constellation using two different radiative transfer models (RTM), namely XCAL RTM which has been used by XCAL group over the past 10 years, and RSS RTM developed by Remote Sensing Systems (RSS). The main difference between these two RTMs lies in calculating the ocean surface emissivity which is crucial for the measurement of spaceborne microwave radiometers. By comparing the simulated Tb's from two RTMs applied on 9 microwave channels ranging from 10 to 90 GHz, we are able to evaluate the robustness of our XCAL RTM, especially the Elsaesser Ocean Surface Emissivity model that has been used within this model. Besides discussing the reliability of these two RTMs, an XCAL approach known as Double Difference (DD) that has been developed and successfully validated by the Central Florida Remote Sensing Lab will be performed between GMI and its constellation imagers, from which the results will enable us to prescreen the consistency of GMI as the new radiometric transfer standard for imager radiometers as well as assessing the impact of the ocean surface emissivity on radiometric inter-calibration of radiometers at imager channels. Index: Inter-satellite calibration, ocean surface emissivity, radiative transfer model, microwave radiometry

  13. Absolute irradiance of the Moon for on-orbit calibration

    USGS Publications Warehouse

    Stone, T.C.; Kieffer, H.H.; ,

    2002-01-01

    The recognized need for on-orbit calibration of remote sensing imaging instruments drives the ROLO project effort to characterize the Moon for use as an absolute radiance source. For over 5 years the ground-based ROLO telescopes have acquired spatially-resolved lunar images in 23 VNIR (Moon diameter ???500 pixels) and 9 SWIR (???250 pixels) passbands at phase angles within ??90 degrees. A numerical model for lunar irradiance has been developed which fits hundreds of ROLO images in each band, corrected for atmospheric extinction and calibrated to absolute radiance, then integrated to irradiance. The band-coupled extinction algorithm uses absorption spectra of several gases and aerosols derived from MODTRAN to fit time-dependent component abundances to nightly observations of standard stars. The absolute radiance scale is based upon independent telescopic measurements of the star Vega. The fitting process yields uncertainties in lunar relative irradiance over small ranges of phase angle and the full range of lunar libration well under 0.5%. A larger source of uncertainty enters in the absolute solar spectral irradiance, especially in the SWIR, where solar models disagree by up to 6%. Results of ROLO model direct comparisons to spacecraft observations demonstrate the ability of the technique to track sensor responsivity drifts to sub-percent precision. Intercomparisons among instruments provide key insights into both calibration issues and the absolute scale for lunar irradiance.

  14. Two methods for absolute calibration of dynamic pressure transducers

    NASA Astrophysics Data System (ADS)

    Swift, G. W.; Migliori, A.; Garrett, S. L.; Wheatley, J. C.

    1982-12-01

    Two techniques are described for absolute calibration of a dynamic pressure transducer from 0 to 400 Hz in 1-MPa helium gas. One technique is based on a comparison to a mercury manometer; the other is based on the principle of reciprocity. The two techniques agree within the instrumental uncertainties of 1%.

  15. Lyman alpha SMM/UVSP absolute calibration and geocoronal correction

    NASA Technical Reports Server (NTRS)

    Fontenla, Juan M.; Reichmann, Edwin J.

    1987-01-01

    Lyman alpha observations from the Ultraviolet Spectrometer Polarimeter (UVSP) instrument of the Solar Maximum Mission (SMM) spacecraft were analyzed and provide instrumental calibration details. Specific values of the instrument quantum efficiency, Lyman alpha absolute intensity, and correction for geocoronal absorption are presented.

  16. A Comparison of Radiometric Calibration Techniques for Lunar Impact Flashes

    NASA Technical Reports Server (NTRS)

    Suggs, R.

    2016-01-01

    Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ways (Bellot Rubio, et al., 2000 [1], Bouley, et al., 2012.[2], Suggs, et al. 2014 [3], Rembold and Ryan 2015 [4], Ortiz, et al. 2015 [5]). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars. An estimate of the color of the impact flash is also needed to correct it to the chosen passband. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter passband according to the stellar atmosphere calibrations of Bessell et al., 1998 [6]. Figure 1 illustrates the problem. The camera pass band is the wide black curve and the blue, green, red, and magenta curves show the band passes of the Johnson-Cousins B, V, R, and I filters for which we have calibration star magnitudes. The blackbody curve of an impact flash of temperature 2800K (Nemtchinov, et al., 1998 [7]) is the dashed line. This paper compares the various photometric calibration techniques and how they address the color corrections necessary for the calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the flux of meteoroids in the 10s of grams to kilogram size range.

  17. Calibration and Measurement Uncertainty Estimation of Radiometric Data: Preprint

    SciTech Connect

    Habte, A.; Sengupta, M.; Reda, I.; Andreas, A.; Konings, J.

    2014-11-01

    Evaluating the performance of photovoltaic cells, modules, and arrays that form large solar deployments relies on accurate measurements of the available solar resource. Therefore, determining the accuracy of these solar radiation measurements provides a better understanding of investment risks. This paper provides guidelines and recommended procedures for estimating the uncertainty in calibrations and measurements by radiometers using methods that follow the International Bureau of Weights and Measures Guide to the Expression of Uncertainty (GUM). Standardized analysis based on these procedures ensures that the uncertainty quoted is well documented.

  18. Sun Photometer Laser and Lamp Based Radiometric Calibrations; Comparison with the Langley Technique and Implications on Remote Sensing

    NASA Astrophysics Data System (ADS)

    Souaidia, N.; Pietras, C.; Brown, S. W.; Lykke, K. R.; Frouin, R.; Deschamps, P.; Fargion, G.; Johnson, B. C.

    2002-12-01

    Satellite-based remote sensing of the earth is a valuable data source for biological and oceanic studies. However when using remote sensing, it is necessary to correct the measured signal for atmospheric effects. As aerosols play a major role in atmospheric scattering, correcting algorithms based on Aerosol Optical Thickness (AOT) data have been developed to describe the scattering of radiation by aerosols. AOT data are collected by filter radiometers measuring the solar irradiance. The AOT is then retrieved applying the Beer-Bouger-Lambert Law to those measurements. Two radiometers, called Satellite Validation for Marine Biology and Aerosol Determination (SimbadA), were calibrated in this study. These instruments measure the upwelling radiance from the ocean as well as the solar irradiance, providing information on both marine reflectance and AOT. The goals of this study were to calibrate the radiometers using independent methods, evaluate the uncertainties for each method, and assess the influence of the results in terms of the science requirements. The radiometers were calibrated in irradiance and radiance mode using a monochromatic, laser-illuminated integrating sphere, in radiance mode using two different lamp-illuminated integrating spheres, and in irradiance mode using the Langley technique. First, a limited characterization of the instrument was conducted. The instrument's temporal stability and its spectral out-of-band response were evaluated. The instrument was then calibrated in radiance mode using a laser-illuminated integrating sphere that overfilled its field of view (FOV). The absolute radiance responsivity from this calibration was compared to results from measurements of two calibrated lamp illuminated spheres. The first comparison, with the NIST portable radiometric source (NPR), was a validation as good agreement between the two methods has been reported in previous studies. The second comparison was with the Hardy sphere from the Goddard Space

  19. Self consistent, absolute calibration technique for photon number resolving detectors.

    PubMed

    Avella, A; Brida, G; Degiovanni, I P; Genovese, M; Gramegna, M; Lolli, L; Monticone, E; Portesi, C; Rajteri, M; Rastello, M L; Taralli, E; Traina, P; White, M

    2011-11-07

    Well characterized photon number resolving detectors are a requirement for many applications ranging from quantum information and quantum metrology to the foundations of quantum mechanics. This prompts the necessity for reliable calibration techniques at the single photon level. In this paper we propose an innovative absolute calibration technique for photon number resolving detectors, using a pulsed heralded photon source based on parametric down conversion. The technique, being absolute, does not require reference standards and is independent upon the performances of the heralding detector. The method provides the results of quantum efficiency for the heralded detector as a function of detected photon numbers. Furthermore, we prove its validity by performing the calibration of a Transition Edge Sensor based detector, a real photon number resolving detector that has recently demonstrated its effectiveness in various quantum information protocols.

  20. A New Automatic System for Angular Measurement and Calibration in Radiometric Instruments

    PubMed Central

    Marquez, Jose Manuel Andujar; Bohórquez, Miguel Ángel Martínez; Garcia, Jonathan Medina; Nieto, Francisco Jose Aguilar

    2010-01-01

    This paper puts forward the design, construction and testing of a new automatic system for angular-response measurement and calibration in radiometric instruments. Its main characteristics include precision, speed, resolution, noise immunity, easy programming and operation. The developed system calculates the cosine error of the radiometer under test by means of a virtual instrument, from the measures it takes and through a mathematical procedure, thus allowing correcting the radiometer with the aim of preventing cosine error in its measurements. PMID:22319320

  1. A new automatic system for angular measurement and calibration in radiometric instruments.

    PubMed

    Marquez, Jose Manuel Andujar; Bohórquez, Miguel Ángel Martínez; Garcia, Jonathan Medina; Nieto, Francisco Jose Aguilar

    2010-01-01

    This paper puts forward the design, construction and testing of a new automatic system for angular-response measurement and calibration in radiometric instruments. Its main characteristics include precision, speed, resolution, noise immunity, easy programming and operation. The developed system calculates the cosine error of the radiometer under test by means of a virtual instrument, from the measures it takes and through a mathematical procedure, thus allowing correcting the radiometer with the aim of preventing cosine error in its measurements.

  2. Radiometric Calibration of a Dual-Wavelength, Full-Waveform Terrestrial Lidar.

    PubMed

    Li, Zhan; Jupp, David L B; Strahler, Alan H; Schaaf, Crystal B; Howe, Glenn; Hewawasam, Kuravi; Douglas, Ewan S; Chakrabarti, Supriya; Cook, Timothy A; Paynter, Ian; Saenz, Edward J; Schaefer, Michael

    2016-03-02

    Radiometric calibration of the Dual-Wavelength Echidna(®) Lidar (DWEL), a full-waveform terrestrial laser scanner with two simultaneously-pulsing infrared lasers at 1064 nm and 1548 nm, provides accurate dual-wavelength apparent reflectance (ρ(app)), a physically-defined value that is related to the radiative and structural characteristics of scanned targets and independent of range and instrument optics and electronics. The errors of ρ(app) are 8.1% for 1064 nm and 6.4% for 1548 nm. A sensitivity analysis shows that ρ(app) error is dominated by range errors at near ranges, but by lidar intensity errors at far ranges. Our semi-empirical model for radiometric calibration combines a generalized logistic function to explicitly model telescopic effects due to defocusing of return signals at near range with a negative exponential function to model the fall-off of return intensity with range. Accurate values of ρ(app) from the radiometric calibration improve the quantification of vegetation structure, facilitate the comparison and coupling of lidar datasets from different instruments, campaigns or wavelengths and advance the utilization of bi- and multi-spectral information added to 3D scans by novel spectral lidars.

  3. Radiometric Calibration of a Dual-Wavelength, Full-Waveform Terrestrial Lidar

    PubMed Central

    Li, Zhan; Jupp, David L. B.; Strahler, Alan H.; Schaaf, Crystal B.; Howe, Glenn; Hewawasam, Kuravi; Douglas, Ewan S.; Chakrabarti, Supriya; Cook, Timothy A.; Paynter, Ian; Saenz, Edward J.; Schaefer, Michael

    2016-01-01

    Radiometric calibration of the Dual-Wavelength Echidna® Lidar (DWEL), a full-waveform terrestrial laser scanner with two simultaneously-pulsing infrared lasers at 1064 nm and 1548 nm, provides accurate dual-wavelength apparent reflectance (ρapp), a physically-defined value that is related to the radiative and structural characteristics of scanned targets and independent of range and instrument optics and electronics. The errors of ρapp are 8.1% for 1064 nm and 6.4% for 1548 nm. A sensitivity analysis shows that ρapp error is dominated by range errors at near ranges, but by lidar intensity errors at far ranges. Our semi-empirical model for radiometric calibration combines a generalized logistic function to explicitly model telescopic effects due to defocusing of return signals at near range with a negative exponential function to model the fall-off of return intensity with range. Accurate values of ρapp from the radiometric calibration improve the quantification of vegetation structure, facilitate the comparison and coupling of lidar datasets from different instruments, campaigns or wavelengths and advance the utilization of bi- and multi-spectral information added to 3D scans by novel spectral lidars. PMID:26950126

  4. L5 TM radiometric recalibration procedure using the internal calibration trends from the NLAPS trending database

    USGS Publications Warehouse

    Chander, G.; Haque, Md. O.; Micijevic, E.; Barsi, J.A.

    2008-01-01

    From the Landsat program's inception in 1972 to the present, the earth science user community has benefited from a historical record of remotely sensed data. The multispectral data from the Landsat 5 (L5) Thematic Mapper (TM) sensor provide the backbone for this extensive archive. Historically, the radiometric calibration procedure for this imagery used the instrument's response to the Internal Calibrator (IC) on a scene-by-scene basis to determine the gain and offset for each detector. The IC system degraded with time causing radiometric calibration errors up to 20 percent. In May 2003 the National Landsat Archive Production System (NLAPS) was updated to use a gain model rather than the scene acquisition specific IC gains to calibrate TM data processed in the United States. Further modification of the gain model was performed in 2007. L5 TM data that were processed using IC prior to the calibration update do not benefit from the recent calibration revisions. A procedure has been developed to give users the ability to recalibrate their existing Level-1 products. The best recalibration results are obtained if the work order report that was originally included in the standard data product delivery is available. However, many users may not have the original work order report. In such cases, the IC gain look-up table that was generated using the radiometric gain trends recorded in the NLAPS database can be used for recalibration. This paper discusses the procedure to recalibrate L5 TM data when the work order report originally used in processing is not available. A companion paper discusses the generation of the NLAPS IC gain and bias look-up tables required to perform the recalibration.

  5. Radiometric Cross-calibration of KOMPSAT-3A with Landsat-8

    NASA Astrophysics Data System (ADS)

    Shin, D. Y.; Ahn, H. Y.; Lee, S. G.; Choi, C. U.; Kim, J. S.

    2016-06-01

    In this study, Cross calibration was conducted at the Libya 4 PICS site on 2015 using Landsat-8 and KOMPSAT-3A. Ideally a cross calibration should be calculated for each individual scene pair because on any given date the TOA spectral profile is influenced by sun and satellite view geometry and the atmospheric conditions. However, using the near-simultaneous images minimizes this effect because the sensors are viewing the same atmosphere. For the cross calibration, the calibration coefficient was calculated by comparing the at sensor spectral radiance for the same location calculated using the Landsat-8 calibration parameters in metadata and the DN of KOMPSAT-3A for the regions of interest (ROI). Cross calibration can be conducted because the satellite sensors used for overpass have a similar bandwidth. However, not all satellites have the same color filter transmittance and sensor reactivity, even though the purpose is to observe the visible bands. Therefore, the differences in the RSR should be corrected. For the cross-calibration, a calibration coefficient was calculated using the TOA radiance and KOMPSAT-3 DN of the Landsat-8 OLI overpassed at the Libya 4 Site, As a result, the accuracy of the calibration coefficient at the site was assumed to be ± 1.0%. In terms of the results, the radiometric calibration coefficients suggested here are thought to be useful for maintaining the optical quality of the KOMPSAT-3A.

  6. Analysis of aerosol properties derived from sun photometer and lidar over Dunhuang radiometric calibration site

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Jing, Yingying; Zhang, Peng; Hu, Xiuqing

    2016-05-01

    Duhuang site has been selected as China Radiation Calibration Site (CRCS) for Remote Sensing Satellite Sensors since 1996. With the economic development of Dunhuang city, the ambient of the radiation calibration field has changed in recent years. Taking into account the key role of aerosol in radiometric calibration, it is essential to investigate the aerosol optical properties over Dunhuang radiometric calibration site. In this paper, the CIMEL sun photometer (CE-318) and Mie-scattering Lidar are simultaneously used to measure aerosol optical properties in Dunhuang site. Data from aerosol-bands of sun photometer are used in a Langley method to determine spectral optical depths of aerosol. And Lidar is utilized to obtain information of vertical profile and integrated aerosol optical depths at different heights. The results showed that the aerosol optical depth at 500 nm wavelength during the in-situ measurement campaigns varied from 0.1 to 0.3 in Dunhuang site. And the observation results also indicated that high aerosol concentration layer mostly located at the height of about 2~4 km. These results implies that the aerosol concentration of atmosphere in Dunhuang was relatively small and suitable for in-flight calibration for remote sensing satellite sensors.

  7. Update of S-NPP VIIRS thermal emissive bands radiometric calibration stability monitoring using the moon

    NASA Astrophysics Data System (ADS)

    Wang, Zhipeng; Xiong, Xiaoxiong; Li, Yonghong

    2016-10-01

    The Suomi-NPP VIIRS thermal emissive bands (TEB) are radiometrically calibrated on-orbit with reference to a blackbody (BB) regularly operated at approximately 292.5 K. The calibration stability at other temperature ranges can be evaluated based on the observations of remote targets with stable thermal properties, such as the Moon. VIIRS has scheduled viewings of the Moon on a nearly monthly basis at a phase angle of nearly -51 degrees. In this paper, the brightness temperatures (BT) of the lunar surface retrieved using the detector gain coefficients calibrated with the BB are trended to monitor the calibration stability of VIIRS TEB. Since the Lunar surface temperatures are spatially nonuniform and vary greatly with the solar illumination geometry, the BT trending must be based on the same regions of the Moon under the same solar illumination condition. Also, the TEB lunar images are always partially saturated because the highest lunar surface temperatures are beyond the dynamic range of all VIIRS TEB detectors. Therefore, a temporally dynamic mask is designed to clip a fraction of the lunar images corresponding to the regions of the Moon that may saturate the detector at any lunar event. The BT trending is then based on the hottest pixels not clipped by the mask. Results show that, since the launch of VIIRS to mid-2016, the radiometric calibration of all TEB detectors has been stable within +/-0.4 K at the BT range of as high as 350-260 K.

  8. Absolute Calibration of the AXAF Telescope Effective Area

    NASA Technical Reports Server (NTRS)

    Kellogg, E.; Cohen, L.; Edgar, R.; Evans, I.; Freeman, M.; Gaetz, T.; Jerius, D.; McDermott, W. C.; McKinnon, P.; Murray, S.; Podgorski, W.; Schwartz, D.; VanSpeybroeck, L.; Wargelin, B.; Zombeck, M.; Weisskopf, M.; Elsner, R.; ODell, S.; Tennant, A.; Kolodziejczak, J.

    1997-01-01

    The prelaunch calibration of AXAF encompasses many aspects of the telescope. In principle, all that is needed is the complete point response function. This is, however, a function of energy, off-axis angle of the source, and operating mode of the facility. No single measurement would yield the entire result. Also, any calibration made prior to launch will be affected by changes in conditions after launch, such as the change from one g to zero g. The reflectivity of the mirror and perhaps even the detectors can change as well, for example by addition or removal of small amounts of material deposited on their surfaces. In this paper, we give a broad view of the issues in performing such a calibration, and discuss how they are being addressed in prelaunch preparation of AXAF. As our title indicates, we concentrate here on the total throughput of the observatory. This can be thought of as the integral of the point response function, i.e. the encircled energy, out ot the largest practical solid angle for an observation. Since there is no standard x-ray source in the sky whose flux is known to the -1% accuracy we are trying to achieve, we must do this calibration on the ground. we also must provide a means for monitoring any possible changes in this calibration from pre-launch until on-orbit operation can transfer the calibration to a celestial x-ray source whose emission is stable. In this paper, we analyze the elements of the absolute throughput calibration, which we call Effective Area. We review the requirements for calibrations of components or subsystems of the AXAF facility, including mirror, detectors, and gratings. We show how it is necessary to calibrate this ground-based detection system at standard man-made x-ray sources, such as electron storage rings. We present the status of all these calibrations, with indications of the measurements remaining to be done, even though the measurements on the AXAF flight optics and detectors will have been completed by the

  9. Radiometric Calibration of an Airborne CO2 Pulsed Doppler Lidar Using a Natural Earth Surface

    NASA Technical Reports Server (NTRS)

    Cutten, Dean R.; Rothermel, Jeffry; Jarzembski, Maurice A.; Hardesty, R. Michael; Howell, James N.; Tratt, David M.; Srivastava, Vandana; Arnold, James E. (Technical Monitor)

    2001-01-01

    Radiometric calibration of an airborne CO2 pulsed Doppler lidar has been accomplished using surface retro-reflection signals from the White Sands National Monument, New Mexico, USA. Two circular passes were made at altitudes of 6.26 and 9.26 km. The computed calibration factors for both altitudes are in excellent agreement with the value derived from standard ground-based measurements involving a fixed sandpaper target of known reflectance. This finding corroborates a previous study that successfully calibrated an airborne continuous-wave Doppler lidar using a variety of natural Earth surfaces. The present results indicate that relatively uniform Earth-surface targets can be used for in-flight calibration of pulsed airborne, and, in principal, spaceborne lidars.

  10. FPGA-based data processing module design of on-board radiometric calibration in visible/near infrared bands

    NASA Astrophysics Data System (ADS)

    Zhou, Guoqing; Li, Chenyang; Yue, Tao; Liu, Na; Jiang, Linjun; Sun, Yue; Li, Mingyan

    2015-12-01

    FPGA technology has long been applied to on-board radiometric calibration data processing however the integration of FPGA program is not good enough. For example, some sensors compressed remote sensing images and transferred to ground station to calculate the calibration coefficients. It will affect the timeliness of on-board radiometric calibration. This paper designs an integrated flow chart of on-board radiometric calibration. Building FPGA-based radiometric calibration data processing modules uses system generator. Thesis focuses on analyzing the calculation accuracy of FPGA-based two-point method and verifies the feasibility of this method. Calibration data was acquired by hardware platform which was built using integrating sphere, CMOS camera (canon 60d), ASD spectrometers and light filter (center wavelength: 690nm, bandwidth: 45nm). The platform can simulate single-band on-board radiometric calibration data acquisition in visible/near infrared band. Making an experiment of calibration coefficients calculation uses obtained data and FPGA modules. Experimental results show that: the camera linearity is above 99% meeting the experimental requirement. Compares with MATLAB the calculation accuracy of two-point method by FPGA are as follows: the error of gain value is 0.0053%; the error of offset value is 0.00038719%. Those results meet experimental accuracy requirement.

  11. Surface and aerosol models for use in radiative transfer codes. [for radiometric calibration of Landsat-5 Thematic Mapper (TM)

    NASA Technical Reports Server (NTRS)

    Hart, Quinn J.

    1991-01-01

    Absolute reflectance-based radiometric calibrations of Landsat-5 Thematic Mapper (TM) are improved with the inclusion of a method to invert optical-depth measurements to obtain aerosol-particle size distributions, and a non-Lambertian surface reflectance model. The inverted size distributions can predict radiances varying from the previously assumed jungian distributions by as much as 5 percent, though the reduction in the estimated error is less than one percent. Comparison with measured diffuse-to-global ratios show that neither distribution consistently predicts the ratio accurately, and this is shown to be a large contributor to calibration uncertainties. An empirical model for the surface reflectance of White Sands, using a two-degree polynomial fit as a function of scattering angle, was employed. The model reduced estimated errors in radiance predictions by up to one percent. Satellite calibrations dating from October, 1984 were reprocessed using the improved methods and linear estimations of satellite counts per unit radiance versus time since launch were determined which showed a decrease over time for the first four bands.

  12. Absolute calibration in the 1750 - 3350 A region

    NASA Technical Reports Server (NTRS)

    Strongylis, G. J.; Bohlin, R. C.

    1977-01-01

    The absolute flux measurements in the rocket ultraviolet made by Bohlin, Frimout, and Lillie (BFL) are revised using a more correct treatment of the air extinction that enters the air calibration of their instrument. The absorption by molecular oxygen and ozone, Rayleigh scattering, and extinction by aerosols is tabulated for general use in ultraviolet calibrations performed in air. The revised absolute flux of eta UMa and final fluxes for alpha Lyr and zeta Oph are presented in the 1750-3350 A region. The absolute flux of the star eta UMa is compared to four other independent determinations in the 1200-3400 A region and a maximum difference of 35% is found near 1500 A between the OAO-2 and Apollo 17 fluxes. The rocket measurements of BFL, the ANS and TD-1 satellite data, and the Apollo 17 data are compared to the ultraviolet fluxes from the OAO-2, demonstrating a photometric reproducibility of about + or - 3 percent. Therefore, all four sets of spectrophotometry can be reduced to a common absolute scale.

  13. Pre-flight radiometric and spectral calibration of Resourcesat-2A-LISS3* payload

    NASA Astrophysics Data System (ADS)

    Seth, Harish; Detroja, M. P.; Padmanabhan, Deepa; Raj, Vedant; Kumar, Anil; Sarkar, S. S.

    2016-05-01

    Resourcesat-2A is a follow-on mission of Resourcesat-2, belongs to Indian Remote Sensing Program. It is expected to be launched in 2016 and is dedicated mainly to agricultural applications. One of the payloads, LISS3* is a medium resolution (23.5 m) sensor having four multispectral bands from 450 to 1650 nm. These spectral bands are named as B2 (550 nm), B3 (650 nm), B4 (815 nm) and B5 (1625 nm) respectively covering Visible, Near Infrared (NIR) and Short Wave Infrared (SWIR) regions. In order to provide quality data to the user community for long term scientific applications pre-flight ground calibration is carried out. This paper describes pre-flight spectral and radiometric calibration of LISS3* payload and its performance evaluation. Since it is a continuity mission to Resourcesat-2, which was launched in April 2011 so for generating long-term data record and correlation with previous observations, its parameters are compared with Resourcesat-2 LISS3* payload. The main spectral parameters like central wavelength, and pass band is determined using system level spectral response and compared for both the mission and differences are outlined. The next important exercise is pre-flight radiometric calibration, which was carried out in laboratory using a standard integrating sphere traceable to NIST standards. This paper highlights the technique adopted during pre-flight calibration of the radiometric response and performance assessment of all 4 bands of LISS3* in terms of major electro-optical parameters like Signal to Noise Ratio (SNR), Saturation Radiance (SR) etc. The observed SR shows that the sensor can measure spectral radiance from Earth up to 100% albedo.

  14. Radiometric error and re-calibration of the MGS TES spectra

    NASA Astrophysics Data System (ADS)

    Pankine, Alexey A.

    2016-12-01

    Several sources of systematic error were identified in the spectra of the Thermal Emission Spectrometer (TES) onboard the Mars Global Surveyor (MGS) spacecraft during its mission. Some of these errors were corrected, some still remain and contaminate spectra. One of the most significant remaining errors is a time-variable systematic radiometric error. This error significantly affects nighttime and polar spectra, and spectra of the Mars' limb. The existence of this error hampered analysis of roughly half of the data collected by TES spectrometer. The error arises due to a periodic sampling error of TES interferograms, which is a common problem in Fourier-transform interferometers. The error negatively affects calibrated TES spectra in two ways: it introduces an error into estimates of the Instrument Response Functions (IRF) and instrument's radiances that are used to calibrate TES spectra, and it introduces an error into TES spectra themselves. This paper presents a new approach to calibrating TES spectra that enables removing the error from the calibration functions. The new approach utilizes long-term averages of uncalibrated TES spectra of deep space to estimate the true shape of the TES IRF and its dependence on instrument temperature. This, and parameterization of the radiometric error spectral shape, enables removing the error from calibration. Examples of re-calibrated spectra are presented. The largest improvement in the quality of the spectra is observed for nighttime and polar spectra, and spectra of the Mars' limb. Re-calibration would significantly improve retrievals of aerosol abundances and surface temperatures from these spectra.

  15. Updated radiometric calibration for the Landsat-5 thematic mapper reflective bands

    USGS Publications Warehouse

    Helder, D.L.; Markham, B.L.; Thome, K.J.; Barsi, J.A.; Chander, G.; Malla, R.

    2008-01-01

    The Landsat-5 Thematic Mapper (TM) has been the workhorse of the Landsat system. Launched in 1984, it continues collecting data through the time frame of this paper. Thus, it provides an invaluable link to the past history of the land features of the Earth's surface, and it becomes imperative to provide an accurate radiometric calibration of the reflective bands to the user community. Previous calibration has been based on information obtained from prelaunch, the onboard calibrator, vicarious calibration attempts, and cross-calibration with Landsat-7. Currently, additional data sources are available to improve this calibration. Specifically, improvements in vicarious calibration methods and development of the use of pseudoinvariant sites for trending provide two additional independent calibration sources. The use of these additional estimates has resulted in a consistent calibration approach that ties together all of the available calibration data sources. Results from this analysis indicate a simple exponential, or a constant model may be used for all bands throughout the lifetime of Landsat-5 TM. Where previously time constants for the exponential models were approximately one year, the updated model has significantly longer time constants in bands 1-3. In contrast, bands 4, 5, and 7 are shown to be best modeled by a constant. The models proposed in this paper indicate calibration knowledge of 5% or better early in life, decreasing to nearly 2% later in life. These models have been implemented at the U.S. Geological Survey Earth Resources Observation and Science (EROS) and are the default calibration used for all Landsat TM data now distributed through EROS. ?? 2008 IEEE.

  16. Novel Hyperspectral Sun Photometer for Satellite Remote Sensing Data Radiometric Calibration and Atmospheric Aerosol Studies

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Ryan, Robert E.; Holekamp, Kara; Harrington, Gary; Frisbie, Troy

    2006-01-01

    A simple and cost-effective, hyperspectral sun photometer for radiometric vicarious remote sensing system calibration, air quality monitoring, and potentially in-situ planetary climatological studies, was developed. The device was constructed solely from off the shelf components and was designed to be easily deployable for support of short-term verification and validation data collects. This sun photometer not only provides the same data products as existing multi-band sun photometers, this device requires a simpler setup, less data acquisition time and allows for a more direct calibration approach. Fielding this instrument has also enabled Stennis Space Center (SSC) Applied Sciences Directorate personnel to cross calibrate existing sun photometers. This innovative research will position SSC personnel to perform air quality assessments in support of the NASA Applied Sciences Program's National Applications program element as well as to develop techniques to evaluate aerosols in a Martian or other planetary atmosphere.

  17. Radiometric calibration of ocean color satellite sensors using AERONET-OC data.

    PubMed

    Hlaing, Soe; Gilerson, Alexander; Foster, Robert; Wang, Menghua; Arnone, Robert; Ahmed, Sam

    2014-09-22

    Radiometric vicarious calibration of ocean color (OC) satellite sensors is carried out through the full sunlight path radiative transfer (RT) simulations of the coupled ocean-atmosphere system based on the aerosol and water-leaving radiance data from AERONET-OC sites for the visible and near-infrared (NIR) bands. Quantitative evaluation of the potential of such approach for achieving the radiometric accuracies of OC satellite sensors is made by means of direct comparisons between simulated and satellite measured top of atmosphere (TOA) radiances. Very high correlations (R ≥ 0.96 for all visible channels) are achieved for the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor when this approach is applied with the data from the LISCO and WaveCIS AERONET-OC sites. Vicarious calibration gain factors derived with this approach are highly consistent, with comparisons between the two sites exhibiting around 0.5% discrepancy in the blue and green parts of the spectrum, while their average temporal variability is also within 0.28% - 1.23% permitting the approach to be used, at this stage, for verification of sensor calibration performance.

  18. The moon as a radiometric reference source for on-orbit sensor stability calibration

    USGS Publications Warehouse

    Stone, T.C.

    2009-01-01

    The wealth of data generated by the world's Earth-observing satellites, now spanning decades, allows the construction of long-term climate records. A key consideration for detecting climate trends is precise quantification of temporal changes in sensor calibration on-orbit. For radiometer instruments in the solar reflectance wavelength range (near-UV to shortwave-IR), the Moon can be viewed as a solar diffuser with exceptional stability properties. A model for the lunar spectral irradiance that predicts the geometric variations in the Moon's brightness with ???1% precision has been developed at the U.S. Geological Survey in Flagstaff, AZ. Lunar model results corresponding to a series of Moon observations taken by an instrument can be used to stabilize sensor calibration with sub-percent per year precision, as demonstrated by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The inherent stability of the Moon and the operational model to utilize the lunar irradiance quantity provide the Moon as a reference source for monitoring radiometric calibration in orbit. This represents an important capability for detecting terrestrial climate change from space-based radiometric measurements.

  19. Extreme Ultraviolet Variability Experiment (EVE) Multiple EUV Grating Spectrographs (MEGS): Radiometric Calibrations and Results

    NASA Astrophysics Data System (ADS)

    Hock, R. A.; Chamberlin, P. C.; Woods, T. N.; Crotser, D.; Eparvier, F. G.; Woodraska, D. L.; Woods, E. C.

    2012-01-01

    The NASA Solar Dynamics Observatory (SDO), scheduled for launch in early 2010, incorporates a suite of instruments including the Extreme Ultraviolet Variability Experiment (EVE). EVE has multiple instruments including the Multiple Extreme ultraviolet Grating Spectrographs (MEGS) A, B, and P instruments, the Solar Aspect Monitor (SAM), and the Extreme ultraviolet SpectroPhotometer (ESP). The radiometric calibration of EVE, necessary to convert the instrument counts to physical units, was performed at the National Institute of Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF III) located in Gaithersburg, Maryland. This paper presents the results and derived accuracy of this radiometric calibration for the MEGS A, B, P, and SAM instruments, while the calibration of the ESP instrument is addressed by Didkovsky et al. ( Solar Phys., 2010, doi:10.1007/s11207-009-9485-8). In addition, solar measurements that were taken on 14 April 2008, during the NASA 36.240 sounding-rocket flight, are shown for the prototype EVE instruments.

  20. Absolute calibration for complex-geometry biomedical diffuse optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Mastanduno, Michael A.; Jiang, Shudong; El-Ghussein, Fadi; diFlorio-Alexander, Roberta; Pogue, Brian W.; Paulsen, Keith D.

    2013-03-01

    We have presented methodology to calibrate data in NIRS/MRI imaging versus an absolute reference phantom and results in both phantoms and healthy volunteers. This method directly calibrates data to a diffusion-based model, takes advantage of patient specific geometry from MRI prior information, and generates an initial guess without the need for a large data set. This method of calibration allows for more accurate quantification of total hemoglobin, oxygen saturation, water content, scattering, and lipid concentration as compared with other, slope-based methods. We found the main source of error in the method to be derived from incorrect assignment of reference phantom optical properties rather than initial guess in reconstruction. We also present examples of phantom and breast images from a combined frequency domain and continuous wave MRI-coupled NIRS system. We were able to recover phantom data within 10% of expected contrast and within 10% of the actual value using this method and compare these results with slope-based calibration methods. Finally, we were able to use this technique to calibrate and reconstruct images from healthy volunteers. Representative images are shown and discussion is provided for comparison with existing literature. These methods work towards fully combining the synergistic attributes of MRI and NIRS for in-vivo imaging of breast cancer. Complete software and hardware integration in dual modality instruments is especially important due to the complexity of the technology and success will contribute to complex anatomical and molecular prognostic information that can be readily obtained in clinical use.

  1. Calibration method of absolute orientation of camera optical axis

    NASA Astrophysics Data System (ADS)

    Xu, Yong; Guo, Pengyu; Zhang, Xiaohu; Ding, Shaowen; Su, Ang; Li, Lichun

    2013-08-01

    Camera calibration is one of the most basic and important processes in optical measuring field. Generally, the objective of camera calibration is to estimate the internal and external parameters of object cameras, while the orientation error of optical axis is not included yet. Orientation error of optical axis is a important factor, which seriously affects measuring precision in high-precision measurement field, especially for those distant aerospace measurement in which object distance is much longer than focal length, that lead to magnifying the orientation errors to thousands times. In order to eliminate the influence of orientation error of camera optical axis, the imaging model of camera is analysed and established in this paper, and the calibration method is also introduced: Firstly, we analyse the reasons that cause optical axis error and its influence. Then, we find the model of optical axis orientation error and imaging model of camera basing on it's practical physical meaning. Furthermore, we derive the bundle adjustment algorithm which could compute the internal and external camera parameters and absolute orientation of camera optical axis simultaneously at high precision. In numeric simulation, we solve the camera parameters by using bundle adjustment optimization algorithm, then we correct the image points by calibration results according to the model of optical axis error, and the simulation result shows that our calibration model is reliable, effective and precise.

  2. Calibrating Late Quaternary terrestrial climate signals: radiometrically dated pollen evidence from the southern Sierra Nevada, USA

    USGS Publications Warehouse

    Litwin, Ronald J.; Smoot, Joseph P.; Durika, Nancy J.; Smith, George I.

    1999-01-01

    We constructed a radiometrically calibrated proxy record of Late Pleistocene and Holocene climate change exceeding 230,000 yr duration, using pollen profiles from two cores taken through age-equivalent dry lakes - one core having greater age control (via 230Th alpha mass-spectrometry) and the other having greater stratigraphic completeness. The better dated of these two serial pollen records (Searles Lake) served as a reference section for improving the effective radiometric age control in a nearby and more complete pollen record (Owens Lake) because they: (1) are situated ~90 km apart in the same drainage system (on, and immediately leeward of, the eastern flank of the Sierra Nevada), and (2) preserved strikingly similar pollen profiles and concordant sequences of sedimentological changes. Pollen assemblages from both lakes are well preserved and diverse, and document serial changes in Late Pleistocene and Holocene plant zone distribution and composition in the westernmost Great Basin; they consist of taxa now inhabiting montane forest, woodland, steppe, and desert-scrub environments. The studied core intervals are interpreted here to be the terrestrial equivalent of marine δ18O stages 1 through 9; these pollen profiles now appear to be among the best radiometrically dated Late Pleistocene records of terrestrial climate change known.

  3. Absolute calibration of vacuum ultraviolet spectrograph system for plasma diagnostics

    SciTech Connect

    Yoshikawa, M.; Kubota, Y.; Kobayashi, T.; Saito, M.; Numada, N.; Nakashima, Y.; Cho, T.; Koguchi, H.; Yagi, Y.; Yamaguchi, N.

    2004-10-01

    A space- and time-resolving vacuum ultraviolet (VUV) spectrograph system has been applied to diagnose impurity ions behavior in plasmas produced in the tandem mirror GAMMA 10 and the reversed field pinch TPE-RX. We have carried out ray tracing calculations for obtaining the characteristics of the VUV spectrograph and calibration experiments to measure the absolute sensitivities of the VUV spectrograph system for the wavelength range from 100 to 1100 A. By changing the incident angle, 50.6 deg. -51.4 deg., to the spectrograph whose nominal incident angle is 51 deg., we can change the observing spectral range of the VUV spectrograph. In this article, we show the ray tracing calculation results and absolute sensitivities when the angle of incidence into the VUV spectrograph is changed, and the results of VUV spectroscopic measurement in both GAMMA 10 and TPE-RX plasmas.

  4. Absolute magnitude calibration using trigonometric parallax - Incomplete, spectroscopic samples

    NASA Technical Reports Server (NTRS)

    Ratnatunga, Kavan U.; Casertano, Stefano

    1991-01-01

    A new numerical algorithm is used to calibrate the absolute magnitude of spectroscopically selected stars from their observed trigonometric parallax. This procedure, based on maximum-likelihood estimation, can retrieve unbiased estimates of the intrinsic absolute magnitude and its dispersion even from incomplete samples suffering from selection biases in apparent magnitude and color. It can also make full use of low accuracy and negative parallaxes and incorporate censorship on reported parallax values. Accurate error estimates are derived for each of the fitted parameters. The algorithm allows an a posteriori check of whether the fitted model gives a good representation of the observations. The procedure is described in general and applied to both real and simulated data.

  5. A Traceable Ground to On-Orbit Radiometric Calibration System for the Solar Reflective Wavelength Region

    NASA Technical Reports Server (NTRS)

    Heath, Donald F.; Georgiev, Georgi

    2012-01-01

    This paper describes the combination of a Mie scattering spectral BSDF and BTDF albedo standard whose calibration is traceable to the NIST SIRCUS Facility or the NIST STARR II Facility. The Space-based Calibration Transfer Spectroradiometer (SCATS) sensor uses a simple, invariant optical configuration and dedicated narrow band spectral channel modules to provide very accurate, polarization-insensitive, stable measurements of earth albedo and lunar disk albedo. Optical degradation effects on calibration stability are eliminated through use of a common optical system for observations of the Sun, Earth, and Moon. The measurements from space would be traceable to SI units through preflight calibrations of radiance and irradiance at NIST's SIRCUS facility and the invariant optical system used in the sensor. Simultaneous measurements are made in multiple spectral channels covering the solar reflective wavelength range of 300 nm to 2.4 microns. The large dynamic range of signals is handled by use of single-element, highly-linear detectors, stable discrete electronic components, and a non imaging optical configuration. Up to 19 spectral modules can be mounted on a single-axis drive to give direct pointing at the Earth and at least once per orbit view of the Sun and Moon. By observing the Sun on every orbit, the most stringent stability requirements of the system are limited to short time periods. The invariant optical system for both radiance and irradiance measurements also give excellent transfer to-orbit SI traceability. Emerging instrumental requirements for remotely sensing tropospheric trace species have led to a rethinking by some of the paradigm for Systeme International d'Unites (SI) traceability of the spectral irradiance and radiance radiometric calibrations to spectral albedo (sr(exp -1)) which is not a SI unit. In the solar reflective wavelength region the spectral albedo calibrations are tied often to either the spectral albedo of a solar diffuser or the Moon

  6. An Empirical Approach to Ocean Color Data: Reducing Bias and the Need for Post-Launch Radiometric Re-Calibration

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Casey, Nancy W.; O'Reilly, John E.; Esaias, Wayne E.

    2009-01-01

    A new empirical approach is developed for ocean color remote sensing. Called the Empirical Satellite Radiance-In situ Data (ESRID) algorithm, the approach uses relationships between satellite water-leaving radiances and in situ data after full processing, i.e., at Level-3, to improve estimates of surface variables while relaxing requirements on post-launch radiometric re-calibration. The approach is evaluated using SeaWiFS chlorophyll, which is the longest time series of the most widely used ocean color geophysical product. The results suggest that ESRID 1) drastically reduces the bias of ocean chlorophyll, most impressively in coastal regions, 2) modestly improves the uncertainty, and 3) reduces the sensitivity of global annual median chlorophyll to changes in radiometric re-calibration. Simulated calibration errors of 1% or less produce small changes in global median chlorophyll (less than 2.7%). In contrast, the standard NASA algorithm set is highly sensitive to radiometric calibration: similar 1% calibration errors produce changes in global median chlorophyll up to nearly 25%. We show that 0.1% radiometric calibration error (about 1% in water-leaving radiance) is needed to prevent radiometric calibration errors from changing global annual median chlorophyll more than the maximum interannual variability observed in the SeaWiFS 9-year record (+/- 3%), using the standard method. This is much more stringent than the goal for SeaWiFS of 5% uncertainty for water leaving radiance. The results suggest ocean color programs might consider less emphasis of expensive efforts to improve post-launch radiometric re-calibration in favor of increased efforts to characterize in situ observations of ocean surface geophysical products. Although the results here are focused on chlorophyll, in principle the approach described by ESRID can be applied to any surface variable potentially observable by visible remote sensing.

  7. Prime candidate earth targets for the post-launch radiometric calibration of space-based optical imaging instruments

    USGS Publications Warehouse

    Teillet, P.M.; Barsi, J.A.; Chander, G.; Thome, K.J.

    2007-01-01

    This paper provides a comprehensive list of prime candidate terrestrial targets for consideration as benchmark sites for the post-launch radiometric calibration of space-based instruments. The key characteristics of suitable sites are outlined primarily with respect to selection criteria, spatial uniformity, and temporal stability. The establishment and utilization of such benchmark sites is considered an important element of the radiometric traceability of satellite image data products for use in the accurate monitoring of environmental change.

  8. Absolute calibration of the EnviSat-1 radar altimeter

    NASA Astrophysics Data System (ADS)

    Roca, Monica; Francis, Richard

    1998-12-01

    The EnviSat-1 satellite will embark an innovative radar altimeter. The calibration of the measurements of range from this instrument will be performed using novel techniques. The range measurement will be calibrated absolutely by establishing the actual geocentric sea-level along the sub- satellite tracks. These tracks are located in a limited and well-controlled region in the western Mediterranean and will include a number of fully-equipped individual sites which will provide higher confidence in the overall analysis, combined with data from the whole area at lower weight. The determination of the geocentric sea-level is performed using tide gauges and geodetic means such as leveling and floating GPS receivers. The altimeter sea-level is derived from the altimeter range corrected for propagation effects and sea- state bias, and a precise restitution of the trajectory of the satellite. These measurements comprise three vectors: range, orbital height and sea-surface height. The difference between orbital-height minus range, and sea-surface height provides the bias. The backscatter coefficient measured by previous altimeters has not been absolutely calibrated. An emerging application of the RA-2 in investigation of surface properties has identified the need to perform this calibration. A number of techniques are under study to determine the feasibility of meeting this need, including the use of well-controlled natural targets, the use of the altimeter receiver as a passive radiometer in order to determine its gain and the use of a transponder to return a precisely known return echo power to the radar.

  9. Monochromator-Based Absolute Calibration of a Standard Radiation Thermometer

    NASA Astrophysics Data System (ADS)

    Mantilla, J. M.; Hernanz, M. L.; Campos, J.; Martín, M. J.; Pons, A.; del Campo, D.

    2014-04-01

    Centro Español de Metrología (CEM) is disseminating the International Temperature Scale (ITS-90), at high temperatures, by using the fixed points of Ag and Cu and a standard radiation thermometer. However, the future mise-en-pratique for the definition of the kelvin ( MeP-K) will include the dissemination of the kelvin by primary methods and by indirect approximations capable of exceptionally low uncertainties or increased reliability. Primary radiometry is, at present, able to achieve uncertainties competitive with the ITS-90 above the silver point with one of the possible techniques the calibration for radiance responsivity of an imaging radiometer (radiance method). In order to carry out this calibration, IO-CSIC (Spanish Designated Institute for luminous intensity and luminous flux) has collaborated with CEM, allowing traceability to its cryogenic radiometer. A monochromator integrating sphere-based spectral comparator facility has been used to calibrate one of the CEM standard radiation thermometers. The absolute calibrated standard radiation thermometer has been used to determine the temperatures of the fixed points of Cu, Co-C, Pt-C, and Re-C. The results obtained are 1357.80 K, 1597.10 K, 2011.66 K, and 2747.64 K, respectively, with uncertainties ranging from 0.4 K to 1.1 K.

  10. Research on radiometric calibration of interline transfer CCD camera based on TDI working mode

    NASA Astrophysics Data System (ADS)

    Wu, Xing-xing; Liu, Jin-guo

    2010-10-01

    Interline transfer CCD camera can be designed to work in time delay and integration mode similar to TDI CCD to obtain higher responsivity and spatial resolution under poor illumination condition. However it was found that outputs of some pixels were much lower than others' as interline transfer CCD camera work in TDI mode in laboratory radiometric calibration experiments. As a result photo response non-uniformity(PRNU) and signal noise ratio(SNR) of the system turned for the worse. This phenomenon's mechanism was analyzed and improved PRNU and SNR algorithms of interline transfer CCD camera were advanced to solve this problem. In this way TDI stage was used as a variant in PRNU and SNR algorithms and system performance was improved observably with few influences on use. In validation experiments the improved algorithms was applied in radiometric calibration of a camera with KAI-0340s as detector. Results of validation experiments proved that the improved algorithms could effectively improve SNR and lower PRNU of the system. At the same time characteristic of the system could be reflected better. As working in 16 TDI stages, PRUN was reduced from 2.25% to 0.82% and SNR was improved about 2%.

  11. Error Budget for a Calibration Demonstration System for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2013-01-01

    A goal of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission is to observe highaccuracy, long-term climate change trends over decadal time scales. The key to such a goal is to improving the accuracy of SI traceable absolute calibration across infrared and reflected solar wavelengths allowing climate change to be separated from the limit of natural variability. The advances required to reach on-orbit absolute accuracy to allow climate change observations to survive data gaps exist at NIST in the laboratory, but still need demonstration that the advances can move successfully from to NASA and/or instrument vendor capabilities for spaceborne instruments. The current work describes the radiometric calibration error budget for the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. The goal of the CDS is to allow the testing and evaluation of calibration approaches, alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The resulting SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climatequality data collections is given. Key components in the error budget are geometry differences between the solar and earth views, knowledge of attenuator behavior when viewing the sun, and sensor behavior such as detector linearity and noise behavior. Methods for demonstrating this error budget are also presented.

  12. In-flight radiometric calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

    NASA Technical Reports Server (NTRS)

    Conel, James E.; Green, Robert O.; Alley, Ronald E.; Bruegge, Carol J.; Carrere, Veronique; Margolis, Jack S.; Vane, Gregg; Chrien, Thomas G.; Slater, Philip N.; Biggard, Stuart F.

    1988-01-01

    A reflectance-based method was used to provide an analysis of the in-flight radiometric performance of AVIRIS. Field spectral reflectance measurements of the surface and extinction measurements of the atmosphere using solar radiation were used as input to atmospheric radiative transfer calculations. Five separate codes were used in the analysis. Four include multiple scattering, and the computed radiances from these for flight conditions were in good agreement. Code-generated radiances were compared with AVIRIS-predicted radiances based on two laboratory calibrations (pre- and post-season of flight) for a uniform highly reflecting natural dry lake target. For one spectrometer (C), the pre- and post-season calibration factors were found to give identical results, and to be in agreement with the atmospheric models that include multiple scattering. This positive result validates the field and laboratory calibration technique. Results for the other spectrometers (A, B and D) were widely at variance with the models no matter which calibration factors were used. Potential causes of these discrepancies are discussed.

  13. Mapping of local-scale flooding on vegetated floodplains from radiometrically calibrated airborne laser scanning data

    NASA Astrophysics Data System (ADS)

    Malinowski, Radosław; Höfle, Bernhard; König, Kristina; Groom, Geoffrey; Schwanghart, Wolfgang; Heckrath, Goswin

    2014-05-01

    The agricultural use of riverine lowlands is often dependent on complex hydrological regimes including localized flooding. Knowledge about spatio-temporal inundation patterns enables a better understanding of the state of agricultural areas in lowlands and provides valuable and objective information on land suitability for land use administration and environmental planning. Data from Airborne Laser Scanning (ALS), also referred to as LiDAR, have become one of the most important sources of elevation data during the last two decades. Recently, geometric and radiometric attributes of ALS have also been explored for analysing the extent of water surfaces. Thus, the main objective of this work is to develop a method for mapping the spatial extent of floodplain inundation by means of remote sensing data. Our study focusses on analysing floodwaters partly covered by some vegetation, which is a major challenge in flood mapping. We hypothesize that ALS data due to its high sampling density and high rate of canopy penetration can effectively be used for floodwater detection in such areas. This research utilizes full-waveform ALS data with an average point density of 20 points/m2 obtained for an area of ca. 8 km2 of the Nørreå River valley in Jutland, Denmark. The study area is characterised by the presence of improved or semi-improved grasslands (meadows and pasture), few arable fields, irregularly scattered group of trees and bushes, and an extensive ditch network. Our approach is based on an inspection of properties of single laser points with regard to water vs. vegetation coverage within the laser footprint, which is compared with very detailed field reference data. Exploratory analysis and classification of ALS data were preceded by radiometric calibration of point cloud data, utilizing in situ measurements of reference targets reflectance. The resulting calibration derivatives provide very stable estimates of surface characteristics and are used as the main input in

  14. Absolute calibration of Apollo lunar orbital mass spectrometer.

    NASA Technical Reports Server (NTRS)

    Yeager, P. R.; Smith, A.; Jackson, J. J.; Hoffman, J. H.

    1973-01-01

    Recent experiments were conducted in Langley Research Center's molecular beam system to perform an absolute calibration of the lunar orbital mass spectrometer which was flown on the Apollo 15 and 16 missions. Tests were performed with several models of the instrument using two test gases, argon and neon, in the 1 ntorr to .1 picotorr range. Sensitivity to argon at spacecraft orbital velocity was .00028 A/torr enabling partial pressures in the .01-picotorr range to be measured at the spacecraft altitude. Neon sensitivity was nearly a factor of 5 less. Test data support the feasibility of using the lunar orbital mass spectrometer as a tool to gather information about the lunar atmosphere.

  15. Initial On-Orbit Radiometric Calibration of the Suomi NPP VIIRS Reflective Solar Bands

    NASA Technical Reports Server (NTRS)

    Lei, Ning; Wang, Zhipeng; Fulbright, Jon; Lee, Shihyan; McIntire, Jeff; Chiang, Vincent; Xiong, Jack

    2012-01-01

    The on-orbit radiometric response calibration of the VISible/Near InfraRed (VISNIR) and the Short-Wave InfraRed (SWIR) bands of the Visible/Infrared Imager/Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (NPP) satellite is carried out through a Solar Diffuser (SD). The transmittance of the SD screen and the SD's Bidirectional Reflectance Distribution Function (BRDF) are measured before launch and tabulated, allowing the VIIRS sensor aperture spectral radiance to be accurately determined. The radiometric response of a detector is described by a quadratic polynomial of the detector?s digital number (dn). The coefficients were determined before launch. Once on orbit, the coefficients are assumed to change by a common factor: the F-factor. The radiance scattered from the SD allows the determination of the F-factor. In this Proceeding, we describe the methodology and the associated algorithms in the determination of the F-factors and discuss the results.

  16. Revised Radiometric Calibration Technique for LANDSAT-4 Thematic Mapper Data by the Canada Centre for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Murphy, J.; Butlin, T.; Duff, P.; Fitzgerald, A.

    1984-01-01

    A technique for the radiometric correction of LANDSAT-4 Thematic Mapper data was proposed by the Canada Center for Remote Sensing. Subsequent detailed observations of raw image data, raw radiometric calibration data and background measurements extracted from the raw data stream on High Density Tape highlighted major shortcomings in the proposed method which if left uncorrected, can cause severe radiometric striping in the output product. Results are presented which correlate measurements of the DC background with variations in both image data background and calibration samples. The effect on both raw data and on data corrected using the earlier proposed technique is explained, and the correction required for these factors as a function of individual scan line number for each detector is described. It is shown how the revised technique can be incorporated into an operational environment.

  17. Radiometric Calibration and Stability of the Landsat-8 Operational Land Imager (OLI)

    NASA Technical Reports Server (NTRS)

    Markham, Brian L.; Barsi, Julia A.; Kaita, Edward; Ong, Lawrence; Morfitt, Ron; Haque, Md Obaidul

    2015-01-01

    Landsat-8 and its two Earth imaging sensors, the Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) have been operating on-orbit for 2 1/2 years. The OLI radiometric calibration, which is monitored using on-board lamps, on-board solar diffusers, the moon and vicarious calibration techniques has been stable to within 1% over this period of time. The Coastal Aerosol band, band 1, shows the largest change at about 1% over the period; all other bands have shown no significant trend. OLI bands 1- 4 show small discontinuities in response (+0.1% to 0.2%) beginning about 7 months after launch and continuing for about 1 month associated with a power cycling of the instrument, though the origin of the recovery is unclear. To date these small changes have not been compensated for, but this will change with a reprocessing campaign that is currently scheduled for Fall 2015. The calibration parameter files (each typically covering a 3 month period) will be updated for these observed gain changes. A fitted response to an adjusted average of the lamps, solar and lunar results will represent the trend, sampled at the rate of one value per CPF.

  18. Landsat 8 OLI radiometric calibration performance after three years (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Morfitt, Ron A.

    2016-09-01

    The Landsat 8 Operational Land Imager (OLI) impressed science users soon after launch in early 2013 with both its radiometric and geometric performance. After three years on-orbit, OLI continues to exceed expectations with its high signal-to-noise ratio, low striping, and stable response. The few artifacts that do exist, such as ghosting, continue to be minimal and show no signs of increasing. The on-board calibration sources showed a small decrease in response during the first six months of operations in the coastal aerosol band, but that decrease has stabilized to less than a half percent per year since that time. The other eight bands exhibit very little change over the past three years and have remained well within a half percent of their initial response to all on-board calibration sources. Analysis of lunar acquisitions also agree with the on-board calibrators. Overall, the OLI on-board the Landsat 8 spacecraft continues to provide exceptional measurements of the Earth's surface to continue the long tradition of Landsat.

  19. Soil mapping in northern Thailand based on an radiometrically calibrated Maximum likelihood approach

    NASA Astrophysics Data System (ADS)

    Schuler, U.; Herrmann, L.; Rangnugpit, W.; Stahr, K.

    2009-04-01

    The highlands of northern Thailand are dominated by the soil reference groups Acrisols and Alisols. The occurrence of these depends mainly on petrography and local climate gradients. The probabilistic Maximum likelihood method locally proved the potential to predict these reference soil groups. However, the available soil information is mostly nested around research stations with vast blank areas in between. Therefore more training data are required. The collection of further soil information is costly and time consuming as the access is often difficult and the determination of the reference soil groups is based on clay content, cation exchange capacity and the organic matter content, which can hardly be determined in the field. Groundbased radiometric data have shown the potential to distinguish Acrisols and Alisols. Therefore, airborne radiometric data, which are available for whole Thailand, might have the potential for regional distinction of those. The airborne data were collected in 1984-89. The sensor was mounted on an airplane flying at approximately 120m altitude, with a distance between the flight lines of approximately 1km and measurements in the flight line of approximately 50m. After orthographic correction a low pass filter (Savitzky Golay) was used for smoothing the data. Corrected output data (grey values) were calibrated and thus transferred to concentration values (K %; Th ppm, U ppm). The standard procedure for interpolation between the flight lines was bidirectional latticing (spline). After interpolation, the data can be presented as a 2D map either as single channel, binary, or ternary presentation. Initial comparisons between the petrography in the field and those ternary maps showed a potential for further subdivision of the existing geological maps. However, smoothing and data interpolation caused numerous artefacts. Therefore it is intended to focus on the primary measuring points. At least, ground measurements of gamma-ray in a limestone

  20. Absolute Calibration of Optical Satellite Sensors Using Libya 4 Pseudo Invariant Calibration Site

    NASA Technical Reports Server (NTRS)

    Mishra, Nischal; Helder, Dennis; Angal, Amit; Choi, Jason; Xiong, Xiaoxiong

    2014-01-01

    The objective of this paper is to report the improvements in an empirical absolute calibration model developed at South Dakota State University using Libya 4 (+28.55 deg, +23.39 deg) pseudo invariant calibration site (PICS). The approach was based on use of the Terra MODIS as the radiometer to develop an absolute calibration model for the spectral channels covered by this instrument from visible to shortwave infrared. Earth Observing One (EO-1) Hyperion, with a spectral resolution of 10 nm, was used to extend the model to cover visible and near-infrared regions. A simple Bidirectional Reflectance Distribution function (BRDF) model was generated using Terra Moderate Resolution Imaging Spectroradiometer (MODIS) observations over Libya 4 and the resulting model was validated with nadir data acquired from satellite sensors such as Aqua MODIS and Landsat 7 (L7) Enhanced Thematic Mapper (ETM+). The improvements in the absolute calibration model to account for the BRDF due to off-nadir measurements and annual variations in the atmosphere are summarized. BRDF models due to off-nadir viewing angles have been derived using the measurements from EO-1 Hyperion. In addition to L7 ETM+, measurements from other sensors such as Aqua MODIS, UK-2 Disaster Monitoring Constellation (DMC), ENVISAT Medium Resolution Imaging Spectrometer (MERIS) and Operational Land Imager (OLI) onboard Landsat 8 (L8), which was launched in February 2013, were employed to validate the model. These satellite sensors differ in terms of the width of their spectral bandpasses, overpass time, off-nadir-viewing capabilities, spatial resolution and temporal revisit time, etc. The results demonstrate that the proposed empirical calibration model has accuracy of the order of 3% with an uncertainty of about 2% for the sensors used in the study.

  1. On-orbit radiometric validation and field-of-view calibration of spaceborne microwave sounding instruments

    NASA Astrophysics Data System (ADS)

    Blackwell, William J.; Bickmeier, Laura J.; Jairam, Laura G.; Leslie, R. Vincent

    2008-12-01

    Two calibration/validation efforts planned for current and future spaceborne microwave sounding instruments will be presented. First, the NPOESS Aircraft Sounder Testbed-Microwave (NAST-M) airborne sensor is used to directly validate the microwave radiometers (AMSU and MHS) on several operational satellites. Comparison results for underflights of the Aqua, NOAA, and MetOp-A satellites will be shown. Second, a potential approach will be presented for on-orbit field-of-view (FOV) calibration of the Advanced Technology Microwave Sounder (ATMS). A variety of proposed spacecraft maneuvers that could facilitate the characterization of the radiometric boresight of all 22 ATMS channels will be discussed. Radiance observations from the NAST-M airborne sensor can be used to directly validate the radiometric performance of spaceborne sensors. NAST-M includes a total of four spectrometers, with three operating near the oxygen lines at 50-57, 118.75, and 424.76 GHz, and a fourth spectrometer centered on the water vapor absorption line at 183.31 GHz. All four feedhorns are co-located, have 3-dB (full-width at half-maximum) beamwidths of 7.5° (translating to 2.5-km nominal pixel diameter at nadir incidence), and are directed at a single mirror that scans cross-track beneath the aircraft with a nominal swath width of 100 km. We will present results for two recent validation efforts: 1) the Pacific THORpex (THe Observing-system Research and predictability experiment) Observing System Test (PTOST 2003, Honolulu, HI) and 2) the Joint Airborne IASI Validation Experiment (JAIVEx 2007, Houston, TX). Radiance differences between the NAST-M sensor and the Advanced Microwave Sounding Unit (AMSU) and the Microwave Humidity Sensor (MHS) were found to be less than 1K for most channels. Comparison results for ocean underflights of the Aqua, NOAA, and MetOp-A satellites are shown. We also present an approach for on-orbit FOV calibration of the ATMS satellite instrument using vicarious

  2. Documentation for the machine-readable version of the Absolute Calibration of Stellar Spectrophotometry

    NASA Technical Reports Server (NTRS)

    Warren, W. H., Jr.

    1982-01-01

    The machine-readable data file of The Absolute Calibration of Stellar Spectrophotometry as distributed by the Astronomical Data Center is described. The data file contains the absolute fluxes for 16 stars published in Tables 1 and 2 of Johnson (1980). The absolute calibrations were accomplished by combining the 13-color photometry calibrations of Johnson and Mitchell (1975) with spectra obtained with a Michelson spectrophotometer and covering the wavelength range 4000 to 10300 A (Johnson 1977). The agreement between this absolute calibration and another recent one based upon data for a Lyr and 109 Vir by Tug, White and Lockwood (1977) is shown by Johnson (1980) to be quite good.

  3. Absolute ages from crater statistics: Using radiometric ages of Martian samples for determining the Martian cratering chronology

    NASA Technical Reports Server (NTRS)

    Neukum, G.

    1988-01-01

    In the absence of dates derived from rock samples, impact crater frequencies are commonly used to date Martian surface units. All models for absolute dating rely on the lunar cratering chronology and on the validity of its extrapolation to Martian conditions. Starting from somewhat different lunar chronologies, rather different Martian cratering chronologies are found in the literature. Currently favored models are compared. The differences at old ages are significant, the differences at younger ages are considerable and give absolute ages for the same crater frequencies as different as a factor of 3. The total uncertainty could be much higher, though, since the ratio of lunar to Martian cratering rate which is of basic importance in the models is believed to be known no better than within a factor of 2. Thus, it is of crucial importance for understanding the the evolution of Mars and determining the sequence of events to establish an unambiguous Martian cratering chronology from crater statistics in combination with clean radiometric ages of returned Martian samples. For the dating goal, rocks should be as pristine as possible from a geologically simple area with a one-stage emplacement history of the local formation. A minimum of at least one highland site for old ages, two intermediate-aged sites, and one very young site is needed.

  4. Atmospheric measurement analysis for the Radiometric Calibration Test Site (RadCaTS)

    NASA Astrophysics Data System (ADS)

    Czapla-Myers, Jeffrey

    2015-09-01

    The Radiometric Calibration Test Site (RadCaTS) was developed by the University of Arizona in the early 2000s to collect ground-based data in support of the calibration and validation of Earth-observing sensors. It uses the reflectance-based approach, which requires measurements of the atmosphere and surface reflectance. The measurements are used in MODTRAN to determine the at-sensor radiance for a given time and date. In the traditional reflectance-based approach, on-site personnel use an automated solar radiometer (ASR) to measure the atmospheric attenuation, but in the case of RadCaTS, an AERONET Cimel sun photometer is used to make atmospheric measurements. This work presents a comparison between the Cimel-derived atmospheric characteristics such as aerosol optical depth, the Angstrom exponent, and the columnar water vapor, to those derived using a traditional solar radiometer. The top-of-atmosphere radiance derived using the Cimel and ASR measurements are compared using Landsat 8 OLI bands as a test case for the period 2012-2014 to determine if any biases exist between the two methodologies.

  5. On-orbit radiometric calibration over time and between spacecraft using the moon

    USGS Publications Warehouse

    Kieffer, H.H.; Stone, T.C.; Barnes, R.A.; Bender, S.; Eplee, R.E.; Mendenhall, J.; Ong, L.; ,

    2002-01-01

    The Robotic Lunar Observatory (ROLO) project has developed a spectral irradiance model of the Moon that accounts for variations with lunar phase through the bright half of a month, lunar librations, and the location of an Earth-orbiting spacecraft. The methodology of comparing spacecraft observations of the Moon with this model has been developed to a set of standardized procedures so that comparisons can be readily made. In the cases where observations extend over several years (e.g., SeaWiFS), instrument response degradation has been determined with precision of about 0.1% per year. Because of the strong dependence of lunar irradiance on geometric angles, observations by two spacecraft cannot be directly compared unless acquired at the same time and location. Rather, the lunar irradiance based on each spacecraft instrument calibration can be compared with the lunar irradiance model. Even single observations by an instrument allow inter-comparison of its radiometric scale with other instruments participating in the lunar calibration program. Observations by SeaWiFS, ALI, Hyperion and MTI are compared here.

  6. Radiometric calibration stability of the EO-1 advanced land imager: 5 years on-orbit

    USGS Publications Warehouse

    Markham, B.L.; Ong, L.; Barsi, J.A.; Mendenhall, J.A.; Lencioni, D.E.; Helder, D.L.; Hollaren, D.M.; Morfitt, R.

    2006-01-01

    The Advanced Land Imager (ALI) was developed as a prototype sensor for follow on missions to Landsat-7. It was launched in November 2000 on the Earth Observing One (EO-1) satellite as a nominal one-year technology demonstration mission. As of this writing, the sensor has continued to operate in excess of 5 years. Six of the ALl's nine multi-spectral (MS) bands and the panchromatic band have similar spectral coverage as those on the Landsat-7 ETM+. In addition to on-board lamps, which have been significantly more stable than the lamps on ETM+, the ALI has a solar diffuser and has imaged the moon monthly since launch. This combined calibration dataset allows understanding of the radiometric stability of the ALI system, its calibrators and some differentiation of the sources of the changes with time. The solar dataset is limited as the mechanism controlling the aperture to the solar diffuser failed approximately 18 months after launch. Results over 5 years indicate that: the shortest wavelength band (443 nm) has degraded in response about 2%; the 482 nm and 565 nm bands decreased in response about 1%; the 660 nm, 790 nm and 868 nm bands each degraded about 5%; the 1250 nm and 1650 nm bands did not change significantly and the 2215 nm band increased in response about 2%.

  7. Consistency of L4 TM absolute calibration with respect to the L5 TM sensor based on near-simultaneous image acquisition

    USGS Publications Warehouse

    Chander, G.; Helder, D.L.; Malla, R.; Micijevic, E.; Mettler, C.J.

    2007-01-01

    The Landsat archive provides more than 35 years of uninterrupted multispectral remotely sensed data of Earth observations. Since 1972, Landsat missions have carried different types of sensors, from the Return Beam Vidicon (RBV) camera to the Enhanced Thematic Mapper Plus (ETM+). However, the Thematic Mapper (TM) sensors on Landsat 4 (L4) and Landsat 5 (L5), launched in 1982 and 1984 respectively, are the backbone of an extensive archive. Effective April 2, 2007, the radiometric calibration of L5 TM data processed and distributed by the U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) was updated to use an improved lifetime gain model, based on the instrument's detector response to pseudo-invariant desert site data and cross-calibration with the L7 ETM+. However, no modifications were ever made to the radiometric calibration procedure of the Landsat 4 (L4) TM data. The L4 TM radiometric calibration procedure has continued to use the Internal Calibrator (IC) based calibration algorithms and the post calibration dynamic ranges, as previously defined. To evaluate the "current" absolute accuracy of these two sensors, image pairs from the L5 TM and L4 TM sensors were compared. The number of coincident image pairs in the USGS EROS archive is limited, so the scene selection for the cross-calibration studies proved to be a challenge. Additionally, because of the lack of near-simultaneous images available over well-characterized and traditionally used calibration sites, alternate sites that have high reflectance, large dynamic range, high spatial uniformity, high sun elevation, and minimal cloud cover were investigated. The alternate sites were identified in Yuma, Iraq, Egypt, Libya, and Algeria. The cross-calibration approach involved comparing image statistics derived from large common areas observed eight days apart by the two sensors. This paper summarizes the average percent differences in reflectance estimates obtained between the

  8. Consistency of L4 TM absolute calibration with respect to the L5 TM sensor based on near-simultaneous image acquisition

    NASA Astrophysics Data System (ADS)

    Chander, Gyanesh; Helder, Dennis L.; Malla, Rimy; Micijevic, Esad; Mettler, Cory J.

    2007-09-01

    The Landsat archive provides more than 35 years of uninterrupted multispectral remotely sensed data of Earth observations. Since 1972, Landsat missions have carried different types of sensors, from the Return Beam Vidicon (RBV) camera to the Enhanced Thematic Mapper Plus (ETM+). However, the Thematic Mapper (TM) sensors on Landsat 4 (L4) and Landsat 5 (L5), launched in 1982 and 1984 respectively, are the backbone of an extensive archive. Effective April 2, 2007, the radiometric calibration of L5 TM data processed and distributed by the U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) was updated to use an improved lifetime gain model, based on the instrument's detector response to pseudo-invariant desert site data and cross-calibration with the L7 ETM+. However, no modifications were ever made to the radiometric calibration procedure of the Landsat 4 (L4) TM data. The L4 TM radiometric calibration procedure has continued to use the Internal Calibrator (IC) based calibration algorithms and the post calibration dynamic ranges, as previously defined. To evaluate the "current" absolute accuracy of these two sensors, image pairs from the L5 TM and L4 TM sensors were compared. The number of coincident image pairs in the USGS EROS archive is limited, so the scene selection for the cross-calibration studies proved to be a challenge. Additionally, because of the lack of near-simultaneous images available over well-characterized and traditionally used calibration sites, alternate sites that have high reflectance, large dynamic range, high spatial uniformity, high sun elevation, and minimal cloud cover were investigated. The alternate sites were identified in Yuma, Iraq, Egypt, Libya, and Algeria. The cross-calibration approach involved comparing image statistics derived from large common areas observed eight days apart by the two sensors. This paper summarizes the average percent differences in reflectance estimates obtained between the

  9. Local-scale flood mapping on vegetated floodplains from radiometrically calibrated airborne LiDAR data

    NASA Astrophysics Data System (ADS)

    Malinowski, Radosław; Höfle, Bernhard; Koenig, Kristina; Groom, Geoff; Schwanghart, Wolfgang; Heckrath, Goswin

    2016-09-01

    Knowledge about the magnitude of localised flooding of riverine areas is crucial for appropriate land management and administration at regional and local levels. However, detection and delineation of localised flooding with remote sensing techniques are often hampered on floodplains by the presence of herbaceous vegetation. To address this problem, this study presents the application of full-waveform airborne laser scanning (ALS) data for detection of floodwater extent. In general, water surfaces are characterised by low values of backscattered energy due to water absorption of the infrared laser shots, but the exact strength of the recorded laser pulse depends on the area covered by the targets located within a laser pulse footprint area. To account for this we analysed the physical quantity of radiometrically calibrated ALS data, the backscattering coefficient, in relation to water and vegetation coverage within a single laser footprint. The results showed that the backscatter was negatively correlated to water coverage, and that of the three distinguished classes of water coverage (low, medium, and high) only the class with the largest extent of water cover (>70%) had relatively distinct characteristics that can be used for classification of water surfaces. Following the laser footprint analysis, three classifiers, namely AdaBoost with Decision Tree, Naïve Bayes and Random Forest, were utilised to classify laser points into flooded and non-flooded classes and to derive the map of flooding extent. The performance of the classifiers is highly dependent on the set of laser points features used. Best performance was achieved by combining radiometric and geometric laser point features. The accuracy of flooding maps based solely on radiometric features resulted in overall accuracies of up to 70% and was limited due to the overlap of the backscattering coefficient values between water and other land cover classes. Our point-based classification methods assure a high

  10. Alignment and absolute wavelength calibration of imaging Bragg spectrometers

    NASA Astrophysics Data System (ADS)

    Bertschinger, G.; Marchuk, O.; Barnsley, R.

    2016-11-01

    In the present and the next generation of fusion devices, imaging Bragg spectrometers are key diagnostics to measure plasma parameters in the hot core, especially ion temperature and plasma rotation. The latter quantities are routinely obtained using the Doppler-width and -shift of the emitted spectral lines, respectively. Line shift measurements require absolute accuracies Δλ/λ of about 10 ppm, where λ-is the observed wavelength. For ITER and the present fusion devices, spectral lines of He-and H-like argon, iron, and krypton as well as Ne-like tungsten are foreseen for the measurements. For these lines, Kα lines can be found, some in higher order, which fit into the narrow energy window of the spectrometers. For arbitrary wavelength settings, Kα lines are also used to measure the miscut of the spherical crystals; afterwards the spectrometers can be set according to the geometrical imaging properties using coordinate measurement machines. For the spectrometers measuring Lyα lines of H-like ions, fluorescence targets can provide in situ localized calibration lines on the spectra. The fluorescence targets are used best in transmission and are excited by the thermal x-ray radiation of the plasma. An analytic theory of fluorescence is worked out.

  11. Radiometric calibration of G-LiHT's imaging spectrometer using GLAMR for satellite sensor intercalibration

    NASA Astrophysics Data System (ADS)

    Angal, Amit; McCorkel, Joel; Cook, Bruce; Corp, Lawrence A.; Thome, Kurt

    2015-09-01

    NASA Goddard's Lidar, Hyperspectral and Thermal Imager (G-LiHT) facilitates simultaneous measurements beneficial to variety of applications. Of the suite of "off-the shelf" instruments of G-LiHT, the Visible Near-Infrared (VNIR) Imaging Spectrometer acquires high resolution spectral measurements (1.5 nm resolution) from 0.4 to 1 μm. Goddard Space Flight Center's Laser for Absolute Measurement of Response (GLAMR) was used to measure the absolute spectral response (ASR) of the G-LiHT's imaging spectrometer. Continuously tunable lasers coupled to an integrating sphere allow a radiance-based calibration for the detectors at reflective solar wavelengths. GLAMR measurements, covering a wavelength range from 0.58 to 0.99 μm were acquired between July 30 to August 2, 2013. In order to account for the large field-of-view (50°), G-LiHT was rotated in 2 degree increments so that the same area of the sphere is viewed by all detectors. Using this data along with the coincident Silicon trap radiometer measurements, the ASR was computed. The derived calibration parameters for G-LiHT's Imaging Spectrometer are to be transferred to near-simultaneous measurements of Landsat sensors. Calibration uncertainty of G-LiHT is 1-3% depending spectral region and transferring this traceability to coincident satellite sensors has 3-5% depending on spectral region.

  12. ScaRaB: first results of absolute and cross calibration

    NASA Astrophysics Data System (ADS)

    Trémas, Thierry L.; Aznay, Ouahid; Chomette, Olivier

    2015-10-01

    ScaRaB (SCAnner for RAdiation Budget) is the name of three radiometers whose two first flight models have been launched in 1994 and 1997. The instruments were mounted on-board Russian satellites, METEOR and RESURS. On October 12th 2011, a last model has been launched from the Indian site of Sriharikota. ScaRaB is a passenger of MEGHA-TROPIQUES, an Indo-French joint Satellite Mission for studying the water cycle and energy exchanges in the tropics. ScaRaB is composed of four parallel and independent channels. Channel-2 and channel-3 are considered as the main ones. Channel-1 is dedicated to measure solar radiance (0.5 to 0.7 μm) while channel-4 (10 to 13 μm) is an infrared window. The absolute calibration of ScaRab is assured by internal calibration sources (black bodies and a lamp for channel-1). However, during the commissioning phase, the lamp used for the absolute calibration of channel-1 revealed to be inaccurate. We propose here an alternative calibration method based on terrestrial targets. Due to the spectral range of channel-1, only calibration over desert sites (temporal monitoring) and clouds (cross band) is suitable. Desert sites have been widely used for sensor calibration since they have a stable spectral response over time. Because of their high reflectances, the atmospheric effect on the upward radiance is relatively minimal. In addition, they are spatially uniform. Their temporal instability without atmospheric correction has been determined to be less than 1-2% over a year. Very-high-altitude (10 km) bright clouds are good validation targets in the visible and near-infrared spectra because of their high spectrally consistent reflectance. If the clouds are very high, there is no need to correct aerosol scattering and water vapor absorption as both aerosol and water vapor are distributed near the surface. Only Rayleigh scattering and ozone absorption need to be considered. This method has been found to give a 4% uncertainty. Radiometric cross

  13. Summary of Current Radiometric Calibration Coefficients for Landsat MSS, TM, ETM+, and EO-1 ALI Sensors

    NASA Technical Reports Server (NTRS)

    Chander, Gyanesh; Markham, Brian L.; Helder, Dennis L.

    2009-01-01

    This paper provides a summary of the current equations and rescaling factors for converting calibrated Digital Numbers (DNs) to absolute units of at-sensor spectral radiance, Top-Of- Atmosphere (TOA) reflectance, and at-sensor brightness temperature. It tabulates the necessary constants for the Multispectral Scanner (MSS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Advanced Land Imager (ALI) sensors. These conversions provide a basis for standardized comparison of data in a single scene or between images acquired on different dates or by different sensors. This paper forms a needed guide for Landsat data users who now have access to the entire Landsat archive at no cost.

  14. Summary of current radiometric calibration coefficients for Landsat MSS, TM, ETM+, and EO-1 ALI sensors

    USGS Publications Warehouse

    Chander, G.; Markham, B.L.; Helder, D.L.

    2009-01-01

    This paper provides a summary of the current equations and rescaling factors for converting calibrated Digital Numbers (DNs) to absolute units of at-sensor spectral radiance, Top-Of-Atmosphere (TOA) reflectance, and at-sensor brightness temperature. It tabulates the necessary constants for the Multispectral Scanner (MSS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Advanced Land Imager (ALI) sensors. These conversions provide a basis for standardized comparison of data in a single scene or between images acquired on different dates or by different sensors. This paper forms a needed guide for Landsat data users who now have access to the entire Landsat archive at no cost.

  15. Methods to calibrate the absolute receive sensitivity of single-element, focused transducers.

    PubMed

    Rich, Kyle T; Mast, T Douglas

    2015-09-01

    Absolute pressure measurements of acoustic emissions by single-element, focused passive cavitation detectors would be facilitated by improved wideband receive calibration techniques. Here, calibration methods were developed to characterize the absolute, frequency-dependent receive sensitivity of a spherically focused, single-element transducer using pulse-echo and pitch-catch techniques. Validation of these calibration methods on a focused receiver were made by generating a pulse from a small diameter source at the focus of the transducer and comparing the absolute pressure measured by a calibrated hydrophone to that of the focused transducer using the receive sensitivities determined here.

  16. The University of Wisconsin Space Science and Engineering Center Absolute Radiance Interferometer (ARI): instrument overview and radiometric performance

    NASA Astrophysics Data System (ADS)

    Taylor, Joseph K.; Revercomb, Henry E.; Best, Fred A.; Gero, P. Jonathan; Genest, Jerome; Buijs, Henry; Grandmont, Frederic J.; Tobin, David C.; Knuteson, Robert O.

    2014-11-01

    Spectrally resolved infrared (IR) and far infrared (FIR) radiances measured from orbit with extremely high absolute accuracy are a critical observation for future climate benchmark missions. For the infrared radiance spectra, it has been determined that a measurement accuracy, expressed as an equivalent brightness temperature error, of 0.1 K (k = 3) confirmed on orbit is required for signal detection above natural variability for decadal climate signatures [1, 2]. The challenge in the sensor development for a climate benchmark measurement mission is to achieve ultra-high accuracy with a design that can be flight qualified, has long design life, and is reasonably small, simple, and affordable. The required simplicity is achievable due to the large differences in the sampling and noise requirements for the benchmark climate measurement from those of the typical remote sensing infrared sounders for weather research or operational weather prediction. The University of Wisconsin Space Science and Engineering Center, with funding from the NASA Instrument Incubator Program (IIP), developed the Absolute Radiance Interferometer (ARI), which is designed to meet the uncertainty requirements needed to establish spectrally resolved thermal infrared climate benchmark measurements from space. The ARI is a prototype instrument designed to have a short upgrade path to a spaceflight instrument. Recent vacuum testing of the ARI, conducted under funding from the NASA Earth Science Technology Office, has demonstrated the capability to meet the 0.1 K (k = 3) uncertainty requirement on-orbit. An overview of the instrument design and summary of the radiometric performance verification of the UW-SSEC ARI will be presented.

  17. Revised radiometric calibration technique for LANDSAT-4 Thematic Mapper data by the Canada Centre for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Murphy, J.; Butlin, T.; Duff, P.; Fitzgerald, A.

    1984-01-01

    Observations of raw image data, raw radiometric calibration data, and background measurements extracted from the raw data streams on high density tape reveal major shortcomings in a technique proposed by the Canadian Center for Remote Sensing in 1982 for the radiometric correction of TM data. Results are presented which correlate measurements of the DC background with variations in both image data background and calibration samples. The effect on both raw data and data corrected using the earlier proposed technique is explained and the correction required for these factors as a function of individual scan line number for each detector is described. How the revised technique can be incorporated into an operational environment is demonstrated.

  18. [Study on the absolute spectral irradiation calibration method for far ultraviolet spectrometer in remote sensing].

    PubMed

    Yu, Lei; Lin, Guan-Yu; Chen, Bin

    2013-01-01

    The present paper studied spectral irradiation responsivities calibration method which can be applied to the far ultraviolet spectrometer for upper atmosphere remote sensing. It is difficult to realize the calibration for far ultraviolet spectrometer for many reasons. Standard instruments for far ultraviolet waveband calibration are few, the degree of the vacuum experiment system is required to be high, the stabilities of the experiment are hardly maintained, and the limitation of the far ultraviolet waveband makes traditional diffuser and the integrating sphere radiance calibration method difficult to be used. To solve these problems, a new absolute spectral irradiance calibration method was studied, which can be applied to the far ultraviolet calibration. We build a corresponding special vacuum experiment system to verify the calibration method. The light source system consists of a calibrated deuterium lamp, a vacuum ultraviolet monochromater and a collimating system. We used the calibrated detector to obtain the irradiance responsivities of it. The three instruments compose the calibration irradiance source. We used the "calibration irradiance source" to illuminate the spectrometer prototype and obtained the spectral irradiance responsivities. It realized the absolute spectral irradiance calibration for the far ultraviolet spectrometer utilizing the calibrated detector. The absolute uncertainty of the calibration is 7.7%. The method is significant for the ground irradiation calibration of the far ultraviolet spectrometer in upper atmosphere remote sensing.

  19. EUV variability experiment (EVE); multiple EUV grating spectrographs (MEGS), radiometric calibrations and results

    NASA Astrophysics Data System (ADS)

    Chamberlin, Phillip C.; Hock, Rachel A.; Crotser, David A.; Eparvier, Francis G.; Furst, Mitch; Triplett, Matthew A.; Woodraska, Donald L.; Woods, Thomas N.

    2007-09-01

    The NASA Solar Dynamics Observatory (SDO), scheduled for launch in early 2009, incorporates a suite of instruments including the EUV Variability Experiment (EVE). Two channels of EVE, the Multiple EUV Grating Spectrograph (MEGS) A and B channels use concave reflection gratings to image solar spectra onto CCDs to measure the solar extreme ultraviolet (EUV) irradiance from 5 to 105 nm. MEGS provides these spectra at 0.1nm spectral resolution every 10 seconds with an absolute accuracy of better than 25% over the SDO 5-year mission. The calibration of the MEGS channels in order to convert the instrument counts in to physical units of W/m2/nm was performed at the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility III (SURF III) located in Gaithersburg, Maryland. Although the final post-environmental calibrations have yet to be performed, preliminary results from the pre-environmental calibrations show very good agreement with the theoretical optical design given by Crotser et al. Further analysis is still needed in regards to the higher order contributions to determine the final first order QT for all channels, but two techniques are currently being analyzed and show promising results.

  20. A first in-flight absolute calibration of the Chilean Earth Observation Satellite

    NASA Astrophysics Data System (ADS)

    Mattar, C.; Hernández, J.; Santamaría-Artigas, A.; Durán-Alarcón, C.; Olivera-Guerra, L.; Inzunza, M.; Tapia, D.; Escobar-lavín, E.

    2014-06-01

    This work describes the first in-flight absolute calibration of the "Sistema Satelital para la Observación de la Tierra" (SSOT or Fasat-C). It was performed on January 29th 2013 at Antumapu site located in the southern area of Santiago, Chile. A description of the procedure is presented which includes both ground measurement and atmospheric characterization. The Chilean satellite for Earth observation carries on board a "New AstroSat Optical Modular Instrument" (NAOMI) high-resolution pushbroom imager which provides a 1.45 m ground sampling distance in the panchromatic (0.455-0.744 μm) channel and a 5.8 m ground sampling distance for the green (0.455-0.52 μm), blue (0.528-0.588 μm), red (0.625-0.695 μm) and near-infrared (0.758-0.881 μm) channels from a 620 km orbit. Radiometric calibration was carried out in order to estimate the land leaving radiance and bidirectional reflectance at the top of the atmosphere. To correct the reflectance data for atmospheric effects, the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) code was used. Aerosol Optical Depth (AOD), water vapor and ozone content were obtained from MOD04, MOD05 and MOD07 products respectively, which are derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) data. Statistical results such as BIAS, SIGMA and RMSE were calculated for the comparison between surface reflectance values and in situ measurements. Results show that the overall accuracy of the atmospherically corrected surface reflectance calculated from Fasat-C imagery can be estimated to around ±5%, with a R2 coefficient of 0.939 between atmospherically corrected reflectance values and in situ measurements. The atmospheric correction applied in this work by combining MODIS data and the 6S radiative transfer code could be used for further calibration of the Fasat-C images, although in situ atmospheric irradiance measurements are necessary to estimate reliable values of surface reflectance. Future

  1. [On-orbit radiometric calibration accuracy of FY-3A MERSI thermal infrared channel].

    PubMed

    Xu, Na; Hu, Xiu-qing; Chen, Lin; Zhang, Yong; Hu, Ju-yang; Sun, Ling

    2014-12-01

    Accurate satellite radiance measurements are significant for data assimilations and quantitative retrieval applications. In the present paper, radiometric calibration accuracy of FungYun-3A (FY-3A) Medium Resolution Spectral Imager (MERSI) thermal infrared (TIR) channel was evaluated based on simultaneous nadir observation (SNO) intercalibration method. Hyperspectral and high-quality measurements of METOP-A/IASI were used as reference. Assessment uncertainty from intercalibration method was also investigated by examining the relation between BT bias against four main collocation factors, i. e. observation time difference, view geometric difference related to zenith angles and azimuth angles, and scene spatial homogeneity. It was indicated that the BT bias is evenly distributed across the collocation variables with no significant linear relationship in MERSI IR channel. Among the four collocation factors, the scene spatial homogeneity may be the most important factor with the uncertainty less than 2% of BT bias. Statistical analysis of monitoring biases during one and a half years indicates that the brightness temperature measured by MERSI is much warmer than that of IASI. The annual mean bias (MERSI-IASI) in 2012 is (3.18±0.34) K. Monthly averaged BT biases show a little seasonal variation character, and fluctuation range is less than 0.8 K. To further verify the reliability, our evaluation result was also compared with the synchronous experiment results at Dunhuang and Qinghai Lake sites, which showed excellent agreement. Preliminary analysis indicates that there are two reasons leading to the warm bias. One is the overestimation of blackbody emissivity, and the other is probably the incorrect spectral respond function which has shifted to window spectral. Considering the variation character of BT biases, SRF error seems to be the dominant factor.

  2. The Laboratory Radiometric Calibration of the CCD Stereo Camera for the Optical Payload of the Lunar Explorer Project

    NASA Astrophysics Data System (ADS)

    Wang, Jue; Li, Chun-Lai; Zhao, Bao-Chang

    2007-03-01

    The system of the optical payload for the Lunar Explorer includes a CCD stereo camera and an imaging interferometer. The former is devised to get the solid images of the lunar surface with a laser altimeter. The camera working principle, calibration purpose, and content, nude chip detection, and the process of the relative and absolute calibration in the laboratory are introduced.

  3. On the absolute calibration of SO2 cameras

    USGS Publications Warehouse

    Lübcke, Peter; Bobrowski, Nicole; Illing, Sebastian; Kern, Christoph; Alvarez Nieves, Jose Manuel; Vogel, Leif; Zielcke, Johannes; Delgados Granados, Hugo; Platt, Ulrich

    2013-01-01

    This work investigates the uncertainty of results gained through the two commonly used, but quite different, calibration methods (DOAS and calibration cells). Measurements with three different instruments, an SO2 camera, a NFOVDOAS system and an Imaging DOAS (I-DOAS), are presented. We compare the calibration-cell approach with the calibration from the NFOV-DOAS system. The respective results are compared with measurements from an I-DOAS to verify the calibration curve over the spatial extent of the image. The results show that calibration cells, while working fine in some cases, can lead to an overestimation of the SO2 CD by up to 60% compared with CDs from the DOAS measurements. Besides these errors of calibration, radiative transfer effects (e.g. light dilution, multiple scattering) can significantly influence the results of both instrument types. The measurements presented in this work were taken at Popocatepetl, Mexico, between 1 March 2011 and 4 March 2011. Average SO2 emission rates between 4.00 and 14.34 kg s−1 were observed.

  4. Simple and accurate empirical absolute volume calibration of a multi-sensor fringe projection system

    NASA Astrophysics Data System (ADS)

    Gdeisat, Munther; Qudeisat, Mohammad; AlSa`d, Mohammed; Burton, David; Lilley, Francis; Ammous, Marwan M. M.

    2016-05-01

    This paper suggests a novel absolute empirical calibration method for a multi-sensor fringe projection system. The optical setup of the projector-camera sensor can be arbitrary. The term absolute calibration here means that the centre of the three dimensional coordinates in the resultant calibrated volume coincides with a preset centre to the three-dimensional real-world coordinate system. The use of a zero-phase fringe marking spot is proposed to increase depth calibration accuracy, where the spot centre is determined with sub-pixel accuracy. Also, a new method is proposed for transversal calibration. Depth and transversal calibration methods have been tested using both single sensor and three-sensor fringe projection systems. The standard deviation of the error produced by this system is 0.25 mm. The calibrated volume produced by this method is 400 mm×400 mm×140 mm.

  5. SeaWiFS Postlaunch Technical Report Series. Volume 4; The 1997 Prelaunch Radiometric Calibration of SeaWiFS

    NASA Technical Reports Server (NTRS)

    Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Johnson, B. Carol; Early, Edward E.; Eplee, Robert E., Jr.; Barnes, Robert A.; Caffrey, Robert T.

    1999-01-01

    The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) was originally calibrated by the instrument's manufacturer, Santa Barbara Research Center (SBRC), in November 1993. In preparation for an August 1997 launch, the SeaWiFS Project and the National Institute of Standards and Technology (NIST) undertook a second calibration of SeaWiFS in January and April 1997 at the facility of the spacecraft integrator, Orbital Sciences Corporation (OSC). This calibration occurred in two phases, the first after the final thermal vacuum test, and the second after the final vibration test of the spacecraft. For the calibration, SeaWiFS observed an integrating sphere from the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) at four radiance levels. The spectral radiance of the sphere at these radiance levels was also measured by the SeaWiFS Transfer Radiometer (SXR). In addition, during the calibration, SeaWiFS and the SXR observed the sphere at 16 radiance levels to determine the linearity of the SeaWiFS response. As part of the calibration analysis, the GSFC sphere was also characterized using a GSFC spectroradiometer. The 1997 calibration agrees with the initial 1993 calibration to within +/- 4%. The new calibration coefficients, computed before and after the vibration test, agree to within 0.5%. The response of the SeaWiFS channels in each band is linear to better than 1%. In order to compare to previous and current methods, the SeaWiFS radiometric responses are presented in two ways: using the nominal center wave-lengths for the eight bands; and using band-averaged spectral radiances. The band-averaged values are used in the flight calibration table. An uncertainty analysis for the calibration coefficients is also presented.

  6. Imager-to-Radiometer In-flight Cross Calibration: RSP Radiometric Comparison with Airborne and Satellite Sensors

    NASA Technical Reports Server (NTRS)

    McCorkel, Joel; Cairns, Brian; Wasilewski, Andrzej

    2016-01-01

    This work develops a method to compare the radiometric calibration between a radiometer and imagers hosted on aircraft and satellites. The radiometer is the airborne Research Scanning Polarimeter (RSP), which takes multi-angle, photo-polarimetric measurements in several spectral channels. The RSP measurements used in this work were coincident with measurements made by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), which was on the same aircraft. These airborne measurements were also coincident with an overpass of the Landsat 8 Operational Land Imager (OLI). First we compare the RSP and OLI radiance measurements to AVIRIS since the spectral response of the multispectral instruments can be used to synthesize a spectrally equivalent signal from the imaging spectrometer data. We then explore a method that uses AVIRIS as a transfer between RSP and OLI to show that radiometric traceability of a satellite-based imager can be used to calibrate a radiometer despite differences in spectral channel sensitivities. This calibration transfer shows agreement within the uncertainty of both the various instruments for most spectral channels.

  7. First Absolutely Calibrated Localized Measurements of Ion Velocity in the MST in Locked and Rotating Plasmas

    NASA Astrophysics Data System (ADS)

    Baltzer, M.; Craig, D.; den Hartog, D. J.; Nornberg, M. D.; Munaretto, S.

    2015-11-01

    An Ion Doppler Spectrometer (IDS) is used on MST for high time-resolution passive and active measurements of impurity ion emission. Absolutely calibrated measurements of flow are difficult because the spectrometer records data within 0.3 nm of the C+5 line of interest, and commercial calibration lamps do not produce lines in this narrow range . A novel optical system was designed to absolutely calibrate the IDS. The device uses an UV LED to produce a broad emission curve in the desired region. A Fabry-Perot etalon filters this light, cutting transmittance peaks into the pattern of the LED emission. An optical train of fused silica lenses focuses the light into the IDS with f/4. A holographic diffuser blurs the light cone to increase homogeneity. Using this light source, the absolute Doppler shift of ion emissions can be measured in MST plasmas. In combination with charge exchange recombination spectroscopy, localized ion velocities can now be measured. Previously, a time-averaged measurement along the chord bisecting the poloidal plane was used to calibrate the IDS; the quality of these central chord calibrations can be characterized with our absolute calibration. Calibration errors may also be quantified and minimized by optimizing the curve-fitting process. Preliminary measurements of toroidal velocity in locked and rotating plasmas will be shown. This work has been supported by the US DOE.

  8. Radiometric Characterization of the IKONOS, QuickBird, and OrbView-3 Sensors

    NASA Technical Reports Server (NTRS)

    Holekamp, Kara

    2006-01-01

    Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities can better understand their properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other systems. To address this calibration need, satellite at-sensor radiance values were compared to those estimated by each independent team member to determine the sensor's radiometric accuracy. The combined results of this evaluation provide the user community with an independent assessment of these commercially available high spatial resolution sensors' absolute calibration values.

  9. The Absolute, Relative and Multi-Wavelength Calibration of the Pierre Auger Observatory Fluorescence Detectors

    SciTech Connect

    Knapik, R.; Bauleo, P.; Becker, B.R.; Brack, J.; Caruso, R.; Fratte, C.Delle; Dorofeev, A.; Harton, J.; Insolia, A.; Matthews, J.A.J.; Menshikov, A.

    2007-08-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a 375 nm light source at the telescope aperture. This end-to-end technique accounts for the combined effects of all detector components in a single measurement. The relative response has been measured at wavelengths of 320, 337, 355, 380 and 405 nm, defining a spectral response curve which has been normalized to the absolute calibration. Before and after each night of data taking a relative calibration of the phototubes is performed. This relative calibration is used to track both short and long term changes in the detector's response. A cross check of the calibration in some phototubes is performed using an independent laser technique. Overall uncertainties, current results and future plans are discussed.

  10. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Steinmetz, T.; Holzwarth, R.; Kentischer, T.; Schmidt, W.

    2012-10-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

  11. Effect of MODIS Terra Radiometric Calibration Improvements on Collection 6 Deep Blue Aerosol Products: Validation and Terra/Aqua Consistency

    NASA Technical Reports Server (NTRS)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.; Jeong, M.-J.; Meister, G.

    2015-01-01

    The Deep Blue (DB) algorithm's primary data product is midvisible aerosol optical depth (AOD). DB applied to Moderate Resolution Imaging Spectroradiometer (MODIS) measurements provides a data record since early 2000 for MODIS Terra and mid-2002 for MODIS Aqua. In the previous data version (Collection 5, C5), DB production from Terra was halted in 2007 due to sensor degradation; the new Collection 6 (C6) has both improved science algorithms and sensor radiometric calibration. This includes additional calibration corrections developed by the Ocean Biology Processing Group to address MODIS Terra's gain, polarization sensitivity, and detector response versus scan angle, meaning DB can now be applied to the whole Terra record. Through validation with Aerosol Robotic Network (AERONET) data, it is shown that the C6 DB Terra AOD quality is stable throughout the mission to date. Compared to the C5 calibration, in recent years the RMS error compared to AERONET is smaller by approximately 0.04 over bright (e.g., desert) and approximately 0.01-0.02 over darker (e.g., vegetated) land surfaces, and the fraction of points in agreement with AERONET within expected retrieval uncertainty higher by approximately 10% and approximately 5%, respectively. Comparisons to the Aqua C6 time series reveal a high level of correspondence between the two MODIS DB data records, with a small positive (Terra-Aqua) average AOD offset <0.01. The analysis demonstrates both the efficacy of the new radiometric calibration efforts and that the C6 MODIS Terra DB AOD data remain stable (to better than 0.01 AOD) throughout the mission to date, suitable for quantitative scientific analyses.

  12. Effect of MODIS Terra radiometric calibration improvements on Collection 6 Deep Blue aerosol products: Validation and Terra/Aqua consistency

    NASA Astrophysics Data System (ADS)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.; Jeong, M.-J.; Meister, G.

    2015-12-01

    The Deep Blue (DB) algorithm's primary data product is midvisible aerosol optical depth (AOD). DB applied to Moderate Resolution Imaging Spectroradiometer (MODIS) measurements provides a data record since early 2000 for MODIS Terra and mid-2002 for MODIS Aqua. In the previous data version (Collection 5, C5), DB production from Terra was halted in 2007 due to sensor degradation; the new Collection 6 (C6) has both improved science algorithms and sensor radiometric calibration. This includes additional calibration corrections developed by the Ocean Biology Processing Group to address MODIS Terra's gain, polarization sensitivity, and detector response versus scan angle, meaning DB can now be applied to the whole Terra record. Through validation with Aerosol Robotic Network (AERONET) data, it is shown that the C6 DB Terra AOD quality is stable throughout the mission to date. Compared to the C5 calibration, in recent years the RMS error compared to AERONET is smaller by ˜0.04 over bright (e.g., desert) and ˜0.01-0.02 over darker (e.g., vegetated) land surfaces, and the fraction of points in agreement with AERONET within expected retrieval uncertainty higher by ˜10% and ˜5%, respectively. Comparisons to the Aqua C6 time series reveal a high level of correspondence between the two MODIS DB data records, with a small positive (Terra-Aqua) average AOD offset <0.01. The analysis demonstrates both the efficacy of the new radiometric calibration efforts and that the C6 MODIS Terra DB AOD data remain stable (to better than 0.01 AOD) throughout the mission to date, suitable for quantitative scientific analyses.

  13. NASA Radiometric Characterization

    NASA Technical Reports Server (NTRS)

    Holekamp, Kara

    2006-01-01

    This viewgraph presentation reviews the characterization of radiometric data by NASA. The objective was to perform radiometric vicarious calibrations of imagery and compare with vendor-provided calibration coefficients. The approach was to use multiple, well-characterized sites. These sites are widely used by the NASA science community for radiometric characterization of airborne and space borne sensors. Using the data from these sites, the investigators performed independent characterizations with independent teams. Each team has slightly different measurement techniques and data processing methods.

  14. NASA IKONOS Radiometric Characterization

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Frisbee, Troy; Zanoni, Vicki; Blonski, Slawek; Daehler, Erik; Grant, Brennan; Holekamp, Kara; Ryan, Robert; Sellers, Richard; Smith, Charles

    2002-01-01

    The objective of this program: Perform radiometric vicarious calibrations of IKQNOS imagery and compare with Space Imaging calibration coefficients The approach taken: utilize multiple well-characterized sites which are widely used by the NASA science community for radiometric characterization of airborne and spaceborne sensors; and to Perform independent characterizations with independent teams. Each team has slightly different measurement techniques and data processing methods.

  15. SeaWiFS technical report series. Volume 23: SeaWiFS prelaunch radiometric calibration and spectral characterization

    NASA Technical Reports Server (NTRS)

    Barnes, Robert A.; Holmes, Alan W.; Barnes, William L.; Esaias, Wayne E.; Mcclain, Charles R.; Svitek, Tomas; Hooker, Stanford B.; Firestone, Elaine R.; Acker, James G.

    1994-01-01

    Based on the operating characteristics of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), calibration equations have been developed that allow conversion of the counts from the radiometer into Earth-existing radiances. These radiances are the geophysical properties the instrument has been designed to measure. SeaWiFS uses bilinear gains to allow high sensitivity measurements of ocean-leaving radiances and low sensitivity measurements of radiances from clouds, which are much brighter than the ocean. The calculation of these bilinear gains is central to the calibration equations. Several other factors within these equations are also included. Among these are the spectral responses of the eight SeaWiFS bands. A band's spectral response includes the ability of the band to isolate a portion of the electromagnetic spectrum and the amount of light that lies outside of that region. The latter is termed out-of-band response. In the calibration procedure, some of the counts from the instrument are produced by radiance in the out-of-band region. The number of those counts for each band is a function of the spectral shape of the source. For the SeaWiFS calibration equations, the out-of-band responses are converted from those for the laboratory source into those for a source with the spectral shape of solar flux. The solar flux, unlike the laboratory calibration, approximates the spectral shape of the Earth-existing radiance from the oceans. This conversion modifies the results from the laboratory radiometric calibration by 1-4 percent, depending on the band. These and other factors in the SeaWiFS calibration equations are presented here, both for users of the SeaWiFS data set and for researchers making ground-based radiance measurements in support of Sea WiFS.

  16. 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.

  17. Absolute sensitivity calibration of an extreme ultraviolet spectrometer for tokamak measurements

    NASA Astrophysics Data System (ADS)

    Guirlet, R.; Schwob, J. L.; Meyer, O.; Vartanian, S.

    2017-01-01

    An extreme ultraviolet spectrometer installed on the Tore Supra tokamak has been calibrated in absolute units of brightness in the range 10-340 Å. This has been performed by means of a combination of techniques. The range 10-113 Å was absolutely calibrated by using an ultrasoft-X ray source emitting six spectral lines in this range. The calibration transfer to the range 113-182 Å was performed using the spectral line intensity branching ratio method. The range 182-340 Å was calibrated thanks to radiative-collisional modelling of spectral line intensity ratios. The maximum sensitivity of the spectrometer was found to lie around 100 Å. Around this wavelength, the sensitivity is fairly flat in a 80 Å wide interval. The spatial variations of sensitivity along the detector assembly were also measured. The observed trend is related to the quantum efficiency decrease as the angle of the incoming photon trajectories becomes more grazing.

  18. Absolute Infrared Calibration of Standard Stars by the Midcourse Space Experiment

    DTIC Science & Technology

    2004-04-01

    fluxes of standard stars. Using standard stars to calibrate space- and ground-based observations of astronomical sources and Earth satellites has the... Satellite (IRAS). "* Cohen et al. (1 992a; Paper I) derived the absolute infrared flux for a Lyr by extrapolating the recommended visual flux of Hayes... characterized spectral bands. Cohen et al. (1992a) assigned the 1.45 percent uncertainty derived by Hayes (1985) for the calibration in the visual to the

  19. Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak

    SciTech Connect

    Liu, X.; Zhao, H. L.; Liu, Y. Li, E. Z.; Han, X.; Ti, A.; Hu, L. Q.; Zhang, X. D.; Domier, C. W.; Luhmann, N. C.

    2014-09-15

    This paper presents the results of the in situ absolute intensity calibration for the 32-channel heterodyne radiometer on the experimental advanced superconducting tokamak. The hot/cold load method is adopted, and the coherent averaging technique is employed to improve the signal to noise ratio. Measured spectra and electron temperature profiles are compared with those from an independent calibrated Michelson interferometer, and there is a relatively good agreement between the results from the two different systems.

  20. A new method to calibrate the absolute sensitivity of a soft X-ray streak camera

    NASA Astrophysics Data System (ADS)

    Yu, Jian; Liu, Shenye; Li, Jin; Yang, Zhiwen; Chen, Ming; Guo, Luting; Yao, Li; Xiao, Shali

    2016-12-01

    In this paper, we introduce a new method to calibrate the absolute sensitivity of a soft X-ray streak camera (SXRSC). The calibrations are done in the static mode by using a small laser-produced X-ray source. A calibrated X-ray CCD is used as a secondary standard detector to monitor the X-ray source intensity. In addition, two sets of holographic flat-field grating spectrometers are chosen as the spectral discrimination systems of the SXRSC and the X-ray CCD. The absolute sensitivity of the SXRSC is obtained by comparing the signal counts of the SXRSC to the output counts of the X-ray CCD. Results show that the calibrated spectrum covers the range from 200 eV to 1040 eV. The change of the absolute sensitivity in the vicinity of the K-edge of the carbon can also be clearly seen. The experimental values agree with the calculated values to within 29% error. Compared with previous calibration methods, the proposed method has several advantages: a wide spectral range, high accuracy, and simple data processing. Our calibration results can be used to make quantitative X-ray flux measurements in laser fusion research.

  1. Electron cyclotron emission measurements on JET: Michelson interferometer, new absolute calibration, and determination of electron temperature.

    PubMed

    Schmuck, S; Fessey, J; Gerbaud, T; Alper, B; Beurskens, M N A; de la Luna, E; Sirinelli, A; Zerbini, M

    2012-12-01

    At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron temperature is determined from the measurements. The current state of the interferometer hardware, the calibration setup, and the analysis technique for calibration and plasma operation are described. A new, full-system, absolute calibration employing continuous data acquisition has been performed recently and the calibration method and results are presented. The noise level in the measurement is very low and as a result the electron cyclotron emission spectrum and thus the spatial profile of the electron temperature are determined to within ±5% and in the most relevant region to within ±2%. The new calibration shows that the absolute response of the system has decreased by about 15% compared to that measured previously and possible reasons for this change are presented. Temperature profiles measured with the Michelson interferometer are compared with profiles measured independently using Thomson scattering diagnostics, which have also been recently refurbished and recalibrated, and agreement within experimental uncertainties is obtained.

  2. Radiometric Characterization of IKONOS Multispectral Imagery

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Ryan, Robert E.; Kelly, Michelle; Holekamp, Kara; Zanoni, Vicki; Thome, Kurtis; Schiller, Stephen

    2002-01-01

    A radiometric characterization of Space Imaging's IKONOS 4-m multispectral imagery has been performed by a NASA funded team from the John C. Stennis Space Center (SSC), the University of Arizona Remote Sensing Group (UARSG), and South Dakota State University (SDSU). Both intrinsic radiometry and the effects of Space Imaging processing on radiometry were investigated. Relative radiometry was examined with uniform Antarctic and Saharan sites. Absolute radiometric calibration was performed using reflectance-based vicarious calibration methods on several uniform sites imaged by IKONOS, coincident with ground-based surface and atmospheric measurements. Ground-based data and the IKONOS spectral response function served as input to radiative transfer codes to generate a Top-of-Atmosphere radiance estimate. Calibration coefficients derived from each vicarious calibration were combined to generate an IKONOS radiometric gain coefficient for each multispectral band assuming a linear response over the full dynamic range of the instrument. These calibration coefficients were made available to Space Imaging, which subsequently adopted them by updating its initial set of calibration coefficients. IKONOS imagery procured through the NASA Scientific Data Purchase program is processed with or without a Modulation Transfer Function Compensation kernel. The radiometric effects of this kernel on various scene types was also investigated. All imagery characterized was procured through the NASA Scientific Data Purchase program.

  3. Toward consistent radiometric calibration of the NOAA AVHRR visible and near-infrared data record

    NASA Astrophysics Data System (ADS)

    Bhatt, Rajendra; Doelling, David R.; Scarino, Benjamin R.; Gopalan, Arun; Haney, Conor O.

    2015-09-01

    The 35-year Advanced Very High Resolution Radiometer (AVHRR) satellite-instrument data record is critical for studying decadal climate change, provided that the AVHRR sensors are consistently calibrated. Owing to the lack of onboard calibration capability, the AVHRR data need to be adjusted using vicarious approaches. One of the greatest challenges hampering these vicarious calibration techniques, however, is the degrading orbits of the NOAA satellites that house the instruments, or, more specifically, the fact that the satellites eventually drift into a terminator orbit several years after launch. This paper presents a uniform sensor calibration approach for the AVHRR visible (VIS) and nearinfrared (NIR) records using specifically designed NOAA-16 AVHRR-based, top-of-atmosphere (TOA) calibration models that take into account orbit degradation. These models are based on multiple invariant Earth targets, including Saharan deserts, polar ice scenes, and tropical deep-convective clouds. All invariant targets are referenced to the Aqua- MODIS Collection-6 calibration via transfer of the Aqua-MODIS calibration to NOAA-16 AVHRR using simultaneous nadir overpass (SNO) comparisons over the North Pole. A spectral band adjustment factor, based on SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY (SCIAMACHY) spectral radiances, is used to account for the spectrally-induced biases caused by the spectral response function (SRF) differences of the AVHRR and MODIS sensors. Validation of the AVHRR Earth target calibration is performed by comparisons with contemporary MODIS SNOs. Calibration consistency between Earth targets validates the historical AVHRR record.

  4. Image plate characterization and absolute calibration to low kilo-electron-volt electrons

    NASA Astrophysics Data System (ADS)

    Busold, S.; Philipp, K.; Otten, A.; Roth, M.

    2014-11-01

    We report on the characterization of an image plate and its absolute calibration to electrons in the low keV energy range (1-30 keV). In our case, an Agfa MD4.0 without protection layer was used in combination with a Fuji FLA7000 scanner. The calibration data are compared to other published data and a consistent picture of the sensitivity of image plates to electrons is obtained, which suggests a validity of the obtained calibration up to 100 keV.

  5. Image plate characterization and absolute calibration to low kilo-electron-volt electrons.

    PubMed

    Busold, S; Philipp, K; Otten, A; Roth, M

    2014-11-01

    We report on the characterization of an image plate and its absolute calibration to electrons in the low keV energy range (1-30 keV). In our case, an Agfa MD4.0 without protection layer was used in combination with a Fuji FLA7000 scanner. The calibration data are compared to other published data and a consistent picture of the sensitivity of image plates to electrons is obtained, which suggests a validity of the obtained calibration up to 100 keV.

  6. Image plate characterization and absolute calibration to low kilo-electron-volt electrons

    SciTech Connect

    Busold, S.; Philipp, K.; Otten, A.; Roth, M.

    2014-11-15

    We report on the characterization of an image plate and its absolute calibration to electrons in the low keV energy range (1–30 keV). In our case, an Agfa MD4.0 without protection layer was used in combination with a Fuji FLA7000 scanner. The calibration data are compared to other published data and a consistent picture of the sensitivity of image plates to electrons is obtained, which suggests a validity of the obtained calibration up to 100 keV.

  7. New PTB Setup for the Absolute Calibration of the Spectral Responsivity of Radiation Thermometers

    NASA Astrophysics Data System (ADS)

    Anhalt, K.; Zelenjuk, A.; Taubert, D. R.; Keawprasert, T.; Hartmann, J.

    2009-02-01

    The paper describes the new experimental setup assembled at the PTB for the absolute spectral responsivity measurement of radiation thermometers. The concept of this setup is to measure the relative spectral responsivity of the radiation thermometer using the conventional monochromator-based spectral comparator facility also used for the calibration of filter radiometers. The absolute spectral responsivity is subsequently measured at one wavelength, supplied by the radiation of a diode laser, using the new setup. The radiation of the diode laser is guided with an optical fiber into an integrating sphere source that is equipped with an aperture of absolutely known area. The spectral radiance of this integrating sphere source is determined via the spectral irradiance measured by a trap detector with an absolutely calibrated spectral responsivity traceable to the primary detector standard of the PTB, the cryogenic radiometer. First results of the spectral responsivity calibration of the radiation thermometer LP3 are presented, and a provisional uncertainty budget of the absolute spectral responsivity is given.

  8. Absolute flux density calibrations of radio sources: 2.3 GHz

    NASA Technical Reports Server (NTRS)

    Freiley, A. J.; Batelaan, P. D.; Bathker, D. A.

    1977-01-01

    A detailed description of a NASA/JPL Deep Space Network program to improve S-band gain calibrations of large aperture antennas is reported. The program is considered unique in at least three ways; first, absolute gain calibrations of high quality suppressed-sidelobe dual mode horns first provide a high accuracy foundation to the foundation to the program. Second, a very careful transfer calibration technique using an artificial far-field coherent-wave source was used to accurately obtain the gain of one large (26 m) aperture. Third, using the calibrated large aperture directly, the absolute flux density of five selected galactic and extragalactic natural radio sources was determined with an absolute accuracy better than 2 percent, now quoted at the familiar 1 sigma confidence level. The follow-on considerations to apply these results to an operational network of ground antennas are discussed. It is concluded that absolute gain accuracies within + or - 0.30 to 0.40 db are possible, depending primarily on the repeatability (scatter) in the field data from Deep Space Network user stations.

  9. Providing radiometric traceability for the calibration home base of DLR by PTB

    NASA Astrophysics Data System (ADS)

    Taubert, D. R.; Hollandt, J.; Sperfeld, P.; Pape, S.; Höpe, A.; Hauer, K.-O.; Gege, P.; Schwarzmaier, T.; Lenhard, K.; Baumgartner, A.

    2013-05-01

    A dedicated calibration technique was applied for the calibration of the spectral radiance transfer standard (RASTA) of the German Aerospace Center (DLR) at the Physikalisch-Technische Bundesanstalt (PTB), consisting of two independent but complementing calibration procedures to provide redundancy and smallest possible calibration uncertainties. Procedure I included two calibration steps: In a first step the optical radiation source of RASTA, an FEL lamp, was calibrated in terms of its spectral irradiance Eλ(λ) in the wavelength range from 350 nm to 2400 nm using the PTB Spectral Irradiance Calibration Equipment (SPICE), while in a second step the spectral radiance factor β0°:45°(λ) of the RASTA reflection standard was calibrated in a 0°:45°-viewing geometry in the wavelength range from 350 nm to 1700 nm at the robot-based gonioreflectometer facility of PTB. The achieved relative standard uncertainties (k = 1) range from 0.6 % to 3.2 % and 0.1 % to 0.6 % respectively. Procedure II was completely independent from procedure I and allowed to cover the entire spectral range of RASTA from 350 nm to 2500 nm. In the second procedure, the 0°:45°-viewing geometry spectral radiance Lλ,0°:45°(λ) of RASTA was directly calibrated at the Spectral Radiance Comparator Facility (SRCF) of PTB. The relative uncertainties for this calibration procedure range from 0.8 % in the visible up to 7.5 % at 2500 nm (k = 1). In the overlapping spectral range of both calibration procedures the calculated spectral radiance Lλ,0°:45°,calc(λ) from procedure I is in good agreement with the direct measurement of procedure II, i.e. well within the combined expanded uncertainties (k = 2) of both procedures.

  10. Providing radiometric traceability for the calibration home base of DLR by PTB

    SciTech Connect

    Taubert, D. R.; Hollandt, J.; Sperfeld, P.; Pape, S.; Hoepe, A.; Hauer, K.-O.; Gege, P.; Schwarzmaier, T.; Lenhard, K.; Baumgartner, A.

    2013-05-10

    A dedicated calibration technique was applied for the calibration of the spectral radiance transfer standard (RASTA) of the German Aerospace Center (DLR) at the Physikalisch-Technische Bundesanstalt (PTB), consisting of two independent but complementing calibration procedures to provide redundancy and smallest possible calibration uncertainties. Procedure I included two calibration steps: In a first step the optical radiation source of RASTA, an FEL lamp, was calibrated in terms of its spectral irradiance E{sub {lambda}}({lambda}) in the wavelength range from 350 nm to 2400 nm using the PTB Spectral Irradiance Calibration Equipment (SPICE), while in a second step the spectral radiance factor {beta}{sub 0 Degree-Sign :45 Degree-Sign }({lambda}) of the RASTA reflection standard was calibrated in a 0 Degree-Sign :45 Degree-Sign -viewing geometry in the wavelength range from 350 nm to 1700 nm at the robot-based gonioreflectometer facility of PTB. The achieved relative standard uncertainties (k= 1) range from 0.6 % to 3.2 % and 0.1 % to 0.6 % respectively. Procedure II was completely independent from procedure I and allowed to cover the entire spectral range of RASTA from 350 nm to 2500 nm. In the second procedure, the 0 Degree-Sign :45 Degree-Sign -viewing geometry spectral radiance L{sub {lambda},0 Degree-Sign :45 Degree-Sign }({lambda}) of RASTA was directly calibrated at the Spectral Radiance Comparator Facility (SRCF) of PTB. The relative uncertainties for this calibration procedure range from 0.8 % in the visible up to 7.5 % at 2500 nm (k= 1). In the overlapping spectral range of both calibration procedures the calculated spectral radiance L{sub {lambda},0 Degree-Sign :45 Degree-Sign ,calc}({lambda}) from procedure I is in good agreement with the direct measurement of procedure II, i.e. well within the combined expanded uncertainties (k= 2) of both procedures.

  11. A new determination of the Geneva photometric passbands and their absolute calibration

    NASA Astrophysics Data System (ADS)

    Rufener, F.; Nicolet, B.

    The consensus regarding the absolute calibrations of the spectra of alpha Lyr and subdwarfs provoked a revision of the calibration of the Geneva photometric system passbands. The alterations made to the earlier version by Rufener and Maeder (1971) are smaller than plus or minus -5 percent. The new response functions are presented in tabular form for an equiphotonic flux. An absolute spectrophotometric adjustment allows to obtain for each entry of the Geneva catalog (28,000 stars) a corresponding spectrophotometric description in SI units. The definition and the means of computing the necessary quasi-isophotal frequencies or wavelengths are given. The coherence of the Geneva catalog with several sets of absolute spectrophotometric data is examined. A correction for the entire Gunn and Stryker (1983) catalog is proposed.

  12. Radiometric calibration of the Coastal Zone Color Scanner on Nimbus 7: a proposed adjustment.

    PubMed

    Viollier, M

    1982-03-15

    Ground measurements of water reflectances for two very clear days, allied with computations of atmospheric effects, are compared with satellite data of the Coastal Zone Color Scanner. This exercise points out significant errors in the calibration of the scanner. A new set of calibration constants, which standardizes radiances relative to the extraterrestrial solar irradiance, is proposed.

  13. Absolute calibration of an ultraviolet spectrometer using a stabilized laser and a cryogenic cavity radiometer

    NASA Technical Reports Server (NTRS)

    Jauniskis, L.; Foukal, P.; Kochling, H.

    1992-01-01

    We carry out the calibration of an ultraviolet spectrometer by using a cryogenic electrical-substitution radiometer and intensity-stabilized laser sources. A comparison of the error budgets for the laser-based calibration described here and for a calibration using a type-FEL tungsten spectral-irradiance standard indicates that this technique could provide an improvement of a factor of about three in the uncertainty of the spectrometer calibration, resulting in an absolute accuracy (standard deviation of three) of about 1 percent at 257 nm. The technique described here might significantly improve the accuracy of calibrations on NASA ozone-monitoring and solar ultraviolet-monitoring spectrophotometers when used to complement present procedures that employ lamps and the SURF II synchrotron ultraviolet radiation facility at the National Institute of Standards and Technology.

  14. Absolute calibration of an ultraviolet spectrometer using a stabilized laser and a cryogenic cavity radiometer.

    PubMed

    Jauniskis, L; Foukal, P; Kochling, H

    1992-09-20

    We carry out the calibration of an ultraviolet spectrometer by using a cryogenic electrical-substitution radiometer and intensity-stabilized laser sources. A comparison of the error budgets for the laser-based calibration described here and for a calibration using a type-FEL tungsten spectral-irradiance standard indicates that this technique could provide an improvement of a factor of ~3 in the uncertainty of the spectrometer calibration, resulting in an absolute accuracy (standard deviation of 3) of ~1% at 257 nm. The technique described here might significantly improve the accuracy of calibrations on NASA ozone-monitoring and solar ultraviolet-monitoring spectrophotometers when used to complement present procedures that employ lamps and the SURF II synchrotron ultraviolet radiation facility at the National Institute of Standards and Technology.

  15. Radiometric calibration of the Visible Infrared Imaging Radiometer Suite reflective solar bands with robust characterizations and hybrid calibration coefficients.

    PubMed

    Sun, Junqiang; Wang, Menghua

    2015-11-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) is now entering its fourth year of in-orbit global environmental observation and is producing a wide range of scientific output. The ocean color products in particular require a level of accuracy from the reflective solar bands (RSBs) that is a magnitude higher than the specification. In this work, we present an updated and completed core calibration pipeline that achieves the best sensor data records (SDR) to date and helps the ocean color products to reach maturity. We review the core calibration methodology of the RSBs and describe each essential input, including the solar diffuser stability monitor, the solar diffuser (SD), and lunar calibrations. Their associated issues, along with the successful mitigation and improved results, are described and presented. In particular, we illuminate the inaccuracy suffered due to the evolving angular dependence in the degradation of the on-board SD that impacts the heart of the RSB calibration, but also show that lunar-based calibration instead provides the correct long-term baseline for the successful restoration of the core methodology. The new look-up tables, which combine the coefficients from the SD-based and lunar-based calibrations, produce the optimal result, with an estimated accuracy of ∼0.2%. This hybrid approach highlights significant progress in the VIIRS RSB calibration and marks a completion of the core calibration result upon which other physical impacts or scientific issues can then be more accurately examined. We demonstrate the significant improvement and its impact on the ocean color products by comparing the current official output to the newly generated result. Lastly, we point out that this hybrid calibration coefficients scheme is made possible by a VIIRS design and layout change over its predecessor, the Moderate Resolution Imaging Spectroradiometer, that allows both the SD and the moon to be viewed by the RSB at the same angle of incidence

  16. Contributed Review: Absolute spectral radiance calibration of fiber-optic shock-temperature pyrometers using a coiled-coil irradiance standard lamp

    NASA Astrophysics Data System (ADS)

    Fat'yanov, O. V.; Asimow, P. D.

    2015-10-01

    We describe an accurate and precise calibration procedure for multichannel optical pyrometers such as the 6-channel, 3-ns temporal resolution instrument used in the Caltech experimental geophysics laboratory. We begin with a review of calibration sources for shock temperatures in the 3000-30 000 K range. High-power, coiled tungsten halogen standards of spectral irradiance appear to be the only practical alternative to NIST-traceable tungsten ribbon lamps, which are no longer available with large enough calibrated area. However, non-uniform radiance complicates the use of such coiled lamps for reliable and reproducible calibration of pyrometers that employ imaging or relay optics. Careful analysis of documented methods of shock pyrometer calibration to coiled irradiance standard lamps shows that only one technique, not directly applicable in our case, is free of major radiometric errors. We provide a detailed description of the modified Caltech pyrometer instrument and a procedure for its absolute spectral radiance calibration, accurate to ±5%. We employ a designated central area of a 0.7× demagnified image of a coiled-coil tungsten halogen lamp filament, cross-calibrated against a NIST-traceable tungsten ribbon lamp. We give the results of the cross-calibration along with descriptions of the optical arrangement, data acquisition, and processing. We describe a procedure to characterize the difference between the static and dynamic response of amplified photodetectors, allowing time-dependent photodiode correction factors for spectral radiance histories from shock experiments. We validate correct operation of the modified Caltech pyrometer with actual shock temperature experiments on single-crystal NaCl and MgO and obtain very good agreement with the literature data for these substances. We conclude with a summary of the most essential requirements for error-free calibration of a fiber-optic shock-temperature pyrometer using a high-power coiled tungsten halogen

  17. Contributed Review: Absolute spectral radiance calibration of fiber-optic shock-temperature pyrometers using a coiled-coil irradiance standard lamp

    SciTech Connect

    Fat’yanov, O. V. Asimow, P. D.

    2015-10-15

    We describe an accurate and precise calibration procedure for multichannel optical pyrometers such as the 6-channel, 3-ns temporal resolution instrument used in the Caltech experimental geophysics laboratory. We begin with a review of calibration sources for shock temperatures in the 3000-30 000 K range. High-power, coiled tungsten halogen standards of spectral irradiance appear to be the only practical alternative to NIST-traceable tungsten ribbon lamps, which are no longer available with large enough calibrated area. However, non-uniform radiance complicates the use of such coiled lamps for reliable and reproducible calibration of pyrometers that employ imaging or relay optics. Careful analysis of documented methods of shock pyrometer calibration to coiled irradiance standard lamps shows that only one technique, not directly applicable in our case, is free of major radiometric errors. We provide a detailed description of the modified Caltech pyrometer instrument and a procedure for its absolute spectral radiance calibration, accurate to ±5%. We employ a designated central area of a 0.7× demagnified image of a coiled-coil tungsten halogen lamp filament, cross-calibrated against a NIST-traceable tungsten ribbon lamp. We give the results of the cross-calibration along with descriptions of the optical arrangement, data acquisition, and processing. We describe a procedure to characterize the difference between the static and dynamic response of amplified photodetectors, allowing time-dependent photodiode correction factors for spectral radiance histories from shock experiments. We validate correct operation of the modified Caltech pyrometer with actual shock temperature experiments on single-crystal NaCl and MgO and obtain very good agreement with the literature data for these substances. We conclude with a summary of the most essential requirements for error-free calibration of a fiber-optic shock-temperature pyrometer using a high-power coiled tungsten halogen

  18. Solar Tower Experiments for Radiometric Calibration and Validation of Infrared Imaging Assets and Analysis Tools for Entry Aero-Heating Measurements

    NASA Technical Reports Server (NTRS)

    Splinter, Scott C.; Daryabeigi, Kamran; Horvath, Thomas J.; Mercer, David C.; Ghanbari, Cheryl M.; Ross, Martin N.; Tietjen, Alan; Schwartz, Richard J.

    2008-01-01

    The NASA Engineering and Safety Center sponsored Hypersonic Thermodynamic Infrared Measurements assessment team has a task to perform radiometric calibration and validation of land-based and airborne infrared imaging assets and tools for remote thermographic imaging. The IR assets and tools will be used for thermographic imaging of the Space Shuttle Orbiter during entry aero-heating to provide flight boundary layer transition thermography data that could be utilized for calibration and validation of empirical and theoretical aero-heating tools. A series of tests at the Sandia National Laboratories National Solar Thermal Test Facility were designed for this task where reflected solar radiation from a field of heliostats was used to heat a 4 foot by 4 foot test panel consisting of LI 900 ceramic tiles located on top of the 200 foot tall Solar Tower. The test panel provided an Orbiter-like entry temperature for the purposes of radiometric calibration and validation. The Solar Tower provided an ideal test bed for this series of radiometric calibration and validation tests because it had the potential to rapidly heat the large test panel to spatially uniform and non-uniform elevated temperatures. Also, the unsheltered-open-air environment of the Solar Tower was conducive to obtaining unobstructed radiometric data by land-based and airborne IR imaging assets. Various thermocouples installed on the test panel and an infrared imager located in close proximity to the test panel were used to obtain surface temperature measurements for evaluation and calibration of the radiometric data from the infrared imaging assets. The overall test environment, test article, test approach, and typical test results are discussed.

  19. Radiometric Modeling and Calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS)Ground Based Measurement Experiment

    NASA Technical Reports Server (NTRS)

    Tian, Jialin; Smith, William L.; Gazarik, Michael J.

    2008-01-01

    The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere s thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As an important step toward realizing this application objective, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) was successfully developed under the NASA New Millennium Program, 2000-2006. The GIFTS-EDU instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The GIFTS calibration is achieved using internal blackbody calibration references at ambient (260 K) and hot (286 K) temperatures. In this paper, we introduce a refined calibration technique that utilizes Principle Component (PC) analysis to compensate for instrument distortions and artifacts, therefore, enhancing the absolute calibration accuracy. This method is applied to data collected during the GIFTS Ground Based Measurement (GBM) experiment, together with simultaneous observations by the accurately calibrated AERI (Atmospheric Emitted Radiance Interferometer), both simultaneously zenith viewing the sky through the same external scene mirror at ten-minute intervals throughout a cloudless day at Logan Utah on September 13, 2006. The accurately calibrated GIFTS radiances are produced using the first four PC scores in the GIFTS-AERI regression model. Temperature and moisture profiles retrieved from the PC-calibrated GIFTS radiances are verified against radiosonde measurements collected throughout the GIFTS sky measurement period. Using the GIFTS GBM calibration model, we compute the calibrated radiances from data

  20. Four Years of Absolutely Calibrated Hyperspectral Data from the Atmospheric Infrared Sounder (AIRS) on the Eos Aqua

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Broberg, Steve; Elliott, Denis; Gregorich, Dave

    2006-01-01

    This viewgraph presentation reviews four years of absolute calibration of hyperspectral data from the AIRS instrument located on the EOS AQUA spacecraft. The following topics are discussed: 1) A quick overview of AIRS; 2) What absolute calibration accuracy and stability are required for climate applications?; 3) Validating of radiance accuracy and stability: Results from four years of AIRS data; and 4) Conclusions.

  1. Absolute calibration of neutron detectors on the C-2U advanced beam-driven FRC

    NASA Astrophysics Data System (ADS)

    Magee, R. M.; Clary, R.; Korepanov, S.; Jauregui, F.; Allfrey, I.; Garate, E.; Valentine, T.; Smirnov, A.

    2016-11-01

    In the C-2U fusion energy experiment, high power neutral beam injection creates a large fast ion population that sustains a field-reversed configuration (FRC) plasma. The diagnosis of the fast ion pressure in these high-performance plasmas is therefore critical, and the measurement of the flux of neutrons from the deuterium-deuterium (D-D) fusion reaction is well suited to the task. Here we describe the absolute, in situ calibration of scintillation neutron detectors via two independent methods: firing deuterium beams into a high density gas target and calibration with a 2 × 107 n/s AmBe source. The practical issues of each method are discussed and the resulting calibration factors are shown to be in good agreement. Finally, the calibration factor is applied to C-2U experimental data where the measured neutron rate is found to exceed the classical expectation.

  2. Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system

    NASA Astrophysics Data System (ADS)

    Baltzer, M. M.; Craig, D.; Den Hartog, D. J.; Nishizawa, T.; Nornberg, M. D.

    2016-11-01

    An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.

  3. Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system.

    PubMed

    Baltzer, M M; Craig, D; Den Hartog, D J; Nishizawa, T; Nornberg, M D

    2016-11-01

    An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.

  4. A Novel Nonintrusive Method to Resolve the Thermal Dome Effect of Pyranometers: Radiometric Calibration and Implications

    NASA Technical Reports Server (NTRS)

    Ji. Q.; Tsay, S.-C.; Lau, K. M.; Hansell, R. A.; Butler, J. J.; Cooper, J. W.

    2011-01-01

    Traditionally the calibration equation for pyranometers assumes that the measured solar irradiance is solely proportional to the thermopile s output voltage; therefore, only a single calibration factor is derived. This causes additional measurement uncertainties because it does not capture sufficient information to correctly account for a pyranometer s thermal effect. In our updated calibration equation, temperatures from the pyranometer's dome and case are incorporated to describe the instrument's thermal behavior, and a new set of calibration constants are determined, thereby reducing measurement uncertainties. In this paper, we demonstrate why a pyranometer's uncertainty using the traditional calibration equation is always larger than a few percent, but with the new approach can become much less than 1% after the thermal issue is resolved. The highlighted calibration results are based on NIST traceable light sources under controlled laboratory conditions. The significance of the new approach lends itself to not only avoiding the uncertainty caused by a pyranometer's thermal effect but also the opportunity to better isolate and characterize other instrumental artifacts, such as angular response and nonlinearity of the thermopile, to further reduce additional uncertainties. We also discuss some of the implications, including an example of how the thermal issue can potentially impact climate studies by evaluating aerosol s direct radiative effect using field measurements with and without considering the pyranometer s thermal effect. The results of radiative transfer model simulation show that a pyranometer s thermal effect on solar irradiance measurements at the surface can be translated into a significant alteration of the calculated distribution of solar energy inside the column atmosphere.

  5. Rapid, Absolute Calibration of X-ray Filters Employed By Laser-Produced Plasma Diagnostics

    SciTech Connect

    Brown, G V; Beiersdorfer, P; Emig, J; Frankel, M; Gu, M F; Heeter, R F; Magee, E; Thorn, D B; Widmann, K; . Kelley, R L; Kilbourne, C A; Porter, F S

    2008-05-11

    The electron beam ion trap (EBIT) facility at the Lawrence Livermore National Laboratory is being used to absolutely calibrate the transmission efficiency of X-ray filters employed by diodes and spectrometers used to diagnose laser-produced plasmas. EBIT emits strong, discrete monoenergetic lines at appropriately chosen X-ray energies. X-rays are detected using the high-resolution EBIT calorimeter spectrometer (ECS), developed for LLNL at the NASA/Goddard Space Flight Center. X-ray filter transmission efficiency is determined by dividing the X-ray counts detected when the filter is in the line of sight by those detected when out of the line of sight. Verification of filter thickness can be completed in only a few hours, and absolute efficiencies can be calibrated in a single day over a broad range from about 0.1 to 15 keV. The EBIT calibration lab has been used to field diagnostics (e.g., the OZSPEC instrument) with fully calibrated X-ray filters at the OMEGA laser. Extensions to use the capability for calibrating filter transmission for the DANTE instrument on the National Ignition Facility are discussed.

  6. Absolute Time Error Calibration of GPS Receivers Using Advanced GPS Simulators

    DTIC Science & Technology

    1997-12-01

    29th Annual Precise Time a d Time Interval (PTTI) Meeting ABSOLUTE TIME ERROR CALIBRATION OF GPS RECEIVERS USING ADVANCED GPS SIMULATORS E.D...DC 20375 USA Abstract Preche time transfer eq)er&nen& using GPS with t h e stabd?v’s under ten nanoseconh are common& being reported willrbr the... time transfer communily. Relarive calibrations are done by naeasurhg the time error of one GPS receiver versus a “known master refmence receiver.” Z?t

  7. Absolute distance measurement using frequency-sweeping heterodyne interferometer calibrated by an optical frequency comb.

    PubMed

    Wu, Xuejian; Wei, Haoyun; Zhang, Hongyuan; Ren, Libing; Li, Yan; Zhang, Jitao

    2013-04-01

    We present a frequency-sweeping heterodyne interferometer to measure an absolute distance based on a frequency-tunable diode laser calibrated by an optical frequency comb (OFC) and an interferometric phase measurement system. The laser frequency-sweeping process is calibrated by the OFC within a range of 200 GHz and an accuracy of 1.3 kHz, which brings about a precise temporal synthetic wavelength of 1.499 mm. The interferometric phase measurement system consisting of the analog signal processing circuit and the digital phase meter achieves a phase difference resolution better than 0.1 deg. As the laser frequency is sweeping, the absolute distance can be determined by measuring the phase difference variation of the interference signals. In the laboratory condition, our experimental scheme realizes micrometer accuracy over meter distance.

  8. Exact Theory of Optical Tweezers and Its Application to Absolute Calibration.

    PubMed

    Dutra, Rafael S; Viana, Nathan B; Neto, Paulo A Maia; Nussenzveig, H Moysés

    2017-01-01

    Optical tweezers have become a powerful tool for basic and applied research in cell biology. Here, we describe an experimentally verified theory for the trapping forces generated by optical tweezers based on first principles that allows absolute calibration. For pedagogical reasons, the steps that led to the development of the theory over the past 15 years are outlined. The results are applicable to a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Protocols for implementing absolute calibration are given, explaining how to measure all required experimental parameters, and including a link to an applet for stiffness calculations.

  9. JACIE Radiometric Assessment of QuickBird Multispectral Imagery

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Carver, David; Holekamp, Kara; Knowlton, Kelly; Ryan, Robert; Zanoni, Vicki; Thome, Kurtis; Aaron, David

    2004-01-01

    Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities can place confidence in the imagery they use and can fully understand its properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other systems. To address this calibration need, the NASA Stennis Space Center (SSC) Earth Science Applications (ESA) directorate,through the Joint Agency for Commercial Imagery Evaluation (JACIE) framework, established a commercial imaging satellite radiometric calibration team consisting of two groups: 1) NASA SSC ESA, supported by South Dakota State University, and 2) the University of Arizona Remote Sensing Group. The two groups determined the absolute radiometric calibration coefficients of the Digital Globe 4-band, 2.4-m QuickBird multispectral product covering the visible through near-infrared spectral region. For a 2-year period beginning in 2002, both groups employed some variant of a reflectance-based vicarious calibration approach, which required ground-based measurements coincident with QuickBird image acquisitions and radiative transfer calculations. The groups chose several study sites throughout the United States that covered nearly the entire dynamic range of the QuickBird sensor. QuickBird at-sensor radiance values were compared with those estimated by the two independent groups to determine the QuickBird sensor's radiometric accuracy. Approximately 20 at-sensor radiance estimates were vicariously determined each year. The estimates were combined to provide a high-precision radiometric gain calibration coefficient. The results of this evaluation provide the user community with an independent assessment of the QuickBird sensor's absolute calibration and stability over the 2-year period. While the techniques and method described reflect those developed at the NASA SSC, the results of both JACIE team groups are

  10. Absolute calibration of photon-number-resolving detectors with an analog output using twin beams

    SciTech Connect

    Peřina, Jan; Haderka, Ondřej; Allevi, Alessia; Bondani, Maria

    2014-01-27

    A method for absolute calibration of a photon-number resolving detector producing analog signals as the output is developed using a twin beam. The method gives both analog-to-digital conversion parameters and quantum detection efficiency for the photon fields. Characteristics of the used twin beam are also obtained. A simplified variant of the method applicable to fields with high signal to noise ratios and suitable for more intense twin beams is suggested.

  11. The on-orbit performance of the Orbiting Carbon Observatory-2 (OCO-2) instrument and its radiometrically calibrated products

    NASA Astrophysics Data System (ADS)

    Crisp, David; Pollock, Harold R.; Rosenberg, Robert; Chapsky, Lars; Lee, Richard A. M.; Oyafuso, Fabiano A.; Frankenberg, Christian; O'Dell, Christopher W.; Bruegge, Carol J.; Doran, Gary B.; Eldering, Annmarie; Fisher, Brendan M.; Fu, Dejian; Gunson, Michael R.; Mandrake, Lukas; Osterman, Gregory B.; Schwandner, Florian M.; Sun, Kang; Taylor, Tommy E.; Wennberg, Paul O.; Wunch, Debra

    2017-01-01

    The Orbiting Carbon Observatory-2 (OCO-2) carries and points a three-channel imaging grating spectrometer designed to collect high-resolution, co-boresighted spectra of reflected sunlight within the molecular oxygen (O2) A-band at 0.765 microns and the carbon dioxide (CO2) bands at 1.61 and 2.06 microns. These measurements are calibrated and then combined into soundings that are analyzed to retrieve spatially resolved estimates of the column-averaged CO2 dry-air mole fraction, XCO2. Variations of XCO2 in space and time are then analyzed in the context of the atmospheric transport to quantify surface sources and sinks of CO2. This is a particularly challenging remote-sensing observation because all but the largest emission sources and natural absorbers produce only small (< 0.25 %) changes in the background XCO2 field. High measurement precision is therefore essential to resolve these small variations, and high accuracy is needed because small biases in the retrieved XCO2 distribution could be misinterpreted as evidence for CO2 fluxes. To meet its demanding measurement requirements, each OCO-2 spectrometer channel collects 24 spectra s-1 across a narrow (< 10 km) swath as the observatory flies over the sunlit hemisphere, yielding almost 1 million soundings each day. On monthly timescales, between 7 and 12 % of these soundings pass the cloud screens and other data quality filters to yield full-column estimates of XCO2. Each of these soundings has an unprecedented combination of spatial resolution (< 3 km2/sounding), spectral resolving power (λ/Δλ > 17 000), dynamic range (˜ 104), and sensitivity (continuum signal-to-noise ratio > 400). The OCO-2 instrument performance was extensively characterized and calibrated prior to launch. In general, the instrument has performed as expected during its first 18 months in orbit. However, ongoing calibration and science analysis activities have revealed a number of subtle radiometric and spectroscopic challenges that affect

  12. First absolutely calibrated on-axis ion flow measurements in MST

    NASA Astrophysics Data System (ADS)

    Schott, B.; Baltzer, M.; Craig, D.; den Hartog, D. J.; Nishizawa, T.; Nornberg, M. D.

    2016-10-01

    Improvements in absolute calibration techniques allow for the first direct measurements of the flow profile in the core of MST. We use both active charge exchange recombination spectroscopy and passive emission near 343 nm to measure ion temperature and flow. It is generally assumed that O VI is the brightest passive emission source. However, we show that there are cases, such as high temperature, pulsed poloidal current drive (PPCD) plasmas where the passive emission is dominated by C VI. Differences in the fine structure for O VI and C VI result in a systematic velocity error of about 12 km/s if the wrong model is assumed. Active measurements, however, are relatively insensitive to background model choice. The dominant source of error in active velocity measurements remains the systematic errors in calibration. The first absolutely calibrated, localized toroidal velocity measurements were obtained using an updated calibration technique. During PPCD, the on-axis ion flow is up to 40 km/s larger than both the n = 6 mode velocity and the line-averaged ion velocity. These measurements provide the first direct look at the flow profile in the core of MST. This work has been supported by the US DOE and the Wheaton College summer research program.

  13. Calibration of Fourier domain short coherence interferometer for absolute distance measurements.

    PubMed

    Montonen, R; Kassamakov, I; Hæggström, E; Österberg, K

    2015-05-20

    We calibrated and determined the measurement uncertainty of a custom-made Fourier domain short coherence interferometer operated in laboratory conditions. We compared the optical thickness of two thickness standards and three coverslips determined with our interferometer to the geometric thickness determined by SEM. Using this calibration data, we derived a calibration function with a 95% confidence level system uncertainty of (5.9×10(-3)r+2.3)  μm, where r is the optical distance in μm, across the 240 μm optical measurement range. The confidence limit includes contributions from uncertainties in the optical thickness, geometric thickness, and refractive index measurements as well as uncertainties arising from cosine errors and thermal expansion. The results show feasibility for noncontacting absolute distance characterization with micrometer-level accuracy. This instrument is intended for verifying the alignment of the discs of an accelerating structure in the possible future compact linear collider.

  14. New apparatus for calibrations in the range of 2 kPa absolute pressure

    NASA Astrophysics Data System (ADS)

    Woo, S. Y.; Choi, I. M.

    2005-12-01

    Capacitance diaphragm gauges (CDGs) are precise electromechanical pressure sensors in which the displacement of a stretched thin metal diaphragm is detected by the measurement of a capacitance. These are very accurate gauges, and are frequently used as transfer gauges. To calibrate such accurate low-pressure gauges, precise mercury manometers have been used. However, complexity, concern about mercury vapour, and cost of mercury manometers have made it difficult to use these manometers in many industrial calibration laboratories. As a substitute, gas-operated piston gauges can be used for the calibration of such low-pressure gauges. However, the minimum pressure that is necessary to balance the tare weight, which generally corresponds to a pressure of several kilopascals, is a major obstacle. To reduce this minimum operating pressure, we adopted a variable bell-jar pressure method. To realize this method effectively, we developed a new mass-handling device that makes it possible to add or remove weights up to 200 g easily, with a resolution of 10 g, without breaking the vacuum during the calibration. This calibration system can be used to measure pressures from 100 Pa to 2 kPa in the absolute mode. In this paper, we also present the calibration results for two types of CDGs with full-scale ranges of 1330 Pa and 1000 Pa, respectively.

  15. Absolute photometric calibration of detectors to 0.3 mmag using amplitude-stabilized lasers and a helium-cooled absolute radiometer

    NASA Technical Reports Server (NTRS)

    Miller, Peter J.

    1988-01-01

    Laser sources whose intensity is determined with a cryogenic electrical substitution radiometer are described. Detectors are then calibrated against this known flux, with an overall error of 0.028 percent (0.3 mmag). Ongoing research has produced laser intensity stabilizers with flicker and drift of less than 0.01 percent. Recently, the useful wavelength limit of these stabilizers have been extended to 1.65 microns by using a new modular technology and InGaAs detector systems. Data from Si photodiode calibration using the method of Zalewski and Geist are compared against an absolute cavity radiometer calibration as an internal check on the calibration system.

  16. Photovoltaics radiometric issues and needs

    SciTech Connect

    Myers, D.R.

    1995-11-01

    This paper presents a summary of issues discussed at the photovoltaic radiometric measurements workshop. Topics included radiometric measurements guides, the need for well-defined goals, documentation, calibration checks, accreditation of testing laboratories and methods, the need for less expensive radiometric instrumentation, data correlations, and quality assurance.

  17. Absolute calibration of a soft X-ray spectrograph for X-ray laser research using white beam.

    PubMed

    Fujikawa, C; Kawachi, T; Ando, K; Yamaguchi, N; Hara, T

    1998-05-01

    Absolute calibration of a soft X-ray spectrograph has been performed using a white beam of synchrotron radiation. The calibrated spectrograph was a flat-field grazing-incidence spectrograph with an X-ray CCD detector for X-ray laser research. Absolute sensitivity of the spectrograph system can be obtained from transmitted spectra using filters made of several different materials, each providing an absorption-edge wavelength standard. The absolute sensitivity determined in this work shows nearly the same behaviour with wavelength as that in another calibration experiment using a laser-produced plasma as an X-ray source.

  18. Improvement in absolute calibration accuracy of Landsat-5 TM with Landsat-7 ETM+ data

    USGS Publications Warehouse

    Chander, G.; Markham, B.L.; Micijevic, E.; Teillet, P.M.; Helder, D.L.; ,

    2005-01-01

    The ability to detect and quantify changes in the Earth's environment depends on satellites sensors that can provide calibrated, consistent measurements of Earth's surface features through time. A critical step in this process is to put image data from subsequent generations of sensors onto a common radiometric scale. To evaluate Landsat-5 (L5) Thematic Mapper's (TM) utility in this role, image pairs from the L5 TM and Landsat-7 (L7) Enhanced Thematic Mapper Plus (ETM+) sensors were compared. This approach involves comparison of surface observations based on image statistics from large common areas observed eight days apart by the two sensors. The results indicate a significant improvement in the consistency of L5 TM data with respect to L7 ETM+ data, achieved using a revised Look-Up-Table (LUT) procedure as opposed to the historical Internal Calibrator (IC) procedure previously used in the L5 TM product generation system. The average percent difference in reflectance estimates obtained from the L5 TM agree with those from the L7 ETM+ in the Visible and Near Infrared (VNIR) bands to within four percent and in the Short Wave Infrared (SWIR) bands to within six percent.

  19. VNIR, MWIR, and LWIR source assemblies for optical quality testing and spectro-radiometric calibration of earth observation satellites

    NASA Astrophysics Data System (ADS)

    Compain, Eric; Maquet, Philippe; Leblay, Pierrick; Gavaud, Eric; Marque, Julien; Glastre, Wilfried; Cortese, Maxime; Sugranes, Pierre; Gaillac, Stephanie; Potheau, Hervé

    2015-09-01

    This document presents several original OGSEs, Optical Ground Support Equipment, specifically designed and realized for the optical testing and calibration of earth observation satellites operating in a large spectral band from 0.4μm to 14.7μm. This work has been mainly supported by recent development dedicated to MTG, Meteosat Third Generation, the ESA next generation of meteorological satellites. The improved measurement capabilities of this new satellite generation has generated new challenging requirements for the associated optical test equipments. These improvements, based on design and component innovation will be illustrated for the MOTA, the GICS and the DEA OGSEs. MOTA and GICS are dedicated to the AIT, Assembly Integration and Test, of FCI, the Flexible Combined Imager of the imaging satellite MTG-I. DEA OGSE is dedicated to the AIT of the DEA, Detection Electronics Assembly, which is part of IRS instrument, an IR sounder part of MTG-S satellite. From an architectural point of view, the presented original designs enable to run many optical tests with a single system thanks to a limited configuration effort. Main measurement capabilities are optical quality testing (MTF based mainly on KEF measurement), Line of Sight (LoS) stability measurement, straylight analyses, VNIR-MWIR-LWIR focal plane array co-registration, and broadband large dynamic spectro-radiometric calibration. Depending on the AIT phase of the satellite, these source assemblies are operated at atmospheric pressure or under secondary vacuum. In operation, they are associated with an opto-mechanical projection system that enables to conjugate the image of the source assembly with the focal plane of the satellite instruments. These conjugation systems are usually based on high resolution, broadband collimator, and are optionally mounted on hexapod to address the entire field of instruments.

  20. Absolute Calibration of Si iRMs used for Si Paleo-nutrient proxies

    NASA Astrophysics Data System (ADS)

    Vocke, Robert; Rabb, Savelas

    2016-04-01

    The Avogadro Project is an ongoing international effort, coordinated by the International Bureau of Weights and Measures (BIPM) and the International Avogadro Coordination (IAC) to redefine the SI unit mole in terms of the Avogadro constant and the SI unit kg in terms of the Planck constant. One of the outgrowths of this effort has been the development of a novel, precise and highly accurate method to measure calibrated (absolute) isotopic ratios that are traceable to the SI (Vocke et al., 2014 Metrologia 51, 361, Azuma et al., 2015 Metrologia 52 360). This approach has also been able to produce absolute Si isotope ratio data with lower levels of uncertainty when compared to the traditional "Atomic Weights" method of absolute isotope ratio measurement. Silicon isotope variations (reported as delta(Si30)and delta(Si29)) in silicic acid dissolved in ocean waters, in biogenic silica and in diatoms are extremely informative paleo-nutrient proxies. The utility and comparability of such measurements however depends on calibration with artifact isotopic Reference Materials (iRMs). We will be reporting new measurements on the iRMs NBS-28 (RM 8546 - Silica Sand), Diatomite, Big Batch and SRM 990 using the Avogadro measurement approach, comparing them with prior assessments of these iRMs.

  1. Radiometric correction procedure study

    NASA Technical Reports Server (NTRS)

    Colby, C.; Sands, R.; Murphrey, S.

    1978-01-01

    A comparison of MSS radiometric processing techniques identified as a preferred radiometric processing technique a procedure which equalizes the mean and standard deviation of detector-specific histograms of uncalibrated scene data. Evaluation of MSS calibration data demonstrated that the relationship between detector responses is essentially linear over the range of intensities typically observed in MSS data, and that the calibration wedge data possess a high degree of temporal stability. An analysis of the preferred radiometric processing technique showed that it could be incorporated into the MDP-MSS system without a major redesign of the system, and with minimal impact on system throughput.

  2. Spectrally and Radiometrically Stable Wide-Band on Board Calibration Source for In-Flight Data Validation in Imaging Spectroscopy Applications

    NASA Technical Reports Server (NTRS)

    Coles, J. B.; Richardson, Brandon S.; Eastwood, Michael L.; Sarture, Charles M.; Quetin, Gregory R.; Hernandez, Marco A.; Kroll, Linley A.; Nolte, Scott H.; Porter, Michael D.; Green, Robert O.

    2011-01-01

    The quality of the quantitative spectral data collected by an imaging spectrometer instrument is critically dependent upon the accuracy of the spectral and radiometric calibration of the system. In order for the collected spectra to be scientifically useful, the calibration of the instrument must be precisely known not only prior to but during data collection. Thus, in addition to a rigorous in-lab calibration procedure, the airborne instruments designed and built by the NASA/JPL Imaging Spectroscopy Group incorporate an on board calibrator (OBC) system with the instrument to provide auxiliary in-use system calibration data. The output of the OBC source illuminates a target panel on the backside of the foreoptics shutter both before and after data collection. The OBC and in-lab calibration data sets are then used to validate and post-process the collected spectral image data. The resulting accuracy of the spectrometer output data is therefore integrally dependent upon the stability of the OBC source. In this paper we describe the design and application of the latest iteration of this novel device developed at NASA/JPL which integrates a halogen-cycle source with a precisely designed fiber coupling system and a fiber-based intensity monitoring feedback loop. The OBC source in this Airborne Testbed Spectrometer was run over a period of 15 hours while both the radiometric and spectral stabilities of the output were measured and demonstrated stability to within 1% of nominal.

  3. Absolute Calibration of the Magnetic Field Measurement for Muon g-2

    NASA Astrophysics Data System (ADS)

    Farooq, Midhat; Chupp, Tim; Muon g-2 Collaboration Collaboration

    2017-01-01

    The muon g-2 experiment at Fermilab (E989) investigates the >3- σ discrepancy between the standard model prediction and the current experimental measurement of the muon magnetic moment anomaly, aμ = (g-2)/2. The effort requires a precise measurement of the 1.45 T magnetic field of the muon storage ring to 70 ppb. The final measurement will employ multiple absolute calibration probes: two water probes and a 3He probe. The 3He probe offers a cross-check of the water probes with different systematic corrections, adding a level of confidence to the measurement. A low-field 3He probe was developed at the Univ. of Michigan by employing a method called MEOP for the hyper-polarization of 3He gas, followed by NMR to determine the frequency proportional to the magnetic field in which the probe is placed. A modified probe design for operation under high fields will be tested at Argonne National Lab. Future development also involves the study of the systematic uncertainties to attain the error budget of <30 ppb for the calibration. Next, the calibration from the probes will be transferred to g-2 through several steps of a calibration chain ending in the final step of calibrating the NMR probes which measure the field in the muon storage ring at Fermilab. NSF PHY-1506021.

  4. TES Level 1 Algorithms: Interferogram Processing, Geolocation, Radiometric, and Spectral Calibration

    NASA Technical Reports Server (NTRS)

    Worden, Helen; Beer, Reinhard; Bowman, Kevin W.; Fisher, Brendan; Luo, Mingzhao; Rider, David; Sarkissian, Edwin; Tremblay, Denis; Zong, Jia

    2006-01-01

    The Tropospheric Emission Spectrometer (TES) on the Earth Observing System (EOS) Aura satellite measures the infrared radiance emitted by the Earth's surface and atmosphere using Fourier transform spectrometry. The measured interferograms are converted into geolocated, calibrated radiance spectra by the L1 (Level 1) processing, and are the inputs to L2 (Level 2) retrievals of atmospheric parameters, such as vertical profiles of trace gas abundance. We describe the algorithmic components of TES Level 1 processing, giving examples of the intermediate results and diagnostics that are necessary for creating TES L1 products. An assessment of noise-equivalent spectral radiance levels and current systematic errors is provided. As an initial validation of our spectral radiances, TES data are compared to the Atmospheric Infrared Sounder (AIRS) (on EOS Aqua), after accounting for spectral resolution differences by applying the AIRS spectral response function to the TES spectra. For the TES L1 nadir data products currently available, the agreement with AIRS is 1 K or better.

  5. Anomalous gain in an isotopically mixed CO2 laser and application to absolute wavelength calibration

    NASA Technical Reports Server (NTRS)

    Hewagama, Tilak; Oppenheim, Uri P.; Mumma, Michael J.

    1991-01-01

    Measurements are reported on a grating-tuned CO2 laser, containing an isotropic mixture of O-16C-12O-16, O-16C-12O-18, and O-18C-12O-18. The P6 and R14 lines of O-16C-12O-16 were found to have anomalously high intensities. These anomalies are produced by the near coincidence of the transition frequencies in two distinct isotopes, permitting them to act as a single indistinguishable population. These two lines can be used to identify the rotational quantum numbers in the P and R branch spectra, thereby permitting absolute wavelength calibration to be achieved.

  6. Absolute Current Calibration of 1$\\mu$A CW Electron Beam

    SciTech Connect

    Arne Freyberger; Mike Bevins; Anthony Day; Arunava Saha; Stephanie Slachtouski; Ronald Gilman; Pavel Degtiarenko

    2005-06-01

    The future experimental program at Jefferson Lab requires an absolute current calibration of a 1 {mu}A CW electron beam to better than 1% accuracy. This paper presents the mechanical and electrical design of a Tungsten calorimeter that is being constructed to provide an accurate measurement of the deposited energy. The energy is determined by measuring the change in temperature after beam exposure. Knowledge of the beam energy then yields number of electrons stopped by the calorimeter during the exposure. Simulations show that the energy lost due to electromagnetic and hadronic particle losses are the dominant uncertainty. Details of the precision thermometry and calibration, mechanical design, thermal simulations and simulations will be presented.

  7. Absolute Current Calibrations of 1muA CW Electron Beam

    SciTech Connect

    A. Freyberger, M.E. Bevins, A.R. Day, P. Degtiarenko, A. Saha, S. Slachtouski, R. Gilman

    2005-06-06

    The future experimental program at Jefferson Lab requires an absolute current calibration of a 1{mu}A CW electron beam to better than 1% accuracy. This paper presents the mechanical and electrical design of a Tungsten calorimeter that is being constructed to provide an accurate measurement of the deposited energy. The energy is determined by measuring the change in temperature after beam exposure. Knowledge of the beam energy then yields number of electrons stopped by the calorimeter during the exposure. Simulations show that the energy losses due to electromagnetic and hadronic losses are the dominant uncertainty. Details of the precision thermometry and calibration, mechanical design, thermal simulations and GEANT simulations will be presented.

  8. An imaging technique for detection and absolute calibration of scintillation light

    SciTech Connect

    Pappalardo, Alfio; Cosentino, Luigi; Finocchiaro, Paolo

    2010-03-15

    Triggered by the need of a detection system to be used in experiments of nuclear fusion in laser-generated plasmas, we developed an imaging technique for the measurement and calibration of the scintillation light yield of scintillating materials. As in such experiments, all the reaction products are generated in an ultrashort time frame, the event-by-event data acquisition scheme is not feasible. As an alternative to the emulsion technique (or the equivalent CR39 sheets) we propose a scintillating screen readout by means of a high performance charge coupled device camera. Even though it is not strictly required in the particular application, this technique allows the absolute calibration of the scintillation light yield.

  9. Investigating the influence of radiometric calibration on tree species determination based on small footprint full-waveform airborne LiDAR

    NASA Astrophysics Data System (ADS)

    Mücke, W.; Briese, C.; Hollaus, M.; Pfeifer, N.; Wagner, W.

    2013-12-01

    Small footprint airborne LiDAR is a well-established measurement technique in forestry, where cost- and time efficient wide-area data acquisition of the vegetation structure is required. Gathering stand-based information about tree species composition is of particular interest for forestry applications. Modern LiDAR systems provide, next to the acquired 3D (i.e. geometric) information, also a quantification of the signal strength of each echo. In order to utilize this information for tree species determination independently from different overlapping LiDAR swaths, different LiDAR sensors or acquisition times, radiometric calibration is a necessity. This contribution summarises the theoretical background of radiometric LiDAR data calibration on the physical basis of the radar equation. Using LiDAR observations of reference targets with known reflectivity the so-called calibration constant is computed. It accounts for sensor specific parameters, as well as atmospheric attenuation of the laser signal. Hence the backscatter properties of the laser echoes can be determined and physical observables characterizing the reflectivity of the scanned surface can be estimated. A practical calibration workflow is demonstrated on the example of a single wavelength full-waveform LiDAR data set from a mixed woodland in Austria. Subsequently, an automated method for tree species determination that is based on the laser light scattering mechanisms in the forest canopy is applied on both (calibrated and un-calibrated) data sets. First, an edge-based segmentation approach is used to aggregate LiDAR echoes to segments representing single tree crowns. Second, metrics are computed for each tree crown describing radiometric and geometric features that are related to foliage composition. Third, these metrics are used in a knowledge-based fuzzy classification scheme for the determination of segments representing coniferous and deciduous trees. Influences of the radiometric calibration on the

  10. First Results of Field Absolute Calibration of the GPS Receiver Antenna at Wuhan University

    PubMed Central

    Hu, Zhigang; Zhao, Qile; Chen, Guo; Wang, Guangxing; Dai, Zhiqiang; Li, Tao

    2015-01-01

    GNSS receiver antenna phase center variations (PCVs), which arise from the non-spherical phase response of GNSS signals have to be well corrected for high-precision GNSS applications. Without using a precise antenna phase center correction (PCC) model, the estimated position of a station monument will lead to a bias of up to several centimeters. The Chinese large-scale research project “Crustal Movement Observation Network of China” (CMONOC), which requires high-precision positions in a comprehensive GPS observational network motived establishment of a set of absolute field calibrations of the GPS receiver antenna located at Wuhan University. In this paper the calibration facilities are firstly introduced and then the multipath elimination and PCV estimation strategies currently used are elaborated. The validation of estimated PCV values of test antenna are finally conducted, compared with the International GNSS Service (IGS) type values. Examples of TRM57971.00 NONE antenna calibrations from our calibration facility demonstrate that the derived PCVs and IGS type mean values agree at the 1 mm level. PMID:26580616

  11. First Results of Field Absolute Calibration of the GPS Receiver Antenna at Wuhan University.

    PubMed

    Hu, Zhigang; Zhao, Qile; Chen, Guo; Wang, Guangxing; Dai, Zhiqiang; Li, Tao

    2015-11-13

    GNSS receiver antenna phase center variations (PCVs), which arise from the non-spherical phase response of GNSS signals have to be well corrected for high-precision GNSS applications. Without using a precise antenna phase center correction (PCC) model, the estimated position of a station monument will lead to a bias of up to several centimeters. The Chinese large-scale research project "Crustal Movement Observation Network of China" (CMONOC), which requires high-precision positions in a comprehensive GPS observational network motived establishment of a set of absolute field calibrations of the GPS receiver antenna located at Wuhan University. In this paper the calibration facilities are firstly introduced and then the multipath elimination and PCV estimation strategies currently used are elaborated. The validation of estimated PCV values of test antenna are finally conducted, compared with the International GNSS Service (IGS) type values. Examples of TRM57971.00 NONE antenna calibrations from our calibration facility demonstrate that the derived PCVs and IGS type mean values agree at the 1 mm level.

  12. Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems

    NASA Astrophysics Data System (ADS)

    Johnston, Mark D.; Oliver, Bryan V.; Droemer, Darryl W.; Frogget, Brent; Crain, Marlon D.; Maron, Yitzhak

    2012-08-01

    This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode ("hotspot") was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons/sec/cm2/steradian/nm). Error analysis shows this method to be accurate to within +/- 20%, which represents a high level of accuracy for this type of measurement.

  13. Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems.

    PubMed

    Johnston, Mark D; Oliver, Bryan V; Droemer, Darryl W; Frogget, Brent; Crain, Marlon D; Maron, Yitzhak

    2012-08-01

    This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode ("hotspot") was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons/sec/cm(2)/steradian/nm). Error analysis shows this method to be accurate to within +∕- 20%, which represents a high level of accuracy for this type of measurement.

  14. Absolute Calibration of the Radio Astronomy Flux Density Scale at 22 to 43 GHz Using Planck

    NASA Astrophysics Data System (ADS)

    Partridge, B.; López-Caniego, M.; Perley, R. A.; Stevens, J.; Butler, B. J.; Rocha, G.; Walter, B.; Zacchei, A.

    2016-04-01

    The Planck mission detected thousands of extragalactic radio sources at frequencies from 28 to 857 GHz. Planck's calibration is absolute (in the sense that it is based on the satellite’s annual motion around the Sun and the temperature of the cosmic microwave background), and its beams are well characterized at sub-percent levels. Thus, Planck's flux density measurements of compact sources are absolute in the same sense. We have made coordinated Very Large Array (VLA) and Australia Telescope Compact Array (ATCA) observations of 65 strong, unresolved Planck sources in order to transfer Planck's calibration to ground-based instruments at 22, 28, and 43 GHz. The results are compared to microwave flux density scales currently based on planetary observations. Despite the scatter introduced by the variability of many of the sources, the flux density scales are determined to 1%-2% accuracy. At 28 GHz, the flux density scale used by the VLA runs 2%-3% ± 1.0% below Planck values with an uncertainty of +/- 1.0%; at 43 GHz, the discrepancy increases to 5%-6% ± 1.4% for both ATCA and the VLA.

  15. Pantomime-Grasping: Advance Knowledge of Haptic Feedback Availability Supports an Absolute Visuo-Haptic Calibration.

    PubMed

    Davarpanah Jazi, Shirin; Heath, Matthew

    2016-01-01

    An emerging issue in movement neurosciences is whether haptic feedback influences the nature of the information supporting a simulated grasping response (i.e., pantomime-grasping). In particular, recent work by our group contrasted pantomime-grasping responses performed with (i.e., PH+ trials) and without (i.e., PH- trials) terminal haptic feedback in separate blocks of trials. Results showed that PH- trials were mediated via relative visual information. In contrast, PH+ trials showed evidence of an absolute visuo-haptic calibration-a finding attributed to an error signal derived from a comparison between expected and actual haptic feedback (i.e., an internal forward model). The present study examined whether advanced knowledge of haptic feedback availability influences the aforementioned calibration process. To that end, PH- and PH+ trials were completed in separate blocks (i.e., the feedback schedule used in our group's previous study) and a block wherein PH- and PH+ trials were randomly interleaved on a trial-by-trial basis (i.e., random feedback schedule). In other words, the random feedback schedule precluded participants from predicting whether haptic feedback would be available at the movement goal location. We computed just-noticeable-difference (JND) values to determine whether responses adhered to, or violated, the relative psychophysical principles of Weber's law. Results for the blocked feedback schedule replicated our group's previous work, whereas in the random feedback schedule PH- and PH+ trials were supported via relative visual information. Accordingly, we propose that a priori knowledge of haptic feedback is necessary to support an absolute visuo-haptic calibration. Moreover, our results demonstrate that the presence and expectancy of haptic feedback is an important consideration in contrasting the behavioral and neural properties of natural and simulated grasping.

  16. Evaluation of relative radiometric correction techniques on Landsat 8 OLI sensor data

    NASA Astrophysics Data System (ADS)

    Novelli, Antonio; Caradonna, Grazia; Tarantino, Eufemia

    2016-08-01

    The quality of information derived from processed remotely sensed data may depend upon many factors, mostly related to the extent data acquisition is influenced by atmospheric conditions, topographic effects, sun angle and so on. The goal of radiometric corrections is to reduce such effects in order enhance the performance of change detection analysis. There are two approaches to radiometric correction: absolute and relative calibrations. Due to the large amount of free data products available, absolute radiometric calibration techniques may be time consuming and financially expensive because of the necessary inputs for absolute calibration models (often these data are not available and can be difficult to obtain). The relative approach to radiometric correction, known as relative radiometric normalization, is preferred with some research topics because no in situ ancillary data, at the time of satellite overpasses, are required. In this study we evaluated three well known relative radiometric correction techniques using two Landsat 8 - OLI scenes over a subset area of the Apulia Region (southern Italy): the IR-MAD (Iteratively Reweighted Multivariate Alteration Detection), the HM (Histogram Matching) and the DOS (Dark Object Subtraction). IR-MAD results were statistically assessed within a territory with an extremely heterogeneous landscape and all computations performed in a Matlab environment. The panchromatic and thermal bands were excluded from the comparisons.

  17. Grasping a 2D object: terminal haptic feedback supports an absolute visuo-haptic calibration.

    PubMed

    Hosang, Stephanie; Chan, Jillian; Davarpanah Jazi, Shirin; Heath, Matthew

    2016-04-01

    Grasping a three-dimensional (3D) object results in the specification of motor output via absolute size information. In contrast, the impoverished visual cues (e.g., binocular and vergence) associated with grasping a two-dimensional (2D) object are reported to render aperture formation via an object's perceptual and relative visual features. It is, however, important to recognize that 3D and 2D grasping differ not only in terms of their visual properties, but also because the latter does not entail the provision of haptic feedback. As such, the present work examined whether haptic feedback influences the nature of the information supporting 2D grasping. Participants grasped differently sized 3D objects (i.e., 3D task) and completed a 'traditional' 2D grasping task to line drawings without receiving haptic feedback (i.e., 2DH- task). As well, we included a separate condition using the same objects as the 2DH- task; however, the experimenter placed a 3D object (i.e., one corresponding to the size of the 2D object) between the thumb and forefinger of participants' grasping limb once they completed their response (i.e., 2DH+ task). Thus, the 2DH+ task provided haptic feedback related to absolute object size. Notably, we computed just-noticeable-difference (JND) scores to determine whether the different tasks adhered to, or violated, the relative psychophysical principles of Weber's law. JNDs for the 2DH- task adhered to Weber's law, whereas 3D and 2DH+ tasks violated the law. Thus, results evince that 2DH- and 2DH+ tasks are specified via relative and absolute object size information, respectively. Accordingly, we propose that haptic feedback supports an absolute visuo-haptic calibration and contend that our results highlight the importance of multi-sensory cue integration in goal-directed grasping.

  18. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials

    DOE PAGES

    Gregor, M. C.; Boni, R.; Sorce, A.; ...

    2016-11-29

    Experiments in high-energy-density physics often use optical pyrometry to determine temperatures of dynamically compressed materials. In combination with simultaneous shock-velocity and optical-reflectivity measurements using velocity interferometry, these experiments provide accurate equation-of-state data at extreme pressures (P > 1 Mbar) and temperatures (T > 0.5 eV). This paper reports on the absolute calibration of the streaked optical pyrometer (SOP) at the Omega Laser Facility. The wavelength-dependent system response was determined by measuring the optical emission from a National Institute of Standards and Technology–traceable tungsten-filament lamp through various narrowband (40 nm-wide) filters. The integrated signal over the SOP’s ~250-nm operating range ismore » then related to that of a blackbody radiator using the calibrated response. We present a simple closed-form equation for the brightness temperature as a function of streak-camera signal derived from this calibration. As a result, error estimates indicate that brightness temperature can be inferred to a precision of <5%.« less

  19. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials

    NASA Astrophysics Data System (ADS)

    Gregor, M. C.; Boni, R.; Sorce, A.; Kendrick, J.; McCoy, C. A.; Polsin, D. N.; Boehly, T. R.; Celliers, P. M.; Collins, G. W.; Fratanduono, D. E.; Eggert, J. H.; Millot, M.

    2016-11-01

    Experiments in high-energy-density physics often use optical pyrometry to determine temperatures of dynamically compressed materials. In combination with simultaneous shock-velocity and optical-reflectivity measurements using velocity interferometry, these experiments provide accurate equation-of-state data at extreme pressures (P > 1 Mbar) and temperatures (T > 0.5 eV). This paper reports on the absolute calibration of the streaked optical pyrometer (SOP) at the Omega Laser Facility. The wavelength-dependent system response was determined by measuring the optical emission from a National Institute of Standards and Technology-traceable tungsten-filament lamp through various narrowband (40-nm-wide) filters. The integrated signal over the SOP's ˜250-nm operating range is then related to that of a blackbody radiator using the calibrated response. We present a simple closed-form equation for the brightness temperature as a function of streak-camera signal derived from this calibration. Error estimates indicate that brightness temperature can be inferred to a precision of <5%.

  20. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials

    SciTech Connect

    Gregor, M. C.; Boni, R.; Sorce, A.; Kendrick, J.; McCoy, C. A.; Polsin, D. N.; Boehly, T. R.; Celliers, P. M.; Collins, G. W.; Fratanduono, D. E.; Eggert, J. H.; Millot, M.

    2016-11-29

    Experiments in high-energy-density physics often use optical pyrometry to determine temperatures of dynamically compressed materials. In combination with simultaneous shock-velocity and optical-reflectivity measurements using velocity interferometry, these experiments provide accurate equation-of-state data at extreme pressures (P > 1 Mbar) and temperatures (T > 0.5 eV). This paper reports on the absolute calibration of the streaked optical pyrometer (SOP) at the Omega Laser Facility. The wavelength-dependent system response was determined by measuring the optical emission from a National Institute of Standards and Technology–traceable tungsten-filament lamp through various narrowband (40 nm-wide) filters. The integrated signal over the SOP’s ~250-nm operating range is then related to that of a blackbody radiator using the calibrated response. We present a simple closed-form equation for the brightness temperature as a function of streak-camera signal derived from this calibration. As a result, error estimates indicate that brightness temperature can be inferred to a precision of <5%.

  1. Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements

    NASA Technical Reports Server (NTRS)

    Domonkos, Matthew T.; Stevens, Richard E.

    2001-01-01

    Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.

  2. Diffusing screen for on-board radiometric calibration of the stereo-spectral-imaging system ARGUS for Mars 94/96 mission.

    NASA Astrophysics Data System (ADS)

    Morozova, S. P.; Sapritsky, V. I.; Morozov, P. A.; Novitsky, A. V.; Khlevnoy, B. B.; Lisiansky, B. E.; Tarnopolsky, V. I.; Belousov, A. V.

    1996-05-01

    A new stereo-spectral-imaging system, ARGUS, has been developed for the Mars 94/96 mission and consists of three videospectrometers with a wide field-of-view covering the spectral range 320 nm to 5200 nm. The on-board radiometric calibration is based on a diffusing target illuminated by the Sun's radiation. The provision for a common target for all the videospectrometers of the ARGUS system allows an intercomparison of instruments to be carried out in addition to individual calibration verification. The development and testing of the target for on-board radiometric calibration is described and techniques for preparing the target surface are given. A brief description of the setup for measurements of the spectral and angular response of the target reflectivity is presented, together with results of the spectral and angular response of the target reflectivity, for an angle of incidence of -70° (relative to the normal) and at viewing angles from 0° to +60° at 2° intervals. The bidirectional reflectance factor of the target is reported for the spectral range 320 nm to 5200 nm at an angle of incidence of -70° and at a viewing angle of +20°.

  3. Pantomime-Grasping: Advance Knowledge of Haptic Feedback Availability Supports an Absolute Visuo-Haptic Calibration

    PubMed Central

    Davarpanah Jazi, Shirin; Heath, Matthew

    2016-01-01

    An emerging issue in movement neurosciences is whether haptic feedback influences the nature of the information supporting a simulated grasping response (i.e., pantomime-grasping). In particular, recent work by our group contrasted pantomime-grasping responses performed with (i.e., PH+ trials) and without (i.e., PH− trials) terminal haptic feedback in separate blocks of trials. Results showed that PH− trials were mediated via relative visual information. In contrast, PH+ trials showed evidence of an absolute visuo-haptic calibration—a finding attributed to an error signal derived from a comparison between expected and actual haptic feedback (i.e., an internal forward model). The present study examined whether advanced knowledge of haptic feedback availability influences the aforementioned calibration process. To that end, PH− and PH+ trials were completed in separate blocks (i.e., the feedback schedule used in our group’s previous study) and a block wherein PH− and PH+ trials were randomly interleaved on a trial-by-trial basis (i.e., random feedback schedule). In other words, the random feedback schedule precluded participants from predicting whether haptic feedback would be available at the movement goal location. We computed just-noticeable-difference (JND) values to determine whether responses adhered to, or violated, the relative psychophysical principles of Weber’s law. Results for the blocked feedback schedule replicated our group’s previous work, whereas in the random feedback schedule PH− and PH+ trials were supported via relative visual information. Accordingly, we propose that a priori knowledge of haptic feedback is necessary to support an absolute visuo-haptic calibration. Moreover, our results demonstrate that the presence and expectancy of haptic feedback is an important consideration in contrasting the behavioral and neural properties of natural and simulated grasping. PMID:27199718

  4. A dedicated pistonphone for absolute calibration of infrasound sensors at very low frequencies

    NASA Astrophysics Data System (ADS)

    He, Wen; He, Longbiao; Zhang, Fan; Rong, Zuochao; Jia, Shushi

    2016-02-01

    Aimed at the absolute calibration of infrasound sensors at very low frequencies, an upgraded and improved infrasonic pistonphone has been developed. The pistonphone was designed such that a very narrow clearance between the piston and its guide was realized based on an automatically-centered clearance-sealing structure, and a large volume rigid-walled chamber was also adopted, which improved the leakage time-constant of the chamber. A composite feedback control system was applied to the electromagnetic vibrator to control the precise motion of the piston. Performance tests and uncertainty analysis show that the leakage time-constant is so large, and the distortion of the sound pressure is so small, that the pistonphone can be used as a standard infrasound source in the frequency range from 0.001 Hz to 20 Hz. The low frequency property of the pistonphone has been verified through calibrating low frequency microphones. Comparison tests with the reciprocity method have shown that the pressure sensitivities from the pistonphone are not only reliable at common frequencies but also have smaller uncertainties at low frequencies.

  5. Absolute calibration of a three-axis SQUID-cascade vector magnetometer

    NASA Astrophysics Data System (ADS)

    Schönau, T.; Zakosarenko, V.; Schmelz, M.; Stolz, R.; Anders, S.; Linzen, S.; Meyer, M.; Faßbinder, J. W. E.; Meyer, H.-G.

    2017-01-01

    We report on the absolute calibration of a three-axis SQUID-cascade vector magnetometer suited for mobile operation in the Earth’s magnetic field. It is based on low temperature superconductor (LTS) dc SQUIDs with sub-micrometer sized cross-type Josephson junctions and exhibits a white noise level of about 10 fT Hz-1/2. Due to the cascaded operation principle, the huge dynamic range required to resolve a measurement range of more than 50 µT with sub-pT resolution is split onto several electronic channels of less demanding precision. As a result, the measurement accuracy is less vulnerable to parameter drifts. Furthermore, the intrinsic redundancy of the setup can be used to check for systematic errors of measurement. The offset as well as scaling and directional errors of the magnetometer have been obtained by the method of scalar calibration in our laboratory, resulting in a residuum with a standard deviation of less than 0.64 nT.

  6. Effects of Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper plus radiometric and geometric calibrations and corrections on landscape characterization

    USGS Publications Warehouse

    Vogelmann, James E.; Helder, Dennis; Morfitt, Ron; Choate, Michael J.; Merchant, James W.; Bulley, Henry

    2001-01-01

    The Thematic Mapper (TM) instruments onboard Landsats 4 and 5 provide high-quality imagery appropriate for many different applications, including land cover mapping, landscape ecology, and change detection. Precise calibration was considered to be critical to the success of the Landsat 7 mission and, thus, issues of calibration were given high priority during the development of the Enhanced Thematic Mapper Plus (ETM+). Data sets from the Landsat 5 TM are not routinely corrected for a number of radiometric and geometric artifacts, including memory effect, gain/bias, and interfocal plane misalignment. In the current investigation, the effects of correcting vs. not correcting these factors were investigated for several applications. Gain/bias calibrations were found to have a greater impact on most applications than did memory effect calibrations. Correcting interfocal plane offsets was found to have a moderate effect on applications. On June 2, 1999, Landsats 5 and 7 data were acquired nearly simultaneously over a study site in the Niobrara, NE area. Field radiometer data acquired at that site were used to facilitate crosscalibrations of Landsats 5 and 7 data. Current findings and results from previous investigations indicate that the internal calibrator of Landsat 5 TM tracked instrument gain well until 1988. After this, the internal calibrator diverged from the data derived from vicarious calibrations. Results from this study also indicate very good agreement between prelaunch measurements and vicarious calibration data for all Landsat 7 reflective bands except Band 4. Values are within about 3.5% of each other, except for Band 4, which differs by 10%. Coefficient of variation (CV) values derived from selected targets in the imagery were also analyzed. The Niobrara Landsat 7 imagery was found to have lower CV values than Landsat 5 data, implying that lower levels of noise characterize Landsat 7 data than current Landsat 5 data. It was also found that following

  7. Use of Proportional Counters for Yield Measurement in Extremely Short Pulses of Fast Neutrons: Counting Statistics and Absolute Calibration

    NASA Astrophysics Data System (ADS)

    Tarifeño-Saldivia, A.; Mayer, R. E.; Pavez, C.; Soto, L.

    2010-08-01

    A method for absolute calibration of proportional counters for pulsed fast neutrons is presented. The method is based on the use of an isotopic standard source and development of a model for counting detected events from area of a signal compounded by single piled up neutron pulses. Effects of detection counting statistics and electrical background noise are also considered.

  8. A BAYESIAN METHOD FOR CALCULATING REAL-TIME QUANTITATIVE PCR CALIBRATION CURVES USING ABSOLUTE PLASMID DNA STANDARDS

    EPA Science Inventory

    In real-time quantitative PCR studies using absolute plasmid DNA standards, a calibration curve is developed to estimate an unknown DNA concentration. However, potential differences in the amplification performance of plasmid DNA compared to genomic DNA standards are often ignore...

  9. Radiometric calibration of optical microscopy and microspectroscopy apparata over a broad spectral range using a special thin-film luminescence standard

    SciTech Connect

    Valenta, J. Greben, M.

    2015-04-15

    Application capabilities of optical microscopes and microspectroscopes can be considerably enhanced by a proper calibration of their spectral sensitivity. We propose and demonstrate a method of relative and absolute calibration of a microspectroscope over an extraordinary broad spectral range covered by two (parallel) detection branches in visible and near-infrared spectral regions. The key point of the absolute calibration of a relative spectral sensitivity is application of the standard sample formed by a thin layer of Si nanocrystals with stable and efficient photoluminescence. The spectral PL quantum yield and the PL spatial distribution of the standard sample must be characterized by separate experiments. The absolutely calibrated microspectroscope enables to characterize spectral photon emittance of a studied object or even its luminescence quantum yield (QY) if additional knowledge about spatial distribution of emission and about excitance is available. Capabilities of the calibrated microspectroscope are demonstrated by measuring external QY of electroluminescence from a standard poly-Si solar-cell and of photoluminescence of Er-doped Si nanocrystals.

  10. Test Plan for a Calibration Demonstration System for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; Hair, Jason; McAndrew, Brendan; Daw, Adrian; Jennings, Donald; Rabin, Douglas

    2012-01-01

    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. One of the major objectives of CLARREO is to advance the accuracy of SI traceable absolute calibration at infrared and reflected solar wavelengths. This advance is required to reach the on-orbit absolute accuracy required to allow climate change observations to survive data gaps while remaining sufficiently accurate to observe climate change to within the uncertainty of the limit of natural variability. While these capabilities exist at NIST in the laboratory, there is a need to demonstrate that it can move successfully from NIST to NASA and/or instrument vendor capabilities for future spaceborne instruments. The current work describes the test plan for the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. The goal of the CDS is to allow the testing and evaluation of calibration approaches , alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The end result of efforts with the SOLARIS CDS will be an SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climate-quality data collections. The CLARREO mission addresses the need to observe high-accuracy, long-term climate change trends and advance the accuracy of SI traceable absolute calibration. The current work describes the test plan for the SOLARIS which is the calibration demonstration

  11. A comparison of absolute calibrations of a radiation thermometer based on a monochromator and a tunable source

    NASA Astrophysics Data System (ADS)

    Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Sperling, A.; Schuster, M.; Nevas, S.

    2013-09-01

    An LP3 radiation thermometer was absolutely calibrated at a newly developed monochromator-based set-up and the TUneable Lasers in Photometry (TULIP) facility of PTB in the wavelength range from 400 nm to 1100 nm. At both facilities, the spectral radiation of the respective sources irradiates an integrating sphere, thus generating uniform radiance across its precision aperture. The spectral irradiance of the integrating sphere is determined via an effective area of a precision aperture and a Si trap detector, traceable to the primary cryogenic radiometer of PTB. Due to the limited output power from the monochromator, the absolute calibration was performed with the measurement uncertainty of 0.17 % (k = 1), while the respective uncertainty at the TULIP facility is 0.14 %. Calibration results obtained by the two facilities were compared in terms of spectral radiance responsivity, effective wavelength and integral responsivity. It was found that the measurement results in integral responsivity at the both facilities are in agreement within the expanded uncertainty (k = 2). To verify the calibration accuracy, the absolutely calibrated radiation thermometer was used to measure the thermodynamic freezing temperatures of the PTB gold fixed-point blackbody.

  12. A comparison of absolute calibrations of a radiation thermometer based on a monochromator and a tunable source

    SciTech Connect

    Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Sperling, A.; Schuster, M.; Nevas, S.

    2013-09-11

    An LP3 radiation thermometer was absolutely calibrated at a newly developed monochromator-based set-up and the TUneable Lasers in Photometry (TULIP) facility of PTB in the wavelength range from 400 nm to 1100 nm. At both facilities, the spectral radiation of the respective sources irradiates an integrating sphere, thus generating uniform radiance across its precision aperture. The spectral irradiance of the integrating sphere is determined via an effective area of a precision aperture and a Si trap detector, traceable to the primary cryogenic radiometer of PTB. Due to the limited output power from the monochromator, the absolute calibration was performed with the measurement uncertainty of 0.17 % (k= 1), while the respective uncertainty at the TULIP facility is 0.14 %. Calibration results obtained by the two facilities were compared in terms of spectral radiance responsivity, effective wavelength and integral responsivity. It was found that the measurement results in integral responsivity at the both facilities are in agreement within the expanded uncertainty (k= 2). To verify the calibration accuracy, the absolutely calibrated radiation thermometer was used to measure the thermodynamic freezing temperatures of the PTB gold fixed-point blackbody.

  13. Absolute fluorescence measurements > 1000 nm: setup design, calibration and standards (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Resch-Genger, Ute; Würth, Christian; Pauli, Jutta; Hatami, Soheil; Kaiser, Martin

    2016-03-01

    There is an increasing interest in optical reporters like semiconductor quantum dots and upconversion nanophosphors with emission < 1000 nm for bioanalysis, medical diagnostics, and safety barcodes and hence, in reliable fluorescence measurements in this wavelength region, e.g., for the comparison of material performance and the rational design of new nanomaterials with improved properties [1-4]. The performance of fluorescence measurements < 800 nm and especially < 1000 nm is currently hampered by the lack of suitable methods and standards for the simple determination of the wavelength-dependent spectral responsivity of fluorescence measuring systems and the control of measured emission spectra and intensities [3-5]. This is of special relevance for nanocrystalline emitters like quantum dots and rods as well as for upconversion nanocrystals, where surface states and the accessibility of emissive states by quenchers largely control accomplishable quantum yields and hence, signal sizes and detection sensitivities from the reporter side. Here, we present the design of an integrating sphere setup for the absolute measurement of emission spectra and quantum yields in the wavelength region of 650 to 1600 nm and its calibration as well as examples for potential fluorescence standards from different reporter classes for the control of the reliability of such measurements [5]. This includes new spectral fluorescence standards for the wavelength region of 650 nm to 1000 nm as well as a set of quantum yield standards covering the wavelength region from 400 nm to 1000 nm.

  14. Improved Strategies and Optimization of Calibration Models for Real-time PCR Absolute Quantification

    EPA Science Inventory

    Real-time PCR absolute quantification applications rely on the use of standard curves to make estimates of DNA target concentrations in unknown samples. Traditional absolute quantification approaches dictate that a standard curve must accompany each experimental run. However, t...

  15. Small satellite radiometric measurements

    SciTech Connect

    Weber, P.G.

    1991-01-01

    A critical need for the Mission to Planet Earth is to provide continuous, well-calibrated radiometric data for the radiation budget. This paper describes a new, compact, flexible radiometer which will provide both spectrally integrated data and data in selected spectral bands. The radiometer design is suitable for use on small satellites, aircraft, or remotely piloted vehicles (RPVs). 12 refs., 2 figs.

  16. SOLAR/SOLSPEC: Scientific Objectives, Instrument Performance and Its Absolute Calibration Using a Blackbody as Primary Standard Source

    NASA Astrophysics Data System (ADS)

    Thuillier, G.; Foujols, T.; Bolsée, D.; Gillotay, D.; Hersé, M.; Peetermans, W.; Decuyper, W.; Mandel, H.; Sperfeld, P.; Pape, S.; Taubert, D. R.; Hartmann, J.

    2009-06-01

    SOLAR is a set of three solar instruments measuring the total and spectral absolute irradiance from 16 nm to 3080 nm for solar, atmospheric and climatology physics. It is an external payload for the COLUMBUS laboratory launched on 7 February 2008. The mission’s primary objective is the measurement of the solar irradiance with the highest possible accuracy, and its variability using the following instruments: SOL-ACES (SOLar Auto-Calibrating EUV/UV Spectrophotometers) consists of four grazing incidence planar gratings measuring from 16 nm to 220 nm; SOLSPEC (SOLar SPECtrum) consists of three double gratings spectrometers, covering the range 165 nm to 3080 nm; and SOVIM (SOlar Variability Irradiance Monitor) is combining two types of absolute radiometers and three-channel filter - radiometers. SOLSPEC and SOL-ACES have been calibrated by primary standard radiation sources of the Physikalisch-Technische Bundesanstalt (PTB). Below we describe SOLSPEC, and its performance.

  17. Absolute Calibration of Image Plate for electrons at energy between 100 keV and 4 MeV

    SciTech Connect

    Chen, H; Back, N L; Eder, D C; Ping, Y; Song, P M; Throop, A

    2007-12-10

    The authors measured the absolute response of image plate (Fuji BAS SR2040) for electrons at energies between 100 keV to 4 MeV using an electron spectrometer. The electron source was produced from a short pulse laser irradiated on the solid density targets. This paper presents the calibration results of image plate Photon Stimulated Luminescence PSL per electrons at this energy range. The Monte Carlo radiation transport code MCNPX results are also presented for three representative incident angles onto the image plates and corresponding electron energies depositions at these angles. These provide a complete set of tools that allows extraction of the absolute calibration to other spectrometer setting at this electron energy range.

  18. Calibration-free absolute quantification of optical absorption coefficients using acoustic spectra in 3D photoacoustic microscopy of biological tissue.

    PubMed

    Guo, Zijian; Hu, Song; Wang, Lihong V

    2010-06-15

    Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of nonfluorescent molecules. We propose a method to use acoustic spectra of photoacoustic signals to quantify the absolute optical absorption. This method is self-calibrating and thus insensitive to variations in the optical fluence. Factors such as system bandwidth and acoustic attenuation can affect the quantification but can be canceled by dividing the acoustic spectra measured at two optical wavelengths. Using optical-resolution photoacoustic microscopy, we quantified the absolute optical absorption of black ink samples with various concentrations. We also quantified both the concentration and oxygen saturation of hemoglobin in a live mouse in absolute units.

  19. Determining the importance of model calibration for forecasting absolute/relative changes in streamflow from LULC and climate changes

    USGS Publications Warehouse

    Niraula, Rewati; Meixner, Thomas; Norman, Laura M.

    2015-01-01

    Land use/land cover (LULC) and climate changes are important drivers of change in streamflow. Assessing the impact of LULC and climate changes on streamflow is typically done with a calibrated and validated watershed model. However, there is a debate on the degree of calibration required. The objective of this study was to quantify the variation in estimated relative and absolute changes in streamflow associated with LULC and climate changes with different calibration approaches. The Soil and Water Assessment Tool (SWAT) was applied in an uncalibrated (UC), single outlet calibrated (OC), and spatially-calibrated (SC) mode to compare the relative and absolute changes in streamflow at 14 gaging stations within the Santa Cruz River Watershed in southern Arizona, USA. For this purpose, the effect of 3 LULC, 3 precipitation (P), and 3 temperature (T) scenarios were tested individually. For the validation period, Percent Bias (PBIAS) values were >100% with the UC model for all gages, the values were between 0% and 100% with the OC model and within 20% with the SC model. Changes in streamflow predicted with the UC and OC models were compared with those of the SC model. This approach implicitly assumes that the SC model is “ideal”. Results indicated that the magnitude of both absolute and relative changes in streamflow due to LULC predicted with the UC and OC results were different than those of the SC model. The magnitude of absolute changes predicted with the UC and SC models due to climate change (both P and T) were also significantly different, but were not different for OC and SC models. Results clearly indicated that relative changes due to climate change predicted with the UC and OC were not significantly different than that predicted with the SC models. This result suggests that it is important to calibrate the model spatially to analyze the effect of LULC change but not as important for analyzing the relative change in streamflow due to climate change. This

  20. The absolute amplitude calibration of the SEASAT synthetic aperture radar - An intercomparison with other L-band radar systems

    NASA Technical Reports Server (NTRS)

    Held, D.; Werner, C.; Wall, S.

    1983-01-01

    The absolute amplitude calibration of the spaceborne Seasat SAR data set is presented based on previous relative calibration studies. A scale factor making it possible to express the perceived radar brightness of a scene in units of sigma-zero is established. The system components are analyzed for error contribution, and the calibration techniques are introduced for each stage. These include: A/D converter saturation tests; prevention of clipping in the processing step; and converting the digital image into the units of received power. Experimental verification was performed by screening and processing the data of the lava flow surrounding the Pisgah Crater in Southern California, for which previous C-130 airborne scatterometer data were available. The average backscatter difference between the two data sets is estimated to be 2 dB in the brighter, and 4 dB in the dimmer regions. For the SAR a calculated uncertainty of 3 dB is expected.

  1. Calibration of a helium-cooled infrared spatial radiometer and grating spectrometer

    NASA Technical Reports Server (NTRS)

    Jacobsen, Larry; Sargent, Steve; Wyatt, Clair L.; Steed, Allan J.

    1992-01-01

    Methods used by the Space Dynamics Laboratory of Utah State University (SDL/USU) to calibrate infrared sensors are described, using the Infrared Background Signature Survey (IBSS) spatial radiometer and grating spectrometer as examples. A calibration equation and a radiometric model are given for each sensor to describe their responsivity in terms of individual radiometric parameters. The calibration equation terms include dark offset, linearity, absolute responsivity, and measurement uncertainty, and the radiometric model domains include spatial, spectral, and temporal domains. A portable calibration facility, designed and fabricated by SDL/USU, provided collimated, extended, diffuse scatter, and Jones sources in a single cryogenic dewar. This multi-function calibrator allowed calibration personnel to complete a full calibration of the IBSS infrared radiometer and spectrometer in two 15-day periods. A calibration data system was developed to control and monitor the calibration facility, and to record and analyze sensor data.

  2. Absolute intensity calibration of the Wendelstein 7-X high efficiency extreme ultraviolet overview spectrometer system

    NASA Astrophysics Data System (ADS)

    Greiche, Albert; Biel, Wolfgang; Marchuk, Oleksandr; Burhenn, Rainer

    2008-09-01

    The new high effiency extreme ultraviolet overview spectrometer (HEXOS) system for the stellarator Wendelstein 7-X is now mounted for testing and adjustment at the tokamak experiment for technology oriented research (TEXTOR). One part of the testing phase was the intensity calibration of the two double spectrometers which in total cover a spectral range from 2.5 to 160.0 nm with overlap. This work presents the current intensity calibration curves for HEXOS and describes the method of calibration. The calibration was implemented with calibrated lines of a hollow cathode light source and the branching ratio technique. The hollow cathode light source provides calibrated lines from 16 up to 147 nm. We could extend the calibrated region in the spectrometers down to 2.8 nm by using the branching line pairs emitted by an uncalibrated pinch extreme ultraviolet light source as well as emission lines from boron and carbon in TEXTOR plasmas. In total HEXOS is calibrated from 2.8 up to 147 nm, which covers most of the observable wavelength region. The approximate density of carbon in the range of the minor radius from 18 to 35 cm in a TEXTOR plasma determined by simulating calibrated vacuum ultraviolet emission lines with a transport code was 5.5×1017 m-3 which corresponds to a local carbon concentration of 2%.

  3. A Novel Non-Intrusive Method to Resolve the Thermal-Dome-Effect of Pyranometers: Radiometric Calibration and Implications

    NASA Technical Reports Server (NTRS)

    Ji, Qiang; Tsay, Si-Chee; Lau, K. M.; Hansell, R. A.; Butler, J. J.; Cooper, J. W.

    2011-01-01

    Traditionally the calibration equation for pyranometers assumes that the measured solar irradiance is solely proportional to the thermopile's output voltage; therefore only a single calibration factor is derived. This causes additional measurement uncertainties because it does not capture sufficient information to correctly account for a pyranometer's thermal effect. In our updated calibration equation, temperatures from the pyranometer's dome and case are incorporated to describe the instrument's thermal behavior, and a new set of calibration constants are determined, thereby reducing measurement uncertainties. In this paper, we demonstrate why a pyranometer's uncertainty using the traditional calibration equation is always larger than a-few-percent, but with the new approach can become much less than 1% after the thermal issue is resolved. The highlighted calibration results are based on NIST-traceable light sources under controlled laboratory conditions. The significance of the new approach lends itself to not only avoiding the uncertainty caused by a pyranometer's thermal effect but also the opportunity to better isolate and characterize other instrumental artifacts, such as angular response and non-linearity of the thermopile, to further reduce additional uncertainties. We also discuss some of the implications, including an example of how the thermal issue can potentially impact climate studies by evaluating aerosol's direct-radiative effect using field measurements with and without considering the pyranometer's thermal effect. The results of radiative transfer model simulation show that a pyranometer's thermal effect on solar irradiance measurements at the surface can be translated into a significant alteration of the calculated distribution of solar energy inside the column atmosphere.

  4. MOBY, A Radiometric Buoy for Performance Monitoring and Vicarious Calibration of Satellite Ocean Color Sensors: Measurement and Data Analysis Protocols. Chapter 2

    NASA Technical Reports Server (NTRS)

    Clark, Dennis K.; Yarbrough, Mark A.; Feinholz, Mike; Flora, Stephanie; Broenkow, William; Kim, Yong Sung; Johnson, B. Carol; Brown, Steven W.; Yuen, Marilyn; Mueller, James L.

    2003-01-01

    The Marine Optical Buoy (MOBY) is the centerpiece of the primary ocean measurement site for calibration of satellite ocean color sensors based on independent in situ measurements. Since late 1996, the time series of normalized water-leaving radiances L(sub WN)(lambda) determined from the array of radiometric sensors attached to MOBY are the primary basis for the on-orbit calibrations of the USA Sea-viewing Wide Field-of-view Sensor (SeaWiFS), the Japanese Ocean Color and Temperature Sensor (OCTS), the French Polarization Detection Environmental Radiometer (POLDER), the German Modular Optoelectronic Scanner on the Indian Research Satellite (IRS1-MOS), and the USA Moderate Resolution Imaging Spectrometer (MODIS). The MOBY vicarious calibration L(sub WN)(lambda) reference is an essential element in the international effort to develop a global, multi-year time series of consistently calibrated ocean color products using data from a wide variety of independent satellite sensors. A longstanding goal of the SeaWiFS and MODIS (Ocean) Science Teams is to determine satellite-derived L(sub WN)(labda) with a relative combined standard uncertainty of 5 %. Other satellite ocean color projects and the Sensor Intercomparison for Marine Biology and Interdisciplinary Oceanic Studies (SIMBIOS) project have also adopted this goal, at least implicitly. Because water-leaving radiance contributes at most 10 % of the total radiance measured by a satellite sensor above the atmosphere, a 5 % uncertainty in L(sub WN)(lambda) implies a 0.5 % uncertainty in the above-atmosphere radiance measurements. This level of uncertainty can only be approached using vicarious-calibration approaches as described below. In practice, this means that the satellite radiance responsivity is adjusted to achieve the best agreement, in a least-squares sense, for the L(sub WN)(lambda) results determined using the satellite and the independent optical sensors (e.g. MOBY). The end result of this approach is to

  5. Urban vegetation detection using radiometrically calibrated small-footprint full-waveform airborne LiDAR data

    NASA Astrophysics Data System (ADS)

    Höfle, Bernhard; Hollaus, Markus; Hagenauer, Julian

    2012-01-01

    This paper introduces a new GIS workflow for urban vegetation mapping from high-density (50 pts./m 2) full-waveform airborne LiDAR data, combining the advantages of both raster and point cloud based analysis. Polygon segments derived by edge-based segmentation of the normalized digital surface model are used for classification. A rich set of segment features based on the point cloud and derived from full-waveform attributes is built, serving as input for a decision tree and artificial neural network (ANN) classifier. Exploratory data analysis and detailed investigation of the discriminative power of selected point cloud and full-waveform LiDAR observables indicate a high value of the occurrence of multiple distinct targets in a laser beam (i.e. 'echo ratio') for vegetation classification (98% correctness). The radiometric full-waveform observables (e.g. backscattering coefficient) do not suffice as single discriminators with low correctness values using a decision tree classifier (⩽72% correctness) but higher values with ANN (⩽95% correctness). Tests using reduced point densities indicate that the derived segment features and classification accuracies remain relatively stable even up to a reduction factor of 10 (5 pts./m 2). In a representative study area in the City of Vienna/Austria the applicability of the developed object-based GIS workflow is demonstrated. The unique high density full-waveform LiDAR data open a new scale in 3D object characterization but demands for novel joint strategies in object-based raster and 3D point cloud analysis.

  6. NIST Standard Reference Material 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering

    PubMed Central

    Zhang, Fan; Kline, R. Joseph; Guthrie, William F.; Ilavsky, Jan

    2017-01-01

    The certification of a new standard reference material for small-angle scattering [NIST Standard Reference Material (SRM) 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering (SAXS)], based on glassy carbon, is presented. Creation of this SRM relies on the intrinsic primary calibration capabilities of the ultra-small-angle X-ray scattering technique. This article describes how the intensity calibration has been achieved and validated in the certified Q range, Q = 0.008–0.25 Å−1, together with the purpose, use and availability of the SRM. The intensity calibration afforded by this robust and stable SRM should be applicable universally to all SAXS instruments that employ a transmission measurement geometry, working with a wide range of X-ray energies or wavelengths. The validation of the SRM SAXS intensity calibration using small-angle neutron scattering (SANS) is discussed, together with the prospects for including SANS in a future renewal certification. PMID:28381972

  7. ABSOLUTE FLUX CALIBRATION OF THE IRAC INSTRUMENT ON THE SPITZER SPACE TELESCOPE USING HUBBLE SPACE TELESCOPE FLUX STANDARDS

    SciTech Connect

    Bohlin, R. C.; Gordon, K. D.; Deustua, S.; Ferguson, H. C.; Flanagan, K.; Kalirai, J.; Meixner, M.; Rieke, G. H.; Engelbracht, C.; Su, K. Y. L.; Ardila, D.; Tremblay, P.-E.

    2011-05-15

    The absolute flux calibration of the James Webb Space Telescope (JWST) will be based on a set of stars observed by the Hubble and Spitzer Space Telescopes. In order to cross-calibrate the two facilities, several A, G, and white dwarf stars are observed with both Spitzer and Hubble and are the prototypes for a set of JWST calibration standards. The flux calibration constants for the four Spitzer IRAC bands 1-4 are derived from these stars and are 2.3%, 1.9%, 2.0%, and 0.5% lower than the official cold-mission IRAC calibration of Reach et al., i.e., in agreement within their estimated errors of {approx}2%. The causes of these differences lie primarily in the IRAC data reduction and secondarily in the spectral energy distributions of our standard stars. The independent IRAC 8 {mu}m band-4 fluxes of Rieke et al. are about 1.5% {+-} 2% higher than those of Reach et al. and are also in agreement with our 8 {mu}m result.

  8. Comparison of absolute gain photometric calibration between Planck/HFI and Herschel/SPIRE at 545 and 857 GHz

    NASA Astrophysics Data System (ADS)

    Bertincourt, B.; Lagache, G.; Martin, P. G.; Schulz, B.; Conversi, L.; Dassas, K.; Maurin, L.; Abergel, A.; Beelen, A.; Bernard, J.-P.; Crill, B. P.; Dole, H.; Eales, S.; Gudmundsson, J. E.; Lellouch, E.; Moreno, R.; Perdereau, O.

    2016-04-01

    We compare the absolute gain photometric calibration of the Planck/HFI and Herschel/SPIRE instruments on diffuse emission. The absolute calibration of HFI and SPIRE each relies on planet flux measurements and comparison with theoretical far-infrared emission models of planetary atmospheres. We measure the photometric cross calibration between the instruments at two overlapping bands, 545 GHz/500 μm and 857 GHz/350 μm. The SPIRE maps used have been processed in the Herschel Interactive Processing Environment (Version 12) and the HFI data are from the 2015 Public Data Release 2. For our study we used 15 large fields observed with SPIRE, which cover a total of about 120 deg2. We have selected these fields carefully to provide high signal-to-noise ratio, avoid residual systematics in the SPIRE maps, and span a wide range of surface brightness. The HFI maps are bandpass-corrected to match the emission observed by the SPIRE bandpasses. The SPIRE maps are convolved to match the HFI beam and put on a common pixel grid. We measure the cross-calibration relative gain between the instruments using two methods in each field, pixel-to-pixel correlation and angular power spectrum measurements. The SPIRE/HFI relative gains are 1.047 (±0.0069) and 1.003 (±0.0080) at 545 and 857 GHz, respectively, indicating very good agreement between the instruments. These relative gains deviate from unity by much less than the uncertainty of the absolute extended emission calibration, which is about 6.4% and 9.5% for HFI and SPIRE, respectively, but the deviations are comparable to the values 1.4% and 5.5% for HFI and SPIRE if the uncertainty from models of the common calibrator can be discounted. Of the 5.5% uncertainty for SPIRE, 4% arises from the uncertainty of the effective beam solid angle, which impacts the adopted SPIRE point source to extended source unit conversion factor, highlighting that as a focus for refinement.

  9. Absolute calibration of a variable attenuator using few-photon pulses.

    PubMed

    Levine, Zachary H; Glebov, Boris L; Pintar, Adam L; Migdall, Alan L

    2015-06-15

    We demonstrate the ability to calibrate a variable optical attenuator directly at the few-photon level using a superconducting Transition Edge Sensor (TES). Because of the inherent linearity of photon-number resolving detection, no external calibrations are required, even for the energy of the laser pulses, which ranged from means of 0.15 to 18 photons per pulse at the detector. To verify this method, calibrations were compared to an independent conventional calibration made at much higher photon fluxes using analog detectors. In all cases, the attenuations estimated by the two methods agree within their uncertainties.Our few-photon measurement determined attenuations using the Poisson-Influenced K-Means Algorithm (PIKA) to extract mean numbers of photons per pulse along with the uncertainties of these means. The robustness of the method is highlighted by the agreement of the two calibrations even in the presence of significant drifts in the optical power over the course of the experiment.Work of the United States Government. Not subject to copyright.

  10. Radiometric calibration of the SwRI ultraviolet reflectance chamber (SwURC) far-ultraviolet reflectometer

    NASA Astrophysics Data System (ADS)

    Karnes, Preston L.; Retherford, Kurt D.; Winters, Gregory S.; Bassett, Eric C.; Escobedo, Stephen M.; Patrick, Edward L.; Richter, Amanda; Davis, Michael W.; Miles, Paul F.; Parker, Joel W.; Gladstone, G. Randall; Greathouse, Thomas K.; Schindhelm, Eric R.; Feaga, Lori M.; Stern, S. Alan

    2013-09-01

    The Southwest Research Institute Ultraviolet Reflectance Chamber (SwURC) is a highly capable UV reflectometer chamber and data acquisition system designed to provide bidirectional scattering data of various surfaces and materials. The chamber provides laboratory-based UV reflectance measurements of water frost/ice, lunar soils, simulants, and analogs to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project (LAMP) Lunar Reconnaissance Orbiter (LRO). A deuterium lamp illuminates a monochromator with a nominal wavelength range of 115 nm to 210 nm. The detector scans emission angles -85° to +85°in the principal plane. Liquid nitrogen passed through the sample mount enables constant refrigeration of tray temperatures down to 78 K to form water ice and other volatile samples. The SwURC can be configured to examine a wide range of samples and materials through the use of custom removable sample trays, connectors, and holders. Calibration reference standard measurements reported here include Al/MgF2 coated mirrors for specular reflection and Fluorilon for diffuse reflectances. This calibration work is a precursor to reports of experiments measuring the far-UV reflectance of water frost, lunar simulants, and Apollo soil sample 10084 in support of LRO-LAMP.

  11. Absolute calibration of the Gamma Knife{sup ®} Perfexion™ and delivered dose verification using EPR/alanine dosimetry

    SciTech Connect

    Hornbeck, Amaury E-mail: tristan.garcia@cea.fr; Garcia, Tristan E-mail: tristan.garcia@cea.fr; Cuttat, Marguerite; Jenny, Catherine

    2014-06-15

    Purpose: Elekta Leksell Gamma Knife{sup ®} (LGK) is a radiotherapy beam machine whose features are not compliant with the international calibration protocols for radiotherapy. In this scope, the Laboratoire National Henri Becquerel and the Pitié-Salpêtrière Hospital decided to conceive a new LKG dose calibration method and to compare it with the currently used one. Furthermore, the accuracy of the dose delivered by the LGK machine was checked using an “end-to-end” test. This study also aims to compare doses delivered by the two latest software versions of the Gammaplan treatment planning system (TPS). Methods: The dosimetric method chosen is the electron paramagnetic resonance (EPR) of alanine. Dose rate (calibration) verification was done without TPS using a spherical phantom. Absolute calibration was done with factors calculated by Monte Carlo simulation (MCNP-X). For “end-to-end” test, irradiations in an anthropomorphic head phantom, close to real treatment conditions, are done using the TPS in order to verify the delivered dose. Results: The comparison of the currently used calibration method with the new one revealed a deviation of +0.8% between the dose rates measured by ion chamber and EPR/alanine. For simple fields configuration (less than 16 mm diameter), the “end-to-end” tests showed out average deviations of −1.7% and −0.9% between the measured dose and the calculated dose by Gammaplan v9 and v10, respectively. Conclusions: This paper shows there is a good agreement between the new calibration method and the currently used one. There is also a good agreement between the calculated and delivered doses especially for Gammaplan v10.

  12. GOES-R Advanced Baseline Imager: spectral response functions and radiometric biases with the NPP Visible Infrared Imaging Radiometer Suite evaluated for desert calibration sites.

    PubMed

    Pearlman, Aaron; Pogorzala, David; Cao, Changyong

    2013-11-01

    The Advanced Baseline Imager (ABI), which will be launched in late 2015 on the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite R-series satellite, will be evaluated in terms of its data quality postlaunch through comparisons with other satellite sensors such as the recently launched Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership satellite. The ABI has completed much of its prelaunch characterization and its developers have generated and released its channel spectral response functions (response versus wavelength). Using these responses and constraining a radiative transfer model with ground reflectance, aerosol, and water vapor measurements, we simulate observed top of atmosphere (TOA) reflectances for analogous visible and near infrared channels of the VIIRS and ABI sensors at the Sonoran Desert and White Sands National Monument sites and calculate the radiometric biases and their uncertainties. We also calculate sensor TOA reflectances using aircraft hyperspectral data from the Airborne Visible/Infrared Imaging Spectrometer to validate the uncertainties in several of the ABI and VIIRS channels and discuss the potential for validating the others. Once on-orbit, calibration scientists can use these biases to ensure ABI data quality and consistency to support the numerical weather prediction community and other data users. They can also use the results for ABI or VIIRS anomaly detection and resolution.

  13. Impact of the angular dependence of the SNPP VIIRS solar diffuser BRDF degradation factor on the radiometric calibration of the reflective solar bands

    NASA Astrophysics Data System (ADS)

    Lei, Ning; Xiong, Xiaoxiong

    2015-09-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership satellite performs radiometric calibration of its reflective solar bands (RSBs) primarily by observing an onboard solar diffuser (SD). The SD optical scattering property is measured by a bidirectional reflectance distribution function (BRDF). Once on orbit, the BRDF degrades over time and the degradation factor is determined by an onboard solar diffuser stability monitor (SDSM) which observes the Sun and the sunlit SD at almost the same time. We showed in a previous SPIE paper that the BRDF degradation factor is angle dependent. Consequently, due to that the SDSM and the VIIRS telescope SD views have very different angles, applying the BRDF degradation factor determined from the SDSM without any adjustments to the VIIRS RSB calibration can result in large systematic errors. In addition, the BRDF angular dependence impacts the determination of the SD screen transmittance viewed by both the SDSM detectors and the VIIRS telescope. We first use yaw maneuver data to determine the product of the SD attenuation screen transmittance and the BRDF at the initial time (when the BRDF just started to degrade) viewed by the VIIRS telescope, removing the impact of the SD BRDF degradation factor angular dependence over satellite orbits. By attributing the large bumps observed in the initially computed VIIRS detector gains for the M1-M4 bands to the angular dependence of the BRDF degradation factor and matching the computed VIIRS detector gains from the SD and the lunar observations, we find the relation between the BRDF degradation factors in the VIIRS telescope and SDSM SD view directions.

  14. Absolute x-ray energy calibration over a wide energy range using a diffraction-based iterative method.

    PubMed

    Hong, Xinguo; Chen, Zhiqiang; Duffy, Thomas S

    2012-06-01

    In this paper, we report a method of precise and fast absolute x-ray energy calibration over a wide energy range using an iterative x-ray diffraction based method. Although accurate x-ray energy calibration is indispensable for x-ray energy-sensitive scattering and diffraction experiments, there is still a lack of effective methods to precisely calibrate energy over a wide range, especially when normal transmission monitoring is not an option and complicated micro-focusing optics are fixed in place. It is found that by using an iterative algorithm the x-ray energy is only tied to the relative offset of sample-to-detector distance, which can be readily varied with high precision of the order of 10(-5) -10(-6) spatial resolution using gauge blocks. Even starting with arbitrary initial values of 0.1 Å, 0.3 Å, and 0.4 Å, the iteration process converges to a value within 3.5 eV for 31.122 keV x-rays after three iterations. Different common diffraction standards CeO(2), Au, and Si show an energy deviation of 14 eV. As an application, the proposed method has been applied to determine the energy-sensitive first sharp diffraction peak of network forming GeO(2) glass at high pressure, exhibiting a distinct behavior in the pressure range of 2-4 GPa. Another application presented is pair distribution function measurement using calibrated high-energy x-rays at 82.273 keV. Unlike the traditional x-ray absorption-based calibration method, the proposed approach does not rely on any edges of specific elements, and is applicable to the hard x-ray region where no appropriate absorption edge is available.

  15. Airborne hyperspectral sensor radiometric self-calibration using near-infrared properties of deep water and vegetation

    NASA Astrophysics Data System (ADS)

    Barbieux, Kévin; Nouchi, Vincent; Merminod, Bertrand

    2016-10-01

    Retrieving the water-leaving reflectance from airborne hyperspectral data implies to deal with three steps. Firstly, the radiance recorded by an airborne sensor comes from several sources: the real radiance of the object, the atmospheric scattering, sky and sun glint and the dark current of the sensor. Secondly, the dispersive element inside the sensor (usually a diffraction grating or a prism) could move during the flight, thus shifting the observed spectra on the wavelengths axis. Thirdly, to compute the reflectance, it is necessary to estimate, for each band, what value of irradiance corresponds to a 100% reflectance. We present here our calibration method, relying on the absorption features of the atmosphere and the near-infrared properties of common materials. By choosing proper flight height and flight lines angle, we can ignore atmospheric and sun glint contributions. Autocorrelation plots allow to identify and reduce the noise in our signals. Then, we compute a signal that represents the high frequencies of the spectrum, to localize the atmospheric absorption peaks (mainly the dioxygen peak around 760 nm). Matching these peaks removes the shift induced by the moving dispersive element. Finally, we use the signal collected over a Lambertian, unit-reflectance surface to estimate the ratio of the system's transmittances to its near-infrared transmittance. This transmittance is computed assuming an average 50% reflectance of the vegetation and nearly 0% for water in the near-infrared. Results show great correlation between the output spectra and ground measurements from a TriOS Ramses and the water-insight WISP-3.

  16. Radiometric Normalization of Large Airborne Image Data Sets Acquired by Different Sensor Types

    NASA Astrophysics Data System (ADS)

    Gehrke, S.; Beshah, B. T.

    2016-06-01

    Generating seamless mosaics of aerial images is a particularly challenging task when the mosaic comprises a large number of im-ages, collected over longer periods of time and with different sensors under varying imaging conditions. Such large mosaics typically consist of very heterogeneous image data, both spatially (different terrain types and atmosphere) and temporally (unstable atmo-spheric properties and even changes in land coverage). We present a new radiometric normalization or, respectively, radiometric aerial triangulation approach that takes advantage of our knowledge about each sensor's properties. The current implementation supports medium and large format airborne imaging sensors of the Leica Geosystems family, namely the ADS line-scanner as well as DMC and RCD frame sensors. A hierarchical modelling - with parameters for the overall mosaic, the sensor type, different flight sessions, strips and individual images - allows for adaptation to each sensor's geometric and radiometric properties. Additional parameters at different hierarchy levels can compensate radiome-tric differences of various origins to compensate for shortcomings of the preceding radiometric sensor calibration as well as BRDF and atmospheric corrections. The final, relative normalization is based on radiometric tie points in overlapping images, absolute radiometric control points and image statistics. It is computed in a global least squares adjustment for the entire mosaic by altering each image's histogram using a location-dependent mathematical model. This model involves contrast and brightness corrections at radiometric fix points with bilinear interpolation for corrections in-between. The distribution of the radiometry fixes is adaptive to each image and generally increases with image size, hence enabling optimal local adaptation even for very long image strips as typi-cally captured by a line-scanner sensor. The normalization approach is implemented in HxMap software. It has been

  17. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

    NASA Astrophysics Data System (ADS)

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-02-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.20, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  18. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata.

    PubMed

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-02-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.2(0), respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  19. The spatial relations between stimulus and response determine an absolute visuo-haptic calibration in pantomime-grasping.

    PubMed

    Davarpanah Jazi, Shirin; Heath, Matthew

    2017-03-24

    Pantomime-grasps entail a response to an area adjacent to (i.e., spatially dissociated pantomime-grasp), or previously occupied by (i.e., no-target pantomime-grasp) a target. Previous work has reported that pantomime-grasps differ kinematically from naturalistic grasps (i.e., grasping a physical target object) - a result taken to evince that pantomime-grasps are perception-based and mediated via relative visual information. However, such actions differ not only in terms of their visual properties, but also because the former precludes haptic feedback related to a target's absolute size. The current study provides four experiments examining whether experimenter-induced haptic feedback influences the information mediating spatially dissociated and no-target pantomime-grasps. Just-noticeable-difference scores were computed to determine whether grasps adhered to, or violated, the relative psychophysical properties of Weber's law. Spatially dissociated pantomime-grasps performed with haptic feedback adhered to Weber's law (Experiments 1-3), whereas their no-target pantomime-grasp counterparts violated the law (Experiment 4). Accordingly, we propose that the top-down demands of decoupling stimulus-response relations in spatially dissociated pantomime-grasping renders aperture shaping via a visual percept that is not directly influenced by the integration of haptic feedback. In turn, the decreased top-down demands of no-target pantomime-grasps allows haptic feedback to serve as a reliable sensory resource supporting an absolute visuo-haptic calibration.

  20. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

    DOE PAGES

    Waugh, C. J.; Rosenberg, M. J.; Zylstra, A. B.; ...

    2015-05-27

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

  1. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

    SciTech Connect

    Waugh, C. J.; Rosenberg, M. J.; Zylstra, A. B.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Glebov, V. Yu.; Sangster, T. C.; Stoeckl, C.

    2015-05-27

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition, comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.

  2. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

    SciTech Connect

    Waugh, C. J. Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.; Petrasso, R. D.; Rosenberg, M. J.; Glebov, V. Yu.; Sangster, T. C.; Stoeckl, C.

    2015-05-15

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition, comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.

  3. Absolute sensitivity calibration of vacuum and extreme ultraviolet spectrometer systems and Z{sub eff} measurement based on bremsstrahlung continuum in HL-2A tokamak

    SciTech Connect

    Zhou Hangyu; Cui Zhengying; Fu Bingzhong; Sun Ping; Gao Yadong; Xu Yuan; Lu Ping; Yang Qingwei; Duan Xuru; Morita, Shigeru; Goto, Motoshi; Dong Chunfeng

    2012-10-15

    A grazing-incidence flat-field extreme ultraviolet (EUV) spectrometer has been newly developed in HL-2A tokamak. Typical spectral lines are observed from intrinsic impurities of carbon, oxygen, iron, and extrinsic impurity of helium in the wavelength range of 20 A-500 A. Bremsstrahlung continuum is measured at different electron densities of HL-2A discharges to calibrate absolute sensitivity of the EUV spectrometer system and to measure effective ionic charge, Z{sub eff}. The sensitivity of a vacuum ultraviolet (VUV) spectrometer system is also absolutely calibrated in overlapped wavelength range of 300 A-500 A by comparing the intensity between VUV and EUV line emissions.

  4. Radiometric calibration for MWIR cameras

    NASA Astrophysics Data System (ADS)

    Yang, Hyunjin; Chun, Joohwan; Seo, Doo Chun; Yang, Jiyeon

    2012-06-01

    Korean Multi-purpose Satellite-3A (KOMPSAT-3A), which weighing about 1,000 kg is scheduled to be launched in 2013 and will be located at a sun-synchronous orbit (SSO) of 530 km in altitude. This is Korea's rst satellite to orbit with a mid-wave infrared (MWIR) image sensor, which is currently being developed at Korea Aerospace Research Institute (KARI). The missions envisioned include forest re surveillance, measurement of the ocean surface temperature, national defense and crop harvest estimate. In this paper, we shall explain the MWIR scene generation software and atmospheric compensation techniques for the infrared (IR) camera that we are currently developing. The MWIR scene generation software we have developed taking into account sky thermal emission, path emission, target emission, sky solar scattering and ground re ection based on MODTRAN data. Here, this software will be used for generating the radiation image in the satellite camera which requires an atmospheric compensation algorithm and the validation of the accuracy of the temperature which is obtained in our result. Image visibility restoration algorithm is a method for removing the eect of atmosphere between the camera and an object. This algorithm works between the satellite and the Earth, to predict object temperature noised with the Earth's atmosphere and solar radiation. Commonly, to compensate for the atmospheric eect, some softwares like MODTRAN is used for modeling the atmosphere. Our algorithm doesn't require an additional software to obtain the surface temperature. However, it needs to adjust visibility restoration parameters and the precision of the result still should be studied.

  5. Computer processing of spectrograms for absolute intensities.

    PubMed

    Guttman, A; Golden, J; Galbraith, H J

    1967-09-01

    A computer program was developed to process photographically recorded spectra for absolute intensity. Test and calibration films are subjected to densitometric scans that provide digitally recorded densities on magnetic tapes. The nonlinear calibration data are fitted by least-squares cubic polynomials to yield a good approximation to the monochromatic H&D curves for commonly used emulsions (2475 recording film, Royal-X, Tri-X, 4-X). Several test cases were made. Results of these cases show that the machine processed absolute intensities are accurate to within 15%o. Arbitrarily raising the sensitivity threshold by 0.1 density units above gross fog yields cubic polynomial fits to the H&D curves that are radiometrically accurate within 10%. In addition, curves of gamma vs wavelength for 2475, Tri-X, and 4-X emulsions were made. These data show slight evidence of the photographic Purkinje effect in the 2475 emulsion.

  6. High-resolution imaging spectrometer for recording absolutely calibrated far ultraviolet spectra from laser-produced plasmas

    SciTech Connect

    Brown, Charles M.; Seely, John F.; Feldman, Uri; Holland, Glenn E.; Weaver, James L.; Obenschain, Steven P.; Kjornrattanawanich, Benjawan; Fielding, Drew

    2008-10-15

    An imaging spectrometer was designed and fabricated for recording far ultraviolet spectra from laser-produced plasmas with wavelengths as short as 155 nm. The spectrometer implements a Cassegrain telescope and two gratings in a tandem Wadsworth optical configuration that provides diffraction limited resolution. Spectral images were recorded from plasmas produced by the irradiation of various target materials by intense KrF laser radiation with 248 nm wavelength. Two pairs of high-resolution gratings can be selected for the coverage of two wavebands, one grating pair with 1800 grooves/mm and covering approximately 155-175 nm and another grating pair with 1200 grooves/mm covering 230-260 nm. The latter waveband includes the 248 nm KrF laser wavelength, and the former waveband includes the wavelength of the two-plasmon decay instability at (2/3) the KrF laser wavelength (165 nm). The detection media consist of a complementary metal oxide semiconductor imager, photostimulable phosphor image plates, and a linear array of 1 mm{sup 2} square silicon photodiodes with 0.4 ns rise time. The telescope mirrors, spectrometer gratings, and 1 mm{sup 2} photodiode were calibrated using synchrotron radiation, and this enables the measurement of the absolute emission from the laser-produced plasmas with temporal, spatial, and spectral resolutions. The spectrometer is capable of measuring absolute spectral emissions at 165 nm wavelength as small as 5x10{sup -7} J/nm from a plasma source area of 0.37 mm{sup 2} and with 0.4 ns time resolution.

  7. (18)F primary standard at ENEA-INMRI by three absolute techniques and calibration of a well-type IG11 ionization chamber.

    PubMed

    Capogni, Marco; Carconi, Pierluigi; De Felice, Pierino; Fazio, Aldo

    2016-03-01

    A new (18)F primary standardization carried out at ENEA-INMRI by three different absolute techniques, i.e. 4πγNaI(Tl)γ high-efficiency counting, TDCR and 4πβ(LS)-γ[NaI(Tl)] coincidence counting method, allowed the calibration of a fixed well-reentrant IG11 ionization chamber (IC), with an uncertainty lower than 1%, and to check the calibration factor of a portable well-type IC NPL-CRC model, previously calibrated. By the new standard the ENEA-INMRI was linked to the BIPM International Reference System (SIR) through the BIPM SIR Transfer Instrument (SIRTI).

  8. Continuous absolute g monitoring of the mobile LNE-SYRTE Cold Atom Gravimeter - a new tool to calibrate superconducting gravimeters -

    NASA Astrophysics Data System (ADS)

    Merlet, Sébastien; Gillot, Pierre; Cheng, Bing; Pereira Dos Santos, Franck

    2016-04-01

    Atom interferometry allows for the realization of a new generation of instruments for inertial sensing based on laser cooled atoms. We have developed an absolute gravimeter (CAG) based on this technic, which can perform continuous gravity measurements at a high cycling rate. This instrument, operating since summer 2009, is the new metrological french standard for gravimetry. The CAG has been designed to be movable, so as to participate to international comparisons and on field measurements. It took part to several comparisons since ICAG'09 and operated in both urban environments and low noise underground facilities. The atom gravimeter operates with a high cycling rate of 3 Hz. Its sensitivity is predominantly limited by ground vibration noise which is rejected thanks to isolation platforms and correlation with other sensors, such as broadband accelerometers or sismometers. These developments allow us to perform continuous gravity measurements, no matter what the sismic conditions are and even in the worst cases such as during earthquakes. At best, a sensitivity of 5.6 μGal at 1 s measurement time has been demonstrated. The long term stability averages down to 0.1 μGal for long term measurements. Presently, the measurement accuracy is 4 μGal, which we plan to reduce to 1 μGal or below. I will present the instrument, the principle of the gravity acceleration measurement and its performances. I will focus on continuous gravity measurements performed over several years and compared with our superconducting gravimeter iGrav signal. This comparison allows us to calibrate the iGrav scale factor and follow its evolution. Especially, we demonstrate that, thanks to the CAG very high cycling rate, a single day gravity measurement allows to calibrate the iGrav scaling factor with a relative uncertainty as good as 4.10-4.

  9. Progress in obtaining an absolute calibration of a total deuterium-tritium neutron yield diagnostic based on copper activation.

    PubMed

    Ruiz, C L; Chandler, G A; Cooper, G W; Fehl, D L; Hahn, K D; Leeper, R J; McWatters, B R; Nelson, A J; Smelser, R M; Snow, C S; Torres, J A

    2012-10-01

    The 350-keV Cockroft-Walton accelerator at Sandia National laboratory's Ion Beam facility is being used to calibrate absolutely a total DT neutron yield diagnostic based on the (63)Cu(n,2n)(62)Cu(β+) reaction. These investigations have led to first-order uncertainties approaching 5% or better. The experiments employ the associated-particle technique. Deuterons at 175 keV impinge a 2.6 μm thick erbium tritide target producing 14.1 MeV neutrons from the T(d,n)(4)He reaction. The alpha particles emitted are measured at two angles relative to the beam direction and used to infer the neutron flux on a copper sample. The induced (62)Cu activity is then measured and related to the neutron flux. This method is known as the F-factor technique. Description of the associated-particle method, copper sample geometries employed, and the present estimates of the uncertainties to the F-factor obtained are given.

  10. DAQ Software Contributions, Absolute Scale Energy Calibration and Background Evaluation for the NOvA Experiment at Fermilab

    SciTech Connect

    Flumerfelt, Eric Lewis

    2015-08-01

    The NOvA (NuMI Off-axis ve [nu_e] Appearance) Experiment is a long-baseline accelerator neutrino experiment currently in its second year of operations. NOvA uses the Neutrinos from the Main Injector (NuMI) beam at Fermilab, and there are two main off-axis detectors: a Near Detector at Fermilab and a Far Detector 810 km away at Ash River, MN. The work reported herein is in support of the NOvA Experiment, through contributions to the development of data acquisition software, providing an accurate, absolute-scale energy calibration for electromagnetic showers in NOvA detector elements, crucial to the primary electron neutrino search, and through an initial evaluation of the cosmic background rate in the NOvA Far Detector, which is situated on the surface without significant overburden. Additional support work for the NOvA Experiment is also detailed, including DAQ Server Administration duties and a study of NOvA’s sensitivity to neutrino oscillations into a “sterile” state.

  11. Stellar spectral flux calibration of auroral H-beta photometer signal and background channels

    NASA Astrophysics Data System (ADS)

    Jackel, Brian J.; Unick, Craig

    2017-01-01

    Observations of optical aurora typically require the operation of sensitive instruments at remote field sites. Absolute radiometric calibration of these devices is essential for quantitative comparison over time and with other measurements. In this study we present absolute calibration of a proton auroral photometer using star transits observed during regular data collection. This requires absolute flux spectra with sufficient resolution to account for structure in stellar Hβ absorption line profiles. Several flux spectral catalogs are combined and corrected for systematic differences. The resulting estimates of instrumental sensitivity are consistent with darkroom calibration to roughly 15%.

  12. Traceable Pyrgeometer Calibrations

    SciTech Connect

    Dooraghi, Mike; Kutchenreiter, Mark; Reda, Ibrahim; Habte, Aron; Sengupta, Manajit; Andreas, Afshin; Newman, Martina

    2016-05-02

    This poster presents the development, implementation, and operation of the Broadband Outdoor Radiometer Calibrations (BORCAL) Longwave (LW) system at the Southern Great Plains Radiometric Calibration Facility for the calibration of pyrgeometers that provide traceability to the World Infrared Standard Group.

  13. Comparison of Spectral Radiance Calibration Techniques Used for Backscatter Ultraviolet Satellite Instruments

    NASA Technical Reports Server (NTRS)

    Kowalewski, Matthew G.; Janz, Scott

    2014-01-01

    Methods for determining the absolute radiometric calibration sensitivities of backscatter ultraviolet (BUV) satellite instruments are compared as part of an effort to minimize pre-launch calibration errors. An internally illuminated integrating sphere source has been used for the Shuttle Solar BUV (SSBUV), Total Ozone Mapping Spectrometer (TOMS), Ozone Mapping Instrument (OMI), and Global Ozone Monitoring Experiment 2 (GOME-2) using standardized procedures traceable to national standards. These sphere-based sensitivities agree to within three percent [k equals 2] relative to calibrations performed using an external diffuser illuminated by standard irradiance sources, the customary radiance calibration method for BUV instruments. The uncertainty for these calibration techniques as implemented at the NASA Goddard Space Flight Centers Radiometric Calibration and Development Laboratory is shown to be 4 percent at 250nm [k equals 2] when using a single traceable calibration standard. Significant reduction in the uncertainty of nearly 1 percent is demonstrated when multiple calibration standards are used.

  14. Radiometric performance of the Viking Mars lander cameras

    NASA Technical Reports Server (NTRS)

    Huck, F. O.; Burcher, E. E.; Taylor, E. J.; Wall, S. D.

    1975-01-01

    The Viking lander cameras feature an array of 12 silicon photodiodes for electronic focus selection and multispectral imaging. Comparisons of absolute radiometric calibrations of the four cameras selected for the mission to Mars with performance predictions based on their design data revealed minor discrepancies. These discrepancies were caused primarily by the method used to calibrate the photosensor array and apparently also from light reflections internal to the array. The sensitivity and dynamic range of all camera channels are found to be sufficient for high quality pictures, providing that the commandable gains and offsets can be optimized for the scene radiance; otherwise, the quantization noise may be too high or the dynamic range too low for an adequate characterization of the scene.

  15. Improved absolute calibration of LOPES measurements and its impact on the comparison with REAS 3.11 and CoREAS simulations

    NASA Astrophysics Data System (ADS)

    Apel, W. D.; Arteaga-Velázquez, J. C.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Fuchs, B.; Gemmeke, H.; Grupen, C.; Haungs, A.; Heck, D.; Hiller, R.; Hörandel, J. R.; Horneffer, A.; Huber, D.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Krömer, O.; Kuijpers, J.; Link, K.; Łuczak, P.; Ludwig, M.; Mathes, H. J.; Melissas, M.; Morello, C.; Nehls, S.; Oehlschläger, J.; Palmieri, N.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Rühle, C.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schoo, S.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Weindl, A.; Wochele, J.; Zabierowski, J.; Zensus, J. A.

    2016-02-01

    LOPES was a digital antenna array detecting the radio emission of cosmic-ray air showers. The calibration of the absolute amplitude scale of the measurements was done using an external, commercial reference source, which emits a frequency comb with defined amplitudes. Recently, we obtained improved reference values by the manufacturer of the reference source, which significantly changed the absolute calibration of LOPES. We reanalyzed previously published LOPES measurements, studying the impact of the changed calibration. The main effect is an overall decrease of the LOPES amplitude scale by a factor of 2.6 ± 0.2, affecting all previously published values for measurements of the electric-field strength. This results in a major change in the conclusion of the paper 'Comparing LOPES measurements of air-shower radio emission with REAS 3.11 and CoREAS simulations' published by Apel et al. (2013) : With the revised calibration, LOPES measurements now are compatible with CoREAS simulations, but in tension with REAS 3.11 simulations. Since CoREAS is the latest version of the simulation code incorporating the current state of knowledge on the radio emission of air showers, this new result indicates that the absolute amplitude prediction of current simulations now is in agreement with experimental data.

  16. Prospects for the Moon as an SI-Traceable Absolute Spectroradiometric Standard for Satellite Remote Sensing

    NASA Astrophysics Data System (ADS)

    Cramer, C. E.; Stone, T. C.; Lykke, K.; Woodward, J. T.

    2015-12-01

    The Earth's Moon has many physical properties that make it suitable for use as a reference light source for radiometric calibration of remote sensing satellite instruments. Lunar calibration has been successfully applied to many imagers in orbit, including both MODIS instruments and NPP-VIIRS, using the USGS ROLO model to predict the reference exoatmospheric lunar irradiance. Sensor response trending was developed for SeaWIFS with a relative accuracy better than 0.1 % per year with lunar calibration techniques. However, the Moon rarely is used as an absolute reference for on-orbit calibration, primarily due to uncertainties in the ROLO model absolute scale of 5%-10%. But this limitation lies only with the models - the Moon itself is radiometrically stable, and development of a high-accuracy absolute lunar reference is inherently feasible. A program has been undertaken by NIST to collect absolute measurements of the lunar spectral irradiance with absolute accuracy <1 % (k=2), traceable to SI radiometric units. Initial Moon observations were acquired from the Whipple Observatory on Mt. Hopkins, Arizona, elevation 2367 meters, with continuous spectral coverage from 380 nm to 1040 nm at ~3 nm resolution. The lunar spectrometer acquired calibration measurements several times each observing night by pointing to a calibrated integrating sphere source. The lunar spectral irradiance at the top of the atmosphere was derived from a time series of ground-based measurements by a Langley analysis that incorporated measured atmospheric conditions and ROLO model predictions for the change in irradiance resulting from the changing Sun-Moon-Observer geometry throughout each night. Two nights were selected for further study. An extensive error analysis, which includes instrument calibration and atmospheric correction terms, shows a combined standard uncertainty under 1 % over most of the spectral range. Comparison of these two nights' spectral irradiance measurements with predictions

  17. In-situ absolute calibration of electric-field amplitude measurements with the LPDA radio detector stations of the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Briechle, Florian

    2017-03-01

    With the Auger Engineering Radio Array (AERA) located at the Pierre Auger Observatory, radio emission of extensive air showers is observed. To exploit the physics potential of AERA, electric-field amplitude measurements with the radio detector stations need to be well-calibrated on an absolute level. A convenient tool for far-field calibration campaigns is a flying drone. Here we make use of an octocopter to place a calibrated source at freely chosen positions above the radio detector array. Special emphasis is put on the reconstruction of the octocopter position and its accuracy during the flights. The antenna response pattern of the radio detector stations was measured in a recent calibration campaign. Results of these measurements are presented and compared to simulations. It is found that measurements and simulations are in good agreement.

  18. The absolute calibration strategy of the ASTRI SST-2M telescope proposed for the Cherenkov Telescope Array and its external ground-based illumination system

    NASA Astrophysics Data System (ADS)

    Segreto, A.; Maccarone, M. C.; Catalano, O.; Biondo, B.; Gargano, C.; La Rosa, G.; Russo, F.; Sottile, G.; Fiorini, M.; Incorvaia, S.; Toso, G.

    2016-07-01

    ASTRI is the end-to-end prototype for the CTA small-size class of telescopes in a dual-mirror configuration (SST-2M) proposed by the Italian National Institute of Astrophysics (INAF) in the framework of the Cherenkov Telescope Array. ASTRI SST-2M has been installed at the Serra La Nave Astrophysical Observatory on Mount Etna (Sicily) and its Performance Verification Phase will start in autumn 2016. For the relative pixel calibration and gain monitoring, the ASTRI SST-2M camera is equipped with an internal illumination device, while an external, portable, illumination system, placed at a few km distance from the telescope, will be used for the absolute end-to-end calibration of the telescope spectral response. Moreover analysis of signals induced in the camera pixels by the night sky background (diffuse emission and reference stars) will be used to monitor the long term evolution of the telescope calibration. We present an overview of the ASTRI SST-2M absolute calibration strategy and the external illuminating device that will be used for its spectral calibration

  19. Evaluation on Radiometric Capability of Chinese Optical Satellite Sensors

    PubMed Central

    Yang, Aixia; Zhong, Bo; Wu, Shanlong; Liu, Qinhuo

    2017-01-01

    The radiometric capability of on-orbit sensors should be updated on time due to changes induced by space environmental factors and instrument aging. Some sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), have onboard calibrators, which enable real-time calibration. However, most Chinese remote sensing satellite sensors lack onboard calibrators. Their radiometric calibrations have been updated once a year based on a vicarious calibration procedure, which has affected the applications of the data. Therefore, a full evaluation of the sensors’ radiometric capabilities is essential before quantitative applications can be made. In this study, a comprehensive procedure for evaluating the radiometric capability of several Chinese optical satellite sensors is proposed. In this procedure, long-term radiometric stability and radiometric accuracy are the two major indicators for radiometric evaluation. The radiometric temporal stability is analyzed by the tendency of long-term top-of-atmosphere (TOA) reflectance variation; the radiometric accuracy is determined by comparison with the TOA reflectance from MODIS after spectrally matching. Three Chinese sensors including the Charge-Coupled Device (CCD) camera onboard Huan Jing 1 satellite (HJ-1), as well as the Visible and Infrared Radiometer (VIRR) and Medium-Resolution Spectral Imager (MERSI) onboard the Feng Yun 3 satellite (FY-3) are evaluated in reflective bands based on this procedure. The results are reasonable, and thus can provide reliable reference for the sensors’ application, and as such will promote the development of Chinese satellite data. PMID:28117745

  20. Evaluation on Radiometric Capability of Chinese Optical Satellite Sensors.

    PubMed

    Yang, Aixia; Zhong, Bo; Wu, Shanlong; Liu, Qinhuo

    2017-01-22

    The radiometric capability of on-orbit sensors should be updated on time due to changes induced by space environmental factors and instrument aging. Some sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), have onboard calibrators, which enable real-time calibration. However, most Chinese remote sensing satellite sensors lack onboard calibrators. Their radiometric calibrations have been updated once a year based on a vicarious calibration procedure, which has affected the applications of the data. Therefore, a full evaluation of the sensors' radiometric capabilities is essential before quantitative applications can be made. In this study, a comprehensive procedure for evaluating the radiometric capability of several Chinese optical satellite sensors is proposed. In this procedure, long-term radiometric stability and radiometric accuracy are the two major indicators for radiometric evaluation. The radiometric temporal stability is analyzed by the tendency of long-term top-of-atmosphere (TOA) reflectance variation; the radiometric accuracy is determined by comparison with the TOA reflectance from MODIS after spectrally matching. Three Chinese sensors including the Charge-Coupled Device (CCD) camera onboard Huan Jing 1 satellite (HJ-1), as well as the Visible and Infrared Radiometer (VIRR) and Medium-Resolution Spectral Imager (MERSI) onboard the Feng Yun 3 satellite (FY-3) are evaluated in reflective bands based on this procedure. The results are reasonable, and thus can provide reliable reference for the sensors' application, and as such will promote the development of Chinese satellite data.

  1. Absolute Radiation Thermometry in the NIR

    NASA Astrophysics Data System (ADS)

    Bünger, L.; Taubert, R. D.; Gutschwager, B.; Anhalt, K.; Briaudeau, S.; Sadli, M.

    2017-04-01

    A near infrared (NIR) radiation thermometer (RT) for temperature measurements in the range from 773 K up to 1235 K was characterized and calibrated in terms of the "Mise en Pratique for the definition of the Kelvin" (MeP-K) by measuring its absolute spectral radiance responsivity. Using Planck's law of thermal radiation allows the direct measurement of the thermodynamic temperature independently of any ITS-90 fixed-point. To determine the absolute spectral radiance responsivity of the radiation thermometer in the NIR spectral region, an existing PTB monochromator-based calibration setup was upgraded with a supercontinuum laser system (0.45 μm to 2.4 μm) resulting in a significantly improved signal-to-noise ratio. The RT was characterized with respect to its nonlinearity, size-of-source effect, distance effect, and the consistency of its individual temperature measuring ranges. To further improve the calibration setup, a new tool for the aperture alignment and distance measurement was developed. Furthermore, the diffraction correction as well as the impedance correction of the current-to-voltage converter is considered. The calibration scheme and the corresponding uncertainty budget of the absolute spectral responsivity are presented. A relative standard uncertainty of 0.1 % (k=1) for the absolute spectral radiance responsivity was achieved. The absolute radiometric calibration was validated at four temperature values with respect to the ITS-90 via a variable temperature heatpipe blackbody (773 K ...1235 K) and at a gold fixed-point blackbody radiator (1337.33 K).

  2. Fine structure of the age-chromospheric activity relation in solar-type stars. I. The Ca II infrared triplet: Absolute flux calibration

    NASA Astrophysics Data System (ADS)

    Lorenzo-Oliveira, D.; Porto de Mello, G. F.; Dutra-Ferreira, L.; Ribas, I.

    2016-10-01

    Context. Strong spectral lines are useful indicators of stellar chromospheric activity. They are physically linked to the convection efficiency, differential rotation, and angular momentum evolution and are a potential indicator of age. However, for ages > 2 Gyr, the age-activity relationship remains poorly constrained thus hampering its full application. Aims: The Ca II infrared triplet (IRT lines, λλ 8498, 8542, and 8662) has been poorly studied compared to classical chromospheric indicators. We report in this paper absolute chromospheric fluxes in the three Ca II IRT lines, based on a new calibration tied to up-to-date model atmospheres. Methods: We obtain the Ca II IRT absolute fluxes for 113 FGK stars from high signal-to-noise ratio (S/N) and high-resolution spectra covering an extensive domain of chromospheric activity levels. We perform an absolute continuum flux calibration for the Ca II IRT lines anchored in atmospheric models calculated as an explicit function of effective temperatures (Teff), metallicity ([Fe/H]), and gravities (log g) avoiding the degeneracy usually present in photometric continuum calibrations based solely on color indices. Results: The internal uncertainties achieved for continuum absolute flux calculations are ≈2% of the solar chromospheric flux, one order of magnitude lower than for photometric calibrations. Using Monte Carlo simulations, we gauge the impact of observational errors on the final chromospheric fluxes due to the absolute continuum flux calibration and find that Teffuncertainties are properly mitigated by the photospheric correction leaving [Fe/H] as the dominating factor in the chromospheric flux uncertainty. Conclusions: Across the FGK spectral types, the Ca II IRT lines are sensitive to chromospheric activity. The reduced internal uncertainties reported here enable us to build a new chromospheric absolute flux scale and explore the age-activity relation from the active regime down to very low activity levels and

  3. Comparison of spectral radiance responsivity calibration techniques used for backscatter ultraviolet satellite instruments

    NASA Astrophysics Data System (ADS)

    Kowalewski, M. G.; Janz, S. J.

    2015-02-01

    Methods of absolute radiometric calibration of backscatter ultraviolet (BUV) satellite instruments are compared as part of an effort to minimize pre-launch calibration uncertainties. An internally illuminated integrating sphere source has been used for the Shuttle Solar BUV, Total Ozone Mapping Spectrometer, Ozone Mapping Instrument, and Global Ozone Monitoring Experiment 2 using standardized procedures traceable to national standards. These sphere-based spectral responsivities agree to within the derived combined standard uncertainty of 1.87% relative to calibrations performed using an external diffuser illuminated by standard irradiance sources, the customary spectral radiance responsivity calibration method for BUV instruments. The combined standard uncertainty for these calibration techniques as implemented at the NASA Goddard Space Flight Center’s Radiometric Calibration and Development Laboratory is shown to less than 2% at 250 nm when using a single traceable calibration standard.

  4. Radiometric and geometric analysis of hyperspectral imagery acquired from an unmanned aerial vehicle

    SciTech Connect

    Hruska, Ryan; Mitchell, Jessica; Anderson, Matthew; Glenn, Nancy F.

    2012-09-17

    During the summer of 2010, an Unmanned Aerial Vehicle (UAV) hyperspectral in-flight calibration and characterization experiment of the Resonon PIKA II imaging spectrometer was conducted at the U.S. Department of Energy’s Idaho National Laboratory (INL) UAV Research Park. The purpose of the experiment was to validate the radiometric calibration of the spectrometer and determine the georegistration accuracy achievable from the on-board global positioning system (GPS) and inertial navigation sensors (INS) under operational conditions. In order for low-cost hyperspectral systems to compete with larger systems flown on manned aircraft, they must be able to collect data suitable for quantitative scientific analysis. The results of the in-flight calibration experiment indicate an absolute average agreement of 96.3%, 93.7% and 85.7% for calibration tarps of 56%, 24%, and 2.5% reflectivity, respectively. The achieved planimetric accuracy was 4.6 meters (based on RMSE).

  5. Data use investigations for applications Explorer Mission A (Heat Capacity Mapping Mission): HCMM's role in studies of the urban heat island, Great Lakes thermal phenomena and radiometric calibration of satellite data. [Buffalo, Syracuse, and Rochester New York and Lake Ontario

    NASA Technical Reports Server (NTRS)

    Schott, J. R. (Principal Investigator); Schimminger, E. W.

    1981-01-01

    The utility of data from NASA'a heat capacity mapping mission satellite for studies of the urban heat island, thermal phenomena in large lakes and radiometric calibration of satellite sensors was assessed. The data were found to be of significant value in all cases. Using HCMM data, the existence and microstructure of the heat island can be observed and associated with land cover within the urban complex. The formation and development of the thermal bar in the Great Lakes can be observed and quantitatively mapped using HCMM data. In addition, the thermal patterns observed can be associated with water quality variations observed both from other remote sensing platforms and in situ. The imaging radiometer on-board the HCMM satellite is shown to be calibratible to within about 1.1 C of actual surface temperatures. These findings, as well as the analytical procedures used in studying the HCMM data, are included.

  6. Results from the radiometric validation of Sentinel-3 optical sensors using natural targets

    NASA Astrophysics Data System (ADS)

    Fougnie, Bertrand; Desjardins, Camille; Besson, Bruno; Bruniquel, Véronique; Meskini, Naceur; Nieke, Jens; Bouvet, Marc

    2016-09-01

    The recently launched SENTINEL-3 mission measures sea surface topography, sea/land surface temperature, and ocean/land surface colour with high accuracy. The mission provides data continuity with the ENVISAT mission through acquisitions by multiple sensing instruments. Two of them, OLCI (Ocean and Land Colour Imager) and SLSTR (Sea and Land Surface Temperature Radiometer) are optical sensors designed to provide continuity with Envisat's MERIS and AATSR instruments. During the commissioning, in-orbit calibration and validation activities are conducted. Instruments are in-flight calibrated and characterized primarily using on-board devices which include diffusers and black body. Afterward, vicarious calibration methods are used in order to validate the OLCI and SLSTR radiometry for the reflective bands. The calibration can be checked over dedicated natural targets such as Rayleigh scattering, sunglint, desert sites, Antarctica, and tentatively deep convective clouds. Tools have been developed and/or adapted (S3ETRAC, MUSCLE) to extract and process Sentinel-3 data. Based on these matchups, it is possible to provide an accurate checking of many radiometric aspects such as the absolute and interband calibrations, the trending correction, the calibration consistency within the field-of-view, and more generally this will provide an evaluation of the radiometric consistency for various type of targets. Another important aspect will be the checking of cross-calibration between many other instruments such as MERIS and AATSR (bridge between ENVISAT and Sentinel-3), MODIS (bridge to the GSICS radiometric standard), as well as Sentinel-2 (bridge between Sentinel missions). The early results, based on the available OLCI and SLSTR data, will be presented and discussed.

  7. Lunar Spectral Irradiance and Radiance (LUSI): New Instrumentation to Characterize the Moon as a Space-Based Radiometric Standard.

    PubMed

    Smith, Allan W; Lorentz, Steven R; Stone, Thomas C; Datla, Raju V

    2012-01-01

    The need to understand and monitor climate change has led to proposed radiometric accuracy requirements for space-based remote sensing instruments that are very stringent and currently outside the capabilities of many Earth orbiting instruments. A major problem is quantifying changes in sensor performance that occur from launch and during the mission. To address this problem on-orbit calibrators and monitors have been developed, but they too can suffer changes from launch and the harsh space environment. One solution is to use the Moon as a calibration reference source. Already the Moon has been used to remove post-launch drift and to cross-calibrate different instruments, but further work is needed to develop a new model with low absolute uncertainties capable of climate-quality absolute calibration of Earth observing instruments on orbit. To this end, we are proposing an Earth-based instrument suite to measure the absolute lunar spectral irradiance to an uncertainty(1) of 0.5 % (k=1) over the spectral range from 320 nm to 2500 nm with a spectral resolution of approximately 0.3 %. Absolute measurements of lunar radiance will also be acquired to facilitate calibration of high spatial resolution sensors. The instruments will be deployed at high elevation astronomical observatories and flown on high-altitude balloons in order to mitigate the effects of the Earth's atmosphere on the lunar observations. Periodic calibrations using instrumentation and techniques available from NIST will ensure traceability to the International System of Units (SI) and low absolute radiometric uncertainties.

  8. Lunar Spectral Irradiance and Radiance (LUSI): New Instrumentation to Characterize the Moon as a Space-Based Radiometric Standard

    PubMed Central

    Smith, Allan W.; Lorentz, Steven R.; Stone, Thomas C.; Datla, Raju V.

    2012-01-01

    The need to understand and monitor climate change has led to proposed radiometric accuracy requirements for space-based remote sensing instruments that are very stringent and currently outside the capabilities of many Earth orbiting instruments. A major problem is quantifying changes in sensor performance that occur from launch and during the mission. To address this problem on-orbit calibrators and monitors have been developed, but they too can suffer changes from launch and the harsh space environment. One solution is to use the Moon as a calibration reference source. Already the Moon has been used to remove post-launch drift and to cross-calibrate different instruments, but further work is needed to develop a new model with low absolute uncertainties capable of climate-quality absolute calibration of Earth observing instruments on orbit. To this end, we are proposing an Earth-based instrument suite to measure the absolute lunar spectral irradiance to an uncertainty1 of 0.5 % (k=1) over the spectral range from 320 nm to 2500 nm with a spectral resolution of approximately 0.3 %. Absolute measurements of lunar radiance will also be acquired to facilitate calibration of high spatial resolution sensors. The instruments will be deployed at high elevation astronomical observatories and flown on high-altitude balloons in order to mitigate the effects of the Earth’s atmosphere on the lunar observations. Periodic calibrations using instrumentation and techniques available from NIST will ensure traceability to the International System of Units (SI) and low absolute radiometric uncertainties. PMID:26900523

  9. Thematic mapper: detailed radiometric and geometric characteristics

    USGS Publications Warehouse

    Kieffer, Hugh

    1983-01-01

    Those radiometric characteristics of the Landsat 4 Thematic Mapper (TM) that can be established without absolute calibration of spectral data have been examined. Subscenes of radiometric all raw data (B-data) were examined on an individual detector basis: areas of uniform radiance were used to characterize subtle radiometric differences and noise problems. A variety of anomalies have been discovered with magnitude of a few digital levels or less: the only problem not addressable by ground processing is irregular width of the digital levels. Essentially all of this non-ideal performance is incorporated in the fully processed (P-type) images, but disguised by the geometric resampling procedure. The overall performance of the Thematic Mapper is a great improvement over previous Landsat scanners. The effective resolution in radiance is degraded by about a factor of two by irregular width of the digital levels. Several detectors have a change of gain with a period of several scans, the largest effect is about 4%. These detectors appear to switch between two response levels during scan direction reversal; there is no apparent periodicity to these changes. This can cause small apparent difference between forward and reverse scans for portions of an image. The high-frequency noise level of each detector was characterized by the standard deviation of the first derivative in the sample direction across a flat field. Coherent sinusoidal noise patterns were determined using one-dimensional Fourier transforms. A "stitching" pattern in Band 1 has a period of 13.8 samples with a peak-to-peak amplitude ranging from 1 to 5 DN. Noise with a period of 3.24 samples is pronounced for most detectors in band 1, to a lesser extent in bands 2, 3, and 4, and below background noise levels in bands 5, 6, and 7. The geometric fidelity of the GSFC film writer used for Thematic Mapper (TM) images was assessed by measurement with accuracy bette than three micrometers of a test grid. A set of 55

  10. Piston manometer as an absolute standard for vacuum-gage calibration in the range 2 to 500 millitorr

    NASA Technical Reports Server (NTRS)

    Warshawsky, I.

    1972-01-01

    A thin disk is suspended, with very small annular clearance, in a cylindrical opening in the base plate of a calibration chamber. A continuous flow of calibration gas passes through the chamber and annular opening to a downstream high vacuum pump. The ratio of pressures on the two faces of the disk is very large, so that the upstream pressure is substantially equal to net force on the disk divided by disk area. This force is measured with a dynamometer that is calibrated in place with dead weights. A probable error of + or - (0.2 millitorr plus 0.2 percent) is attainable when downstream pressure is known to 10 percent.

  11. Systematic Uncertainties in the Spectroscopic Measurements of Neutron-star Masses and Radii from Thermonuclear X-Ray Bursts. III. Absolute Flux Calibration

    NASA Astrophysics Data System (ADS)

    Güver, Tolga; Özel, Feryal; Marshall, Herman; Psaltis, Dimitrios; Guainazzi, Matteo; Díaz-Trigo, Maria

    2016-09-01

    Many techniques for measuring neutron star radii rely on absolute flux measurements in the X-rays. As a result, one of the fundamental uncertainties in these spectroscopic measurements arises from the absolute flux calibrations of the detectors being used. Using the stable X-ray burster, GS 1826-238, and its simultaneous observations by Chandra HETG/ACIS-S and RXTE/PCA as well as by XMM-Newton EPIC-pn and RXTE/PCA, we quantify the degree of uncertainty in the flux calibration by assessing the differences between the measured fluxes during bursts. We find that the RXTE/PCA and the Chandra gratings measurements agree with each other within their formal uncertainties, increasing our confidence in these flux measurements. In contrast, XMM-Newton EPIC-pn measures 14.0 ± 0.3% less flux than the RXTE/PCA. This is consistent with the previously reported discrepancy with the flux measurements of EPIC-pn, compared with EPIC MOS1, MOS2, and ACIS-S detectors. We also show that any intrinsic time-dependent systematic uncertainty that may exist in the calibration of the satellites has already been implicity taken into account in the neutron star radius measurements.

  12. Absolute-energy-scale calibration of ARGO-YBJ for light primaries in multi-TeV region with the Moon shadow observation

    NASA Astrophysics Data System (ADS)

    Bartoli, B.; Bernardini, P.; Bi, X. J.; Cao, Z.; Catalanotti, S.; Chen, S. Z.; Chen, T. L.; Cui, S. W.; Dai, B. Z.; D'Amone, A.; Danzengluobu; De Mitri, I.; D'Ettorre Piazzoli, B.; Di Girolamo, T.; Di Sciascio, G.; Feng, C. F.; Feng, Zhaoyang; Feng, Zhenyong; Gou, Q. B.; Guo, Y. Q.; He, H. H.; Hu, Haibing; Hu, Hongbo; Iacovacci, M.; Iuppa, R.; Jia, H. Y.; Labaciren; Li, H. J.; Liu, C.; Liu, J.; Liu, M. Y.; Lu, H.; Ma, L. L.; Ma, X. H.; Mancarella, G.; Mari, S. M.; Marsella, G.; Mastroianni, S.; Montini, P.; Ning, C. C.; Perrone, L.; Pistilli, P.; Salvini, P.; Santonico, R.; Shen, P. R.; Sheng, X. D.; Shi, F.; Surdo, A.; Tan, Y. H.; Vallania, P.; Vernetto, S.; Vigorito, C.; Wang, H.; Wu, C. Y.; Wu, H. R.; Xue, L.; Yang, Q. Y.; Yang, X. C.; Yao, Z. G.; Yuan, A. F.; Zha, M.; Zhang, H. M.; Zhang, L.; Zhang, X. Y.; Zhang, Y.; Zhao, J.; Zhaxiciren; Zhaxisangzhu; Zhou, X. X.; Zhu, F. R.; Zhu, Q. Q.; collaboration), (The ARGO-YBJ

    2017-04-01

    In 2011 ARGO-YBJ experiment has reported a work to study the absolute rigidity scale of the primary cosmic ray particles based on the Moon's shadow observation. Given the progress in high energy hadronic interaction models with LHC data, in cosmic ray chemical composition measurement and in experimental data accumulation, more updates can be researched. This paper aims to further disentangle the composition dependence in absolute-energy-scale calibration by using specific moon-shadow data which mainly is comprised of light component cosmic rays. Results show that, 17% energy scale error is estimated from 3 TeV to 50 TeV. To validate the performance of this technique, the light component cosmic ray spectrum in the same energy region is shown.

  13. Absolute calibration of the Agfa Structurix series films at energies between 2.7 and 6.2 keVa)

    NASA Astrophysics Data System (ADS)

    Lanier, N. E.; Cowan, J. S.

    2014-11-01

    Although photo-emulsion technology is many decades old, x-ray film still remains a key asset for diagnosing hydrodynamic features in High-Energy Density (HED) experiments. For decades, the preferred option had been Kodak's direct exposure film. After its discontinuance in 2004, the push to find alternatives began. In many situations, the Agfa Structurix series offers the most favorable substitute, but being new to the HED community, its characterization was lacking. To remedy this, recent experiments, conducted at Brookhaven's National Synchrotron Light Source, provide absolute, monochromatic calibration data for the Agfa Structurix series films at K-shell backlighter energies between 2.7 and 6.2 keV. Absolute response curves are presented for Agfa D8, D7, D4, D4sc, D3, and D2. Moreover, the transmission of each film type is also measured.

  14. Absolute calibration of the Agfa Structurix series films at energies between 2.7 and 6.2 keV.

    PubMed

    Lanier, N E; Cowan, J S

    2014-11-01

    Although photo-emulsion technology is many decades old, x-ray film still remains a key asset for diagnosing hydrodynamic features in High-Energy Density (HED) experiments. For decades, the preferred option had been Kodak's direct exposure film. After its discontinuance in 2004, the push to find alternatives began. In many situations, the Agfa Structurix series offers the most favorable substitute, but being new to the HED community, its characterization was lacking. To remedy this, recent experiments, conducted at Brookhaven's National Synchrotron Light Source, provide absolute, monochromatic calibration data for the Agfa Structurix series films at K-shell backlighter energies between 2.7 and 6.2 keV. Absolute response curves are presented for Agfa D8, D7, D4, D4sc, D3, and D2. Moreover, the transmission of each film type is also measured.

  15. Airborne stellar spectrophotometry from 1.2 to 5.5 microns - Absolute calibration and spectra of stars earlier than M3

    NASA Technical Reports Server (NTRS)

    Strecker, D. W.; Erickson, E. F.; Witteborn, F. C.

    1979-01-01

    Airborne infrared spectrophotometry (1.2-5.5 microns, 1.5% resolution) is presented for 13 stars which have been extensively used as infrared calibration objects: alpha Lyr, alpha CMA, alpha UMi, beta Dra, and mu Her; the K giants beta Gem, alpha UMa, alpha Boo, gamma-1 And, and alpha Tau; and the M giants beta And, beta Peg, and alpha Cet. These spectra, obtained using NASA's Kuiper Airborne Observatory and Lear Jet Observatory, are virtually free of the interfering effects of terrestrial absorptions. Absolute calibration of the spectrophotometry was based on the theoretical model of alpha Lyr by Schild, Peterson, and Oke (1971), which fits photometric measurements at shorter wavelengths. The resulting flux densities are compared with previous ground-based photometry.

  16. Piston manometer as an absolute standard for vacuum gage calibration in the range 10 to 700 microtorr

    NASA Technical Reports Server (NTRS)

    Warshawsky, I.

    1972-01-01

    Total pressure in a calibration chamber is determined by measuring the force on a disk suspended in an orifice in the baseplate of the chamber. The disk forms a narrow annular gap with the orifice. A continuous flow of calibration gas passes through the chamber and annulus to a downstream pumping system. The ratio of pressures on the two faces of the disk exceeds 100:1, so that chamber pressure is substantially equal to the product of disk area and net force on the disk. This force is measured with an electrodynamometer that can be calibrated in situ with dead weights. Probable error in pressure measurement is plus or minus (0.5 microtorr + 0.6 percent).

  17. Absolute elastic differential electron scattering cross sections for He - A proposed calibration standard from 5 to 200 eV

    NASA Technical Reports Server (NTRS)

    Register, D. F.; Trajmar, S.; Srivastava, S. K.

    1980-01-01

    Absolute differential, integral, and momentum-transfer cross sections for electrons elastically scattered from helium are reported for the impact energy range of 5 to 200 eV. Angular distributions for elastically scattered electrons are measured in a crossed-beam geometry using a collimated, differentially pumped atomic-beam source which requires no effective-path-length correction. Below the first inelastic threshold the angular distributions were placed on an absolute scale by use of a phase-shift analysis. Above this threshold, the angular distributions from 10 to 140 deg were fitted using the phase-shift technique, and the resulting integral cross sections were normalized to a semiempirically derived integral elastic cross section. Depending on the impact energy, the data are estimated to be accurate to within 5 to 9%.

  18. Radiometric instrumentation and measurements guide for photovoltaic performance testing

    SciTech Connect

    Myers, D.

    1997-04-01

    The Photovoltaic Module and Systems Performance and Engineering Project at the National Renewable Energy Laboratory performs indoor and outdoor standardization, testing, and monitoring of the performance of a wide range of photovoltaic (PV) energy conversion devices and systems. The PV Radiometric Measurements and Evaluation Team (PVSRME) within that project is responsible for measurement and characterization of natural and artificial optical radiation which stimulates the PV effect. The PV manufacturing and research and development community often approaches project members for technical information and guidance. A great area of interest is radiometric instrumentation, measurement techniques, and data analysis applied to understanding and improving PV cell, module, and system performance. At the Photovoltaic Radiometric Measurements Workshop conducted by the PVSRME team in July 1995, the need to communicate knowledge of solar and optical radiometric measurements and instrumentation, gained as a result of NREL`s long-term experiences, was identified as an activity that would promote improved measurement processes and measurement quality in the PV research and manufacturing community. The purpose of this document is to address the practical and engineering need to understand optical and solar radiometric instrument performance, selection, calibration, installation, and maintenance applicable to indoor and outdoor radiometric measurements for PV calibration, performance, and testing applications. An introductory section addresses radiometric concepts and definitions. Next, concepts essential to spectral radiometric measurements are discussed. Broadband radiometric instrumentation and measurement concepts are then discussed. Each type of measurement serves as an important component of the PV cell, module, and system performance measurement and characterization process.

  19. Evaluation of the Applicability of Solar and Lamp Radiometric Calibrations of a Precision Sun Photometer Operating Between 300 and 1025 nm.

    PubMed

    Schmid, B; Spyak, P R; Biggar, S F; Wehrli, C; Sekler, J; Ingold, T; Mätzler, C; Kämpfer, N

    1998-06-20

    Over a period of 3 years a precision Sun photometer (SPM) operating between 300 and 1025 nm was calibrated four times at three different high-mountain sites in Switzerland, Germany, and the United States by means of the Langley-plot technique. We found that for atmospheric window wavelengths the total error (2varsigma-statistical plus systematic errors) of the calibration constants V(0) (lambda), the SPM voltage in the absence of any attenuating atmosphere, can be kept below 1.6% in the UV-A and blue, 0.9% in the mid-visible, and 0.6% in the near-infrared spectral region. For SPM channels within strong water-vapor or ozone absorption bands a modified Langley-plot technique was used to determine V(0) (lambda) with a lower accuracy. Within the same period of time, we calibrated the SPM five times using irradiance standard lamps in the optical labs of the Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center, Switzerland, and of the Remote Sensing Group of the Optical Sciences Center, University of Arizona, Tucson, Arizona. The lab calibration method requires knowledge of the extraterrestrial spectral irradiance. When we refer the standard lamp results to the World Radiation Center extraterrestrial solar irradiance spectrum, they agree with the Langley results within 2% at 6 of 13 SPM wavelengths. The largest disagreement (4.4%) is found for the channel centered at 610 nm. The results of these intercomparisons change significantly when the lamp results are referred to two different extraterrestrial solar irradiance spectra that have become recently available.

  20. Absolute calibration of Kodak Biomax-MS film response to x rays in the 1.5- to 8-keV energy range

    SciTech Connect

    Marshall, F. J.; Knauer, J. P.; Anderson, D.; Schmitt, B. L

    2006-10-15

    The absolute response of Kodak Biomax-MS film to x rays in the range from 1.5- to 8-keV has been measured using a laboratory electron-beam generated x-ray source. The measurements were taken at specific line energies by using Bragg diffraction to produce monochromatic beams of x rays. Multiple exposures were taken on Biomax MS film up to levels exceeding optical densities of 2 as measured by a microdensitometer. The absolute beam intensity for each exposure was measured with a Si(Li) detector. Additional response measurements were taken with Kodak direct exposure film (DEF) so as to compare the results of this technique to previously published calibrations. The Biomax-MS results have been fitted to a semiempirical mathematical model (Knauer et al., these proceedings). Users of the model can infer absolute fluences from observed exposure levels at either interpolated or extrapolated energies. To summarize the results: Biomax MS has comparable sensitivity to DEF film below 3 keV but has reduced sensitivity above 3 keV ({approx}50%). The lower exposure results from thinner emulsion layers, designed for use with phosphor screens. The ease with which Biomax-MS can be used in place of DEF (same format film, same developing process, and comparable sensitivity) makes it a good replacement.

  1. An absolute calibration method of an ethyl alcohol biosensor based on wavelength-modulated differential photothermal radiometry

    SciTech Connect

    Liu, Yi Jun; Mandelis, Andreas; Guo, Xinxin

    2015-11-15

    In this work, laser-based wavelength-modulated differential photothermal radiometry (WM-DPTR) is applied to develop a non-invasive in-vehicle alcohol biosensor. WM-DPTR features unprecedented ethanol-specificity and sensitivity by suppressing baseline variations through a differential measurement near the peak and baseline of the mid-infrared ethanol absorption spectrum. Biosensor signal calibration curves are obtained from WM-DPTR theory and from measurements in human blood serum and ethanol solutions diffused from skin. The results demonstrate that the WM-DPTR-based calibrated alcohol biosensor can achieve high precision and accuracy for the ethanol concentration range of 0-100 mg/dl. The high-performance alcohol biosensor can be incorporated into ignition interlocks that could be fitted as a universal accessory in vehicles in an effort to reduce incidents of drinking and driving.

  2. A new solar irradiance calibration from 3295 A to 8500 A derived from absolute spectrophotometry of Vega

    NASA Technical Reports Server (NTRS)

    Lockwood, G. W.; Tueg, H.; White, N. M.

    1992-01-01

    By imaging sunlight diffracted by 20- and 30-micron diameter pinholes onto the entrance aperture of a photoelectric grating scanner, the solar spectral irradiance was determined relative to the spectrophotometric standard star Vega, observed at night with the same instrument. Solar irradiances are tabulated at 4 A increments from 3295 A to 8500 A. Over most of the visible spectrum, the internal error of measurement is less than 2 percent. This calibration is compared with earlier irradiance measurements by Neckel and Labs (1984) and by Arvesen et al. (1969) and with the high-resolution solar atlas by Kurucz et al. The three calibrations agree well in visible light but differ by as much as 10 percent in the ultraviolet.

  3. An absolute calibration method of an ethyl alcohol biosensor based on wavelength-modulated differential photothermal radiometry.

    PubMed

    Liu, Yi Jun; Mandelis, Andreas; Guo, Xinxin

    2015-11-01

    In this work, laser-based wavelength-modulated differential photothermal radiometry (WM-DPTR) is applied to develop a non-invasive in-vehicle alcohol biosensor. WM-DPTR features unprecedented ethanol-specificity and sensitivity by suppressing baseline variations through a differential measurement near the peak and baseline of the mid-infrared ethanol absorption spectrum. Biosensor signal calibration curves are obtained from WM-DPTR theory and from measurements in human blood serum and ethanol solutions diffused from skin. The results demonstrate that the WM-DPTR-based calibrated alcohol biosensor can achieve high precision and accuracy for the ethanol concentration range of 0-100 mg/dl. The high-performance alcohol biosensor can be incorporated into ignition interlocks that could be fitted as a universal accessory in vehicles in an effort to reduce incidents of drinking and driving.

  4. An absolute calibration method of an ethyl alcohol biosensor based on wavelength-modulated differential photothermal radiometry

    NASA Astrophysics Data System (ADS)

    Liu, Yi Jun; Mandelis, Andreas; Guo, Xinxin

    2015-11-01

    In this work, laser-based wavelength-modulated differential photothermal radiometry (WM-DPTR) is applied to develop a non-invasive in-vehicle alcohol biosensor. WM-DPTR features unprecedented ethanol-specificity and sensitivity by suppressing baseline variations through a differential measurement near the peak and baseline of the mid-infrared ethanol absorption spectrum. Biosensor signal calibration curves are obtained from WM-DPTR theory and from measurements in human blood serum and ethanol solutions diffused from skin. The results demonstrate that the WM-DPTR-based calibrated alcohol biosensor can achieve high precision and accuracy for the ethanol concentration range of 0-100 mg/dl. The high-performance alcohol biosensor can be incorporated into ignition interlocks that could be fitted as a universal accessory in vehicles in an effort to reduce incidents of drinking and driving.

  5. An atlas of selected calibrated stellar spectra

    NASA Technical Reports Server (NTRS)

    Walker, Russell G.; Cohen, Martin

    1992-01-01

    Five hundred and fifty six stars in the IRAS PSC-2 that are suitable for stellar radiometric standards and are brighter than 1 Jy at 25 microns were identified. In addition, 123 stars that meet all of our criteria for calibration standards, but which lack a luminosity class were identified. An approach to absolute stellar calibration of broadband infrared filters based upon new models of Vega and Sirius due to Kurucz (1992) is presented. A general technique used to assemble continuous wide-band calibrated infrared spectra is described and an absolutely calibrated 1-35 micron spectrum of alpha(Tau) is constructed and the method using new and carefully designed observations is independently validated. The absolute calibration of the IRAS Low Resolution Spectrometer (LRS) database is investigated by comparing the observed spectrum of alpha(Tau) with that assumed in the original LRS calibration scheme. Neglect of the SiO fundamental band in alpha(Tau) has led to the presence of a specious 'emission' feature in all LRS spectra near 8.5 microns, and to an incorrect spectral slope between 8 and 12 microns. Finally, some of the properties of asteroids that effect their utility as calibration objects for the middle and far infrared region are examined. A technique to determine, from IRAS multiwaveband observations, the basic physical parameters needed by various asteroid thermal models that minimize the number of assumptions required is developed.

  6. Radiometric cloud imaging with an uncooled microbolometer thermal infrared camera.

    PubMed

    Shaw, Joseph; Nugent, Paul; Pust, Nathan; Thurairajah, Brentha; Mizutani, Kohei

    2005-07-25

    An uncooled microbolometer-array thermal infrared camera has been incorporated into a remote sensing system for radiometric sky imaging. The radiometric calibration is validated and improved through direct comparison with spectrally integrated data from the Atmospheric Emitted Radiance Interferometer (AERI). With the improved calibration, the Infrared Cloud Imager (ICI) system routinely obtains sky images with radiometric uncertainty less than 0.5 W/(m(2 )sr) for extended deployments in challenging field environments. We demonstrate the infrared cloud imaging technique with still and time-lapse imagery of clear and cloudy skies, including stratus, cirrus, and wave clouds.

  7. The use of thematic mapper simulator calibration data for assessment of data quality

    NASA Technical Reports Server (NTRS)

    Forman, M. L.

    1980-01-01

    In flight calibration data collected from the thematic mapper simulator (TMS) were used to assess the quality of Earth scan data. The following results are indicated: (1) based on limited samples, individual TMS channels have noise which varies from channel to channel, but remains constant within a channel; (2) short term variations of more than 5% in the average values of calibration source responses indicate problems; and (3) absolute radiometric calibration is unlikely to be meaningful in a temporal sense due to single point calibration methods used.

  8. Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for Δ 14C

    NASA Astrophysics Data System (ADS)

    Shackleton, N. J.; Fairbanks, R. G.; Chiu, Tzu-chien; Parrenin, F.

    2004-07-01

    We propose a new age scale for the two ice cores (GRIP and GISP2) that were drilled at Greenland summit, based on accelerator mass spectrometry 14C dating of foraminifera in core MD95-2042 (Paleoceanography 15 (2000) 565), calibrated by means of recently obtained paired 14C and 230Th measurements on pristine corals (Marine radiocarbon calibration curve spanning 10,500 to 50,000 years BP (thousand years before present) Based on paired 230Th/ 234U/ 238U and 14C dates on Pristine Corals Geological Society of America Bulletin, 2003, submitted for publication). The record of core MD95-2042 can be correlated very precisely to the Greenland ice cores. Between 30 and 40 ka BP our scale is 1.4 ka older than the GRIP SS09sea time scale (Journal of Quaternary Science 16 (2001) 299). At the older end of Marine Isotope Stage 3 we use published 230Th dates from speleothems to calibrate the record. Using this scale we show a Δ 14C record that is broadly consistent with the modelled record (Earth Planet. Sci. Lett. 200 (2002) 177) and with the data of Hughen et al. (Science 303 (2004) 202), but not consistent with the high values obtained by Beck et al. (Science 292 (2001) 2453) or by Voelker et al. (Radiocarbon 40 (1998) 517). We show how a set of age scales for the Antarctic ice cores can be derived that are both fully consistent with the Greenland scale, and glaciologically reasonable.

  9. Absolute calibration and beam reconstruction of MITO(a ground-based instrument in the millimetric region)

    NASA Astrophysics Data System (ADS)

    Savini, G.; Orlando, A.; Battistelli, E. S.; De Petris, M.; Lamagna, L.; Luzzi, G.; Palladino, E.

    2003-09-01

    An efficient sky data reconstruction derives from a precise characterization of the observing instrument. Here we describe the reconstruction of performances of a single-pixel 4-band photometer installed at MITO (Millimeter and Infrared Testagrigia Observatory) focal plane. The strategy of differential sky observations at millimeter wavelengths, by scanning the field of view at constant elevation wobbling the subreflector, induces a good knowledge of beam profile and beam-throw amplitude, allowing efficient data recovery. The problems that arise estimating the detectors throughput by drift scanning on planets are shown. Atmospheric transmission, monitored by skydip technique, is considered for deriving final responsivities for the 4 channels using planets as primary calibrators.

  10. Absolute Doppler shift calibration of laser induced fluorescence signals using optogalvanic measurements in a hollow cathode lamp

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.; Keefer, Dennis

    1992-01-01

    The paper investigates the use of optogalvanic (OG) measurements on the neutral 3P1 and 3P2 levels of argon in a hollow cathode lamp for the purpose of calibrating Doppler shifts of laser-induced fluorescence signals from an arcjet plume. It is shown that, even with non-Doppler-free OG detection, accuracy to better than 10 MHz is possible but that, depending on the experiment geometry, corrections of 10-35 MHz may be necessary to offset small axial drift velocities of neutral atoms in the hollow cathode lamp.

  11. Development of a low-level 39Ar calibration standard – Analysis by absolute gas counting measurements augmented with simulation

    DOE PAGES

    Williams, Richard M.; Aalseth, C. E.; Brandenberger, J. M.; ...

    2017-02-17

    Here, this paper describes the generation of 39Ar, via reactor irradiation of potassium carbonate, followed by quantitative analysis (length-compensated proportional counting) to yield two calibration standards that are respectively 50 and 3 times atmospheric background levels. Measurements were performed in Pacific Northwest National Laboratory's shallow underground counting laboratory studying the effect of gas density on beta-transport; these results are compared with simulation. The total expanded uncertainty of the specific activity for the ~50 × 39Ar in P10 standard is 3.6% (k=2).

  12. Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response.

    PubMed

    Troussel, Ph; Villette, B; Emprin, B; Oudot, G; Tassin, V; Bridou, F; Delmotte, F; Krumrey, M

    2014-01-01

    CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.

  13. Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response

    SciTech Connect

    Troussel, Ph.; Villette, B.; Oudot, G.; Tassin, V.; Bridou, F.; Delmotte, F.; Krumrey, M.

    2014-01-15

    CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.

  14. Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response

    NASA Astrophysics Data System (ADS)

    Troussel, Ph.; Villette, B.; Emprin, B.; Oudot, G.; Tassin, V.; Bridou, F.; Delmotte, F.; Krumrey, M.

    2014-01-01

    CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.

  15. Tissue-specific Calibration of Real-time PCR Facilitates Absolute Quantification of Plasmid DNA in Biodistribution Studies

    PubMed Central

    Ho, Joan K; White, Paul J; Pouton, Colin W

    2016-01-01

    Analysis of the tissue distribution of plasmid DNA after administration of nonviral gene delivery systems is best accomplished using quantitative real-time polymerase chain reaction (qPCR), although published strategies do not allow determination of the absolute mass of plasmid delivered to different tissues. Generally, data is expressed as the mass of plasmid relative to the mass of genomic DNA (gDNA) in the sample. This strategy is adequate for comparisons of efficiency of delivery to a single site but it does not allow direct comparison of delivery to multiple tissues, as the mass of gDNA extracted per unit mass of each tissue is different. We show here that by constructing qPCR standard curves for each tissue it is possible to determine the dose of intact plasmid remaining in each tissue, which is a more useful parameter when comparing the fates of different formulations of DNA. We exemplify the use of this tissue-specific qPCR method by comparing the delivery of naked DNA, cationic DNA complexes, and neutral PEGylated DNA complexes after intramuscular injection. Generally, larger masses of intact plasmid were present 24 hours after injection of DNA complexes, and neutral complexes resulted in delivery of a larger mass of intact plasmid to the spleen. PMID:27701400

  16. Initial lunar calibration observations by the EO-1 Hyperion imaging spectrometer

    USGS Publications Warehouse

    Kieffer, H.H.; Jarecke, P.; Pearlman, Jay; ,

    2002-01-01

    The Moon provides an exo-atmospheric radiance source that can be used to determine trends in instrument radio-metric responsivity with high precision. Lunar observations can also be used for absolute radiometric calibration; knowledge of the radiometric scale will steadily improve through independent study of lunar spectral photometry and with sharing of the Moon as a calibration target by increasing numbers of spacecraft, each with its own calibration history. EO-1 calibration includes periodic observation of the Moon by all three of its instruments. Observations are normally made with a phase angle of about 7 degrees (or about 12 hours from the time of Full Moon). Also, SeaWiFS has been making observations at such phase angles for several years, and observations of the Moon by instrument pairs, even if at different times, can be used to transfer absolute calibration. A challenge for EO-1 is pointing to include the entire full Moon in the narrow Hyperion scan. Three Hyperion observations in early 2001 covering an order-of-magnitude difference in lunar irradiance show good agreement for responsivity; the SWIR detector has undergone some changes in responsivity. Small discrepancies of calibration with wavelength could be smoothed using the Moon as a source. Off-axis scattered light response and cross-track response variations can be assessed using the lunar image.

  17. Preliminary results of calibration for ALOS optical sensors and validation of generated PRISM DSM

    NASA Astrophysics Data System (ADS)

    Tadono, Takeo; Shimada, Masanobu; Murakami, Hiroshi; Mukaida, Akira; Takaku, Junichi; Kawamoto, Sachi

    2006-09-01

    The Advanced Land Observing Satellite (ALOS) was successfully launched on January 24 th, 2006. This paper introduces the preliminary results of calibration and validation for two optical sensors of ALOS i.e., the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). PRISM consists of three independent panchromatic radiometers, and is used to derive a digital surface model (DSM) with high spatial resolution, which is also an objective of the ALOS mission. So, the geometric calibration is important in generating a highly accurate DSM by stereo pair image of PRISM. The radiometric calibration is also important for AVNIR-2 as well as PRISM. The relative radiometric calibration is carrying out using acquired images over homogeneous targets such as ocean, deserts, ice and snow areas and the nighttime observation. The absolute radiometric calibration is applied the cross calibration method using calibrated satellite images i.e., MODIS onboard Terra/Aqua satellites, ASTER, SPOT-5 etc. In this paper, results of the first images acquisition and preliminary analysis for calibration and validation are described.

  18. The Radiometric Map of Australia

    NASA Astrophysics Data System (ADS)

    Minty, Brian; Franklin, Ross; Milligan, Peter; Richardson, Murray; Wilford, John

    2009-12-01

    Geoscience Australia and the Australian State and Territory Geological Surveys have systematically surveyed most of the Australian continent over the past 40 years using airborne gamma-ray spectrometry to map potassium, uranium and thorium elemental concentrations at the Earth's surface. However, the individual surveys that comprise the national gamma-ray spectrometric radioelement database are not all registered to the same datum. This limits the usefulness of the database as it is not possible to easily combine surveys into regional compilations or make accurate comparisons between radiometric signatures in different survey areas. To solve these problems, Geoscience Australia has undertaken an Australia-Wide Airborne Geophysical Survey (AWAGS), funded under the Australian Government's Onshore Energy Security Program, to serve as a radioelement baseline for all current and future airborne gamma-ray spectrometric surveys in Australia. The AWAGS survey has been back-calibrated to the International Atomic Energy Agency's (IAEA) radioelement datum. We have used the AWAGS data to level the national radioelement database by estimating survey correction factors that, once applied, minimise both the differences in radioelement estimates between surveys (where these surveys overlap) and the differences between the surveys and the AWAGS traverses. The database is thus effectively levelled to the IAEA datum. The levelled database has been used to produce the first `Radiometric Map of Australia' - levelled and merged composite potassium (% K), uranium (ppm eU) and thorium (ppm eTh) grids over Australia at 100m resolution. Interpreters can use the map to reliably compare the radiometric signatures observed over different parts of Australia. This enables the assessment of key mineralogical and geochemical properties of bedrock and regolith materials from different geological provinces and regions with contrasting landscape histories.

  19. Landsat Data Continuity Mission Calibration and Validation

    NASA Technical Reports Server (NTRS)

    Markham, Brian L.; Dabney, Philip W.; Storey, James C.; Morfitt, Ron; Knight, Ed; Kvaran, Geir; Lee, Kenton

    2008-01-01

    The primary payload for the Landsat Data Continuity Mission (LDCM) is the Operational Land Imager (OLI), being built by Ball Aerospace and Technologies, under contract to NASA. The OLI has spectral bands similar to the Landsat-7 ETM+, minus the thermal band and with two new bands, a 443 nm band and 1375 nm cirrus detection band. On-board calibration systems include two solar diffusers (routine and pristine), a shutter and three sets of internal lamps (routine, backup and pristine). Being a pushbroom opposed to a whiskbroom design of ETM+, the system poses new challenges for characterization and calibration, chief among them being the large focal plane with 75000+ detectors. A comprehensive characterization and calibration plan is in place for the instrument and the data throughout the mission including Ball, NASA and the United States Geological Survey, which will take over operations of LDCM after on-orbit commissioning. Driving radiometric calibration requirements for OLI data include radiance calibration to 5% uncertainty (1 q); reflectance calibration to 3% uncertainty (1 q) and relative (detector-to-detector) calibration to 0.5% (J (r). Driving geometric calibration requirements for OLI include bandto- band registration of 4.5 meters (90% confidence), absolute geodetic accuracy of 65 meters (90% CE) and relative geodetic accuracy of 25 meters (90% CE). Key spectral, spatial and radiometric characterization of the OLI will occur in thermal vacuum at Ball Aerospace. During commissioning the OLI will be characterized and calibrated using celestial (sun, moon, stars) sources and terrestrial sources. The USGS EROS ground processing system will incorporate an image assessment system similar to Landsat-7 for characterization and calibration. This system will have the added benefit that characterization data will be extracted as part of the normal image data processing, so that the characterization data available will be significantly larger than for Landsat-7 ETM+.

  20. Vicarious Calibration of EO-1 Hyperion

    NASA Technical Reports Server (NTRS)

    McCorkel, Joel; Thome, Kurt; Lawrence, Ong

    2012-01-01

    The Hyperion imaging spectrometer on the Earth Observing-1 satellite is the first high-spatial resolution imaging spectrometer to routinely acquire science-grade data from orbit. Data gathered with this instrument needs to be quantitative and accurate in order to derive meaningful information about ecosystem properties and processes. Also, comprehensive and long-term ecological studies require these data to be comparable over time, between coexisting sensors and between generations of follow-on sensors. One method to assess the radiometric calibration is the reflectance-based approach, a common technique used for several other earth science sensors covering similar spectral regions. This work presents results of radiometric calibration of Hyperion based on the reflectance-based approach of vicarious calibration implemented by University of Arizona during 2001 2005. These results show repeatability to the 2% level and accuracy on the 3 5% level for spectral regions not affected by strong atmospheric absorption. Knowledge of the stability of the Hyperion calibration from moon observations allows for an average absolute calibration based on the reflectance-based results to be determined and applicable for the lifetime of Hyperion.

  1. Sentinel-1 In-Orbit Calibration Approach

    NASA Astrophysics Data System (ADS)

    Østergaard, A.; Navas-Traver, I.; Snoeij, P.; Brown, M.; Rommen, B.; Geudtner, D.; Bibby, D.; Torres, R.; Schied, E.; Rostan, F.; Schwerdt, M.; Zink, M.; Bauleo, A.; Croci, R.; Pietropaolo, A.

    2013-12-01

    ESA is developing the Sentinel-1 European Radar Observatory, a constellation of two polar orbiting satellites that provide C-band SAR products for operational applications. The Sentinel-1 mission has been designed to comply with stringent radiometric stability and accuracy requirements. To ensure these requirements are achieved, the mission relies on an efficient and robust strategy for in-flight calibration. This consists of (a) pulse-coded Internal Calibration pulses that achieve leakage cancellation and robust estimation and separation of different types of leakage signals and (b) an Antenna Model that estimates very accurately the antenna radiation patterns based on the instrument configuration and pre-launch measurements. Usage of calibration data and the Antenna Model supports maintaining the long-term absolute radiometric accuracy and enables a graceful degradation of performance in the event of unrecoverable failures of individual transmit/receive modules. During the commissioning phase, calibration also relies on precise external calibration transponders and measurements with notch patterns over the rainforest and transponders for accurate pointing determination.

  2. Verification of the radiometric map of the Czech Republic.

    PubMed

    Matolín, Milan

    2017-01-01

    The radiometric map of the Czech Republic is based on uniform regional airborne radiometric total count measurements (1957-1959) which covered 100% of the country. The airborne radiometric instrument was calibrated to a (226)Ra point source. The calibration facility for field gamma-ray spectrometers, established in the Czech Republic in 1975, significantly contributed to the subsequent radiometric data standardization. In the 1990's, the original analogue airborne radiometric data were digitized and using the method of back-calibration (IAEA, 2003) converted to dose rate. The map of terrestrial gamma radiation expressed in dose rate (nGy/h) was published on the scale 1:500,000 in 1995. Terrestrial radiation in the Czech Republic, formed by magmatic, sedimentary and metamorphic rocks of Proterozoic to Quaternary age, ranges mostly from 6 to 245 nGy/h, with a mean of 65.6 ± 19.0 nGy/h. The elevated terrestrial radiation in the Czech Republic, in comparison to the global dose rate average of 54 nGy/h, reflects an enhanced content of natural radioactive elements in the rocks. The 1995 published radiometric map of the Czech Republic was successively studied and verified by additional ground gamma-ray spectrometric measurements and by comparison to radiometric maps of Germany, Poland and Slovakia in border zones. A ground dose rate intercomparison measurement under participation of foreign and domestic professional institutions revealed mutual dose rate deviations about 20 nGy/h and more due to differing technical parameters of applied radiometric instruments. Studies and verification of the radiometric map of the Czech Republic illustrate the magnitude of current deviations in dose rate data. This gained experience can assist in harmonization of dose rate data on the European scale.

  3. Demonstrating the Error Budget for the Climate Absolute Radiance and Refractivity Observatory Through Solar Irradiance Measurements

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2016-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe highaccuracy, long-term climate change trends and to use decadal change observations as a method to determine the accuracy of climate change. A CLARREO objective is to improve the accuracy of SI-traceable, absolute calibration at infrared and reflected solar wavelengths to reach on-orbit accuracies required to allow climate change observations to survive data gaps and observe climate change at the limit of natural variability. Such an effort will also demonstrate National Institute of Standards and Technology (NIST) approaches for use in future spaceborne instruments. The current work describes the results of laboratory and field measurements with the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. SOLARIS allows testing and evaluation of calibration approaches, alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. Results of laboratory calibration measurements are provided to demonstrate key assumptions about instrument behavior that are needed to achieve CLARREO's climate measurement requirements. Absolute radiometric response is determined using laser-based calibration sources and applied to direct solar views for comparison with accepted solar irradiance models to demonstrate accuracy values giving confidence in the error budget for the CLARREO reflectance retrieval.

  4. SkyProbe: Real-Time Precision Monitoring in the Optical of the Absolute Atmospheric Absorption on the Telescope Science and Calibration Fields

    NASA Astrophysics Data System (ADS)

    Cuillandre, J.-C.; Magnier, E.; Sabin, D.; Mahoney, B.

    2016-05-01

    Mauna Kea is known for its pristine seeing conditions but sky transparency can be an issue for science operations since at least 25% of the observable (i.e. open dome) nights are not photometric, an effect mostly due to high-altitude cirrus. Since 2001, the original single channel SkyProbe mounted in parallel on the Canada-France-Hawaii Telescope (CFHT) has gathered one V-band exposure every minute during each observing night using a small CCD camera offering a very wide field of view (35 sq. deg.) encompassing the region pointed by the telescope for science operations, and exposures long enough (40 seconds) to capture at least 100 stars of Hipparcos' Tycho catalog at high galactic latitudes (and up to 600 stars at low galactic latitudes). The measurement of the true atmospheric absorption is achieved within 2%, a key advantage over all-sky direct thermal infrared imaging detection of clouds. The absolute measurement of the true atmospheric absorption by clouds and particulates affecting the data being gathered by the telescope's main science instrument has proven crucial for decision making in the CFHT queued service observing (QSO) representing today all of the telescope time. Also, science exposures taken in non-photometric conditions are automatically registered for a new observation at a later date at 1/10th of the original exposure time in photometric conditions to ensure a proper final absolute photometric calibration. Photometric standards are observed only when conditions are reported as being perfectly stable by SkyProbe. The more recent dual color system (simultaneous B & V bands) will offer a better characterization of the sky properties above Mauna Kea and should enable a better detection of the thinnest cirrus (absorption down to 0.01 mag., or 1%).

  5. Small satellite radiometric measurement system

    SciTech Connect

    Weber, P.G.

    1992-01-01

    A critical need for the US Global Change Research Program is to provide continuous, well-calibrated radiometric data for the earth`s radiation budget. This paper describes a new, compact, relatively light-weight, adaptable radiometer which will provide both spectrally integrated measurements and data in selected spectral bands. The radiometer design is suitable for use on small satellites, aircraft, or remotely piloted aircraft (RPAs). An example of the implementation of this radiometer on a small satellite is given. Significant benefits derive from simultaneous measurements of specific narrow (in wavelength) spectral features; such data may be obtained by combining LARI with a compact spectrometer on the same platform. Well-chosen satellite orbits allow one to use data from other satellites (e.g. DMSP) to enhance the data product, or to provide superior coverage of specific locations. 23 refs.

  6. Small satellite radiometric measurement system

    SciTech Connect

    Weber, P.G.

    1992-01-01

    A critical need for the US Global Change Research Program is to provide continuous, well-calibrated radiometric data for the earth's radiation budget. This paper describes a new, compact, relatively light-weight, adaptable radiometer which will provide both spectrally integrated measurements and data in selected spectral bands. The radiometer design is suitable for use on small satellites, aircraft, or remotely piloted aircraft (RPAs). An example of the implementation of this radiometer on a small satellite is given. Significant benefits derive from simultaneous measurements of specific narrow (in wavelength) spectral features; such data may be obtained by combining LARI with a compact spectrometer on the same platform. Well-chosen satellite orbits allow one to use data from other satellites (e.g. DMSP) to enhance the data product, or to provide superior coverage of specific locations. 23 refs.

  7. Laboratory Measurement of Bidirectional Reflectance of Radiometric Tarps

    NASA Technical Reports Server (NTRS)

    Knowlton, Kelly

    2006-01-01

    Objectives: a) To determine the magnitude of radiometric tarp BRDF; b) To determine whether an ASD FieldSpec Pro spectroradiometer can be used to perform the experiment. Radiometric tarps with nominal reflectance values of 52%, 35%, and 3.5%, deployed for IKONOS. QuickBird, and OrbView-3 overpasses Ground-based spectroradiometric measurements of tarp and Spectralon@ panel taken during overpass using ASD FieldSpec Pro spectroradiometer, and tarp reflectance calculated. Reflectance data used in atmospheric radiative transfer model (MODTRAN) to predict satellite at-sensor radiance for radiometric calibration. Reflectance data also used to validate atmospheric correction of high-spatial-resolution multispectral image products

  8. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  9. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  10. Energy and directional response for the Harshaw dosemeter holders 8814 and 8891, and its effect on the appropriate radiation qualities for absolute calibration.

    PubMed

    Børretzen, I; Wøhni, T

    2003-01-01

    The personal dosimetry laboratory at the Norwegian radiation protection authority utilises a two-element dosemeter card for measuring Hp(10) and Hp(0.07), in a Harshaw dosemeter holder type 8814. Energy and directional responses for photons and betas for this holder have been assessed, as well as for the new Harshaw holder type 8891. The energy response characteristics for the 12-1250 keV photon energy range, in terms of TL output per unit Hp(10) and Hp(0.07) have been evaluated. The maximum over-response to under-response ratio for the Hp(10) element was found to be 1.46 for the new type 8891 holder, as compared to 1.55 for the older type 8814. The new holder also displays a more favourable directional response for this element. For the Hp(0.07) element, no significant differences with regard to energy or directional responses were found. Selecting radiation energy for absolute calibration of the Hp(10) and Hp(0.07) elements are discussed.

  11. Determination of Delta m(d) and absolute calibration of flavor taggers for the Delta m(s) analysis, in fully reconstructed decays at the CDF experiment

    SciTech Connect

    Gomez, Jonatan Piedra

    2005-04-21

    The new trigger processor, the Silicon Vertex Tracking (SVT), has dramatically improved the B physics capabilities of the upgraded CDF II Detector; for the first time in a hadron collider, the SVT has enabled the access to non-lepton-triggered B meson decays. Within the new available range of decay modes, the B$0\\atop{s}$ → D$-\\atop{s}$π+ signature is of paramount importance in the measurement of the Δms mixing frequency. The analysis reported here is a step towards the measurement of this frequency; two where our goals: carrying out the absolute calibration of the opposite side flavor taggers, used in the Δms measurement; and measuring the B$0\\atop{d}$ mixing frequency in a B → Dπ sample, establishing the feasibility of the mixing measurement in this sample whose decay-length is strongly biased by the selective SVT trigger. We analyze a total integrated luminosity of 355 pb-1 collected with the CDF II Detector. By triggering on muons, using the conventional di-muon trigger; or displaced tracks, using the SVT trigger, we gather a sample rich in bottom and charm mesons.

  12. The radiometric characteristics of KOMPSAT-3A by using reference radiometric tarps and ground measurement

    NASA Astrophysics Data System (ADS)

    Yeom, Jong-Min

    2016-09-01

    In this study, we performed the vicarious radiometric calibration of KOMPSAT-3A multispectral bands by using 6S radiative transfer model, radiometric tarps, MFRSR measurements. Furthermore, to prepare the accurate input parameter, we also did experiment work to measure the BRDF of radiometric tarps based on hyperspectral gonioradiometer to compensate the observation geometry difference between satellite and ASD Fieldspec 3. Also, we measured point spread function (PSF) by using the bright star and corrected multispectral bands based on the Wiener filter. For accurate atmospheric constituent effects such as aerosol optical depth, column water, and total ozone, we used MFRSR instrument and estimated related optical depth of each gases. Based on input parameters for 6S radiative transfer model, we simulated top of atmosphere (TOA) radiance by observed by KOMPSAT-3A and matched-up the digital number. Consequently, DN to radiance coefficients was determined based on aforementioned methods and showed reasonable statistics results.

  13. Design and realization of an active SAR calibrator for TerraSAR-X

    NASA Astrophysics Data System (ADS)

    Dummer, Georg; Lenz, Rainer; Lutz, Benjamin; Kühl, Markus; Müller-Glaser, Klaus D.; Wiesbeck, Werner

    2005-10-01

    TerraSAR-X is a new earth observing satellite which will be launched in spring 2006. It carries a high resolution X-band SAR sensor. For high image data quality, accurate ground calibration targets are necessary. This paper describes a novel system concept for an active and highly integrated, digitally controlled SAR system calibrator. A total of 16 active transponder and receiver systems and 17 receiver only systems will be fabricated for a calibration campaign. The calibration units serve for absolute radiometric calibration of the SAR image data. Additionally, they are equipped with an extra receiver path for two dimensional satellite antenna pattern recognition. The calibrator is controlled by a dedicated digital Electronic Control Unit (ECU). The different voltages needed by the calibrator and the ECU are provided by the third main unit called Power Management Unit (PMU).

  14. Radiometric Dating Does Work!

    ERIC Educational Resources Information Center

    Dalrymple, G. Brent

    2000-01-01

    Discusses the accuracy of dating methods and creationist arguments that radiometric dating does not work. Explains the Manson meteorite impact and the Pierre shale, the ages of meteorites, the K-T tektites, and dating the Mount Vesuvius eruption. (Author/YDS)

  15. The Candela and Photometric and Radiometric Measurements

    PubMed Central

    Parr, Albert C.

    2001-01-01

    The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements. PMID:27500020

  16. Cross-calibration between airborne SAR sensors

    NASA Technical Reports Server (NTRS)

    Zink, Manfred; Olivier, Philippe; Freeman, Anthony

    1993-01-01

    As Synthetic Aperture Radar (SAR) system performance and experience in SAR signature evaluation increase, quantitative analysis becomes more and more important. Such analyses require an absolute radiometric calibration of the complete SAR system. To keep the expenditure on calibration of future multichannel and multisensor remote sensing systems (e.g., X-SAR/SIR-C) within a tolerable level, data from different tracks and different sensors (channels) must be cross calibrated. The 1989 joint E-SAR/DC-8 SAR calibration campaign gave a first opportunity for such an experiment, including cross sensor and cross track calibration. A basic requirement for successful cross calibration is the stability of the SAR systems. The calibration parameters derived from different tracks and the polarimetric properties of the uncalibrated data are used to describe this stability. Quality criteria for a successful cross calibration are the agreement of alpha degree values and the consistency of radar cross sections of equally sized corner reflectors. Channel imbalance and cross talk provide additional quality in case of the polarimetric DC-8 SAR.

  17. The OLI Radiometric Scale Realization Round Robin Measurement Campaign

    NASA Technical Reports Server (NTRS)

    Cutlip, Hansford; Cole,Jerold; Johnson, B. Carol; Maxwell, Stephen; Markham, Brian; Ong, Lawrence; Hom, Milton; Biggar, Stuart

    2011-01-01

    A round robin radiometric scale realization was performed at the Ball Aerospace Radiometric Calibration Laboratory in January/February 2011 in support of the Operational Land Imager (OLI) Program. Participants included Ball Aerospace, NIST, NASA Goddard Space Flight Center, and the University of Arizona. The eight day campaign included multiple observations of three integrating sphere sources by nine radiometers. The objective of the campaign was to validate the radiance calibration uncertainty ascribed to the integrating sphere used to calibrate the OLI instrument. The instrument level calibration source uncertainty was validated by quatnifying: (1) the long term stability of the NIST calibrated radiance artifact, (2) the responsivity scale of the Ball Aerospace transfer radiometer and (3) the operational characteristics of the large integrating sphere.

  18. Xenon arc lamp spectral radiance modelling for satellite instrument calibration

    NASA Astrophysics Data System (ADS)

    Rolt, Stephen; Clark, Paul; Schmoll, Jürgen; Shaw, Benjamin J. R.

    2016-07-01

    Precise radiometric measurements play a central role in many areas of astronomical and terrestrial observation. We focus on the use of continuum light sources in the absolute radiometric calibration of detectors in an imaging spectrometer for space applications. The application, in this instance, revolves around the ground based calibration of the Sentinel-4/UVN instrument. This imaging spectrometer instrument is expected to be deployed in 2019 and will make spatially resolved spectroscopic measurements of atmospheric chemistry. The instrument, which operates across the UV/VIS and NIR spectrum from 305-775 nm, is designed to measure the absolute spectral radiance of the Earth and compare it with the absolute spectral irradiance of the Sun. Of key importance to the fidelity of these absolute measurements is the ground based calibration campaign. Continuum lamp sources that are temporally stable and are spatially well defined are central to this process. Xenon short arc lamps provide highly intense and efficient continuum illumination in a range extending from the ultra-violet to the infra-red and their spectrum is well matched to this specific application. Despite their widespread commercial use, certain aspects of their performance are not well documented in the literature. One of the important requirements in this calibration application is the delivery of highly uniform, collimated illumination at high radiance. In this process, it cannot be assumed that the xenon arc is a point source; the spatial distribution of the radiance must be characterised accurately. We present here careful measurements that thoroughly characterise the spatial distribution of the spectral radiance of a 1000W xenon lamp. A mathematical model is presented describing the spatial distribution. Temporal stability is another exceptionally important requirement in the calibration process. As such, the paper also describes strategies to re-inforce the temporal stability of the lamp output by

  19. Spectroradiometric calibration of the thematic mapper and multispectral scanner system

    NASA Technical Reports Server (NTRS)

    Slater, Philip N.; Palmer, James M.

    1986-01-01

    A list of personnel who have contributed to the program is provided. Sixteen publications and presentations are also listed. A preprint summarizing five in-flight absolute radiometric calibrations of the solar reflective bands of the LANDSAT-5 Thematic Mapper is presented. The 23 band calibrations made on the five dates show a 2.5% RMS variation from the mean as a percentage of the mean. A preprint is also presented that discusses the reflectance-based results of the above preprint. It proceeds to analyze and present results of a second, independent calibration method based on radiance measurements from a helicopter. Radiative transfer through the atmosphere, model atmospheres, the calibration methodology used at White Sands and the results of a sensitivity analysis of the reflectance-based approach is also discussed.

  20. Electron cyclotron emission spectra in X- and O-mode polarisation at JET: Martin-Puplett interferometer, absolute calibration, revised uncertainties, inboard/outboard temperature profile, and wall properties

    NASA Astrophysics Data System (ADS)

    Schmuck, S.; Fessey, J.; Boom, J. E.; Meneses, L.; Abreu, P.; Belonohy, E.; Lupelli, I.

    2016-09-01

    At the tokamak Joint European Torus (JET), the electron cyclotron emission spectra in O-mode and X-mode polarisations are diagnosed simultaneous in absolute terms for several harmonics with two Martin-Puplett interferometers. From the second harmonic range in X-mode polarisation, the electron temperature profile can be deduced for the outboard side (low magnetic field strength) of JET but only for some parts of the inboard side (high magnetic field strength). This spatial restriction can be bypassed, if a cutoff is not present inside the plasma for O-mode waves in the first harmonic range. Then, from this spectral domain, the profile on the entire inboard side is accessible. The profile determination relies on the new absolute and independent calibration for both interferometers. During the calibration procedure, the antenna pattern was investigated as well, and, potentially, an increase in the diagnostic responsivity of about 5% was found for the domain 100-300 GHz. This increase and other uncertainty sources are taken into account in the thorough revision of the uncertainty for the diagnostic absolute calibration. The uncertainty deduced and the convolution inherent for Fourier spectroscopy diagnostics have implications for the temperature profile inferred. Having probed the electron cyclotron emission spectra in orthogonal polarisation directions for the first harmonic range, a condition is derived for the reflection and polarisation-scrambling coefficients of the first wall on the outboard side of JET.

  1. Radiometric and geometric analysis of hyperspectral imagery acquired from an unmanned aerial vehicle

    DOE PAGES

    Hruska, Ryan; Mitchell, Jessica; Anderson, Matthew; ...

    2012-09-17

    During the summer of 2010, an Unmanned Aerial Vehicle (UAV) hyperspectral in-flight calibration and characterization experiment of the Resonon PIKA II imaging spectrometer was conducted at the U.S. Department of Energy’s Idaho National Laboratory (INL) UAV Research Park. The purpose of the experiment was to validate the radiometric calibration of the spectrometer and determine the georegistration accuracy achievable from the on-board global positioning system (GPS) and inertial navigation sensors (INS) under operational conditions. In order for low-cost hyperspectral systems to compete with larger systems flown on manned aircraft, they must be able to collect data suitable for quantitative scientific analysis.more » The results of the in-flight calibration experiment indicate an absolute average agreement of 96.3%, 93.7% and 85.7% for calibration tarps of 56%, 24%, and 2.5% reflectivity, respectively. The achieved planimetric accuracy was 4.6 meters (based on RMSE).« less

  2. RapidEye constellation relative radiometric accuracy measurement using lunar images

    NASA Astrophysics Data System (ADS)

    Steyn, Joe; Tyc, George; Beckett, Keith; Hashida, Yoshi

    2009-09-01

    The RapidEye constellation includes five identical satellites in Low Earth Orbit (LEO). Each satellite has a 5-band (blue, green, red, red-edge and near infrared (NIR)) multispectral imager at 6.5m GSD. A three-axes attitude control system allows pointing the imager of each satellite at the Moon during lunations. It is therefore possible to image the Moon from near identical viewing geometry within a span of 80 minutes with each one of the imagers. Comparing the radiometrically corrected images obtained from each band and each satellite allows a near instantaneous relative radiometric accuracy measurement and determination of relative gain changes between the five imagers. A more traditional terrestrial vicarious radiometric calibration program has also been completed by MDA on RapidEye. The two components of this program provide for spatial radiometric calibration ensuring that detector-to-detector response remains flat, while a temporal radiometric calibration approach has accumulated images of specific dry dessert calibration sites. These images are used to measure the constellation relative radiometric response and make on-ground gain and offset adjustments in order to maintain the relative accuracy of the constellation within +/-2.5%. A quantitative comparison between the gain changes measured by the lunar method and the terrestrial temporal radiometric calibration method is performed and will be presented.

  3. The Landsat Data Continuity Mission Operational Land Imager: Radiometric Performance

    NASA Technical Reports Server (NTRS)

    Markham, Brian; Dabney, Philip; Pedelty, Jeffrey

    2011-01-01

    The Operational Land Imager (OLI) is one of two instruments to fly on the Landsat Data Continuity Mission (LDCM), which is scheduled to launch in December 2012 to become the 8th in the series of Landsat satellites. The OLI images in the solar reflective part of the spectrum, with bands similar to bands 1-5, 7 and the panchromatic band on the Landsat-7 ETM+ instrument. In addition, it has a 20 nm bandpass spectral band at 443 nm for coastal and aerosol studies and a 30 nm band at 1375 nm to aid in cirrus cloud detection. Like ETM+, spatial resolution is 30 m in the all but the panchromatic band, which is 15 meters. OLI is a pushbroom radiometer with approximately 6000 detectors per 30 meter band as opposed to the 16 detectors per band on the whiskbroom ETM+. Data are quantized to 12 bits on OLI as opposed to 8 bits on ETM+ to take advantage of the improved signal to noise ratio provided by the pushbroom design. The saturation radiances are higher on OLI than ETM+ to effectively eliminate saturation issues over bright Earth targets. OLI includes dual solar diffusers for on-orbit absolute and relative (detector to detector) radiometric calibration. Additionally, OLI has 3 sets of on-board lamps that illuminate the OLI focal plane through the full optical system, providing additional checks on the OLI's response[l]. OLI has been designed and built by Ball Aerospace & Technology Corp. (BATC) and is currently undergoing testing and calibration in preparation for delivery in Spring 2011. Final pre-launch performance results should be available in time for presentation at the conference. Preliminary results will be presented below. These results are based on the performance of the Engineering Development Unit (EDU) that was radiometrically tested at the integrated instrument level in 2010 and assembly level measurements made on the flight unit. Signal-to-Noise (SNR) performance: One of the advantages of a pushbroom system is the increased dwell time of the detectors

  4. Lansat MSS, Radiometric Processing Improvement

    NASA Astrophysics Data System (ADS)

    Saunier, Sebastien; Salgues, Germain; Gascon, Ferran; Biaasutti, Roberto

    2016-08-01

    The reprocessing campaigns of Landsat European Space Agency (ESA) data archive have been initiated since 3 years [1]. As part of this project, the processing algorithms have been upgraded. This article focuses on the radiometric processing of historical data observed with the Multi Spectral Scanner (MSS) instruments on board Landsat 1, 2, 3, 4 and 5.The Landsat MSS data have been recorded data from 1972 up to 1990. The MSS instruments have been designed with four visible bands covering the near / infrared regions of the electromagnetic spectrum, allowing the spatial sampling of our Earth surface at 60 meter.The current calibration method has shown some limitations in case of data observed out of mid latitude areas, where the Earth surface is bright because of desert or snow. The resulting image data suffers from saturations and is not fit for the potential application purposes.Although, when saturation exist, further investigations have shown that the radiometry of the raw data involved in the production of the Level 1 images is generally correct. As consequences, experiments have been undertaken to adapt the current processing in order to produce image data saturation free products.

  5. Flight Technology Improvement. [spaceborne optical radiometric instruments, attitude control, and electromechanical and power subsystems

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Shortcomings in spaceborne instrumentation technology are analyzed and recommendations are given for corrections and technology development. The technologies discussed are optical radiometric instruments and calibration, attitude control and determination, and electromechanical and power subsystems.

  6. Invited Article: Deep Impact instrument calibration.

    PubMed

    Klaasen, Kenneth P; A'Hearn, Michael F; Baca, Michael; Delamere, Alan; Desnoyer, Mark; Farnham, Tony; Groussin, Olivier; Hampton, Donald; Ipatov, Sergei; Li, Jianyang; Lisse, Carey; Mastrodemos, Nickolaos; McLaughlin, Stephanie; Sunshine, Jessica; Thomas, Peter; Wellnitz, Dennis

    2008-09-01

    Calibration of NASA's Deep Impact spacecraft instruments allows reliable scientific interpretation of the images and spectra returned from comet Tempel 1. Calibrations of the four onboard remote sensing imaging instruments have been performed in the areas of geometric calibration, spatial resolution, spectral resolution, and radiometric response. Error sources such as noise (random, coherent, encoding, data compression), detector readout artifacts, scattered light, and radiation interactions have been quantified. The point spread functions (PSFs) of the medium resolution instrument and its twin impactor targeting sensor are near the theoretical minimum [ approximately 1.7 pixels full width at half maximum (FWHM)]. However, the high resolution instrument camera was found to be out of focus with a PSF FWHM of approximately 9 pixels. The charge coupled device (CCD) read noise is approximately 1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to approximately 1%. Spectrometer read noise is approximately 2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to approximately 10 DN at best. Wavelength mapping onto the detector is known within 1 pixel; spectral lines have a FWHM of approximately 2 pixels. About 1% of the IR detector pixels behave badly and remain uncalibrated. The spectrometer exhibits a faint ghost image from reflection off a beamsplitter. Instrument absolute radiometric calibration accuracies were determined generally to <10% using star imaging. Flat-field calibration reduces pixel-to-pixel response differences to approximately 0.5% for the cameras and <2% for the spectrometer. A standard calibration image processing pipeline is used to produce archival image files for analysis by researchers.

  7. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  8. ASD FieldSpec Calibration Setup and Techniques

    NASA Technical Reports Server (NTRS)

    Olive, Dan

    2001-01-01

    This paper describes the Analytical Spectral Devices (ASD) Fieldspec Calibration Setup and Techniques. The topics include: 1) ASD Fieldspec FR Spectroradiometer; 2) Components of Calibration; 3) Equipment list; 4) Spectral Setup; 5) Spectral Calibration; 6) Radiometric and Linearity Setup; 7) Radiometric setup; 8) Datadets Required; 9) Data files; and 10) Field of View Measurement. This paper is in viewgraph form.

  9. Radiometric Characterization of Hyperspectral Imagers using Multispectral Sensors

    NASA Technical Reports Server (NTRS)

    McCorkel, Joel; Kurt, Thome; Leisso, Nathan; Anderson, Nikolaus; Czapla-Myers, Jeff

    2009-01-01

    The Remote Sensing Group (RSG) at the University of Arizona has a long history of using ground-based test sites for the calibration of airborne and satellite based sensors. Often, ground-truth measurements at these test sites are not always successful due to weather and funding availability. Therefore, RSG has also automated ground instrument approaches and cross-calibration methods to verify the radiometric calibration of a sensor. The goal in the cross-calibration method is to transfer the calibration of a well-known sensor to that of a different sensor, This work studies the feasibility of determining the radiometric calibration of a hyperspectral imager using multispectral a imagery. The work relies on the Moderate Resolution Imaging Spectroradiometer (M0DIS) as a reference for the hyperspectral sensor Hyperion. Test sites used for comparisons are Railroad Valley in Nevada and a portion of the Libyan Desert in North Africa. Hyperion bands are compared to MODIS by band averaging Hyperion's high spectral resolution data with the relative spectral response of M0DlS. The results compare cross-calibration scenarios that differ in image acquisition coincidence, test site used for the calibration, and reference sensor. Cross-calibration results are presented that show agreement between the use of coincident and non-coincident image pairs within 2% in most brands as well as similar agreement between results that employ the different MODIS sensors as a reference.

  10. Preflight and in-flight calibration plan for ASTER

    USGS Publications Warehouse

    Ono, A.; Sakuma, F.; Arai, K.; Yamaguchi, Y.; Fujisada, H.; Slater, P.N.; Thome, K.J.; Palluconi, Frank Don; Kieffer, H.H.

    1996-01-01

    Preflight and in-flight radiometric calibration plans are described for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) that is a multispectral optical imager of high spatial resolution. It is designed for the remote sensing from orbit of land surfaces and clouds, and is expected to be launched in 1998 on NASA's EOS AM-1 spacecraft. ASTER acquires images in three separate spectral regions, the visible and near-infrared (VNIR), the shortwave infrared (SWIR), and the thermal infrared (TIR) with three imaging radiometer subsystems. The absolute radiometric accuracy is required to be better than 4% for VNIR and SWIR radiance measurements and 1 to 3 K, depending on the temperature regions from 200 to 370 K, for TIR temperature measurements. A reference beam is introduced at the entrance pupil of each imaging radiometer to provide the in-flight calibration Thus, the ASTER instrument includes internal onboard calibration units that comprise incandescent lamps for the VNIR and SWIR and a blackbody radiator for the TIR as reference sources. The calibration reliability of the VNIR and SWIR is enhanced by a dual system of onboard calibration units as well as by high-stability halogen lamps. A ground calibration system of spectral radiances traceable to fixed-point blackbodies is used for the preflight VNIR and SWIR calibration. Because of the possibility of nonuniform contamination effects on the partial-aperture onboard calibration, it is desirable to check their results with respect to other methods. Reflectance- and radiance-based vicarious methods have been developed for this purpose. These, and methods involving in-flight cross-calibration with other sensors are also described.

  11. On-orbit calibration of SeaWiFS.

    PubMed

    Eplee, Robert E; Meister, Gerhard; Patt, Frederick S; Barnes, Robert A; Bailey, Sean W; Franz, Bryan A; McClain, Charles R

    2012-12-20

    Ocean color climate data records (CDRs) require water-leaving radiances with 5% absolute and 1% relative accuracies as input. Because of the amplification of any sensor calibration errors by the atmospheric correction, the 1% relative accuracy requirement translates into a 0.1% long-term radiometric stability requirement for top-of-the-atmosphere (TOA) radiances. The rigorous prelaunch and on-orbit calibration program developed and implemented for Sea-viewing Wide Field-of-view Sensor (SeaWiFS) by the NASA Ocean Biology Processing Group (OBPG) has led to the incorporation of significant changes into the on-orbit calibration methodology over the 13-year lifetime of the instrument. Evolving instrument performance and ongoing algorithm refinement have resulted in updates to approaches for the lunar, solar, and vicarious calibration of SeaWiFS. The uncertainties in the calibrated TOA radiances are addressed in terms of accuracy (biases in the measurements), precision (scatter in the measurements), and stability (repeatability of the measurements). The biases are 2%-3% from lunar calibration and 1%-2% from vicarious calibration. The precision is 0.16% from solar signal-to-noise ratios, 0.13% from lunar residuals, and 0.10% from vicarious gains. The long-term stability of the TOA radiances, derived from the lunar time series, is 0.13%. The stability of the vicariously calibrated TOA radiances, incorporating the uncertainties of the in situ measurements and the atmospheric correction, is 0.30%. This stability of the radiometric calibration of SeaWiFS over its 13-year on-orbit lifetime has allowed the OBPG to produce CDRs from the ocean color data set.

  12. Proposed low-energy absolute calibration of nuclear recoils in a dual-phase noble element TPC using D-D neutron scattering kinematics

    NASA Astrophysics Data System (ADS)

    Verbus, J. R.; Rhyne, C. A.; Malling, D. C.; Genecov, M.; Ghosh, S.; Moskowitz, A. G.; Chan, S.; Chapman, J. J.; de Viveiros, L.; Faham, C. H.; Fiorucci, S.; Huang, D. Q.; Pangilinan, M.; Taylor, W. C.; Gaitskell, R. J.

    2017-04-01

    We propose a new technique for the calibration of nuclear recoils in large noble element dual-phase time projection chambers used to search for WIMP dark matter in the local galactic halo. This technique provides an in situ measurement of the low-energy nuclear recoil response of the target media using the measured scattering angle between multiple neutron interactions within the detector volume. The low-energy reach and reduced systematics of this calibration have particular significance for the low-mass WIMP sensitivity of several leading dark matter experiments. Multiple strategies for improving this calibration technique are discussed, including the creation of a new type of quasi-monoenergetic neutron source with a minimum possible peak energy of 272 keV. We report results from a time-of-flight-based measurement of the neutron energy spectrum produced by an Adelphi Technology, Inc. DD108 neutron generator, confirming its suitability for the proposed nuclear recoil calibration.

  13. Detection of 15 dB Squeezed States of Light and their Application for the Absolute Calibration of Photoelectric Quantum Efficiency

    NASA Astrophysics Data System (ADS)

    Vahlbruch, Henning; Mehmet, Moritz; Danzmann, Karsten; Schnabel, Roman

    2016-09-01

    Squeezed states of light belong to the most prominent nonclassical resources. They have compelling applications in metrology, which has been demonstrated by their routine exploitation for improving the sensitivity of a gravitational-wave detector since 2010. Here, we report on the direct measurement of 15 dB squeezed vacuum states of light and their application to calibrate the quantum efficiency of photoelectric detection. The object of calibration is a customized InGaAs positive intrinsic negative (p-i-n) photodiode optimized for high external quantum efficiency. The calibration yields a value of 99.5% with a 0.5% (k =2 ) uncertainty for a photon flux of the order 1 017 s-1 at a wavelength of 1064 nm. The calibration neither requires any standard nor knowledge of the incident light power and thus represents a valuable application of squeezed states of light in quantum metrology.

  14. Landsat radiometric continuity using airborne imaging spectrometry

    NASA Astrophysics Data System (ADS)

    McCorkel, J.; Angal, A.; Thome, K.; Cook, B.

    2015-12-01

    NASA Goddard's Lidar, Hyperspectral and Thermal Imager (G-LiHT) includes a scanning lidar, an imaging spectrometer and a thermal camera. The Visible Near-Infrared (VNIR) Imaging Spectrometer acquires high resolution spectral measurements (1.5 nm resolution) from 0.4 to 1.0 µm. The SIRCUS-based calibration facility at NASA's Goddard Space Flight Center was used to measure the absolute spectral response (ASR) of the G-LiHT's imaging spectrometer. Continuously tunable lasers coupled to an integrating sphere facilitated a radiance-based calibration for the detectors in the reflective solar bands. The transfer of the SIRCUS-based laboratory calibration of G-LiHT's Imaging Spectrometer to the Landsat sensors (Landsat 7 ETM+ and Landsat 8 OLI) is demonstrated using simultaneous overpasses over the Red Lake Playa and McClaw's Playa sites during the commissioning phase of Landsat 8 in March 2013. Solar Lunar Absolute Imaging Spectrometer (SOLARIS) is the calibration demonstration system for the reflected solar instrument of CLARREO. A portable version of SOLARIS, known as Suitcase SOLARIS, also calibrated using a SIRCUS-based setup, was deployed for ground measurements as a part of both the field campaigns. Simultaneous measurements of SOLARIS allow cross-comparison with G-LiHT and Landsat sensors. The transfer of the lab-based calibration of G-LiHT to Landsat sensors show that the sensors agree within 5% with a 1-3% calibration uncertainty of G-LiHT's Imaging Spectrometer.

  15. Improved Thermal-Vacuum Compatible Flat Plate Radiometric Souce for System-Level Testing of Optical Sensors

    NASA Technical Reports Server (NTRS)

    Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.

    2015-01-01

    This work describes the development of an improved vacuum compatible flat plate radiometric source used for characterizing and calibrating remote optical sensors, in situ, throughout their testing period. The original flat plate radiometric source was developed for use by the VIIRS instrument during the NPOESS Preparatory Project (NPP). Following this effort, the FPI has had significant upgrades in order to improve both the radiometric throughput and uniformity. Results of the VIIRS testing with the reconfigured FPI are reported and discussed.

  16. Radiometric and Spectral Measurement Instruments

    DTIC Science & Technology

    1992-03-18

    NSWCCR/RDTN-92/0003 AD-A250 771LI~ llliii11l li l l iillt111 RADIOMETRIC AND SPECTRAL MEASUREMENT INSTRUMENTS CRANE DIVISION NAVAL SURFACE WARFARE... INSTRUMENTS 6. AUTHOR(S) B. E. DOUDA H. A. WEBSTER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) a. PERFORMING ORGANIZATION REPORT NIJMBER...Maxiry-um 200 w ords) THIS IS A DESCRIPTION OF AN ASSORTMENT OF RADIOMETRIC AND SPECTRAL INSTRUMENTATION USED FOR MEASUREMENT OF THE RADIATIVE OUTPUT OF

  17. Calibration of the Microwave Limb Sounder on the Upper Atmosphere Research Satellite

    NASA Technical Reports Server (NTRS)

    Jarnot, Robert R.; Waters, Joe W.

    1994-01-01

    This paper describes pre-launch radiometric and spectral calibrations of the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS). Use of in-flight data for validation or refinement of calibration is described. The estimated uncertaint in calibrated radiance from pre-launch radiometric and spectral calibration data is better than 2% in most bands.

  18. Absolute x-ray and neutron calibration of CVD-diamond-based time-of-flight detectors for the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Rosenthal, A.; Kabadi, N. V.; Sio, H.; Rinderknecht, H.; Gatu Johnson, M.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Glebov, V.; Forrest, C.; Knauer, J.

    2016-10-01

    The particle-time-of-flight (pTOF) detector at the National Ignition Facility routinely measures proton and neutron nuclear bang-times in inertial confinement fusion (ICF) implosions. The active detector medium in pTOF is a chemical vapor deposition (CVD) diamond biased to 250 - 1500 V. This work discusses an absolute measurement of CVD diamond sensitivity to continuous neutrons and x-rays. Although the impulse response of the detector is regularly measured on a diagnostic timing shot, absolute sensitivity of the detector's response to neutrons and x-rays has not been fully established. X-ray, DD-n, and DT-n sources at the MIT HEDP Accelerator Facility provide continuous sources for testing. CVD diamond detectors are also fielded on OMEGA experiments to measure sensitivity to impulse DT-n. Implications for absolute neutron yield measurements at the NIF using pTOF detectors will be discussed. This work was supported in part by the U.S. DoE and LLNL.

  19. Assessment of uncertainty in ROLO lunar irradiance for on-orbit calibration

    USGS Publications Warehouse

    Stone, T.C.; Kieffer, H.H.; Barnes, W.L.; Butler, J.J.

    2004-01-01

    A system to provide radiometric calibration of remote sensing imaging instruments on-orbit using the Moon has been developed by the US Geological Survey RObotic Lunar Observatory (ROLO) project. ROLO has developed a model for lunar irradiance which treats the primary geometric variables of phase and libration explicitly. The model fits hundreds of data points in each of 23 VNIR and 9 SWIR bands; input data are derived from lunar radiance images acquired by the project's on-site telescopes, calibrated to exoatmospheric radiance and converted to disk-equivalent reflectance. Experimental uncertainties are tracked through all stages of the data processing and modeling. Model fit residuals are ???1% in each band over the full range of observed phase and libration angles. Application of ROLO lunar calibration to SeaWiFS has demonstrated the capability for long-term instrument response trending with precision approaching 0.1% per year. Current work involves assessing the error in absolute responsivity and relative spectral response of the ROLO imaging systems, and propagation of error through the data reduction and modeling software systems with the goal of reducing the uncertainty in the absolute scale, now estimated at 5-10%. This level is similar to the scatter seen in ROLO lunar irradiance comparisons of multiple spacecraft instruments that have viewed the Moon. A field calibration campaign involving NASA and NIST has been initiated that ties the ROLO lunar measurements to the NIST (SI) radiometric scale.

  20. In situ radiometric dating on Mars: Investigation of the feasibility of K-Ar dating using flight-type mass and X-ray spectrometers

    NASA Astrophysics Data System (ADS)

    Talboys, D. L.; Barber, S.; Bridges, J. C.; Kelley, S. P.; Pullan, D.; Verchovsky, A. B.; Butcher, G.; Fazel, A.; Fraser, G. W.; Pillinger, C. T.; Sims, M. R.; Wright, I. P.

    2009-09-01

    The absolute chronology of Mars is poorly known and, as a consequence, a key science aim is to perform accurate radiometric dating of martian geological materials. The scientific benefits of in situ radiometric dating are significant and arguably of most importance is the calibration of the martian cratering rate, similar to what has been achieved for the Moon, to reduce the large uncertainties on absolute boundary ages of martian epochs. The Beagle 2 Mars lander was capable of performing radiometric date measurements of rocks using the analyses from two instruments in its payload: (i) the X-ray Spectrometer (XRS) and (ii) the Gas Analysis Package (GAP). We have investigated the feasibility of in situ radiometric dating using the K-Ar technique employing flight-like versions of Beagle 2 instrumentation. The K-Ar ages of six terrestrial basalts were measured and compared to the 'control' Ar-Ar radiometric ages in the range 171-1141 Ma. The K content of each basalt was measured by the flight spare XRS and the 40Ar content using a laboratory analogue of the GAP. The K-Ar ages of five basalts broadly agreed with their corresponding Ar-Ar ages. For one final basalt, the 40Ar content was below the detection limit and so an age could not be derived. The precision of the K-Ar ages was ˜30% on average. The conclusions from this study are that careful attention must be paid to improving the analytical performance of the instruments, in particular the accuracy and detection limits. The accuracy of the K and Ar measurements are the biggest source of uncertainty in the derived K-Ar age. Having investigated the technique using flight-type planetary instrumentation, we conclude that come of the principle challenges of conducting accurate in situ radiometric dating on Mars using instruments of these types include determining the sample mass, ensuring all the argon is liberated from the sample given the maximum achievable temperature of the mass spectrometer ovens, and argon loss

  1. Landsat-7 ETM+: 12 years on-orbit reflective-band radiometric performance

    USGS Publications Warehouse

    Markham, B.L.; Haque, M.O.; Barsi, J.A.; Micijevic, E.; Helder, D.L.; Thome, K.J.; Aaron, D.; Czapla-Myers, J. S.

    2012-01-01

    The Landsat-7 ETM+ sensor has been operating on orbit for more than 12 years, and characterizations of its performance have been ongoing over this period. In general, the radiometric performance of the instrument has been remarkably stable: 1) noise performance has degraded by 2% or less overall, with a few detectors displaying step changes in noise of 2% or less; 2) coherent noise frequencies and magnitudes have generally been stable, though the within-scan amplitude variation of the 20 kHz noise in bands 1 and 8 disappeared with the failure of the scan line corrector and a new similar frequency noise (now about 18 kHz) has appeared in two detectors in band 5 and increased in magnitude with time; 3) bias stability has been better than 0.25 DN out of a normal value of 15 DN in high gain; 4) relative gains, the differences in response between the detectors in the band, have generally changed by 0.1% or less over the mission, with the exception of a few detectors with a step response change of 1% or less; and 5) gain stability averaged across all detectors in a band, which is related to the stability of the absolute calibration, has been more stable than the techniques used to measure it. Due to the inability to confirm changes in the gain (beyond a few detectors that have been corrected back to the band average), ETM+ reflective band data continues to be calibrated with the prelaunch measured gains. In the worst case, some bands may have changed as much as 2% in uncompensated absolute calibration over the 12 years.

  2. Laboratory-based bidirectional reflectance distribution functions of radiometric tarps

    SciTech Connect

    Georgiev, Georgi T.; Butler, James J

    2008-06-20

    Laboratory-based bidirectional reflectance distribution functions (BRDFs) of radiometric tarp samples used in the vicarious calibration of Earth remote sensing satellite instruments are presented in this paper. The results illustrate the BRDF dependence on the orientation of the tarps' weft and warp threads. The study was performed using the GSFC scatterometer at incident zenith angles of 0 deg., 10 deg., and 30 deg.; scatter zenith angles from 0 deg. to 60 deg.; and scatter azimuth angles of 0 deg., 45 deg., 90 deg., 135 deg., and 180 deg.. The wavelengths were 485 nm, 550 nm, 633 nm, and 800 nm. The tarp's weft and warp dependence on BRDF is well defined at all measurement geometries and wavelengths. The BRDF difference can be as high as 8% at 0 deg. incident angle and 12% at 30 deg. incident angle. The fitted BRDF data show a very small discrepancy from the measured ones. New data on the forward and backscatter properties of radiometric tarps are reported. The backward scatter is well pronounced for the white samples. The black sample has well-pronounced forward scatter. The provided BRDF characterization of radiometric tarps is an excellent reference for anyone interested in using tarps for radiometric calibrations. The results are NIST traceable.

  3. Sentinel-2 diffuser on-ground calibration

    NASA Astrophysics Data System (ADS)

    Mazy, E.; Camus, F.; Chorvalli, V.; Domken, I.; Laborie, A.; Marcotte, S.; Stockman, Y.

    2013-10-01

    The Sentinel-2 multi-spectral instrument (MSI) will provide Earth imagery in the frame of the Global Monitoring for Environment and Security (GMES) initiative which is a joint undertaking of the European Commission and the Agency. MSI instrument, under Astrium SAS responsibility, is a push-broom spectro imager in 13 spectral channels in VNIR and SWIR. The instrument radiometric calibration is based on in-flight calibration with sunlight through a quasi Lambertian diffuser. The diffuser covers the full pupil and the full field of view of the instrument. The on-ground calibration of the diffuser BRDF is mandatory to fulfil the in-flight performances. The diffuser is a 779 x 278 mm2 rectangular flat area in Zenith-A material. It is mounted on a motorised door in front of the instrument optical system entrance. The diffuser manufacturing and calibration is under the Centre Spatial of Liege (CSL) responsibility. The CSL has designed and built a completely remote controlled BRDF test bench able to handle large diffusers in their mount. As the diffuser is calibrated directly in its mount with respect to a reference cube, the error budget is significantly improved. The BRDF calibration is performed directly in MSI instrument spectral bands by using dedicated band-pass filters (VNIR and SWIR up to 2200 nm). Absolute accuracy is better than 0.5% in VNIR spectral bands and 1% in SWIR spectral bands. Performances were cross checked with other laboratories. The first MSI diffuser for flight model was calibrated mid 2013 on CSL BRDF measurement bench. The calibration of the diffuser consists mainly in thermal vacuum cycles, BRDF uniformity characterisation and BRDF angular characterisation. The total amount of measurement for the first flight model diffuser corresponds to more than 17500 BRDF acquisitions. Performance results are discussed in comparison with requirements.

  4. Microwave and Millimeter Wave Forward Modeling Results from the 2004 North Slope of Alaska Arctic Winter Radiometric Experiment

    SciTech Connect

    Westwater, E.R.; Cimini, D.; Klein, M.; Leuski, V.; Mattioli, V.; Gasiewski, A.J.; Dowlatshahi, S.; Liljegren, J.S.; Lesht, B.M.; Shaw, J.A.

    2005-03-18

    The 2004 Arctic Winter Radiometric Experiment was conducted at the North Slope of Alaska (NSA) Atmospheric Radiation Measurement (ARM) Program field site near Barrow, Alaska from March 9 to April 9, 2004. The goals of the experiment were: to study the microwave and millimeter wave radiometric response to water vapor and clouds during cold and dry conditions; to obtain data for forward model studies at frequencies ranging from 22.235 to 400 GHz, to demonstrate new Environmental Technology Laboratory's (ETL) radiometric receiver and calibration technology and to compare both radiometric and in situ measurements of water vapor.

  5. Absolute vicarious calibration of Landsat-8 OLI and Resourcesat-2 AWiFS sensors over Rann of Kutch site in Gujarat

    NASA Astrophysics Data System (ADS)

    Sharma, Shweta; Sridhar, V. N.; Prajapati, R. P.; Rao, K. M.; Mathur, A. K.

    2016-05-01

    In this work, vicarious calibration coefficients for all the four bands (green, red, NIR and SWIR) of Resourcesat-2 AWiFS sensor for four dates during Dec 2013-Nov 2014 and for seven bands (blue, green, red, NIR, SWIR1, SWIR2 and PAN) of OLI sensor onboard Landsat-8 for six dates during Dec 2013-Feb 2015 were estimated using field measured reflectance and measured atmospheric parameters during sensor image acquisition over Rann of Kutch site in Gujarat. The top of atmosphere (TOA) at-satellite radiances for all the bands were simulated using 6S radiative transfer code with field measured reflectance, synchronous atmospheric measurements and respective sensor's spectral response functions as an input. These predicted spectral radiances were compared with the radiances from the respective sensor's image in the respective band over the calibration site. Cross-calibration between the sensors AWiFS and OLI was also attempted using near-simultaneous same day image acquisition. Effect of spectral band adjustment factor was also studied with OLI sensor taken as reference sensor. Results show that the variation in average estimated radiance ratio for the AWiFS sensor was found to be within 10% for all the bands, whereas, for OLI sensor, the variation was found to be within 6% for all the bands except green and SWIR2 for which the variation was 8% and 11% respectively higher than the 5% uncertainty of the OLI sensor specification for TOA spectral radiance. At the 1σ level, red, NIR, SWIR1 and Panchromatic bands of OLI sensor showed close agreement between sensor-measured and vicarious TOA radiance resulting no change in calibration coefficient and hence indicating no sensor degradation. Two sets of near-simultaneous SBAFs were derived from respective ground measured target reflectance profiles and applied to the AWiFS and it was observed that overall, SBAF compensation provides a significant improvement in sensor agreement. The reduction in the difference between AWiFS and

  6. LANDSAT-4 multispectral scanner (MSS) subsystem radiometric characterization

    NASA Technical Reports Server (NTRS)

    Alford, W. (Editor); Barker, J. (Editor); Clark, B. P.; Dasgupta, R.

    1983-01-01

    The multispectral band scanner (mass) and its spectral characteristics are described and methods are given for relating video digital levels on computer compatible tapes to radiance into the sensor. Topics covered include prelaunch calibration procedures and postlaunch radiometric processng. Examples of current data resident on the MSS image processing system are included. The MSS on LANDSAT 4 is compared with the scanners on earlier LANDSAT satellites.

  7. Thematic Mapper. Volume 1: Calibration report flight model, LANDSAT 5

    NASA Technical Reports Server (NTRS)

    Cooley, R. C.; Lansing, J. C.

    1984-01-01

    The calibration of the Flight 1 Model Thematic Mapper is discussed. Spectral response, scan profile, coherent noise, line spread profiles and white light leaks, square wave response, radiometric calibration, and commands and telemetry are specifically addressed.

  8. Airborne microwave radiometric imaging system

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Zhang, Zuyin; Chen, Zhengwen

    1998-08-01

    A dual channel Airborne Microwave Radiometric Imaging system (AMRI) was designed and constructed for regional environment mapping. The system operates at 35GHz, which collects radiation at horizontal and vertical polarized. It runs at mechanical conical scanning with 45 degrees incidence angle. Two Cassegrain antennas with 1.5 degrees 3 dB beamwidth scan the scene alternately and two pseudo-color images of two channels are displayed on the screen of PC in real time. Simultaneously all parameters of flight and radiometric data are stored in hard disk for postprocessing. The sensitivity of the radiometers of flight and radiometric data are stored in hard disk for postprocessing. The sensitivity of the radiometers (Delta) T equals 0.16K. A new display method, unequal size element arc displaying method, is used in image displaying. Several experiments on mobile tower were carried out and the images demonstrate the AMRI is available to work steadily and accurately.

  9. Radiometric framework for image mosaicking.

    PubMed

    Litvinov, Anatoly; Schechner, Yoav Y

    2005-05-01

    Nonuniform exposures often affect imaging systems, e.g., owing to vignetting. Moreover, the sensor's radiometric response may be nonlinear. These characteristics hinder photometric measurements. They are particularly annoying in image mosaicking, in which images are stitched to enhance the field of view. Mosaics suffer from seams stemming from radiometric inconsistencies between raw images. Prior methods feathered the seams but did not address their root cause. We handle these problems in a unified framework. We suggest a method for simultaneously estimating the radiometric response and the camera nonuniformity, based on a frame sequence acquired during camera motion. The estimated functions are then compensated for. This permits image mosaicking, in which no seams are apparent. There is no need to resort to dedicated seam-feathering methods. Fundamental ambiguities associated with this estimation problem are stated.

  10. [On-orbit response variation analysis of FY-3 MERSI reflective solar bands based on Dunhuang site calibration].

    PubMed

    Sun, Ling; Guo, Mao-Hua; Xu, Na; Zhang, Li-Jun; Liu, Jing-Jing; Hu, Xiu-Qing; Li, Yuan; Rong, Zhi-Guo; Zhao, Ze-Hui

    2012-07-01

    MERSI is the keystone payload of FengYun-3 and there have been two sensors operating on-orbit since 2008. The on-orbit response changes obviously at reflective solar bands (RSBs) and must be effectively monitored and corrected. However MERSI can not realize the RSBs onboard absolute radiometric calibration. This paper presents a new vicarious calibration (VC) method for RSBs based on in-situ BRDF model, and vector radiometric transfer model 6SV with gaseous absorption correction using MOTRAN. The results of synchronous VC experiments in 4 years show that the calibration uncertainties are within 5% except for band at the center of water vapor absorption, and 3% for most bands. Aqua MODIS was taken as the radiometric reference to evaluate the accuracy of this VC method. By comparison of the simulated radiation at top of atmosphere (TOA) with MODIS measurement, it was revealed that the average relative differences are within 3% for window bands with wavelengths less than 1 microm, and 5% for bands with wavelengths larger than 1 microm (except for band 7 at 2.1 microm). Besides, the synchronous nadir observation cross analysis shows the excellent agreement between re-calibrated MERSI TOA apparent reflectance and MODIS measurements. Based on the multi-year site calibration results, it was found that the calibration coefficients could be fitted with two-order polynomials, thus the daily calibration updates could be realized and the response variation between two calibration experiments could be corrected timely; there are large response changes at bands with wavelengths less than 0.6 microm, the degradation rate of the first year at band 8 (0.41 microm) is about 14%; the on-orbit response degradation is maximum at the beginning, the degradation rates slow down after one year in operation, and after two years the responses even increase at some band with wavelengths larger than 0.6 microm.

  11. Absolute Energy Calibration of X-ray TESs with 0.04 eV Uncertainty at 6.4 keV in a Hadron-Beam Environment

    NASA Astrophysics Data System (ADS)

    Tatsuno, H.; Doriese, W. B.; Bennett, D. A.; Curceanu, C.; Fowler, J. W.; Gard, J.; Gustafsson, F. P.; Hashimoto, T.; Hayano, R. S.; Hays-Wehle, J. P.; Hilton, G. C.; Iliescu, M.; Ishimoto, S.; Itahashi, K.; Iwasaki, M.; Kuwabara, K.; Ma, Y.; Marton, J.; Noda, H.; O'Neil, G. C.; Okada, S.; Outa, H.; Reintsema, C. D.; Sato, M.; Schmidt, D. R.; Shi, H.; Suzuki, K.; Suzuki, T.; Uhlig, J.; Ullom, J. N.; Widmann, E.; Yamada, S.; Zmeskal, J.; Swetz, D. S.

    2016-08-01

    A performance evaluation of superconducting transition-edge sensors (TESs) in the environment of a pion beam line at a particle accelerator is presented. Averaged across the 209 functioning sensors in the array, the achieved energy resolution is 5.2 eV FWHM at Co K_{α } (6.9 keV) when the pion beam is off and 7.3 eV at a beam rate of 1.45 MHz. Absolute energy uncertainty of ± 0.04 eV is demonstrated for Fe K_{α } (6.4 keV) with in-situ energy calibration obtained from other nearby known X-ray lines. To achieve this small uncertainty, it is essential to consider the non-Gaussian energy response of the TESs and thermal cross-talk pile-up effects due to charged particle hits in the silicon substrate of the TES array.

  12. Evaluation of S190A radiometric exposure test data

    NASA Technical Reports Server (NTRS)

    Lockwood, H. E.; Goodding, R. A.

    1974-01-01

    The S190A preflight radiometric exposure test data generated as part of preflight and system test of KM-002 Sequence 29 on flight camera S/N 002 was analyzed. The analysis was to determine camera system transmission using available data which included: (1) films exposed to a calibrated light source subject; (2) filter transmission data; (3) calibrated light source data; (4) density vs. log10 exposure curves for the films; and (5) spectral sensitometric data for the films. The procedure used is outlined, and includes the data and a transmission matrix as a function of field position for nine measured points on each station-film-filter-aperture-shutter speed combination.

  13. Calibration of diffuse correlation spectroscopy with a time-resolved near-infrared technique to yield absolute cerebral blood flow measurements

    PubMed Central

    Diop, Mamadou; Verdecchia, Kyle; Lee, Ting-Yim; St Lawrence, Keith

    2011-01-01

    A primary focus of neurointensive care is the prevention of secondary brain injury, mainly caused by ischemia. A noninvasive bedside technique for continuous monitoring of cerebral blood flow (CBF) could improve patient management by detecting ischemia before brain injury occurs. A promising technique for this purpose is diffuse correlation spectroscopy (DCS) since it can continuously monitor relative perfusion changes in deep tissue. In this study, DCS was combined with a time-resolved near-infrared technique (TR-NIR) that can directly measure CBF using indocyanine green as a flow tracer. With this combination, the TR-NIR technique can be used to convert DCS data into absolute CBF measurements. The agreement between the two techniques was assessed by concurrent measurements of CBF changes in piglets. A strong correlation between CBF changes measured by TR-NIR and changes in the scaled diffusion coefficient measured by DCS was observed (R2 = 0.93) with a slope of 1.05 ± 0.06 and an intercept of 6.4 ± 4.3% (mean ± standard error). PMID:21750781

  14. Calibrating ground-based microwave radiometers: Uncertainty and drifts

    NASA Astrophysics Data System (ADS)

    Küchler, N.; Turner, D. D.; Löhnert, U.; Crewell, S.

    2016-04-01

    The quality of microwave radiometer (MWR) calibrations, including both the absolute radiometric accuracy and the spectral consistency, determines the accuracy of geophysical retrievals. The Microwave Radiometer Calibration Experiment (MiRaCalE) was conducted to evaluate the performance of MWR calibration techniques, especially of the so-called Tipping Curve Calibrations (TCC) and Liquid Nitrogen Calibrations (LN2cal), by repeatedly calibrating a fourth-generation Humidity and Temperature Profiler (HATPRO-G4) that measures downwelling radiance between 20 GHz and 60 GHz. MiRaCalE revealed two major points to improve MWR calibrations: (i) the necessary repetition frequency for MWR calibration techniques to correct drifts, which ensures stable long-term measurements; and (ii) the spectral consistency of control measurements of a well known reference is useful to estimate calibration accuracy. Besides, we determined the accuracy of the HATPRO's liquid nitrogen-cooled blackbody's temperature. TCCs and LN2cals were found to agree within 0.5 K when observing the liquid nitrogen-cooled blackbody with a physical temperature of 77 K. This agreement of two different calibration techniques suggests that the brightness temperature of the LN2 cooled blackbody is accurate within at least 0.5 K, which is a significant reduction of the uncertainties that have been assumed to vary between 0.6 K and 1.5 K when calibrating the HATPRO-G4. The error propagation of both techniques was found to behave almost linearly, leading to maximum uncertainties of 0.7 K when observing a scene that is associated with a brightness temperature of 15 K.

  15. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  16. Mapping the pharmacological modulation of brain oxygen metabolism: the effects of caffeine on absolute CMRO2 measured using dual calibrated fMRI.

    PubMed

    Merola, Alberto; Germuska, Michael A; Warnert, Esther Ah; Richmond, Lewys; Helme, Daniel; Khot, Sharmila; Murphy, Kevin; Rogers, Peter J; Hall, Judith E; Wise, Richard G

    2017-03-17

    This study aims to map the acute effects of caffeine ingestion on grey matter oxygen metabolism and haemodynamics with a novel MRI method. Sixteen healthy caffeine consumers (8 males, age = 24.7±5.1) were recruited to this randomised, double-blind, placebo-controlled study. Each participant was scanned on two days before and after the delivery of an oral caffeine (250mg) or placebo capsule. Our measurements were obtained with a newly proposed estimation approach applied to data from a dual calibration fMRI experiment that uses hypercapnia and hyperoxia to modulate brain blood flow and oxygenation. Estimates were based on a forward model that describes analytically the contributions of cerebral blood flow (CBF) and of the measured end-tidal partial pressures of CO2 and O2 to the acquired dual-echo GRE signal. The method allows the estimation of grey matter maps of: oxygen extraction fraction (OEF), CBF, CBF-related cerebrovascular reactivity (CVR) and cerebral metabolic rate of oxygen consumption (CMRO2). Other estimates from a multi inversion time ASL acquisition (mTI-ASL), salivary samples of the caffeine concentration and behavioural measurements are also reported. We observed significant differences between caffeine and placebo on average across grey matter, with OEF showing an increase of 15.6% (SEM ±4.9%, p <0.05) with caffeine, while CBF and CMRO2 showed differences of -30.4% (SEM ±1.6%, p <0.01) and -18.6% (SEM ±2.9%, p <0.01) respectively with caffeine administration. The reduction in oxygen metabolism found is somehow unexpected, but consistent with a hypothesis of decreased energetic demand, supported by previous electrophysiological studies reporting reductions in spectral power with EEG. Moreover the maps of the physiological parameters estimated illustrate the spatial distribution of changes across grey matter enabling us to localise the effects of caffeine with voxel-wise resolution. CBF changes were widespread as reported by previous findings

  17. Instrumentation and First Results of the Reflected Solar Demonstration System for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    McCorkel, Joel; Thome, Kurtis; Hair, Jason; McAndrew, Brendan; Jennings, Don; Rabin, Douglas; Daw, Adrian; Lundsford, Allen

    2012-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission key goals include enabling observation of high accuracy long-term climate change trends, use of these observations to test and improve climate forecasts, and calibration of operational and research sensors. The spaceborne instrument suites include a reflected solar spectroradiometer, emitted infrared spectroradiometer, and radio occultation receivers. The requirement for the RS instrument is that derived reflectance must be traceable to Sl standards with an absolute uncertainty of <0.3% and the error budget that achieves this requirement is described in previo1L5 work. This work describes the Solar/Lunar Absolute Reflectance Imaging Spectroradiometer (SOLARIS), a calibration demonstration system for RS instrument, and presents initial calibration and characterization methods and results. SOLARIS is an Offner spectrometer with two separate focal planes each with its own entrance aperture and grating covering spectral ranges of 320-640, 600-2300 nm over a full field-of-view of 10 degrees with 0.27 milliradian sampling. Results from laboratory measurements including use of integrating spheres, transfer radiometers and spectral standards combined with field-based solar and lunar acquisitions are presented. These results will be used to assess the accuracy and repeatability of the radiometric and spectral characteristics of SOLARIS, which will be presented against the sensor-level requirements addressed in the CLARREO RS instrument error budget.

  18. Uncertainty Assessment of the SeaWiFS On-Orbit Calibration

    NASA Technical Reports Server (NTRS)

    Eplee, Robert E., Jr.; Meister, Gerhard; Patt, Frederick S.; Franz, Bryan A.; McClain, Charles R.

    2011-01-01

    Ocean color climate data records require water-leaving radiances with 5% absolute and 1% relative accuracies as input. Because of the amplification of any sensor calibration errors by the atmospheric correction, the 1% relative accuracy requirement translates into a 0.1% long-term radiometric stability requirement for top-of-the atmosphere radiances. The rigorous on-orbit calibration program developed and implemented for SeaWiFS by the NASA Ocean Biology Processing Group (OBPG) Calibration and Validation Team (CVT) has allowed the CVT to maintain the stability of the radiometric calibration of SeaWiFS at 0.13% or better over the mission. The uncertainties in the resulting calibrated top-of-the-atmosphere (TOA) radiances can be addressed in terms of accuracy (biases in the measurements), precision (scatter in the measurements), and stability (repeatability of the measurements). The calibration biases of lunar observations relative to the USGS RObotic Lunar Observatory (ROLO) photometric model of the Moon are 2-3%. The biases from the vicarious calibration against the Marine Optical Buoy (MOBY) are 1-2%. The precision of the calibration derived from the solar calibration signal-tonoise ratios are 0.16%, from the lunar residuals are 0.13%, and from the vicarious gains are 0.10%. The long-term stability of the TOA radiances, derived from the lunar time series, is 0.13%. The stability of the vicariouslycalibrated TOA radiances, incorporating the uncertainties in the MOBY measurements and the atmospheric correction, is 0.30%. These results allow the OBPG to produce climate data records from the SeaWiFS ocean color data.

  19. Transportable high sensitivity small sample radiometric calorimeter

    SciTech Connect

    Wetzel, J.R.; Biddle, R.S.; Cordova, B.S.; Sampson, T.E.; Dye, H.R.; McDow, J.G.

    1998-12-31

    A new small-sample, high-sensitivity transportable radiometric calorimeter, which can be operated in different modes, contains an electrical calibration method, and can be used to develop secondary standards, will be described in this presentation. The data taken from preliminary tests will be presented to indicate the precision and accuracy of the instrument. The calorimeter and temperature-controlled bath, at present, require only a 30-in. by 20-in. tabletop area. The calorimeter is operated from a laptop computer system using unique measurement module capable of monitoring all necessary calorimeter signals. The calorimeter can be operated in the normal calorimeter equilibration mode, as a comparison instrument, using twin chambers and an external electrical calibration method. The sample chamber is 0.75 in (1.9 cm) in diameter by 2.5 in. (6.35 cm) long. This size will accommodate most {sup 238}Pu heat standards manufactured in the past. The power range runs from 0.001 W to <20 W. The high end is only limited by sample size.

  20. Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot

    NASA Astrophysics Data System (ADS)

    Clausen, J. V.; Frandsen, S.; Bruntt, H.; Olsen, E. H.; Helt, B. E.; Gregersen, K.; Juncher, D.; Krogstrup, P.

    2010-06-01

    Context. Double-lined, detached eclipsing binaries are our main source for accurate stellar masses and radii. In this paper we focus on the 1.15-1.70 M⊙ interval where convective core overshoot is gradually ramped up in theoretical evolutionary models. Aims: We aim to determine absolute dimensions and abundances for the F-type detached eclipsing binary BK Peg, and to perform a detailed comparison with results from recent stellar evolutionary models, including a sample of previously studied systems with accurate parameters. Methods: uvby light curves and uvbyβ standard photometry were obtained with the Strömgren Automatic Telescope, ESO, La Silla, and high-resolution spectra were acquired with the FIES spectrograph at the Nordic Optical Telescope, La Palma. Results: The 5 fd 49 period orbit of BK Peg is slightly eccentric (e = 0.053). The two components are quite different with masses and radii of (1.414 ± 0.007 M⊙, 1.988 ± 0.008 Rsun) and (1.257 ± 0.005 M⊙, 1.474 ± 0.017 Rsun), respectively. The measured rotational velocities are 16.6 ± 0.2 (primary) and 13.4 ± 0.2 (secondary) km s-1. For the secondary component this corresponds to (pseudo)synchronous rotation, whereas the primary component seems to rotate at a slightly lower rate. We derive an iron abundance of [Fe/H] = -0.12 ± 0.07 and similar abundances for Si, Ca, Sc, Ti, Cr and Ni. The stars have evolved to the upper half of the main-sequence band. Yonsei-Yale and Victoria-Regina evolutionary models for the observed metal abundance reproduce BK Peg at ages of 2.75 and 2.50 Gyr, respectively, but tend to predict a lower age for the more massive primary component than for the secondary. We find the same age trend for three other upper main-sequence systems in a sample of well studied eclipsing binaries with components in the 1.15-1.70 M⊙ range. We also find that the Yonsei-Yale models systematically predict higher ages than the Victoria-Regina models. The sample includes BW Aqr, and as a

  1. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  2. Radiometric consistency assessment of hyperspectral infrared sounders

    NASA Astrophysics Data System (ADS)

    Wang, L.; Han, Y.; Jin, X.; Chen, Y.; Tremblay, D. A.

    2015-07-01

    The radiometric and spectral consistency among the Atmospheric Infrared Sounder (AIRS), the Infrared Atmospheric Sounding Interferometer (IASI), and the Cross-track Infrared Sounder (CrIS) is fundamental for the creation of long-term infrared (IR) hyperspectral radiance benchmark datasets for both inter-calibration and climate-related studies. In this study, the CrIS radiance measurements on Suomi National Polar-orbiting Partnership (SNPP) satellite are directly compared with IASI on MetOp-A and -B at the finest spectral scale and with AIRS on Aqua in 25 selected spectral regions through one year of simultaneous nadir overpass (SNO) observations to evaluate radiometric consistency of these four hyperspectral IR sounders. The spectra from different sounders are paired together through strict spatial and temporal collocation. The uniform scenes are selected by examining the collocated Visible Infrared Imaging Radiometer Suite (VIIRS) pixels. Their brightness temperature (BT) differences are then calculated by converting the spectra onto common spectral grids. The results indicate that CrIS agrees well with IASI on MetOp-A and IASI on MetOp-B at the longwave IR (LWIR) and middle-wave IR (MWIR) bands with 0.1-0.2 K differences. There are no apparent scene-dependent patterns for BT differences between CrIS and IASI for individual spectral channels. CrIS and AIRS are compared at the 25 spectral regions for both Polar and Tropical SNOs. The combined global SNO datasets indicate that, the CrIS-AIRS BT differences are less than or around 0.1 K among 21 of 25 comparison spectral regions and they range from 0.15 to 0.21 K in the remaining 4 spectral regions. CrIS-AIRS BT differences in some comparison spectral regions show weak scene-dependent features.

  3. Airborne microwave radiometric imaging system

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Li, Futang; Zhang, Zuyin

    1999-09-01

    A dual channel Airborne Microwave Radiometric Imaging system (AMRI) was designed and constructed for regional environment mapping. The system operates at 35GHz, which collects radiation at horizontal and vertical polarized channels. It runs at mechanical conical scanning with 45 degrees incidence angle. Two Cassegrain antennas with 1.5 degrees beamwidth scan the scene alternately and two pseudo- color images of two channels are displayed on the screen of PC in real time. Simultaneously, all parameters of flight and radiometric data are sorted in hard disk for post- processing. The sensitivity of the radiometer (Delta) T equals 0.16K. A new displaying method, unequal size element arc displaying method, is used in image displaying. Several experiments on mobile tower were carried out and the images demonstrate that the AMRI is available to work steadily and accurately.

  4. A fast RCS accuracy assessment method for passive radar calibrators

    NASA Astrophysics Data System (ADS)

    Zhou, Yongsheng; Li, Chuanrong; Tang, Lingli; Ma, Lingling; Liu, QI

    2016-10-01

    In microwave radar radiometric calibration, the corner reflector acts as the standard reference target but its structure is usually deformed during the transportation and installation, or deformed by wind and gravity while permanently installed outdoor, which will decrease the RCS accuracy and therefore the radiometric calibration accuracy. A fast RCS accuracy measurement method based on 3-D measuring instrument and RCS simulation was proposed in this paper for tracking the characteristic variation of the corner reflector. In the first step, RCS simulation algorithm was selected and its simulation accuracy was assessed. In the second step, the 3-D measuring instrument was selected and its measuring accuracy was evaluated. Once the accuracy of the selected RCS simulation algorithm and 3-D measuring instrument was satisfied for the RCS accuracy assessment, the 3-D structure of the corner reflector would be obtained by the 3-D measuring instrument, and then the RCSs of the obtained 3-D structure and corresponding ideal structure would be calculated respectively based on the selected RCS simulation algorithm. The final RCS accuracy was the absolute difference of the two RCS calculation results. The advantage of the proposed method was that it could be applied outdoor easily, avoiding the correlation among the plate edge length error, plate orthogonality error, plate curvature error. The accuracy of this method is higher than the method using distortion equation. In the end of the paper, a measurement example was presented in order to show the performance of the proposed method.

  5. Laboratory Measurement of Bidirectional Reflectance of Radiometric Tarps

    NASA Technical Reports Server (NTRS)

    Knowlton, Kelly

    2004-01-01

    This experiment measured the reflectance of tarps with ground instruments in order to check radiometric calibration, validate atmospheric correction, and predict at-sensor radiance for satellite instruments. The procedure of this experiment is as follows: 1) Assemble laboratory apparatus to duplicate ground reference measurement geometry and satellite measurement geometry; 2) Measure spectral radiance with Optronics OL 750 double monochromator/spectroradiometer; 3) Measure radiance of NIST-calibrated Spectralon panel irradiated by collimated light at incidence angle of calibrated reflectance (20 deg, 30 deg, 40 deg, or 50 deg), viewing normal to panel surface; 4) Measure radiance of Spectralon panel irradiated at incidence angle equal to solar zenith angle at time of overpass; 5) Calculate reflectance of Spectralon panel irradiated at solar zenith angle, viewing normal to panel surface (ground geometry).

  6. Intercomparison of the LBIR Absolute Cryogenic Radiometers to the NIST Optical Power Measurement Standard

    PubMed Central

    Fedchak, James A.; Carter, Adriaan C.; Datla, Raju

    2006-01-01

    The Low Background Infrared calibration (LBIR) facility at the National Institute of Standards and Technology (NIST) presently maintains four absolute cryogenic radiometers (ACRs) which serve as standard reference detectors for infrared calibrations performed by the facility. The primary standard for optical power measurements at NIST-Gaithersburg has been the High Accuracy Cryogenic Radiometer (HACR). Recently, an improved radiometer, the Primary Optical Watt Radiometer (POWR), has replaced the HACR as the primary standard. In this paper, we present the results of comparisons between the radiometric powers measured by the four ACRs presently maintained by the LBIR facility to that measured by the HACR and POWR. This was done by using a Si photodiode light-trapping detector as a secondary transfer standard to compare the primary national standards to the ACRs maintained by the LBIR facility. The technique used to compare an ACR to the trap detector is described in detail. The absolute optical power measurements are found to be within 0.1 % of the primary standard for all the ACRs examined in this study. PMID:27274936

  7. The 238U/235U isotope ratio of the Earth and the solar system: Constrains from a gravimetrically calibrated U double spike and implications for absolute Pb-Pb ages

    NASA Astrophysics Data System (ADS)

    Weyer, Stefan; Noordmann, Janine; Brennecka, Greg; Richter, Stephan

    2010-05-01

    The ratio of 238U and 235U, the two primordial U isotopes, has been assumed to be constant on Earth and in the solar system. The commonly accepted value for the 238U/235U ratio, which has been used in Pb-Pb dating for the last ~ 30 years, was 137.88. Within the last few years, it has been shown that 1) there are considerable U isotope variations (~1.3‰) within terrestrial material produced by isotope fractionation during chemical reactions [1-3] and 2) there are even larger isotope variations (at least 3.5‰) in calcium-aluminum-rich inclusions (CAIs) in meoteorites that define the currently accepted age of the solar system [4]. These findings are dramatic for geochronology, as a known 238U/235U is a requirement for Pb-Pb dating, the most precise dating technique for absolute ages. As 238U/235U variations can greatly affect the reported absolute Pb-Pb age, understanding and accurately measuring variation of the 238U/235U ratio in various materials is critical, With these new findings, the questions also arises of "How well do we know the average U isotope composition of the Earth and the solar system?" and "How accurate can absolute Pb-Pb ages be?" Our results using a gravimetrically calibrated 233U/236U double spike IRMM 3636 [5] indicate that the U standard NBL 950a, which was commonly used to define the excepted "natural" 238U/235U isotope ratio, has a slightly lower 238U/235U of 137.836 ± 0.024. This value is indistinguishable from the U isotope compositions for NBL 960 and NBL112A, which have been determined by several laboratories, also using the newly calibrated U double spike IRMM 3636 [6]. These findings provide new implications about the average U isotope composition of the Earth and the solar system. Basalts display a very tight range of U isotope variations (~0.25-0.32‰ relative to SRM 950a). Their U isotope composition is also very similar to that of chondrites [4], which however appear to show a slightly larger spread. Accepting terrestrial

  8. Mars Exploration Rover Navigation Camera in-flight calibration

    USGS Publications Warehouse

    Soderblom, J.M.; Bell, J.F.; Johnson, J. R.; Joseph, J.; Wolff, M.J.

    2008-01-01

    The Navigation Camera (Navcam) instruments on the Mars Exploration Rover (MER) spacecraft provide support for both tactical operations as well as scientific observations where color information is not necessary: large-scale morphology, atmospheric monitoring including cloud observations and dust devil movies, and context imaging for both the thermal emission spectrometer and the in situ instruments on the Instrument Deployment Device. The Navcams are a panchromatic stereoscopic imaging system built using identical charge-coupled device (CCD) detectors and nearly identical electronics boards as the other cameras on the MER spacecraft. Previous calibration efforts were primarily focused on providing a detailed geometric calibration in line with the principal function of the Navcams, to provide data for the MER navigation team. This paper provides a detailed description of a new Navcam calibration pipeline developed to provide an absolute radiometric calibration that we estimate to have an absolute accuracy of 10% and a relative precision of 2.5%. Our calibration pipeline includes steps to model and remove the bias offset, the dark current charge that accumulates in both the active and readout regions of the CCD, and the shutter smear. It also corrects pixel-to-pixel responsivity variations using flat-field images, and converts from raw instrument-corrected digital number values per second to units of radiance (W m-2 nm-1 sr-1), or to radiance factor (I/F). We also describe here the initial results of two applications where radiance-calibrated Navcam data provide unique information for surface photometric and atmospheric aerosol studies. Copyright 2008 by the American Geophysical Union.

  9. A calibration concept for passive MW imaging using beam steering by frequency shift and aperture synthesis

    NASA Astrophysics Data System (ADS)

    Schreiber, Eric; Peichl, Markus; Jirousek, Matthias

    2013-10-01

    Passive microwave (MW) remote sensing is used in Earth observation missions for example to estimate the salinity of oceans or the soil moisture of landscapes. In these cases the absolute brightness temperature numbers are important for sufficient accuracy of the estimated geo-physical parameters. Consequently a suitable system calibration network is required. At DLR a radiometric demonstrator for fully-electronic MW imaging was set up at Ka-band, which is based on a combination of beam steering by frequency shift using a broadband slotted-waveguide antenna for one scanning direction, and the application of aperture synthesis for the other direction. Aperture synthesis is well known from radio astronomy, but it is still a new imaging principle for Earth observation or security applications. Hence as well new calibration techniques have to be developed for this kind of scanning mechanism. In this paper a novel approach for a noise-source based calibration method taking into account the antenna losses will be introduced. When using aperture synthesis techniques to determine the absolute brightness temperature values, it is very important, among other things, to know the exact phase transfer function of the system in order to achieve the desired radiometric resolution. Consequently our approach enables phase calibration as well. The paper outlines a proof of concept for this calibration method using a two-element interferometer called VESAS (Voll Elektronischer Scanner mit AperturSynthese) as a demonstrator. The functionality of the demonstrator and the proof of concept of the imaging principle mentioned before are written in detail in [1].

  10. Improved thermal-vacuum compatible flat plate radiometric source for system-level testing of remote optical sensors

    NASA Astrophysics Data System (ADS)

    Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.

    2016-09-01

    In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance. Keywords: Calibration, radiometry, remote sensing, source.

  11. High speed radiometric measurements of IED detonation fireballs

    NASA Astrophysics Data System (ADS)

    Spidell, Matthew T.; Gordon, J. Motos; Pitz, Jeremey; Gross, Kevin C.; Perram, Glen P.

    2010-04-01

    Continuum emission is predominant in fireball spectral phenomena and in some demonstrated cases, fine detail in the temporal evolution of infrared spectral emissions can be used to estimate size and chemical composition of the device. Recent work indicates that a few narrow radiometric bands may reveal forensic information needed for the explosive discrimination and classification problem, representing an essential step in moving from "laboratory" measurements to a rugged, fieldable system. To explore phenomena not observable in previous experiments, a high speed (10μs resolution) radiometer with four channels spanning the infrared spectrum observed the detonation of nine home made explosive (HME) devices in the < 100lb class. Radiometric measurements indicate that the detonation fireball is well approximated as a single temperature blackbody at early time (0 < t <~ 3ms). The effective radius obtained from absolute intensity indicates fireball growth at supersonic velocity during this time. Peak fireball temperatures during this initial detonation range between 3000.3500K. The initial temperature decay with time (t <~ 10ms) can be described by a simple phenomenological model based on radiative cooling. After this rapid decay, temperature exhibits a small, steady increase with time (10 <~ t <~ 50ms) and peaking somewhere between 1000.1500K-likely the result of post-detonation combustion-before subsequent cooling back to ambient conditions . Radius derived from radiometric measurements can be described well (R2 > 0.98) using blast model functional forms, suggesting that energy release could be estimated from single-pixel radiometric detectors. Comparison of radiometer-derived fireball size with FLIR infrared imagery indicate the Planckian intensity size estimates are about a factor of two smaller than the physical extent of the fireball.

  12. Detecting the radiometric changes of FY-3A/MERSI reflective solar bands by use of stable desert sites

    NASA Astrophysics Data System (ADS)

    Wang, Ling; Chen, Lin; Hu, Xiuqing

    2014-11-01

    To monitor changes in sensor performance and sensor calibration is a critical step to ensure data quality and to meet the needs of quantitative remote sensing in a broad range of scientific applications. One of the least expensive and increasingly popular methods of on-orbit calibration has been the use of large-area stable terrestrial sites. In this study, three stable desert sites of Libya-1, Sonora, and Arabia-2 are used to assessment the radiometric changes of reflective solar bands of FY-3A/MERSI from May 2008 to Dec. 2013. For each site, two BRDF models are established using the TOA reflectance measurements in the winter half-year and summer half-year late in the mission. Then, the degradation rates of RSBs of MERSI are predicted using an exponential fit of the BRDF-corrected time series. Results show that the use of two BRDF models is effective to removal of seasonal oscillation caused by angular effects. Degradation rates from three desert sites are in good agreement, with the standard deviation less than 1.5% for most of the bands. When compared with the DCC method, consistent detecting results are found, and the absolute deviation is less than 3% for most of the channels.

  13. Absolute Standards for Climate Measurements

    NASA Astrophysics Data System (ADS)

    Leckey, J.

    2016-10-01

    In a world of changing climate, political uncertainty, and ever-changing budgets, the benefit of measurements traceable to SI standards increases by the day. To truly resolve climate change trends on a decadal time scale, on-orbit measurements need to be referenced to something that is both absolute and unchanging. One such mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) that will measure a variety of climate variables with an unprecedented accuracy to definitively quantify climate change. In the CLARREO mission, we will utilize phase change cells in which a material is melted to calibrate the temperature of a blackbody that can then be observed by a spectrometer. A material's melting point is an unchanging physical constant that, through a series of transfers, can ultimately calibrate a spectrometer on an absolute scale. CLARREO consists of two primary instruments: an infrared (IR) spectrometer and a reflected solar (RS) spectrometer. The mission will contain orbiting radiometers with sufficient accuracy to calibrate other space-based instrumentation and thus transferring the absolute traceability. The status of various mission options will be presented.

  14. MODIS Cloud Optical Property Retrieval Uncertainties Derived from Pixel-Level VNIR/SWIR Radiometric Uncertainties

    NASA Technical Reports Server (NTRS)

    Platnick, S.; Wind, G.; Xiong, X.

    2011-01-01

    Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals of optical thickness and effective particle radius for liquid water and ice phase clouds employ a well-known VNIR/ SWIR solar reflectance technique. For this type of algorithm, we evaluate the quantitative uncertainty in simultaneous retrievals of these two cloud parameters to pixel-level radiometric calibration estimates and other fundamental (and tractable) error sources.

  15. Landsat-8 Operational Land Imager (OLI) radiometric performance on-orbit

    USGS Publications Warehouse

    Morfitt, Ron; Barsi, Julia A.; Levy, Raviv; Markham, Brian L.; Micijevic, Esad; Ong, Lawrence; Scaramuzza, Pat; Vanderwerff, Kelly

    2015-01-01

    Expectations of the Operational Land Imager (OLI) radiometric performance onboard Landsat-8 have been met or exceeded. The calibration activities that occurred prior to launch provided calibration parameters that enabled ground processing to produce imagery that met most requirements when data were transmitted to the ground. Since launch, calibration updates have improved the image quality even more, so that all requirements are met. These updates range from detector gain coefficients to reduce striping and banding to alignment parameters to improve the geometric accuracy. This paper concentrates on the on-orbit radiometric performance of the OLI, excepting the radiometric calibration performance. Topics discussed in this paper include: signal-to-noise ratios that are an order of magnitude higher than previous Landsat missions; radiometric uniformity that shows little residual banding and striping, and continues to improve; a dynamic range that limits saturation to extremely high radiance levels; extremely stable detectors; slight nonlinearity that is corrected in ground processing; detectors that are stable and 100% operable; and few image artifacts.

  16. Radiometric studies of Mycobacterium lepraemurium.

    PubMed

    Camargo, E E; Larson, S M; Tepper, B S; Wagner, H N

    1976-01-01

    The radiometric method has been applied for studying the metabolism of M. lepraemurium and the conditions which might force or inhibit its metabolic activity in vitro. These organisms assimilate and oxidize (U-14C) glycerol, and (U-14C) acetate, but are unable to oxidize (U-14C) glucose, (U-14C) pyruvate, (U-14C) glycine and 14C-formate. When incubated at 30 degrees C M. lepraemurium oxidizes (U-14C) acetate to 14CO2 faster than 37 degrees C. The smae effect was observed with increasing concentrations of polysorbate 80 (Tween 80), or the 14C-substrate. No change in metabolic rate was observed when the organisms were kept at -20 degrees C for 12 days. Although tried several times, it was not possible to demonstrate any "inhibitors" of bacterial metabolism in the reaction system. The radiometric method seems to be an important tool for studying metabolic pathways and the influence of physical and biochemical factors on the metabolism of M. lepraemurium in vitro.

  17. ASTER preflight and inflight calibration and the validation of level 2 products

    USGS Publications Warehouse

    Thome, K.; Aral, K.; Hook, S.; Kieffer, H.; Lang, H.; Matsunaga, T.; Ono, A.; Palluconi, F. D.; Sakuma, H.; Slater, P.; Takashima, T.; Tonooka, H.; Tsuchida, S.; Welch, R.M.; Zalewski, E.

    1998-01-01

    This paper describes the preflight and inflight calibration approaches used for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The system is a multispectral, high-spatial resolution sensor on the Earth Observing System's (EOS)-AMl platform. Preflight calibration of ASTER uses well-characterized sources to provide calibration and preflight round-robin exercises to understand biases between the calibration sources of ASTER and other EOS sensors. These round-robins rely on well-characterized, ultra-stable radiometers. An experiment held in Yokohama, Japan, showed that the output from the source used for the visible and near-infrared (VNIR) subsystem of ASTER may be underestimated by 1.5%, but this is still within the 4% specification for the absolute, radiometric calibration of these bands. Inflight calibration will rely on vicarious techniques and onboard blackbodies and lamps. Vicarious techniques include ground-reference methods using desert and water sites. A recent joint field campaign gives confidence that these methods currently provide absolute calibration to better than 5%, and indications are that uncertainties less than the required 4% should be achievable at launch. The EOS-AMI platform will also provide a spacecraft maneuver that will allow ASTER to see the moon, allowing further characterization of the sensor. A method for combining the results of these independent calibration results is presented. The paper also describes the plans for validating the Level 2 data products from ASTER. These plans rely heavily upon field campaigns using methods similar to those used for the ground-reference, vicarious calibration methods. ?? 1998 IEEE.

  18. Novel techniques for the analysis of the TOA radiometric uncertainty

    NASA Astrophysics Data System (ADS)

    Gorroño, Javier; Banks, Andrew; Gascon, Ferran; Fox, Nigel P.; Underwood, Craig I.

    2016-10-01

    In the framework of the European Copernicus programme, the European Space Agency (ESA) has launched the Sentinel-2 (S2) Earth Observation (EO) mission which provides optical high spatial -resolution imagery over land and coastal areas. As part of this mission, a tool (named S2-RUT, from Sentinel-2 Radiometric Uncertainty Tool) estimates the radiometric uncertainties associated to each pixel using as input the top-of-atmosphere (TOA) reflectance factor images provided by ESA. The initial version of the tool has been implemented — code and user guide available1 — and integrated as part of the Sentinel Toolbox. The tool required the study of several radiometric uncertainty sources as well as the calculation and validation of the combined standard uncertainty in order to estimate the TOA reflectance factor uncertainty per pixel. Here we describe the recent research in order to accommodate novel uncertainty contributions to the TOA reflectance uncertainty estimates in future versions of the tool. The two contributions that we explore are the radiometric impact of the spectral knowledge and the uncertainty propagation of the resampling associated to the orthorectification process. The former is produced by the uncertainty associated to the spectral calibration as well as the spectral variations across the instrument focal plane and the instrument degradation. The latter results of the focal plane image propagation into the provided orthoimage. The uncertainty propagation depends on the radiance levels on the pixel neighbourhood and the pixel correlation in the temporal and spatial dimensions. Special effort has been made studying non-stable scenarios and the comparison with different interpolation methods.

  19. Imager for Mars Pathfinder (IMP) image calibration

    USGS Publications Warehouse

    Reid, R.J.; Smith, P.H.; Lemmon, M.; Tanner, R.; Burkland, M.; Wegryn, E.; Weinberg, J.; Marcialis, R.; Britt, D.T.; Thomas, N.; Kramm, R.; Dummel, A.; Crowe, D.; Bos, B.J.; Bell, J.F.; Rueffer, P.; Gliem, F.; Johnson, J. R.; Maki, J.N.; Herkenhoff, K. E.; Singer, Robert B.

    1999-01-01

    The Imager for Mars Pathfinder returned over 16,000 high-quality images from the surface of Mars. The camera was well-calibrated in the laboratory, with <5% radiometric uncertainty. The photometric properties of two radiometric targets were also measured with 3% uncertainty. Several data sets acquired during the cruise and on Mars confirm that the system operated nominally throughout the course of the mission. Image calibration algorithms were developed for landed operations to correct instrumental sources of noise and to calibrate images relative to observations of the radiometric targets. The uncertainties associated with these algorithms as well as current improvements to image calibration are discussed. Copyright 1999 by the American Geophysical Union.

  20. Performance Assessment and Geometric Calibration of RESOURCESAT-2

    NASA Astrophysics Data System (ADS)

    Radhadevi, P. V.; Solanki, S. S.; Akilan, A.; Jyothi, M. V.; Nagasubramanian, V.

    2016-06-01

    Resourcesat-2 (RS-2) has successfully completed five years of operations in its orbit. This satellite has multi-resolution and multi-spectral capabilities in a single platform. A continuous and autonomous co-registration, geo-location and radiometric calibration of image data from different sensors with widely varying view angles and resolution was one of the challenges of RS-2 data processing. On-orbit geometric performance of RS-2 sensors has been widely assessed and calibrated during the initial phase operations. Since then, as an ongoing activity, various geometric performance data are being generated periodically. This is performed with sites of dense ground control points (GCPs). These parameters are correlated to the direct geo-location accuracy of the RS-2 sensors and are monitored and validated to maintain the performance. This paper brings out the geometric accuracy assessment, calibration and validation done for about 500 datasets of RS-2. The objectives of this study are to ensure the best absolute and relative location accuracy of different cameras, location performance with payload steering and co-registration of multiple bands. This is done using a viewing geometry model, given ephemeris and attitude data, precise camera geometry and datum transformation. In the model, the forward and reverse transformations between the coordinate systems associated with the focal plane, payload, body, orbit and ground are rigorously and explicitly defined. System level tests using comparisons to ground check points have validated the operational geo-location accuracy performance and the stability of the calibration parameters.

  1. A procedure for radiometric recalibration of Landsat 5 TM reflective-band data

    USGS Publications Warehouse

    Chander, G.; Haque, M.O.; Micijevic, E.; Barsi, J.A.

    2010-01-01

    From the Landsat program's inception in 1972 to the present, the Earth science user community has been benefiting from a historical record of remotely sensed data. The multispectral data from the Landsat 5 (L5) Thematic Mapper (TM) sensor provide the backbone for this extensive archive. Historically, the radiometric calibration procedure for the L5 TM imagery used the detectors' response to the internal calibrator (IC) on a scene-by-scene basis to determine the gain and offset for each detector. The IC system degraded with time, causing radiometric calibration errors up to 20%. In May 2003, the L5 TM data processed and distributed by the U.S. Geological Survey (USGS) Earth Resources Observation and Science Center through the National Landsat Archive Production System (NLAPS) were updated to use a lifetime lookup-table (LUT) gain model to radiometrically calibrate TM data instead of using scene-specific IC gains. Further modification of the gain model was performed in 2007. The L5 TM data processed using IC prior to the calibration update do not benefit from the recent calibration revisions. A procedure has been developed to give users the ability to recalibrate their existing level-1 products. The best recalibration results are obtained if the work-order report that was included in the original standard data product delivery is available. However, if users do not have the original work-order report, the IC trends can be used for recalibration. The IC trends were generated using the radiometric gain trends recorded in the NLAPS database. This paper provides the details of the recalibration procedure for the following: 1) data processed using IC where users have the work-order file; 2) data processed using IC where users do not have the work-order file; 3) data processed using prelaunch calibration parameters; and 4) data processed using the previous version of the LUT (e.g., LUT03) that was released before April 2, 2007.

  2. Modeling the Radiance of the Moon for On-orbit Calibration

    USGS Publications Warehouse

    Stone, T.C.; Kieffer, H.H.; Becker, K.J.; ,

    2003-01-01

    The RObotic Lunar Observatory (ROLO) project has developed radiometric models of the Moon for disk-integrated irradiance and spatially resolved radiance. Although the brightness of the Moon varies spatially and with complex dependencies upon illumination and viewing geometry, the surface photometric properties are extremely stable, and therefore potentially knowable to high accuracy. The ROLO project has acquired 5+ years of spatially resolved lunar images in 23 VNIR and 9 SWIR filter bands at phase angles up to 90??. These images are calibrated to exoatmospheric radiance using nightly stellar observations in a band-coupled extinction algorithm and a radiometric scale based upon observations of the star Vega. An effort is currently underway to establish an absolute scale with direct traceability to NIST radiometric standards. The ROLO radiance model performs linear fitting of the spatially resolved lunar image data on an individual pixel basis. The results are radiance images directly comparable to spacecraft observations of the Moon. Model-generated radiance images have been produced for the ASTER lunar view conducted on 14 April 2003. The radiance model is still experimental - simplified photometric functions have been used, and initial results show evidence of computational instabilities, particularly at the lunar poles. The ROLO lunar image dataset is unique and extensive and presents opportunities for development of novel approaches to lunar photometric modeling.

  3. Reduction of radiometric miscalibration--applications to pushbroom sensors.

    PubMed

    Rogass, Christian; Spengler, Daniel; Bochow, Mathias; Segl, Karl; Lausch, Angela; Doktor, Daniel; Roessner, Sigrid; Behling, Robert; Wetzel, Hans-Ulrich; Kaufmann, Hermann

    2011-01-01

    The analysis of hyperspectral images is an important task in Remote Sensing. Foregoing radiometric calibration results in the assignment of incident electromagnetic radiation to digital numbers and reduces the striping caused by slightly different responses of the pixel detectors. However, due to uncertainties in the calibration some striping remains. This publication presents a new reduction framework that efficiently reduces linear and nonlinear miscalibrations by an image-driven, radiometric recalibration and rescaling. The proposed framework-Reduction Of Miscalibration Effects (ROME)-considering spectral and spatial probability distributions, is constrained by specific minimisation and maximisation principles and incorporates image processing techniques such as Minkowski metrics and convolution. To objectively evaluate the performance of the new approach, the technique was applied to a variety of commonly used image examples and to one simulated and miscalibrated EnMAP (Environmental Mapping and Analysis Program) scene. Other examples consist of miscalibrated AISA/Eagle VNIR (Visible and Near Infrared) and Hawk SWIR (Short Wave Infrared) scenes of rural areas of the region Fichtwald in Germany and Hyperion scenes of the Jalal-Abad district in Southern Kyrgyzstan. Recovery rates of approximately 97% for linear and approximately 94% for nonlinear miscalibrated data were achieved, clearly demonstrating the benefits of the new approach and its potential for broad applicability to miscalibrated pushbroom sensor data.

  4. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  5. Spectroradiometric considerations for advanced land observing systems

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1986-01-01

    Research aimed at improving the inflight absolute radiometric calibration of advanced land observing systems was initiated. Emphasis was on the satellite sensor calibration program at White Sands. Topics addressed include: absolute radiometric calibration of advanced remote sensing; atmospheric effects on reflected radiation; inflight radiometric calibration; field radiometric methods for reflectance and atmospheric measurement; and calibration of field relectance radiometers.

  6. Forty-Year Calibrated Record of Earth-Surface Reflected Radiance from Landsat: A Review

    NASA Technical Reports Server (NTRS)

    Markham, Brian; Helder, Dennis

    2011-01-01

    system to which the radiometric scale was extended. The limited and broken use of the Landsat-4 TM made this analysis more difficult. Eight-day separated image pairs from Landsat-5 combined with analysis of pseudo invariant sites established this history. The fourth and most challenging effort was making the Landsat-1 to -5 MSS sensors' data internally radiometrically consistent. This effort was particularly complicated by the age of the MSS data, varying formats and processing levels in the archive, limited datasets, and limited documentation available. Ultimately, pseudo-invariant sites were identified in North America and used for this effort. Note that most of the Landsat-MSS archived data had already been calibrated using the MSS internal calibrators, so this processing was imbedded in the result. The final effort was developing an absolute scale for Landsat MSS similar to what was already established for the "TM" sensors. This was accomplished by using simultaneous data from Landsat-5 MSS and Landsat-5 TM, accounting for spectral differences between the sensors using EO-1 Hyperion data. The recalibrated history of the Landsat data and implications to users are discussed. The key result from this work is a consistently calibrated Landsat data archive that spans nearly 40 years with total uncertainties on the order of 10% or less for most sensors and bands.

  7. Radiometric responsivity determination for Feature Identification and Location Experiment (FILE) flown on space shuttle mission

    NASA Technical Reports Server (NTRS)

    Wilson, R. G.; Davis, R. E.; Wright, R. E., Jr.; Sivertson, W. E., Jr.; Bullock, G. F.

    1986-01-01

    A procedure was developed to obtain the radiometric (radiance) responsivity of the Feature Identification and Local Experiment (FILE) instrument in preparation for its flight on Space Shuttle Mission 41-G (November 1984). This instrument was designed to obtain Earth feature radiance data in spectral bands centered at 0.65 and 0.85 microns, along with corroborative color and color-infrared photographs, and to collect data to evaluate a technique for in-orbit autonomous classification of the Earth's primary features. The calibration process incorporated both solar radiance measurements and radiative transfer model predictions in estimating expected radiance inputs to the FILE on the Shuttle. The measured data are compared with the model predictions, and the differences observed are discussed. Application of the calibration procedure to the FILE over an 18-month period indicated a constant responsivity characteristic. This report documents the calibration procedure and the associated radiometric measurements and predictions that were part of the instrument preparation for flight.

  8. Chasing the TIRS ghosts: calibrating the Landsat 8 thermal bands

    NASA Astrophysics Data System (ADS)

    Schott, John R.; Gerace, Aaron; Raqueno, Nina; Ientilucci, Emmett; Raqueno, Rolando; Lunsford, Allen W.

    2014-10-01

    The Thermal Infrared Sensor (TIRS) on board Landsat 8 has exhibited a number of anomalous characteristics that have made it difficult to calibrate. These anomalies include differences in the radiometric appearance across the blackbody pre- and post-launch, variations in the cross calibration ratios between detectors that overlap on adjacent arrays (resulting in banding) and bias errors in the absolute calibration that can change spatially/temporally. Several updates to the TIRS calibration procedures were made in the months after launch to attempt to mitigate the impact of these anomalies on flat fielding (cosmetic removal of banding and striping) and mean level bias correction. As a result, banding and striping variations have been reduced but not eliminated and residual bias errors in band 10 should be less than 2 degrees for most targets but can be significantly more in some cases and are often larger in band 11. These corrections have all been essentially ad hoc without understanding or properly accounting for the source of the anomalies, which were, at the time unknown. This paper addresses the procedures that have been undertaken to; better characterize the nature of these anomalies, attempt to identify the source(s) of the anomalies, quantify the phenomenon responsible for them, and develop correction procedures to more effectively remove the impacts on the radiometric products. Our current understanding points to all of the anomalies being the result of internal reflections of energy from outside the target detector's field-of-view, and often outside the telescope field-of-view, onto the target detector. This paper discusses how various members of the Landsat calibration team discovered the clues that led to how; these "ghosts" were identified, they are now being characterized, and their impact can hopefully eventually be corrected. This includes use of lunar scans to generate initial maps of influence regions, use of long path overlap ratios to explore

  9. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  10. Calibration of the visible and near-infrared channels of the LANDSAT-5 Thematic Mapper using high-altitude aircraft measurements

    NASA Technical Reports Server (NTRS)

    Smith, G. R.; Levin, R. H.; Knoll, J. S.; Koyanagi, R. S.; Wrigley, R. C.

    1990-01-01

    Visible near-infrared sensors mounted on operational satellites now in use do not have on-board full aperture absolute calibration devices. One means of establishing an in-orbit calibration for a satellite sensor is to make simultaneous measurements of a bright, uniform scene along the satellite view vector from a calibrated instrument on board a high altitude aircraft. In the work reported here, aircraft data were recorded over White Sands, New Mexico at satellite overpass time for the LANDSAT-5 Thematic Mapper (TM). A comparison of the coincident aircraft and orbiting satellite data showed the radiometric gain for TM channel 1 had degraded 4.7 percent by August 28, 1985; gains for TM channels 2 and 3 were within 1 percent of prelaunch values.

  11. Deep Space Network Radiometric Remote Sensing Program

    NASA Technical Reports Server (NTRS)

    Walter, Steven J.

    1994-01-01

    Planetary spacecraft are viewed through a troposphere that absorbs and delays radio signals propagating through it. Tropospheric water, in the form of vapor, cloud liquid, and precipitation, emits radio noise which limits satellite telemetry communication link performance. Even at X-band, rain storms have severely affected several satellite experiments including a planetary encounter. The problem will worsen with DSN implementation of Ka-band because communication link budgets will be dominated by tropospheric conditions. Troposphere-induced propagation delays currently limit VLBI accuracy and are significant sources of error for Doppler tracking. Additionally, the success of radio science programs such as satellite gravity wave experiments and atmospheric occultation experiments depends on minimizing the effect of water vapor-induced propagation delays. In order to overcome limitations imposed by the troposphere, the Deep Space Network has supported a program of radiometric remote sensing. Currently, water vapor radiometers (WVRs) and microwave temperature profilers (MTPs) support many aspects of the Deep Space Network operations and research and development programs. Their capability to sense atmospheric water, microwave sky brightness, and atmospheric temperature is critical to development of Ka-band telemetry systems, communication link models, VLBI, satellite gravity wave experiments, and radio science missions. During 1993, WVRs provided data for propagation model development, supported planetary missions, and demonstrated advanced tracking capability. Collection of atmospheric statistics is necessary to model and predict performance of Ka-band telemetry links, antenna arrays, and radio science experiments. Since the spectrum of weather variations has power at very long time scales, atmospheric measurements have been requested for periods ranging from one year to a decade at each DSN site. The resulting database would provide reliable statistics on daily

  12. Improved Thermal-Vacuum Compatible Flat Plate Radiometric Source For System-Level Testing Of Optical Sensors

    NASA Technical Reports Server (NTRS)

    Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.

    2016-01-01

    In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance.

  13. Extended- and Point-Source Radiometric Program

    DTIC Science & Technology

    1962-08-08

    Radiometric Measurements of Cs1 37 Sources Made with NaI Detector. . 60 6.2 Aerial Radiometric Measurements of Co 60 Sources Made with Bioplastic ...Hanford aircraft consisted of an NaI scintillator, bioplastic scintillator, and a 40-liter ionization chamber. The aircraft employed was a twin-engine...supply, amplifier, and count rate, was transistorized portable equipment designed and fabricated at Hanford. The bioplastic instrument consisted of a 5

  14. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  15. Flight Calibration of the LROC Narrow Angle Camera

    NASA Astrophysics Data System (ADS)

    Humm, D. C.; Tschimmel, M.; Brylow, S. M.; Mahanti, P.; Tran, T. N.; Braden, S. E.; Wiseman, S.; Danton, J.; Eliason, E. M.; Robinson, M. S.

    2016-04-01

    Characterization and calibration are vital for instrument commanding and image interpretation in remote sensing. The Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) takes 500 Mpixel greyscale images of lunar scenes at 0.5 meters/pixel. It uses two nominally identical line scan cameras for a larger crosstrack field of view. Stray light, spatial crosstalk, and nonlinearity were characterized using flight images of the Earth and the lunar limb. These are important for imaging shadowed craters, studying ˜1 meter size objects, and photometry respectively. Background, nonlinearity, and flatfield corrections have been implemented in the calibration pipeline. An eight-column pattern in the background is corrected. The detector is linear for DN = 600--2000 but a signal-dependent additive correction is required and applied for DN<600. A predictive model of detector temperature and dark level was developed to command dark level offset. This avoids images with a cutoff at DN=0 and minimizes quantization error in companding. Absolute radiometric calibration is derived from comparison of NAC images with ground-based images taken with the Robotic Lunar Observatory (ROLO) at much lower spatial resolution but with the same photometric angles.

  16. The First SIMBIOS Radiometric Intercomparison (SIMRIC-1), April-September 2001

    NASA Technical Reports Server (NTRS)

    Meister, Gerhard; Abel, Peter; McClain, Charles; Barnes, Robert; Fargion, Giulietta; Cooper, John; Davis, Curtiss; Korwan, Daniel; Godin, Mike; Maffione, Robert

    2002-01-01

    This report describes the first SIMBIOS (Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies) Radiometric Intercomparison (SIMRIC-1). The purpose of the SIMRIC-1 is to ensure a common radiometric scale of the calibration facilities that are engaged in calibrating in situ radiometers used for ocean color related research and to document the calibration procedures and protocols. SIMBIOS staff visited the seven participating laboratories for at least two days each. The SeaWiFS Transfer Radiometer SXR-II measured the calibration radiances produced in the laboratories. The measured radiances were compared with the radiances expected by the laboratories. Typically, the measured radiances were higher than the expected radiances by 0 to 2%. This level of agreement is satisfactory. Several issues were identified, where the calibration protocols need to be improved, especially the reflectance calibration of the reference plaques and the distance correction when using the irradiance standards at distances greater than the 50 cm. The responsivity of the SXR-II changed between 0.3% (channel 6) and 1.6% (channel 2) from December 2000 to December 2001. Monitoring the SXR-II with a portable light source showed a linear drift of the calibration, except for channel 1, where a 2% drop occurred in summer.

  17. A plan for the characterization, calibration, and evaluation of LAPR-2

    NASA Technical Reports Server (NTRS)

    Ilrons, J. R.; Smith, J. C.; Blaine, L. R.; Finkel, M. W.

    1982-01-01

    A new airborne Linear Array Pushbroom Radiometer (LAPR-II) was built. LAPR-II will use linear arrays of silicon detectors to acquire four channels of digital image data for spectral bands within the visible and near infrared portions of the spectrum (0.4 - 1.0 micrometers). The data will be quantized to 10 bits, and spectral filters for each channel will be changeable in flight. The instrument will initially be flown aboard a NASA/Wallo