Science.gov

Sample records for absolute radiance calibration

  1. A new method for the absolute radiance calibration for UV-vis measurements of scattered sunlight

    NASA Astrophysics Data System (ADS)

    Wagner, T.; Beirle, S.; Dörner, S.; Penning de Vries, M.; Remmers, J.; Rozanov, A.; Shaiganfar, R.

    2015-10-01

    Absolute radiometric calibrations are important for measurements of the atmospheric spectral radiance. Such measurements can be used to determine actinic fluxes, the properties of aerosols and clouds, and the shortwave energy budget. Conventional calibration methods in the laboratory are based on calibrated light sources and reflectors and are expensive, time consuming and subject to relatively large uncertainties. Also, the calibrated instruments might change during transport from the laboratory to the measurement sites. Here we present a new calibration method for UV-vis instruments that measure the spectrally resolved sky radiance, for example zenith sky differential optical absorption spectroscopy (DOAS) instruments or multi-axis (MAX)-DOAS instruments. Our method is based on the comparison of the solar zenith angle dependence of the measured zenith sky radiance with radiative transfer simulations. For the application of our method, clear-sky measurements during periods with almost constant aerosol optical depth are needed. The radiative transfer simulations have to take polarisation into account. We show that the calibration results are almost independent from the knowledge of the aerosol optical properties and surface albedo, which causes a rather small uncertainty of about < 7 %. For wavelengths below about 330 nm it is essential that the ozone column density during the measurements be constant and known.

  2. 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.

  3. Reflectance- and radiance-based methods for the in-flight absolute calibration of multispectral sensors

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.

    1987-01-01

    Variations reported in the in-flight absolute radiometric calibration of the Coastal Zone Color Scanner (CZCS) and the Thematic Mapper (TM) on Landsat 4 are reviewed. At short wavelengths these sensors exhibited a gradual reduction in response, while in the midinfrared the TM showed oscillatory variations, according to the results of TM internal calibration. The methodology and results are presented for five reflectance-based calibrations of the Landsat 5 TM at White Sands, NM, in the period July 1984 to November 1985. These show a + or - 2.8 percent standard deviation for the six solar-reflective bands. Analysis and preliminary results of a second, independent calibration method, based on radiance measurements from a helicopter at White Sands, indicate that this is potentially an accurate method for corroborating the results from the reflectance-based method.

  4. Reflectance- and radiance-based methods for the in-flight absolute calibration of multispectral sensors

    NASA Astrophysics Data System (ADS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.

    1987-06-01

    Variations reported in the in-flight absolute radiometric calibration of the Coastal Zone Color Scanner (CZCS) and the Thematic Mapper (TM) on Landsat 4 are reviewed. At short wavelengths these sensors exhibited a gradual reduction in response, while in the midinfrared the TM showed oscillatory variations, according to the results of TM internal calibration. The methodology and results are presented for five reflectance-based calibrations of the Landsat 5 TM at White Sands, NM, in the period July 1984 to November 1985. These show a + or - 2.8 percent standard deviation for the six solar-reflective bands. Analysis and preliminary results of a second, independent calibration method, based on radiance measurements from a helicopter at White Sands, indicate that this is potentially an accurate method for corroborating the results from the reflectance-based method.

  5. A new method for the absolute radiance calibration for UV/vis measurements of scattered sun light

    NASA Astrophysics Data System (ADS)

    Wagner, T.; Beirle, S.; Dörner, S.; Penning de Vries, M.; Remmers, J.; Rozanov, A.; Shaiganfar, R.

    2015-05-01

    Absolute radiometric calibrations are important for measurements of the atmospheric spectral radiance. Such measurements can be used to determine actinic fluxes, the properties of aerosols and clouds and the short wave energy budget. Conventional calibration methods in the laboratory are based on calibrated light sources and reflectors and are expensive, time consuming and subject to relatively large uncertainties. Also, the calibrated instruments might change during transport from the laboratory to the measurement sites. Here we present a new calibration method for UV/vis instruments that measure the spectrally resolved sky radiance, like for example zenith sky Differential Optical Absorption Spectroscopy (DOAS-) instruments or Multi-AXis (MAX-) DOAS instruments. Our method is based on the comparison of the solar zenith angle dependence of the measured zenith sky radiance with radiative transfer simulations. For the application of our method clear sky measurements during periods with almost constant aerosol optical depth are needed. The radiative transfer simulations have to take polarisation into account. We show that the calibration results are almost independent from the knowledge of the aerosol optical properties and surface albedo, which causes a rather small uncertainty of about <7%. For wavelengths below about 330 nm it is essential that the ozone column density during the measurements is constant and known.

  6. 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.

  7. 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

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

    PubMed

    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

  9. 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

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

    PubMed

    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

  11. 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

  12. Climate Absolute Radiance and Refractivity Observatory (CLARREO)

    NASA Technical Reports Server (NTRS)

    Leckey, John P.

    2015-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.

  13. Intercomparison of Laboratory Radiance Calibration Standards

    NASA Technical Reports Server (NTRS)

    Pavri, Betina; Chrien, Tom; Green, Robert; Williams, Orlesa

    2000-01-01

    Several standards for radiometric calibration were measured repeatedly with a spectroradiometer in order to understand how they compared in accuracy and stability. The tested radiance standards included a NIST 1000 W bulb and halon panel, two calibrated and stabilized integrating spheres, and a cavity blackbody. Results indicate good agreement between the blackbody and 1000 W bulb/spectralon panel, If these two radiance sources are assumed correct, then the integrating spheres did not conform. to their manufacturer-reported radiances in several regions of the spectrum. More detailed measurements am underway to investigate the discrepancy.

  14. Absolute calibration of remote sensing instruments

    NASA Astrophysics Data System (ADS)

    Biggar, S. F.; Bruegge, C. J.; Capron, B. A.; Castle, K. R.; Dinguirard, M. C.; Holm, R. G.; Lingg, L. J.; Mao, Y.; Palmer, J. M.; Phillips, A. L.

    1985-12-01

    Source-based and detector-based methods for the absolute radiometric calibration of a broadband field radiometer are described. Using such a radiometer, calibrated by both methods, the calibration of the integrating sphere used in the preflight calibration of the Thematic Mapper was redetermined. The results are presented. The in-flight calibration of space remote sensing instruments is discussed. A method which uses the results of ground-based reflectance and atmospheric measurements as input to a radiative transfer code to predict the radiance at the instrument is described. A calibrated, helicopter-mounted radiometer is used to determine the radiance levels at intermediate altitudes to check the code predictions. Results of such measurements for the calibration of the Thematic Mapper on Landsat 5 and an analysis that shows the value of such measurements are described.

  15. 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

  16. 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.

  17. Absolute radiometric calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.

    1986-01-01

    Calibration data for the solar reflective bands of the Landsat-5 TM obtained from five in-flight absolute radiometric calibrations from July 1984-November 1985 at White Sands, New Mexico are presented and analyzed. Ground reflectance and atmospheric data were utilized to predict the spectral radiance at the entrance pupil of the TM and the average number of digital counts in each TM band. The calibration of each of the TM solar reflective bands was calculated in terms of average digital counts/unit spectral radiance for each band. It is observed that for the 12 reflectance-based measurements the rms variation from the means as a percentage of the mean is + or - 1.9 percent; for the 11 measurements in the IR bands, it is + or - 3.4 percent; and the rms variation for all 23 measurements is + or - 2.8 percent.

  18. Issues in Absolute Spectral Radiometric Calibration: Intercomparison of Eight Sources

    NASA Technical Reports Server (NTRS)

    Goetz, Alexander F. H.; Kindel, Bruce; Pilewskie, Peter

    1998-01-01

    The application of atmospheric models to AVIRIS and other spectral imaging data to derive surface reflectance requires that the sensor output be calibrated to absolute radiance. Uncertainties in absolute calibration are to be expected, and claims of 92% accuracy have been published. Measurements of accurate surface albedos and cloud absorption to be used in radiative balance calculations depend critically on knowing the absolute spectral-radiometric response of the sensor. The Earth Observing System project is implementing a rigorous program of absolute radiometric calibration for all optical sensors. Since a number of imaging instruments that provide output in terms of absolute radiance are calibrated at different sites, it is important to determine the errors that can be expected among calibration sites. Another question exists about the errors in the absolute knowledge of the exoatmospheric spectral solar irradiance.

  19. Spectral radiance source based on supercontinuum laser and wavelength tunable bandpass filter: the spectrally tunable absolute irradiance and radiance source.

    PubMed

    Levick, Andrew P; Greenwell, Claire L; Ireland, Jane; Woolliams, Emma R; Goodman, Teresa M; Bialek, Agnieszka; Fox, Nigel P

    2014-06-01

    A new spectrally tunable source for calibration of radiometric detectors in radiance, irradiance, or power mode has been developed and characterized. It is termed the spectrally tunable absolute irradiance and radiance source (STAIRS). It consists of a supercontinuum laser, wavelength tunable bandpass filter, power stabilization feedback control scheme, and output coupling optics. It has the advantages of relative portability and a collimated beam (low étendue), and is an alternative to conventional sources such as tungsten lamps, blackbodies, or tunable lasers. The supercontinuum laser is a commercial Fianium SC400-6-02, which has a wavelength range between 400 and 2500 nm and a total power of 6 W. The wavelength tunable bandpass filter, a PhotonEtc laser line tunable filter (LLTF), is tunable between 400 and 1000 nm and has a bandwidth of 1 or 2 nm depending on the wavelength selected. The collimated laser beam from the LLTF filter is converted to an appropriate spatial and angular distribution for the application considered (i.e., for radiance, irradiance, or power mode calibration of a radiometric sensor) with the output coupling optics, for example, an integrating sphere, and the spectral radiance/irradiance/power of the source is measured using a calibration optical sensor. A power stabilization feedback control scheme has been incorporated that stabilizes the source to better than 0.01% for averaging times longer than 100 s. The out-of-band transmission of the LLTF filter is estimated to be < -65 dB (0.00003%), and is sufficiently low for many end-user applications, for example the spectral radiance calibration of earth observation imaging radiometers and the stray light characterization of array spectrometers (the end-user optical sensor). We have made initial measurements of two end-user instruments with the STAIRS source, an array spectrometer and ocean color radiometer.

  20. Prelaunch absolute radiometric calibration of 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

    Results are summarized and analyzed from several prelaunch tests with a 122 cm integrating sphere used as part of the absolute radiometric calibration experiments for the protoflight TM sensor carried on the LANDSAT-4 satellite. The calibration procedure is presented and the radiometric sensitivity of the TM is assessed. The internal calibrator and dynamic range after calibration are considered. Tables show dynamic range after ground processing, spectral radiance to digital number and digital number to spectral radiance values for TM bands 1, 2, 3, 4, 5, 7 and for channel 4 of band 6.

  1. The Absolute Radiometric Calibration of Space - Sensors.

    NASA Astrophysics Data System (ADS)

    Holm, Ronald Gene

    1987-09-01

    The need for absolute radiometric calibration of space-based sensors will continue to increase as new generations of space sensors are developed. A reflectance -based in-flight calibration procedure is used to determine the radiance reaching the entrance pupil of the sensor. This procedure uses ground-based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of five calibrations of the Landsat-5 Thematic Mapper (TM). For the 12 measurements made in TM bands 1-3, the RMS variation from the mean as a percentage of the mean is (+OR-) 1.9%, and for measurements in the IR, TM bands 4,5, and 7, the value is (+OR-) 3.4%. The RMS variation for all 23 measurements is (+OR-) 2.8%. The absolute calibration techniques were put to another test with a series of three calibration of the SPOT-1 High Resolution Visible, (HRV), sensors. The ratio, HRV-2/HRV-1, of absolute calibration coefficients compared very well with ratios of histogrammed data obtained when the cameras simultaneously imaged the same ground site. Bands PA, B1 and B3 agreed to within 3%, while band B2 showed a 7% difference. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft -based radiometer data. This procedure was applied on four dates with two different surface conditions per date. A strong correlation, R('2) = .996, was shown between reflectance values determined from satellite imagery and low-flying aircraft

  2. Normalization and calibration of geostationary satellite radiances for the International Satellite Cloud Climatology Project

    NASA Technical Reports Server (NTRS)

    Desormeaux, Yves; Rossow, William B.; Brest, Christopher L.; Campbell, G. G.

    1993-01-01

    Procedures are described for normalizing the radiometric calibration of image radiances obtained from geostationary weather satellites that contributed data to the International Satellite Cloud Climatology Project. The key step is comparison of coincident and collocated measurements made by each satellite and the concurrent AVHRR on the 'afternoon' NOAA polar-orbiting weather satellite at the same viewing geometry. The results of this comparison allow transfer of the AVHRR absolute calibration, which has been established over the whole series, to the radiometers on the geostationary satellites. Results are given for Meteosat-2, 3, and 4, for GOES-5, 6, and 7, for GMS-2, 3, and 4 and for Insat-1B. The relative stability of the calibrations of these radiance data is estimated to be within +/- 3 percent; the uncertainty of the absolute calibrations is estimated to be less than 10 percent. The remaining uncertainties are at least two times smaller than for the original radiance data.

  3. 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.

  4. On-Orbit Absolute Radiance Standard for Future IR Remote Sensing Instruments

    NASA Astrophysics Data System (ADS)

    Best, F. A.; Adler, D. P.; Pettersen, C.; Revercomb, H. E.; Gero, P. J.; Taylor, J. K.; Knuteson, R. O.; Perepezko, J. H.

    2010-12-01

    Future NASA infrared remote sensing missions, including the climate benchmark CLARREO mission will require better absolute measurement accuracy than now available, and will most certainly rely on the emerging capability to fly SI traceable standards that provide irrefutable absolute measurement accuracy. As an example, instrumentation designed to measure spectrally resolved infrared radiances with an absolute brightness temperature error of better than 0.1 K will require high-emissivity (>0.999) calibration blackbodies with emissivity uncertainty of better than 0.06%, and absolute temperature uncertainties of better than 0.045K (3 sigma). Key elements of an On-Orbit Absolute Radiance Standard (OARS) meeting these stringent requirements have been demonstrated in the laboratory at the University of Wisconsin and are undergoing Technology Readiness Level (TRL) advancement under the NASA Instrument Incubator Program (IIP). We present the new technologies that underlie the OARS and the results of laboratory testing that demonstrate the required accuracy is being met. The underlying technologies include on-orbit absolute temperature calibration using the transient melt signatures of small quantities (<1g) of reference materials (gallium, water, and mercury) imbedded in the blackbody cavity; and on-orbit cavity spectral emissivity measurement using a heated halo. For these emissivity measurements, a carefully baffled heated cylinder is placed in front of a blackbody in the infrared spectrometer system, and the combined radiance of the blackbody and Heated Halo reflection is observed. Knowledge of key temperatures and the viewing geometry allow the blackbody cavity spectral emissivity to be calculated. This work will culminate with an integrated subsystem that can provide on-orbit end-to-end radiometric accuracy validation for infrared remote sensing instruments.

  5. Radiance calibration of the High Altitude Observatory white-light coronagraph on Skylab

    NASA Technical Reports Server (NTRS)

    Poland, A. I.; Macqueen, R. M.; Munro, R. H.; Gosling, J. T.

    1977-01-01

    The processing of over 35,000 photographs of the solar corona obtained by the white-light coronograph on Skylab is described. Calibration of the vast amount of data was complicated by temporal effects of radiation fog and latent image loss. These effects were compensated by imaging a calibration step wedge on each data frame. Absolute calibration of the wedge was accomplished through comparison with a set of previously calibrated glass opal filters. Analysis employed average characteristic curves derived from measurements of step wedges from many frames within a given camera half-load. The net absolute accuracy of a given radiance measurement is estimated to be 20%.

  6. 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.

  7. Demonstrating the error budget for the Climate Absolute Radiance and Refractivity Observatory through solar irradiance measurements

    NASA Astrophysics Data System (ADS)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2015-09-01

    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 testbed 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.

  8. 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.

  9. In-flight absolute radiometric calibration of the thematic mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1983-01-01

    The TM multispectral scanner system was calibrated in an absolute manner before launch. To determine the temporal changes of the absolute radiometric calibration of the entire system, spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM collections over White Sands, New Mexico. By entering the measured values in an atmospheric radiative transfer program, the radiance levels of the in four of the spectral bands of the TM were determined. Tables show values for the reflectance of snow at White Sands measured by a modular 8 channel radiometer, and values for exoatmospheric irradiance within the TM passbands, calculated for the Earth-Sun distance using a solar radiometer.

  10. 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.

  11. 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.

  12. 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.

  13. The absolute radiometric calibration of space-based sensors

    NASA Astrophysics Data System (ADS)

    Holm, Ronald Gene

    A reflectance based inflight calibration procedure is used to determine the radiance reaching the entrance pupil of a sensor. This procedure uses ground based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of 5 calibrations of the LANDSAT-5 Thematic Mapper. The absolute calibration techniques were put to another test with a series of 3 calibration of the SPOT-1 High Resolution Visible sensors. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft based radiometer data. A strong correlation was shown between reflectance values determined from satellite imagery and low flying aircraft data.

  14. Evaluation of ISCCP multisatellite radiance calibration for geostationary imager visible channels using the moon

    USGS Publications Warehouse

    Stone, Thomas C.; William B. Rossow,; Joseph Ferrier,; Laura M. Hinkelman,

    2013-01-01

    Since 1983, the International Satellite Cloud Climatology Project (ISCCP) has collected Earth radiance data from the succession of geostationary and polar-orbiting meteorological satellites operated by weather agencies worldwide. Meeting the ISCCP goals of global coverage and decade-length time scales requires consistent and stable calibration of the participating satellites. For the geostationary imager visible channels, ISCCP calibration provides regular periodic updates from regressions of radiances measured from coincident and collocated observations taken by Advanced Very High Resolution Radiometer instruments. As an independent check of the temporal stability and intersatellite consistency of ISCCP calibrations, we have applied lunar calibration techniques to geostationary imager visible channels using images of the Moon found in the ISCCP data archive. Lunar calibration enables using the reflected light from the Moon as a stable and consistent radiometric reference. Although the technique has general applicability, limitations of the archived image data have restricted the current study to Geostationary Operational Environmental Satellite and Geostationary Meteorological Satellite series. The results of this lunar analysis confirm that ISCCP calibration exhibits negligible temporal trends in sensor response but have revealed apparent relative biases between the satellites at various levels. However, these biases amount to differences of only a few percent in measured absolute reflectances. Since the lunar analysis examines only the lower end of the radiance range, the results suggest that the ISCCP calibration regression approach does not precisely determine the intercept or the zero-radiance response level. We discuss the impact of these findings on the development of consistent calibration for multisatellite global data sets.

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

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; Gubbels, Timothy; Barnes, Robert

    2011-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) plans to observe climate change trends over decadal time scales to determine the accuracy of climate projections. The project relies on spaceborne earth observations of SI-traceable variables sensitive to key decadal change parameters. The mission includes a reflected solar instrument retrieving at-sensor reflectance over the 320 to 2300 nm spectral range with 500-m spatial resolution and 100-km swath. Reflectance is obtained from the ratio of measurements of the earth s surface to those while viewing the sun relying on a calibration approach that retrieves reflectance with uncertainties less than 0.3%. The calibration is predicated on heritage hardware, reduction of sensor complexity, adherence to detector-based calibration standards, and an ability to simulate in the laboratory on-orbit sources in both size and brightness to provide the basis of a transfer to orbit of the laboratory calibration including a link to absolute solar irradiance measurements. The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe high-accuracy, long-term climate change trends and to use decadal change observations as the most critical method to determine the accuracy of climate change projections such as those in the IPCC Report. A rigorously known accuracy of both decadal change observations as well as climate projections is critical in order to enable sound policy decisions. The CLARREO Project will implement a spaceborne earth observation mission designed to provide rigorous SI traceable observations (i.e., radiance, reflectance, and refractivity) that are sensitive to a wide range of key decadal change variables, including: 1) Surface temperature and atmospheric temperature profile 2) Atmospheric water vapor profile 3) Far infrared water vapor greenhouse 4) Aerosol properties and anthropogenic aerosol direct radiative forcing 5) Total and spectral solar

  16. In-flight Absolute Radiometric Calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, D.; Savage, R. K.

    1984-01-01

    The Thematic Mapper (TM) multispectral scanner system was placed into Earth orbit on July 16, 1982, as part of NASA's LANDSAT 4 payload. To determine temporal changes of the absolute radiometric calibration of the entire system in flight, spectroradiometric measurements of the ground and the atmosphere are made simultaneously with TM image acquisitions over the White Sands, New Mexico area. By entering the measured values into an atmospheric radiative transfer program, the radiance levels at the entrance pupil of the TM in four of the TM spectral bands are determined. These levels are compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors. By reference to an adjacent, larger uniform area, the calibration is extended to all 16 detectors in each of the three bands.

  17. Radiance factor calibration of near-infrared spectral images of Mars

    NASA Astrophysics Data System (ADS)

    Klassen, David R.; Bell, James F.

    2003-05-01

    We present radiometrically calibrated spectrophotometric images of Mars taken at the NASA Infrared Telescope Facility (IRTF) near and during the 1995 and 1999 oppositions. Absolute intensity and radiance factor ( r F = I/F) values have been calculated for approximately 95% of the surface over all longitudes between -70° to 90° latitude in the 1.5- to 4.1-μm spectral region at a spectral resolution (Δλ/λ) of 1.5%. Values of radiance factor range from r F = 0.4 to 0.6 at 2.2 μm for the bright regions such as Moab and Arabia to r F = 0.12 to 0.3 at 2.2 μm around the dark regions Syrtis Major and Acidalia Planitia. Variations are seen due to seasonal dust and/or condensate cloud cover and viewing geometry. Our results are generally consistent with the few reported previous radiance factor determinations for Mars. These data are unique among ground-based data in their relatively high spatial resolution (≲200 km/pixel at the sub-Earth point) and coverage combined with their spectral resolution and coverage. These radiometrically calibrated observations can be used as input to studies focusing on spectral unmixing of surface and atmospheric components, radiative transfer modeling of disk and limb radiances, and photometric modeling of the martian phase function.

  18. Evaluation of Long-Term Calibrations of the AVHRR Visible Radiances

    NASA Technical Reports Server (NTRS)

    Rossow, William B.; Ferrier, Joseph

    2015-01-01

    Two systematic calibrations have been compiled for the visible radiances measured by the series of AVHRR instruments flown on the NOAA operational polar weather satellites: one by the International Satellite Cloud Climatology Project (ISCCP), anchored on NASA ER-2 underflights in the 1980s and early 1990s and covering the period 1981-2009, and one by the PATMOS-x project, anchored on comparisons to the MODIS instruments on the Aqua and Terra satellites in the 2000s and covering the period 1979-2010 (this result also includes calibration for the near-IR channels). Both methods have had to extend their anchor calibrations over a long series of instruments using different vicarious approaches, so a comparison provides an opportunity to evaluate how well this extension works by cross-checking the results at the anchor points. The basic result of this comparison is that for the ''afternoon'' series of AVHRRs, the calibrations agree to within their mutual uncertainties. However, this retrospective evaluation also shows that the representation of the time variations can be simplified. The ISCCP procedure had much more difficulty extending the calibration to the ''morning'' series of AVHRRs with the calibrations for NOAA-15 and NOAA-17 exceeding the estimated uncertainties. Given the general agreement, a new calibration for all AVHRR visible radiances (except TIROS-N, NOAA-6, NOAA-19, and MetOp-A) is proposed that is based on the average of the best linear fits to the two time records. The estimated uncertainty of these calibrations is 63% absolute (scaled radiance units).

  19. In-flight absolute radiometric calibration of the thematic mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1984-01-01

    In order to determine temporal changes of the absolute radiometric calibration of the entire TM system in flight spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM image collections over the White Sands, New Mexico area. By entering the measured values in an atmospheric radiative transfer program, the radiance levels in four of the spectral bands of the TM were determined, band 1:0.45 to 0.52 micrometers, band 2:0.53 to 0.61 micrometers band 3:0.62 to 0.70 micrometers and 4:0.78 to 0.91 micrometers. These levels were compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors.

  20. In-flight absolute radiometric calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1984-01-01

    In order to determine temporal changes of the absolute radiometric calibration of the entire TM system in flight spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM image collections over the White Sands, NM area. By entering the measured values in an atmospheric radiative transfer program, the radiance levels in four of the spectral bands of the TM were determined, band 1: 0.45 to 0.52 micrometers, band 2: 0.53 to 0.61 micrometers, band 3: 0.62 to 0.70 micrometers, and 4: 0.78 to 0.91 micrometers. These levels were compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors. Previously announced in STAR as N84-15633

  1. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  2. 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.

  3. 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.

  4. Variations in in-flight absolute radiometric calibration. [satellite remote sensors

    NASA Technical Reports Server (NTRS)

    Slater, Philip N.

    1986-01-01

    Variations in the in-flight absolute radiometric calibration of the Coastal Zone Color Scanner and the Thematic Mapper (TM) are reviewed. At short wavelengths, the sensors show a gradual reduction in response, while in the mid-IR the TM shows oscillatory variations. One set of measurements made at White Sands, New Mexico shows anomalous results in TM bands 2 and 4. The results of a reflectance-based and a radiance-based calibration method at White Sands are described. An analysis of the radiance-based method shows the value of such measurements from helicopter altitudes for calibration.

  5. Absolute calibration of the Auger fluorescence detectors

    SciTech Connect

    Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; Tamashiro, A.; Warner, D.

    2005-07-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

  6. Pleiades Absolute Calibration : Inflight Calibration Sites and Methodology

    NASA Astrophysics Data System (ADS)

    Lachérade, S.; Fourest, S.; Gamet, P.; Lebègue, L.

    2012-07-01

    In-flight calibration of space sensors once in orbit is a decisive step to be able to fulfil the mission objectives. This article presents the methods of the in-flight absolute calibration processed during the commissioning phase. Four In-flight calibration methods are used: absolute calibration, cross-calibration with reference sensors such as PARASOL or MERIS, multi-temporal monitoring and inter-bands calibration. These algorithms are based on acquisitions over natural targets such as African deserts, Antarctic sites, La Crau (Automatic calibration station) and Oceans (Calibration over molecular scattering) or also new extra-terrestrial sites such as the Moon and selected stars. After an overview of the instrument and a description of the calibration sites, it is pointed out how each method is able to address one or several aspects of the calibration. We focus on how these methods complete each other in their operational use, and how they help building a coherent set of information that addresses all aspects of in-orbit calibration. Finally, we present the perspectives that the high level of agility of PLEIADES offers for the improvement of its calibration and a better characterization of the calibration sites.

  7. Reflectance-based calibration of SeaWiFS. II. Conversion to radiance.

    PubMed

    Barnes, Robert A; Zalewski, Edward F

    2003-03-20

    For instruments that carry onboard solar diffusers to orbit, such as the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS), it is possible to convert the instrument's reflectance measurements to radiance measurements by knowledge of the solar irradiance. This process, which generally requires the application of a solar irradiance model, is described. The application of the irradiance model is separate from the measurements by the instrument and from the instrument's reflectance calibration. In addition, SeaWiFS was calibrated twice before launch for radiance response by use of radiance sources with calibrations traceable to the National Institute of Standards and Technology. With the inclusion of the at-launch diffuser-based radiance calibration, SeaWiFS has three possible radiance calibrations forthe start of on-orbit operations. The combination of these three into a single calibration requires changes of 4% or less for the current at-launch radiance calibration of the instrument. Finally, this process requires changes of 4% or less for the reflectance calibration coefficients to provide consistency among the radiance calibration, the reflectance calibration, and the solar irradiance.

  8. Absolute Radiometric Calibration Of The Thematic Mapper

    NASA Astrophysics Data System (ADS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.; Moran, M. S.; Palmer, J. M.; Yuan, B.

    1986-11-01

    The results are presented of five in-flight absolute radiometric calibrations, made in the period July 1984 to November 1985, at White Sands, New Mexico, of the solar reflective bands of the Landsat-5 Thematic Mapper (TM) . The 23 bandcalibrations made on the five dates show a ± 2.8% RMS variation from the mean as a percentage of the mean.

  9. 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.

  10. 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.

  11. The Carina Project: Absolute and Relative Calibrations

    NASA Astrophysics Data System (ADS)

    Corsi, C. E.; Bono, G.; Walker, A. R.; Brocato, E.; Buonanno, R.; Caputo, F.; Castellani, M.; Castellani, V.; Dall'Ora, M.; Marconi, M.; Monelli, M.; Nonino, M.; Pulone, L.; Ripepi, V.; Smith, H. A.

    We discuss the reduction strategy adopted to perform the relative and the absolute calibration of the Wide Field Imager (WFI) available at the 2.2m ESO/MPI telescope and of the Mosaic Camera (MC) available at the 4m CTIO Blanco telescope. To properly constrain the occurrence of deceptive systematic errors in the relative calibration we observed with each chip the same set of stars. Current photometry seems to suggest that the WFI shows a positional effect when moving from the top to the bottom of individual chips. Preliminary results based on an independent data set collected with the MC suggest that this camera is only marginally affected by the same problem. To perform the absolute calibration we observed with each chip the same set of standard stars. The sample covers a wide color range and the accuracy both in the B and in the V-band appears to be of the order of a few hundredths of magnitude. Finally, we briefly outline the observing strategy to improve both relative and absolute calibrations of mosaic CCD cameras.

  12. [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.

  13. 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.

  14. Sentinel-2/MSI absolute calibration: first results

    NASA Astrophysics Data System (ADS)

    Lonjou, V.; Lachérade, S.; Fougnie, B.; Gamet, P.; Marcq, S.; Raynaud, J.-L.; Tremas, T.

    2015-10-01

    Sentinel-2 is an optical imaging mission devoted to the operational monitoring of land and coastal areas. It is developed in partnership between the European Commission and the European Space Agency. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. It will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). CNES is involved in the instrument commissioning in collaboration with ESA. This paper reviews all the techniques that will be used to insure an absolute calibration of the 13 spectral bands better than 5% (target 3%), and will present the first results if available. First, the nominal calibration technique, based on an on-board sun diffuser, is detailed. Then, we show how vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) will be used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over Lacrau plain, is described. A synthesis, including spectral coherence, inter-methods agreement and temporal evolution, will conclude the paper.

  15. Absolute radiometric calibration of the CCRS SAR

    NASA Astrophysics Data System (ADS)

    Ulander, Lars M. H.; Hawkins, Robert K.; Livingstone, Charles E.; Lukowski, Tom I.

    1991-11-01

    Determining the radar scattering coefficients from SAR (synthetic aperture radar) image data requires absolute radiometric calibration of the SAR system. The authors describe an internal calibration methodology for the airborne Canada Centre for Remote Sensing (CCRS) SAR system, based on radar theory, a detailed model of the radar system, and measurements of system parameters. The methodology is verified by analyzing external calibration data acquired over a 6-month period in 1988 by the C-band radar using HH polarization. The results indicate that the overall error is +/- 0.8 dB (1-sigma) for incidence angles +/- 20 deg from antenna boresight. The dominant error contributions are due to the antenna radome and uncertainties in the elevation angle relative to the antenna boresight.

  16. Uncertainty propagation algorithm from the radiometric calibration to the restored earth observation radiance.

    PubMed

    Guorui, Jia; Huijie, Zhao; Hao, Lei

    2014-04-21

    The uncertainty of the radiometric calibration affects the accuracy of the earth observation (EO) radiance restored from the remote sensing digital number (DN) data. However, it has not been intensively analyzed whether they are equivalent to each other. The algorithm to deduce the uncertainty of the restored EO radiance in the solar-reflective spectral range (400-2500 nm) along the uncertainty propagation chain in the radiometric calibration process is proposed. It was validated compared with the traditional calibration uncertainty algorithm through an example of calibrating an imaging spectrometer. The interval about the real EO radiance and the corresponding level of confidence was reported as a result, which shows the possibility to accurately expressing the quality of the restored EO radiance following the rules used in the field of metrology.

  17. Facility for spectral irradiance and radiance responsivity calibrations using uniform sources

    SciTech Connect

    Brown, Steven W.; Eppeldauer, George P.; Lykke, Keith R

    2006-11-10

    Detectors have historically been calibrated for spectral power responsivity at the National Institute of Standards and Technology by using a lamp-monochromator system to tune the wavelength of the excitation source. Silicon detectors can be calibrated in the visible spectral region with combined standard uncertainties at the 0.1% level. However,uncertainties increase dramatically when measuring an instrument's spectral irradiance or radiance responsivity. We describe what we believe to be a new laser-based facility for spectral irradiance and radiance responsivity calibrations using uniform sources (SIRCUS) that was developed to calibrate instruments directly in irradiance or radiance mode with uncertainties approaching or exceeding those available for spectral power responsivity calibrations. In SIRCUS, the emission from high-power, tunable lasers is introduced into an integrating sphere using optical fibers, producing uniform, quasi-Lambertian, high-radiant-flux sources. Reference standard irradiance detectors, calibrated directly against national primary standards for spectral power responsivity and aperture area measurement,are used to determine the irradiance at a reference plane. Knowing the measurement geometry, the source radiance can be readily determined as well. The radiometric properties of the SIRCUS source coupled with state-of-the-art transfer standard radiometers whose responsivities are directly traceable to primary national radiometric scales result in typical combined standard uncertainties in irradiance and radiance responsivity calibrations of less than 0.1%. The details of the facility and its effect on primary national radiometric scales are discussed.

  18. Absolute calibration of ultraviolet filter photometry

    NASA Technical Reports Server (NTRS)

    Bless, R. C.; Fairchild, T.; Code, A. D.

    1972-01-01

    The essential features of the calibration procedure can be divided into three parts. First, the shape of the bandpass of each photometer was determined by measuring the transmissions of the individual optical components and also by measuring the response of the photometer as a whole. Secondly, each photometer was placed in the essentially-collimated synchrotron radiation bundle maintained at a constant intensity level, and the output signal was determined from about 100 points on the objective. Finally, two or three points on the objective were illuminated by synchrotron radiation at several different intensity levels covering the dynamic range of the photometers. The output signals were placed on an absolute basis by the electron counting technique described earlier.

  19. Cross-calibration of Imaging Sensors using Model-based, SI-traceable Predictions of At-sensor Radiance

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel

    2012-01-01

    Many inter-consistency efforts force empirical agreement between sensors viewing a source nearly coincident in time and geometry that ensures consistency between sensors rather than obtain an SI-traceable calibration with documented error budgets. The method described here provides interconsistency via absolute radiometric calibration with defensible error budget avoiding systematic errors through prediction of at-sensor radiance for a site viewed by multiple sensors but not necessarily viewed at coincident times. The method predicts spectral radiance over a given surface site for arbitrary view and illumination angles and for any date dominated by clear-sky conditions. The foundation is a model-based, SI-traceable prediction of at-sensor radiance over selected sites based on physical understanding of the surface and atmosphere. The calibration of the ground site will include spatial, spectral, and sunview geometric effects based on satellite and ground-based data. The result is an interconsistency of hyperspectral and multispectral sensors spanning spatial resolutions from meters to kilometers all relative to the surface site rather than a single sensor. The source-centric philosophy of calibrating the site inherently accounts for footprint size mismatch, spectral band mismatch, and temporal and spatial sampling effects. The method for characterizing the test site allows its use for SI-traceable calibration of any sensor that can view the calibrated test site. Interconsistency is obtained through the traceability and error budget rather than coincident views. Such an approach to inter-consistency provides better understanding of biases between sensors as well producing more accurate results with documented SI-traceability that reduces the need for overlapping data sets.

  20. Results from recent vacuum testing of an on-orbit absolute radiance standard (OARS) intended for the next generation of infrared remote sensing instruments

    NASA Astrophysics Data System (ADS)

    Best, Fred A.; Adler, Douglas P.; Pettersen, Claire; Revercomb, Henry E.; Gero, P. Jonathan; Taylor, Joseph K.; Knuteson, Robert O.

    2014-11-01

    Future NASA infrared remote sensing missions will require better absolute measurement accuracies than now available, and will most certainly rely on the emerging capability to fly SI traceable standards that provide irrefutable absolute measurement accuracy. To establish a CLARRREO-type climate benchmark, instrumentation will need to measure spectrally resolved infrared radiances with an absolute brightness temperature error of better than 0.1 K, verified onorbit. This will require an independent high-emissivity (<0.999) verification blackbody with an emissivity uncertainty of better than 0.06%, an absolute temperature uncertainty of better than 0.045K (3 sigma), and the capability of operation over a wide range of (Earth scene) temperatures. Key elements of an On-Orbit Absolute Radiance Standard (OARS) meeting these stringent requirements have been demonstrated in the laboratory at the University of Wisconsin and have undergone further refinement under funding from NASA's Earth Science and Technology Office, culminating in an end-to-end demonstration under vacuum with a prototype climate benchmark instrument. We present the new technologies that underlie the OARS, and the results of testing that demonstrate the required accuracy is being met in a vacuum environment. The underlying technologies include: on-orbit absolute temperature calibration using the transient melt signatures of small quantities (<1g) of reference materials (gallium, water, and mercury) imbedded in the blackbody cavity; and on-orbit cavity spectral emissivity measurement using a carefully baffled heated halo placed in front of the OARS blackbody viewed by the infrared spectrometer system. Emissivity is calculated from the radiance measured from the blackbody combined with the knowledge of key temperatures and radiometric view factors.

  1. Operational calibration of the METEOSAT water vapor channel by calculated radiances.

    PubMed

    Schmetz, J

    1989-08-01

    A method is presented for calibrating the water vapor channel (5.7-7.1 microm) of the geostationary meteorological satellite METEOSAT by radiative transfer calculations. Radiances are calculated from the temperature and moisture profiles of conventional radiosondes and linearly related to collocated satellite measured digital counts. Collocations are considered only for areas with neither medium nor high level cloud. Radiosonde data are routinely received twice per day (1200 and 2400 UT). Radiosonde profiles from an 8-day period in May 1988, and simultaneous Meteosat-2 water vapor measurements are analyzed. The total of 340 collocations provides a calibration coefficient with a precision of 2% assuming a 95% confidence. A preliminary analysis of calibration coefficients of the recently launched METEOSAT-3 shows a significant increase of 6% over a period of 48 days in Sept./Oct. 1988. The calibrated water vapor radiances are operationally used to estimate the upper tropospheric humidity field and to correct the height assignment of semitransparent clouds.

  2. Absolute calibration of sniffer probes on Wendelstein 7-X

    NASA Astrophysics Data System (ADS)

    Moseev, D.; Laqua, H. P.; Marsen, S.; Stange, T.; Braune, H.; Erckmann, V.; Gellert, F.; Oosterbeek, J. W.

    2016-08-01

    Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m2 per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m2 per MW injected beam power is measured.

  3. Absolute calibration of sniffer probes on Wendelstein 7-X.

    PubMed

    Moseev, D; Laqua, H P; Marsen, S; Stange, T; Braune, H; Erckmann, V; Gellert, F; Oosterbeek, J W

    2016-08-01

    Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m(2) per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m(2) per MW injected beam power is measured. PMID:27587121

  4. A practical method for sensor absolute calibration.

    PubMed

    Meisenholder, G W

    1966-04-01

    This paper describes a method of performing sensor calibrations using an NBS standard of spectral irradiance. The method shown, among others, was used for calibration of the Mariner IV Canopus sensor. Agreement of inflight response to preflight calibrations performed by this technique has been found to be well within 10%. PMID:20048890

  5. 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

  6. Spectral radiance calibrations between 165-300 nm - An interlaboratory comparison

    NASA Technical Reports Server (NTRS)

    Bridges, J. M.; Ott, W. R.; Pitz, E.; Schulz, A.; Einfeld, D.; Stuck, D.

    1977-01-01

    The spectral radiance of deuterium lamps calibrated by the Max-Planck-Institut fuer Astronomie (MPI), by the U.S. National Bureau of Standards (NBS), and by the Physikalisch-Technische Bundesanstalt (PTB) are compared to check the agreement of UV radiometric scales. The NBS group used the optically thin continuum radiation from a wall-stabilized hydrogen arc as its fundamental radiometric standard, while the MPI and PTB groups used the synchrotron radiation facility in DESY. It is found that the spectral radiance scales based upon the DESY synchrotron and the NBS hydrogen arc are consistent, at least for one wavelength relative to another.

  7. 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.

  8. In-Flight Absolute Radiometric Calibration of the Landsat Thematic Mapper

    NASA Astrophysics Data System (ADS)

    Kastner, Carol Jane

    The in-flight absolute radiometric calibration of the Thematic Mapper (TM) is being conducted using the results of field measurements at White Sands, New Mexico. These measurements are made to characterize the ground and atmosphere at the time the TM is acquiring an image of White Sands. The data are used as input to a radiative transfer code that computes the radiance at the entrance pupil of the TM. The calibration is obtained by comparing the digital counts associated with the TM image of the measured ground site with the radiative transfer code result. The calibrations discussed here are for the first four visible and near -infrared bands of the TM. In this dissertation the data reduction for the first calibration attempts on January 3, 1983, and July 8, 1984, is discussed. Included are a review of radiative transfer theory and a discussion of model atmospheric parameters as defined for the White Sands area. These model parameters are used to assess the errors associated with the calibration procedure. Each input parameter to the radiative transfer code is varied from its model value in proportion to the uncertainty with which it can be determined. The effects of these uncertainties on the predicted radiances are determined. It is thought that the optical depth components (tau)(,Ray), (tau)(,Mie), (tau)(,oz), and (tau)(,H(,2)O) can be measured to within 10%, 2%, 10%, and 30%, respectively. For the white gypsum sand, surface reflectance uniformity is on the order of 1.5%, and the overall uncertainty in measured reflectance is about 2%. This is due to an uncertainty in the reflectance factor of the calibration plates. The greatest uncertainty in calibration is attributed to our uncertainty in the aerosol parameters, in particular the imaginary component of refractive index. The cumulative effect of these uncertainties is thought to produce an uncertainty in computed radiance of about 5%.

  9. [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.

  10. -30° C to 960° C Variable Temperature Blackbody (VTBB) Radiance Temperature Calibration Facility

    NASA Astrophysics Data System (ADS)

    Yuan, Z.; Wang, J.; Hao, X.; Wang, T.; Dong, W.

    2015-12-01

    A blackbody radiance temperature calibration facility (RTCF) has recently been established at the National Institute of Metrology, China, offering calibration and verification services for variable temperature blackbody (VTBB) radiation sources. The RTCF includes reference VTBBs in the range of -30° C to 960° C and consists of a stirred liquid bath blackbody of -30° C to 80° C and water, cesium, and sodium heat-pipe blackbodies spanning 50° C to 960° C. In addition, the facility is equipped with a set of radiation thermometers with different working wavelengths (or wavebands); these thermometers are used to transfer radiance temperatures from the reference to customers' VTBBs. Cavities with V-notch grooves in the inner surface have an estimated emissivity from 0.99986 to 0.99994. The temperature control stability and temperature uniformity of VTBBs are characterized. Furthermore, we test the difference between a cavity and thermometer well temperatures and compare the radiance temperatures of the Cs and Na heat-pipe blackbodies. The expanded uncertainty (k = 2) of VTBBs' radiance temperatures at 10 \\upmu m (8 \\upmu m to 14 \\upmu m) is evaluated from 0.016° C to 0.23° C. The facility has been used to calibrate and characterize customers' VTBBs.

  11. Characterization of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) ability to serve as an infrared satellite intercalibration reference

    NASA Astrophysics Data System (ADS)

    Tobin, David; Holz, Robert; Nagle, Fred; Revercomb, Henry

    2016-04-01

    Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a future mission employing an infrared spectrometer with unprecedented calibration accuracy and the ability to assess its calibration on-orbit using a novel verification system. Utilizing this capability for satellite intercalibration is a primary objective of the mission. This paper presents a new infrared intercalibration methodology that minimizes the intercalibration uncertainties and provides uncertainty estimates resulting from the scene variability and instrument noise. Results of a simulation study to characterize realistic spatial and temporal matching differences for simultaneous nadir overpasses (SNOs) of CLARREO and existing hyperspectral sounders are presented. This study, along with experience with intercalibration of real data, finds that intercalibration uncertainties are minimized when the SNOs are not screened for sky conditions but instead weighted based on the observed scene variability. Intercalibration performance is investigated for a 90° polar orbit mission and for a Pathfinder mission on the International Space Station, for various potential CLARREO footprint sizes, and as a function of mission length, scene brightness temperature, and wavelength. The results are encouraging and suggest that biases between CLARREO and sounder observations can be determined with low uncertainty and with high time frequency during a CLARREO mission. For example, the simulations suggest that a CLARREO footprint of 50 to 100 km in diameter is optimal for intercalibration, and that the 3 sigma intercalibration uncertainty is less than 0.1 K for channels at infrared window wavelengths using 2 months of accumulated SNOs, and for more absorbing channels with less scene variability the uncertainties are less than 50 mK.

  12. Climate Quality Broadband and Narrowband Solar Reflected Radiance Calibration Between Sensors in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Doelling, David R.; Young, David F.; Loeb, Norman G.; Garber, Donald P.; MacDonnell, David G.

    2008-01-01

    vAs the potential impacts of global climate change become more clear [1], the need to determine the accuracy of climate prediction over decade-to-century time scales has become an urgent and critical challenge. The most critical tests of climate model predictions will occur using observations of decadal changes in climate forcing, response, and feedback variables. Many of these key climate variables are observed by remotely sensing the global distribution of reflected solar spectral and broadband radiance. These "reflected solar" variables include aerosols, clouds, radiative fluxes, snow, ice, vegetation, ocean color, and land cover. Achieving sufficient satellite instrument accuracy, stability, and overlap to rigorously observe decadal change signals has proven very difficult in most cases and has not yet been achieved in others [2]. One of the earliest efforts to make climate quality observations was for Earth Radiation Budget: Nimbus 6/7 in the late 1970s, ERBE in the 1980s/90s, and CERES in 2000s are examples of the most complete global records. The recent CERES data products have carried out the most extensive intercomparisons because if the need to merge data from up to 11 instruments (CERES, MODIS, geostationary imagers) on 7 spacecraft (Terra, Aqua, and 5 geostationary) for any given month. In order to achieve climate calibration for cloud feedbacks, the radiative effect of clear-sky, all-sky, and cloud radiative effect must all be made with very high stability and accuracy. For shortwave solar reflected flux, even the 1% CERES broadband absolute accuracy (1-sigma confidence bound) is not sufficient to allow gaps in the radiation record for decadal climate change. Typical absolute accuracy for the best narrowband sensors like SeaWiFS, MISR, and MODIS range from 2 to 4% (1-sigma). IPCC greenhouse gas radiative forcing is approx. 0.6 W/sq m per decade or 0.6% of the global mean shortwave reflected flux, so that a 50% cloud feedback would change the global

  13. In-flight absolute calibration of the CBERS-2 CCD sensor data.

    PubMed

    Ponzoni, Flávio J; Zullo Junior, Jurandir; Lamparelli, Rubens A C

    2008-06-01

    Since the first images of the sensors on board of CBERS-2 (China-Brazil Earth Resources Satellite) satellite were made available by the National Institute for Space Research (INPE), users have asked information about the conversion of image digital numbers to physical data (radiance or reflectance). This paper describes the main steps that were carried out to calculate the in-flight absolute calibration coefficients for CBERS-2 CCD level 2 (radiometric and geometric correction) images considering the reflectance-based method. Remarks about the preliminary evaluation of these coefficients application are also presented.

  14. 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.

  15. 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

  16. 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.

  17. Estimates of absolute flux and radiance factor of localized regions on Mars in the 2-4 micron wavelength region

    NASA Technical Reports Server (NTRS)

    Roush, Ted L.; Roush, Eileen A.; Singer, Robert B.; Lucey, Paul G.

    1992-01-01

    IRTF spectrophotometric observations of Mars obtained during the 1986 opposition are the bases for the present estimates of 2.0-4.15 micron absolute flux and radiance factor values. The bright/dark ratios obtained show a wavelength dependence similar to that observed by Bell and Crisp (1991) in 1990, but the spectral contrast for 1986 is lower than in those observations; this difference could be due to changes in the location, sample are size, and/or suspended atmospheric dust.

  18. 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.

  19. Absolute calibration technique for broadband ultrasonic transducers

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H. (Inventor)

    1994-01-01

    Calibrating an ultrasonic transducer can be performed with a reduced number of calculations and testing. A wide-band pulser is connected to an ultrasonic transducer under test to generate ultrasonic waves in a liquid. A single frequency is transmitted to the electrostatic acoustic transducer (ESAT) and the voltage change produced is monitored. Then a broadband ultrasonic pulse is generated by the ultrasonic transducer and received by the ESAT. The output of the ESAT is amplified and input to a digitized oscilloscope for fast Fourier transform. The resulting plot is normalized with the monitored signal from the single frequency pulse. The plot is then corrected for characteristics of the membrane and diffraction effects. The transfer function of the final plot is determined. The transfer function gives the final sensitivity of the ultrasonic transducer as a function of frequency. The advantage of the system is the speed of calibrating the transducer by a reduced number of measurements and removal of the membrane and diffraction effects.

  20. 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.

  1. 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.

  2. In-progress absolute radiometric inflight calibration of the LANDSAT-4 sensors

    NASA Technical Reports Server (NTRS)

    Castle, K.; Dinguirard, M.; Ezra, C. E.; Holm, R. G.; Jackson, R. J.; Kastner, C. J.; Palmer, J. M.; Savage, R.; Slater, P. N.

    1983-01-01

    An approach is described for providing periodic inflight absolute radiometric calibrations of the LANDSAT-4 sensors by reference to selected, instrumented ground areas. Results of some early ground measurements and computer simulations are presented. Selection of a suitable ground reference site, accurate measurement of the spectral reflectance of the selected area, determination of atmospheric characteristics during the morning of the sensor overpass, reduction of the measured data and their use in an appropriate atmospheric radiative transfer program, and comparison of the radiance level data with the digital counts of for the images of the selected areas are discussed. Preliminary measurements of gypsum are being made as an aid in defining the characteristics of field equipment to be constructed and calibrated for use over the White Sands Missile Range.

  3. Operational calibration of the METEOSAT water vapor channel by calculated radiances.

    PubMed

    Schmetz, J

    1989-08-01

    A method is presented for calibrating the water vapor channel (5.7-7.1 microm) of the geostationary meteorological satellite METEOSAT by radiative transfer calculations. Radiances are calculated from the temperature and moisture profiles of conventional radiosondes and linearly related to collocated satellite measured digital counts. Collocations are considered only for areas with neither medium nor high level cloud. Radiosonde data are routinely received twice per day (1200 and 2400 UT). Radiosonde profiles from an 8-day period in May 1988, and simultaneous Meteosat-2 water vapor measurements are analyzed. The total of 340 collocations provides a calibration coefficient with a precision of 2% assuming a 95% confidence. A preliminary analysis of calibration coefficients of the recently launched METEOSAT-3 shows a significant increase of 6% over a period of 48 days in Sept./Oct. 1988. The calibrated water vapor radiances are operationally used to estimate the upper tropospheric humidity field and to correct the height assignment of semitransparent clouds. PMID:20555647

  4. GNSS Absolute Antenna Calibration at the National Geodetic Survey

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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. To help meet the needs of the high-precision GNSS community, the National Geodetic Survey (NGS) now operates an absolute antenna calibration facility. Located in Corbin, Virginia, this facility uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. The NGS facility was built to serve traditional NGS constituents such as the surveying and geodesy communities, however calibration services are open and available to all GNSS users as the calibration schedule permits. All phase center patterns computed by this facility will be publicly available and disseminated in both the ANTEX and NGS formats. We describe the NGS calibration facility, and discuss the observation models and strategy currently used to generate NGS absolute calibrations. We demonstrate that NGS absolute phase center variation (PCV) patterns are consistent with published values determined by other absolute antenna calibration facilities, and compare absolute calibrations to the traditional NGS relative calibrations.

  5. 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

  6. 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.

  7. 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.

  8. An Investigation of Mars NIR Spectral Features using Absolutely Calibrated Images

    NASA Astrophysics Data System (ADS)

    Klassen, D. R.; Bell, J. F., III

    1998-09-01

    We used the NSFCAM 256x256 InSb array camera at the NASA Infrared Telescope Facility to gather near-infrared (NIR) spectral image sets of Mars through the 1995 opposition. In previous studies with these data [1-6] we noted several interesting spectral features, some of which are diagnostic volatile absorption bands that allow the discrimination between CO_2 or H_2O ices. Band depth maps of these regions show polar and morning and evening limb ices composed of water and some indication of polar CO_2 ices. Other features, near 3.33 and 3.4\\micron, appear to be confined to particular geographic regions; specifically Syrtis Major. However, the images used in these previous studies were calibrated to either the disk average or only to a rough scaled reflectance by simple division by solar-type star data gathered at the same time as the images. This only allowed determinations of spectral features either relative to some global average of the feature, or to some unit not directly comparable to other published data. For at least three of our observation nights the conditions and data are sufficient to absolutely calibrate the images to radiance factors. For this work we reinvestigate the spectra and band depth mapping results using these absolutely calibrated images. In general we find that bright regions have peak radiance factors of 0.5 to 0.6 at 2.25\\micron\\ and 0.3 to 0.4 at 3.5\\micron; dark regions have radiance factors of 0.2 to 0.25 at 2.25\\micron\\ and 0.1 to 0.15 at 3.5\\micron. Overall, precision errors are about 0.025 in radiance factor and absolute errors are at the 10-15% level. These results are consistent with previous studies that found radiance factors of 0.35 in Tharsis, 0.47 in Elysium, and 0.26 in dark regions at 2.25\\micron\\ [7,8] and 0.3 in bright regions and 0.1 in dark regions at 3.5\\micron\\ [8]. These absolute flux values will allow direct comparison of these results to radiative transfer models of the behavior of the surface and

  9. 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.

  10. Absolute calibration of Landsat instruments using the moon.

    USGS Publications Warehouse

    Kieffer, H.H.; Wildey, R.L.

    1985-01-01

    A lunar observation by Landsat could provide improved radiometric and geometric calibration of both the Thematic Mapper and the Multispectral Scanner in terms of absolute radiometry, determination of the modulation transfer function, and sensitivity to scattered light. A pitch of the spacecraft would be required. -Authors

  11. 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.

  12. Absolute GNSS Antenna Calibration at the National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G.; Bilich, A.; Geoghegan, C.

    2012-04-01

    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. To help meet the needs of the high-precision GNSS community, the National Geodetic Survey (NGS) now operates an absolute antenna calibration facility. Located in Corbin, Virginia, this facility uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. The NGS facility was built to serve traditional NGS constituents such as the surveying and geodesy communities, however calibration services are open and available to all GNSS users as the calibration schedule permits. All phase center patterns computed by this facility will be publicly available and disseminated in both the ANTEX and NGS formats. We describe the NGS calibration facility, and discuss the observation models and strategy currently used to generate NGS absolute calibrations. We demonstrate that NGS absolute phase center variation (PCV) patterns are consistent with published values determined by other absolute antenna calibration facilities, and outline future planned refinements to the system.

  13. Instrument development for atmospheric radiation measurement (ARM): Status of the Atmospheric Emitted Radiance Interferometer - extended Resolution (AERI-X), the Solar Radiance Transmission Interferometer (SORTI), and the Absolute Solar Transmission Inferometer (ASTI)

    SciTech Connect

    Murcray, F.; Stephen, T.; Kosters, J.

    1996-04-01

    This paper describes three instruments currently under developemnt for the Atmospheric Radiation Measurement (ARM) Program at the University of Denver: the AERI-X (Atmospheric Emitted Radiance Interferometer-Extended Resolution) and the SORTI (Solar R adiance Transmission Interferometer), and ASTI (Absolute Solar transmission Interferometer).

  14. [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%.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Markham, Brian L.; Barker, John L.; Barsi, Julia A.; Kaita, Ed; Thome, Kurtis J.; Helder, Dennis L.; Palluconi, Frank D.; Schott, John R.; Scaramuzza, Pat

    2003-04-01

    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/m2 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.

  17. 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.

  18. Inter-Calibration and Concatenation of Climate Quality Infrared Cloudy Radiances from Multiple Instruments

    NASA Technical Reports Server (NTRS)

    Behrangi, Ali; Aumann, Hartmut H.

    2013-01-01

    A change in climate is not likely captured from any single instrument, since no single instrument can span decades of time. Therefore, to detect signals of global climate change, observations from many instruments on different platforms have to be concatenated. This requires careful and detailed consideration of instrumental differences such as footprint size, diurnal cycle of observations, and relative biases in the spectral brightness temperatures. Furthermore, a common basic assumption is that the data quality is independent of the observed scene and therefore can be determined using clear scene data. However, as will be demonstrated, this is not necessarily a valid assumption as the globe is mostly cloudy. In this study we highlight challenges in inter-calibration and concatenation of infrared radiances from multiple instruments by focusing on the analysis of deep convective or anvil clouds. TRMM/VIRS is potentially useful instrument to make correction for observational differences in the local time and foot print sizes, and thus could be applied retroactively to vintage instruments such as AIRS, IASI, IRIS, AVHRR, and HIRS. As the first step, in this study, we investigate and discuss to what extent AIRS and VIRS agree in capturing deep cloudy radiances at the same local time. The analysis also includes comparisons with one year observations from CrIS. It was found that the instruments show calibration differences of about 1K under deep cloudy scenes that can vary as a function of land type and local time of observation. The sensitivity of footprint size, view angle, and spectral band-pass differences cannot fully explain the observed differences. The observed discrepancies can be considered as a measure of the magnitude of issues which will arise in the comparison of legacy data with current data.

  19. Updated Absolute Flux Calibration of the COS FUV Modes

    NASA Astrophysics Data System (ADS)

    Massa, D.; Ely, J.; Osten, R.; Penton, S.; Aloisi, A.; Bostroem, A.; Roman-Duval, J.; Proffitt, C.

    2014-03-01

    We present newly derived point source absolute flux calibrations for the COS FUV modes at both the original and second lifetime positions. The analysis includes observa- tions through the Primary Science Aperture (PSA) of the standard stars WD0308-565, GD71, WD1057+729 and WD0947+857 obtained as part of two calibration programs. Data were were obtained for all of the gratings at all of the original CENWAVE settings at both the original and second lifetime positions and for the G130M CENWAVE = 1222 at the second lifetime position. Data were also obtained with the FUVB segment for the G130M CENWAVE = 1055 and 1096 setting at the second lifetime position. We also present the derivation of L-flats that were used in processing the data and show that the internal consistency of the primary standards is 1%. The accuracy of the absolute flux calibrations over the UV are estimated to be 1-2% for the medium resolution gratings, and 2-3% over most of the wavelength range of the G140L grating, although the uncertainty can be as large as 5% or more at some G140L wavelengths. We note that these errors are all relative to the optical flux near the V band and small additional errors may be present due to inaccuracies in the V band calibration. In addition, these error estimates are for the time at which the flux calibration data were obtained; the accuracy of the flux calibration at other times can be affected by errors in the time dependent sensitivity (TDS) correction.

  20. On the Error Sources in Absolute Individual Antenna Calibrations

    NASA Astrophysics Data System (ADS)

    Aerts, Wim; Baire, Quentin; Bilich, Andria; Bruyninx, Carine; Legrand, Juliette

    2013-04-01

    field) multi path errors, both during calibration and later on at the station, absolute sub-millimeter positioning with GPS is not (yet) possible. References [1] G. Wübbena, M. Schmitz, G. Boettcher, C. Schumann, "Absolute GNSS Antenna Calibration with a Robot: Repeatability of Phase Variations, Calibration of GLONASS and Determination of Carrier-to-Noise Pattern", International GNSS Service: Analysis Center workshop, 8-12 May 2006, Darmstadt, Germany. [2] P. Zeimetz, H. Kuhlmann, "On the Accuracy of Absolute GNSS Antenna Calibration and the Conception of a New Anechoic Chamber", FIG Working Week 2008, 14-19 June 2008, Stockholm, Sweden. [3] P. Zeimetz, H. Kuhlmann, L. Wanninger, V. Frevert, S. Schön and K. Strauch, "Ringversuch 2009", 7th GNSS-Antennen-Workshop, 19-20 March 2009, Dresden, Germany.

  1. 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.

  2. 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. PMID:22938275

  3. 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.

  4. Flow rate calibration for absolute cell counting rationale and design.

    PubMed

    Walker, Clare; Barnett, David

    2006-05-01

    There is a need for absolute leukocyte enumeration in the clinical setting, and accurate, reliable (and affordable) technology to determine absolute leukocyte counts has been developed. Such technology includes single platform and dual platform approaches. Derivations of these counts commonly incorporate the addition of a known number of latex microsphere beads to a blood sample, although it has been suggested that the addition of beads to a sample may only be required to act as an internal quality control procedure for assessing the pipetting error. This unit provides the technical details for undertaking flow rate calibration that obviates the need to add reference beads to each sample. It is envisaged that this report will provide the basis for subsequent clinical evaluations of this novel approach. PMID:18770842

  5. 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.

  6. 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.

  7. Absolute calibration of a laser system for atmospheric probing.

    PubMed

    Hall, F F; Ageno, H Y

    1970-08-01

    In order to obtain quantitative data on the backscatter function from laser irradiance backscattered from the atmosphere, the ratio of power transmitted to power received must be accurately known. No absolute measurements of power, optical system transmittance, detector quantum efficiency, or electronic gain are necessarily required. The technique of measuring the power ratio by irradiating a smoked or painted target of known diffuse reflectance at a fixed range is used to calibrate a complete lidar system. The relative area of the output power pulse is monitored by a fast response photodiode, and the relative area of the returned pulse is also recorded after passing through a filter of known high optical density. It is essential to control the temperatures of the laser rod and receiver interference prefilter to ensure proper spectral matching. Field experience gained using this technique is described, and examples of calibration measurements and backscatter functions for smog and cirrus clouds are presented.

  8. 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.

  9. The Absolute Calibration of the HiRes Detectors

    NASA Astrophysics Data System (ADS)

    Matthews, J. N.; Thomas, S. B.; HiRes Collaboration

    2003-07-01

    The HiRes experiment studies ultra high energy cosmic rays using the air fluorescence technique. The experiment uses large mirrors that collect the fluorescence light and fo cus it onto arrays of photomultiplier tubes (PMTs). The PMTs measure the intensity and time of arrival of the collected light. Our primary system for in situ calibration of the PMTs uses a high stability (<1%) portable light source. This source is transferred from the lab to the field where it is employed as a standard candle to calibrate the 64 detectors (>16,000 PMTs). To determine the absolute response it is necessary to understand the absolute light output of this source. We have measured the source irradiance using a hybrid photo dio de system, two NIST calibrated photo-dio des, and by observing the photo electron statistics of the PMTs. 2. Introduction The goal of the High Resolution Fly's Eye (HiRes) project is to study cosmic rays at the highest energies. An ultra high energy cosmic ray entering the earth's atmosphere collides with atmospheric nuclei triggering the development of an Extensive Air Shower (EAS). The EAS emits fluorescence light as it develops. HiRes uses the air fluorescence signal to measure properties of the primary cosmic ray particle. The fundamental detector elements in HiRes are photomultiplier tubes (PMTs). The light from an EAS is collected by large mirrors and fo cused into cameras each consisting of 256 PMTs [1]. Routine monitoring and calibration of the PMTs and associated electronics are crucial to the proper interpretation of the data. The primary system for in situ calibration of the PMTs involves the use of a high stability portable xenon flash lamp. The Roving Xenon Flasher (RXF) offers several advantages. The pulse-to-pulse variation in intensity is very small ˜0.3% and the stability over a night is better than 2%. The emission spectrum of the RXF is sufficiently broad to allow calibration over a wide range of wavelengths. It is also readily transported

  10. On the absolute calibration of SO2 cameras

    NASA Astrophysics Data System (ADS)

    Lübcke, P.; Bobrowski, N.; Illing, S.; Kern, C.; Alvarez Nieves, J. M.; Vogel, L.; Zielcke, J.; Delgado Granados, H.; Platt, U.

    2012-09-01

    Sulphur dioxide emission flux measurements are an important tool for volcanic monitoring and eruption risk assessment. The SO2 camera technique remotely measures volcanic emissions by analysing the ultraviolet absorption of SO2 in a narrow spectral window between 305 nm and 320 nm using solar radiation scattered in the atmosphere. The SO2 absorption is selectively detected by mounting band-pass interference filters in front of a two-dimensional, UV-sensitive CCD detector. While this approach is simple and delivers valuable insights into the two-dimensional SO2 distribution, absolute calibration has proven to be difficult. An accurate calibration of the SO2 camera (i.e., conversion from optical density to SO2 column density, CD) is crucial to obtain correct SO2 CDs and flux measurements that are comparable to other measurement techniques and can be used for volcanological applications. The most common approach for calibrating SO2 camera measurements is based on inserting quartz cells (cuvettes) containing known amounts of SO2 into the light path. It has been found, however, that reflections from the windows of the calibration cell can considerably affect the signal measured by the camera. Another possibility for calibration relies on performing simultaneous measurements in a small area of the camera's field-of-view (FOV) by a narrow-field-of-view Differential Optical Absorption Spectroscopy (NFOV-DOAS) system. This procedure combines the very good spatial and temporal resolution of the SO2 camera technique with the more accurate column densities obtainable from DOAS measurements. 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 NFOV-DOAS system and an Imaging DOAS (IDOAS), are presented. We compare the calibration-cell approach with the calibration from the NFOV-DOAS system. The respective

  11. Absolute calorimetric calibration of low energy brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Stump, Kurt E.

    In the past decade there has been a dramatic increase in the use of permanent radioactive source implants in the treatment of prostate cancer. A small radioactive source encapsulated in a titanium shell is used in this type of treatment. The radioisotopes used are generally 125I or 103Pd. Both of these isotopes have relatively short half-lives, 59.4 days and 16.99 days, respectively, and have low-energy emissions and a low dose rate. These factors make these sources well suited for this application, but the calibration of these sources poses significant metrological challenges. The current standard calibration technique involves the measurement of ionization in air to determine the source air-kerma strength. While this has proved to be an improvement over previous techniques, the method has been shown to be metrologically impure and may not be the ideal means of calbrating these sources. Calorimetric methods have long been viewed to be the most fundamental means of determining source strength for a radiation source. This is because calorimetry provides a direct measurement of source energy. However, due to the low energy and low power of the sources described above, current calorimetric methods are inadequate. This thesis presents work oriented toward developing novel methods to provide direct and absolute measurements of source power for low-energy low dose rate brachytherapy sources. The method is the first use of an actively temperature-controlled radiation absorber using the electrical substitution method to determine total contained source power of these sources. The instrument described operates at cryogenic temperatures. The method employed provides a direct measurement of source power. The work presented here is focused upon building a metrological foundation upon which to establish power-based calibrations of clinical-strength sources. To that end instrument performance has been assessed for these source strengths. The intent is to establish the limits of

  12. THE ABSOLUTE CALIBRATION OF THE EUV IMAGING SPECTROMETER ON HINODE

    SciTech Connect

    Warren, Harry P.; Ugarte-Urra, Ignacio; Landi, Enrico

    2014-07-01

    We investigate the absolute calibration of the EUV Imaging Spectrometer (EIS) on Hinode by comparing EIS full-disk mosaics with irradiance observations from the EUV Variability Experiment on the Solar Dynamics Observatory. We also use extended observations of the quiet corona above the limb combined with a simple differential emission measure model to establish new effective area curves that incorporate information from the most recent atomic physics calculations. We find that changes to the EIS instrument sensitivity are a complex function of both time and wavelength. We find that the sensitivity is decaying exponentially with time and that the decay constants vary with wavelength. The EIS short wavelength channel shows significantly longer decay times than the long wavelength channel.

  13. 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.

  14. 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.

  15. Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS 1A) Earth limb spectral measurements, calibration, and atmospheric O3, HNO3, CFC-12, and CFC-11 profile retrieval

    NASA Astrophysics Data System (ADS)

    Bingham, G. E.; Zhou, D. K.; Bartschi, B. Y.; Anderson, G. P.; Smith, D. R.; Chetwynd, J. H.; Nadile, R. M.

    1997-02-01

    During the Space Transportation System 39 (STS 39) flight of April 28 to May 6, 1991, the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS 1A) measured spectral and spatial ("Earth limb scan") distributions of the atmospheric infrared (IR) emissions using a Michelson interferometer. The IR spectral radiant emissions from the greenhouse gases were collected at a shuttle altitude of 260 km in the 9-13 μm atmosphere infrared window. Before and after the flight, the response of CIRRIS 1A to the IR spectral emission sources was calibrated using absolute and spectral source types. The Fast Atmospheric Signature Code 3, which used the HITRAN92 database and predetermined temperature-pressure profiles from the National Meteorological Center, was used in an onion-peeling routine to retrieve gas concentrations from absolutely calibrated spectral data (moderate resolution ˜1.0 cm-1). Vertical profiles of O3, HNO3, CFC-12, and CFC-11 are presented. An error analysis is presented to show the quality of the measured spectral data and the accuracy of these retrieval results. The concentrations of CFC-11 (3.0×10-4 ppmv) and CFC-12 (4.9×10-4 ppmv) in the tropopause region are consistent with a global flux increment rate of about 5% yr-1. The observed concentrations of HNO3 are consistent with previous reports for a relatively clean stratosphere.

  16. 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.

  17. Relative vs Absolute Antenna Calibrations: How, when, and why do they differ? A Comparison of Antenna Calibration Catalogs

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Since 1994, NGS has computed relative antenna calibrations for more than 350 antenna models used by NGS customers and geodetic networks worldwide. In a 'relative' calibration, the antenna under test is calibrated relative to a standard reference antenna, the AOA D/M_T chokering. The majority of NGS calibrations have been made publicly available at the web site www.ngs.noaa.gov/ANTCAL as well as via the NGS master calibrations file ant_info.003. In the mid-2000's, institutions in Germany began distributing 'absolute' antenna calibrations, where the antenna under test is calibrated independent of any reference antenna. These calibration methods also overcame some limitations of relative calibrations by going to lower elevation angles and capturing azimuthal variations. Soon thereafter (2008), the International GNSS Service (IGS) initiated a geodetic community movement away from relative calibrations and toward absolute calibrations as the defacto standard. The IGS now distributes a catalog of absolute calibrations taken from several institutions, distributed as the IGS master calibrations file igs08.atx. The competing methods and files have raised many questions about when it is or is not valid to process a geodetic network using a combination of relative and absolute calibrations, and if/when it is valid to combine the NGS and IGS catalogs. Therefore, in this study, we compare the NGS catalog of relative calibrations against the IGS catalog of absolute calibrations. As of the writing of this abstract, there are 77 antenna+radome combinations which are common to both the NGS relative and IGS absolute catalogs, spanning 16 years of testing (1997 to present). 50 different antenna models and 8 manufacturers are represented in the study sample. We apply the widely-accepted standard method for converting relative to absolute, then difference the calibrations. Various statistics describe the observed differences between phase center offset (PCO), phase center variation

  18. 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. PMID:26428812

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

    PubMed Central

    Rich, Kyle T.; Mast, T. Douglas

    2015-01-01

    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. PMID:26428812

  20. High Altitude Measurements of Radiance at High Spectral and Spatial Resolution for SIMBIOS Sensor Calibration, Validation, and Intercomparisons. Chapter 11

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Pavri, Betina; Chrien, Thomas G.

    2001-01-01

    The successful combination of data from different ocean color sensors depends on the correct interpretation of signal from each of these sensors. Ideally, the sensor measured signals are calibrated to geophysical units of spectral radiance, and sensor artifacts are removed and corrected. The calibration process resamples the signal into a common radiometric data space so that subsequent ocean color algorithms that are applied to the data are based on physical processes and are inherently sensor independent. The objective of this project is to calibrate and validate the on-orbit radiometric characteristics of Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) with underflights of NASA's calibrated Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). This objective is feasible because AVIRIS measures the same spectral range as SeaWIFS at higher spectral resolution. In addition to satellite sensor underflights, the AVIRIS project has supported comparison and analysis of the radiometric calibration standards used for AVIRIS and SeaWIFS. To date, both the OCTS and SeaWIFS satellite sensors have been underflown by AVIRIS with matching spectral, spatial, geometric, radiometric, and temporal domains. The calibration and validation objective of this project is pursued for the following reasons: (1) Calibration is essential for the quantitative use of SeaWIFS and other SIMBIOS (Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies) sensor data; (2) Calibration in the laboratory of spaceborne sensors is challenging; (3) Satellite sensors are subjected aging on the ground and to trauma during launch; (4) The Earth orbit environment is significantly different than the laboratory calibration environment; (5) Through years of effort AVIRIS has been demonstrated to be well calibrated; and (6) AVIRIS can match the spectral and spatial observation characteristics near the top of the atmosphere at the time of SeaWIFS measurements.

  1. Absolute calibration of space-resolving soft X-ray spectrograph for plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Yoshikawa, M.; Okamoto, Y.; Kawamori, E.; Watanabe, Y.; Watabe, C.; Yamaguchi, N.; Tamano, T.

    2001-07-01

    A grazing incidence flat-field soft X-ray (20-350 Å) spectrograph was constructed and applied for impurity diagnostics in the GAMMA 10 fusion plasma. The spectrograph consisted of a limited height entrance slit, an aberration-corrected concave grating, a microchannel-plate intensified detector and an instant camera/a high speed solid state camera. An absolute calibration experiment for the SX spectrograph was performed at the Photon Factory in the High Energy Accelerator Research Organization with monitoring the incident synchrotron beam intensity by using an absolutely calibrated XUV silicon photodiode. From the results of absolute calibration of the spectrograph, the radiation loss from the plasma was obtained.

  2. 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.

  3. The Use of Transfer Radiometers in Validating the Visible through Shortwave Infrared Calibrations of Radiance Sources Used by Instruments in NASA's Earth Observing System

    NASA Technical Reports Server (NTRS)

    Butler, James J.; Barnes, Robert A.

    2002-01-01

    The detection and study of climate change over a time frame of decades requires successive generations of satellite, airborne, and ground-based instrumentation carefully calibrated against a common radiance scale. In NASA s Earth Observing System (EOS) program, the pre-launch radiometric calibration of these instruments in the wavelength region from 400 nm to 2500 nm is accomplished using internally illuminated integrating spheres and diffuse reflectance panels illuminated by irradiance standard lamps. Since 1995, the EOS Calibration Program operating within the EOS Project Science Office (PSO) has enlisted the expertise of national standards laboratories and government and university metrology laboratories in an effort to validate the radiance scales assigned to sphere and panel radiance sources by EOS instrument calibration facilities. This state-of-the-art program has been accomplished using ultra-stable transfer radiometers independently calibrated by the above participating institutions. In ten comparisons since February 1995, the agreement between the radiance measurements of the transfer radiometers is plus or minus 1.80% at 411 nm, plus or minus 1.31% at 552.5 nm, plus or minus 1.32% at 868.0 nm, plus or minus 2.54% at 1622nm, and plus or minus 2.81% at 2200nm (sigma =1).

  4. Confidence-Accuracy Calibration in Absolute and Relative Face Recognition Judgments

    ERIC Educational Resources Information Center

    Weber, Nathan; Brewer, Neil

    2004-01-01

    Confidence-accuracy (CA) calibration was examined for absolute and relative face recognition judgments as well as for recognition judgments from groups of stimuli presented simultaneously or sequentially (i.e., simultaneous or sequential mini-lineups). When the effect of difficulty was controlled, absolute and relative judgments produced…

  5. On the absolute calibration of SO2 cameras

    NASA Astrophysics Data System (ADS)

    Lübcke, P.; Bobrowski, N.; Illing, S.; Kern, C.; Alvarez Nieves, J. M.; Vogel, L.; Zielcke, J.; Delgado Granados, H.; Platt, U.

    2013-03-01

    Sulphur dioxide emission rate measurements are an important tool for volcanic monitoring and eruption risk assessment. The SO2 camera technique remotely measures volcanic emissions by analysing the ultraviolet absorption of SO2 in a narrow spectral window between 300 and 320 nm using solar radiation scattered in the atmosphere. The SO2 absorption is selectively detected by mounting band-pass interference filters in front of a two-dimensional, UV-sensitive CCD detector. One important step for correct SO2 emission rate measurements that can be compared with other measurement techniques is a correct calibration. This requires conversion from the measured optical density to the desired SO2 column density (CD). The conversion factor is most commonly determined by inserting quartz cells (cuvettes) with known amounts of SO2 into the light path. Another calibration method uses an additional narrow field-of-view Differential Optical Absorption Spectroscopy system (NFOV-DOAS), which measures the column density simultaneously in a small area of the camera's field-of-view. This procedure combines the very good spatial and temporal resolution of the SO2 camera technique with the more accurate column densities obtainable from DOAS measurements. 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 NFOV-DOAS 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

  6. Absolute calibration of the RADSCAT scatterometer using precision spheres

    NASA Technical Reports Server (NTRS)

    Grantham, W. L.; Schroeder, L. C.; Mitchell, J. L.

    1976-01-01

    Tests using precision sphere targets suspended from balloons were conducted to calibrate the received-power/transmitted-power tatio of the RADSCAT scatterometer. Comparisons were made of these measured results with theoretical return from spheres. The RADSCAT scatterometer measurements at 13.9 GHz should be corrected by -2.4 dB, and those at 9.3 GHz, by -4.3 dB. The techniques described should be generally applicable to calibration of scatterometers where measurement precision is of prime importance. Inferred from the magnitude of these RADSCAT corrections was the present state of technology in building precision scatterometers.

  7. High accuracy absolute laser powermeter calibrated over the whole range

    SciTech Connect

    Miron, N.; Korony, G.; Velculescu, V.G.

    1994-12-31

    The main contribution to this laser powermeter is the capability of its detector to be electrically calibrated over the whole measuring range (0 ... 100W), with an accuracy better than 1%. This allows an improved accuracy in determining the second-order polynomial coefficients describing thermocouple electric response.

  8. 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.

  9. 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.

  10. Strategies for absolute calibration of near infrared tomographic tissue imaging.

    PubMed

    McBride, Troy O; Pogue, Brian W; Osterberg, Ulf L; Paulsen, Keith D

    2003-01-01

    Quantitative near infrared (NIR) imaging of tissue requires the use of a diffusion model-based reconstruction algorithm, which solves for the absorption and scattering coefficients of a tissue volume by matching transmission measurements of light to the predictive diffusion equation solution. Calibration problems as well as other practical considerations arise for an imaging system when using a model-based method for a real system. For example, systematic noise in the data acquisition hardware and source/detector fibers must be removed to prevent spurious results in the reconstructed image. Practical considerations for a NIR diffuse tomographic imaging system include: (1) calibration with a homogeneous phantom, (2) use of a homogenous fitting algorithm to arrive at an initial optical property estimate for image reconstruction of a heterogeneous medium, and (3) correction for fluctuations in source strength and initial phase offset during data acquisition. These practical considerations, which rely on an accurate homogeneous fitting algorithm are described. They have allowed demonstration of a prototype imaging system that has the ability to quantitatively reconstruct heterogeneous images of hemoglobin concentrations within a highly scattering medium with no a priori information.

  11. Absolutely calibrated soft-x-ray streak camera for laser-fusion applications

    SciTech Connect

    Kauffman, R.L.; Medecki, H.; Stradling, G.

    1982-01-01

    The intensity output of a soft-x-ray streak camera was calibrated (SXRSC) in order to make absolute flux measurements of x rays emitted from laser-produced plasmas. The SXRSC developed at LLNL is used to time-resolve x-ray pulses to better than 20 ps. The SXRSC uses a Au photocathode on a thin carbon substrate which is sensitive to x rays from 100 eV to greater than 10 keV. Calibrations are done in the dynamic mode using a small laser-produced x-ray source. The SXRSC is calibrated by comparing its integrated signal to the output of calibrated x-ray diodes monitoring the source strength. The measured SXRSC response is linear over greater than two orders of magnitude. Using these calibrations, absolute intensities can be measured to an accuracy of +-30%.

  12. 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.

  13. 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.

  14. 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.

  15. Glassy carbon as an absolute intensity calibration standard for small-angle scattering.

    SciTech Connect

    Zhang, F.; Ilavsky, J.; Long, G.; Allen, A.; Quintana, J.; Jemian, P.; NIST

    2010-05-01

    Absolute calibration of small-angle scattering (SAS) intensity data (measured in terms of the differential scattering cross section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number density, volume fraction, and specific surface area of the scatterers. It also enables scattering data from different instruments (light, X-ray, or neutron scattering) to be combined, and it can even be useful to detect the existence of artifacts in the experimental data. Different primary or secondary calibration methods are available. In the latter case, absolute intensity calibration requires a stable artifact with the necessary scattering profile. Glassy carbon has sometimes been selected as this intensity calibration standard. Here we review the spatial homogeneity and temporal stability of one type of commercially available glassy carbon that is being used as an intensity calibration standard at a number of SAS facilities. We demonstrate that glassy carbon is sufficiently homogeneous and stable during routine use to be relied upon as a suitable standard for absolute intensity calibration of SAS data.

  16. 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.

  17. Absolute flux calibration for the Mg II observations near 2800 angstroms

    NASA Technical Reports Server (NTRS)

    Kondo, Y.; Duval, J. E.; Modisette, J. L.; Morgan, T. H.

    1976-01-01

    Observations of the Mg II features near 2800 A, obtained with a balloon-borne ultraviolet stellar spectrometer for five stars, have been calibrated against the absolute flux measures from OAO-2 spectrometer results. Equivalent widths of the Mg II resonance doublet and their respective subordinate lines, as well as the emission intensities, were evaluated where applicable.

  18. [Research on absolute calibration of sun channel of sun photometer using laser raster scanning method].

    PubMed

    Xu, Wen-Bin; Li, Jian-Jun; Zheng, Xiao-Bing

    2013-01-01

    In the present paper, a new calibration method of absolute spectral irradiance responsivity of sun channel of sun photometer was developed. A tunable laser was used as source and a standard tranfer detector, calibrated against cryogenic absolute radiometer, was used to measure laser beam power. By raster scanning of a single collimated laser beam to generate the uniform irradiance field at the plane of effective aperture stop of sun photometer, the absolute irradiance responsivity of center wavelength of the 870 nm unpolarized sun channels of sun photometer was obtained accurately. The relative spectral irradiance responsivity of corresponding channel was obtained by using lamp-monochromator system and then used to acquire the absolute spectral irradiance responsivity in the laboratory. On the basis of the above results, the top-of-the-atmosphere responsive constant V0 was obtained by integration with extraterrestrial solar spectral irradiance data. Comparing the calibration result with that from GSFC, NASA in 2009, the difference is only 3.75%. In the last, the uncertainties of calibration were evaluated and reached to 2.06%. The principle feasibility of the new method was validated.

  19. Possibility of absolute calibration of analog detectors by using parametric downconversion: a systematic study

    SciTech Connect

    Brida, Giorgio; Genovese, Marco; Ruo-Berchera, Ivano; Chekhova, Maria; Penin, Alexander

    2006-10-15

    Prompted by the need for various studies ranging from quantum information to foundations of quantum mechanics, we systematically study the possibility of the absolute calibration of analog photodetectors based on the properties of parametric amplifiers. Our results show that such a method can be effectively developed with interesting possible applications in metrology.

  20. Performance Demonstration of Miniature Phase Transition Cells in Microgravity as a Validation for their use in the Absolute Calibration of Temperature Sensors On-Orbit

    NASA Astrophysics Data System (ADS)

    Pettersen, C.; Best, F. A.; Adler, D. P.; Aguilar, D. M.; Perepezko, J. H.

    2012-12-01

    The next generation of infrared remote sensing missions, including the climate benchmark missions, will require better absolute measurement accuracy than now available, and will most certainly rely on the emerging capability to fly SI traceable standards that provide irrefutable absolute measurement accuracy. As an example, instrumentation designed to measure spectrally resolved infrared radiances with an absolute brightness temperature error of better than 0.1 K will require high-emissivity (>0.999) calibration blackbodies requiring absolute temperature uncertainties of better than 0.045K (k=3). Key elements of an On-Orbit Absolute Radiance Standard (OARS) meeting these stringent requirements have been demonstrated in the laboratory at the University of Wisconsin and were further refined under the NASA Instrument Incubator Program (IIP). In particular, the OARS has imbedded thermistors that can be periodically calibrated on-orbit using the melt signatures of small quantities (<0.5g) of three reference materials - mercury, water, and gallium, providing calibration from 233K to 303K. One of the many tests to determine the readiness of this technology for on-orbit application is a demonstration of performance in microgravity to be conducted on the International Space Station (ISS). This demonstration will make use of an Experiment Support Package developed by Utah State Space Dynamics Laboratory to continuously run melt cycles on miniature phase change cells containing gallium, a gallium-tin eutectic, and water. The phase change cells will be mounted in a small aluminum block along with a thermistor temperature sensor. A thermoelectric cooler will be used to change the temperature of the block. The demonstration will use the configuration of the phase transition cells developed under our NASA IIP that has been tested extensively in the laboratory under simulated mission life cycle scenarios - these included vibration, thermal soaks, and deep cycling. Melt signatures

  1. 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.

  2. 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.

  3. Relative and absolute intensity calibrations of a modern broadband echelle spectrometer

    NASA Astrophysics Data System (ADS)

    Bibinov, N.; Halfmann, H.; Awakowicz, P.; Wiesemann, K.

    2007-05-01

    We report on relative and absolute intensity calibrations of a modern broadband echelle spectrometer (type ESA 3000® trademark of LLA Instruments GmbH, Berlin) for use in the diagnostics of low-temperature plasma. This type of device measures simultaneously complete emission spectra in the spectral range from 200 to 800 nm with a spectral resolution of several picometres by using more than 90 spectral orders, causing a strongly structured efficiency function. The assumptions and approximations entering the calibration procedure under these conditions are discussed in section 3. For coping with the strongly structured efficiency function a continuum light source is needed, which covers the entire spectral range. Furthermore, the variation of its intensity must be low enough to ensure that neither statistical errors perturb the calibration in regions with low photon flux and/or low efficiency, nor local memory overflow in regions with high photon flux or high efficiency. In our case this requires that during calibration over the whole spectral range of the spectrometer the counts per pixel in one measurement vary at highest by a factor 10 to 12. Usual broadband light sources do not meet this latter requirement. We, therefore, use an uncalibrated 'composite' source, an adjustable combination of a standard tungsten strip lamp and a deuterium lamp, and calibrate the spectrometer in a two-step process against the tungsten strip lamp and well-known rovibrational intensity distributions in the emission spectra of NO and N2. We adjust the composite source in a way to produce a perturbation-free first approximation of an (uncalibrated) efficiency function, which is then corrected and thus calibrated by comparison with the (secondary) standards mentioned above. For absolute calibration we use the tungsten strip lamp. The uncertainty attained in this way for the relative calibration depends on the wavelength and varies between 5% and 10%. For the absolute calibration we

  4. Rapid, absolute calibration of x-ray filters employed by laser-produced plasma diagnostics.

    PubMed

    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

    2008-10-01

    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. PMID:19044471

  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.

    2008-10-15

    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. 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.

  7. Calibration-free absolute frequency response measurement of directly modulated lasers based on additional modulation.

    PubMed

    Zhang, Shangjian; Zou, Xinhai; Wang, Heng; Zhang, Yali; Lu, Rongguo; Liu, Yong

    2015-10-15

    A calibration-free electrical method is proposed for measuring the absolute frequency response of directly modulated semiconductor lasers based on additional modulation. The method achieves the electrical domain measurement of the modulation index of directly modulated lasers without the need for correcting the responsivity fluctuation in the photodetection. Moreover, it doubles measuring frequency range by setting a specific frequency relationship between the direct and additional modulation. Both the absolute and relative frequency response of semiconductor lasers are experimentally measured from the electrical spectrum of the twice-modulated optical signal, and the measured results are compared to those obtained with conventional methods to check the consistency. The proposed method provides calibration-free and accurate measurement for high-speed semiconductor lasers with high-resolution electrical spectrum analysis.

  8. 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.

  9. 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.

  10. Absolute calibration of a charge-coupled device camera with twin beams

    SciTech Connect

    Meda, A.; Ruo-Berchera, I. Degiovanni, I. P.; Brida, G.; Rastello, M. L.; Genovese, M.

    2014-09-08

    We report on the absolute calibration of a Charge-Coupled Device (CCD) camera by exploiting quantum correlation. This method exploits a certain number of spatial pairwise quantum correlated modes produced by spontaneous parametric-down-conversion. We develop a measurement model accounting for all the uncertainty contributions, and we reach the relative uncertainty of 0.3% in low photon flux regime. This represents a significant step forward for the characterization of (scientific) CCDs used in mesoscopic light regime.

  11. Absolute calibration in the 1750 A-3350 A region. [revisions for air extinction

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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 A-3350 A region. The absolute flux of the star Eta UMa (B3 V) is compared to four other independent determinations in the 1200 A-3400 A region and a maximum difference of 35% is found near 1500 A between the OAO-2 and Apollo 17 fluxes. Longward of 1700 A the typical scatter in the different determinations is only plus or minus 5%. 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 plus or minus 3%. Therefore, all four sets of spectrophotometry can be reduced to a common absolute scale.

  12. Vacuum compatible large uniform-radiance source for ground calibration of satellite cameras inside a thermal vacuum environment

    NASA Astrophysics Data System (ADS)

    Arecchi, Angelo V.; Pal, Samir; Jablonski, Joseph W.; Gervais, Marc; Gugliotta, Mark; Seth, Harish; Bhardwaj, Arun; Sahoo, Hari Sankar

    2008-08-01

    A vacuum compatible integrating sphere was built to operate inside a thermal vacuum chamber. This paper presents the design and test results for a 1.65 meter diameter vacuum compatible integrating sphere with a 1.0 meter diameter exit port and approximately 10kW of internal tungsten lamps. Liquid nitrogen is used as cooling medium to remove the heat generated by these lamps. There are no moving parts inside the vacuum chamber. The radiance is monitored with two filter-wheel detectors, one TE-cooled silicon and one TE-cooled germanium, as well as a TE-cooled silicon array spectrometer. All three detectors are located outside the thermal vacuum chamber and view the sphere radiance through fiber optic cables. The system was tested inside a thermal vacuum chamber at NASA Goddard Space Flight Center before commissioning in the 5.5 meter thermal vacuum chamber at Space Applications Centre in Ahmedabad, India. Results of tests of radiance uniformity, radiance levels, and radiance stability are presented. Comparisons of the filter radiometers with the array spectrometer are also presented.

  13. Absolute calibration of a hydrogen discharge lamp in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Nealy, J. E.

    1975-01-01

    A low-pressure hydrogen discharge lamp was calibrated for radiant intensity in the vacuum ultraviolet spectral region on an absolute basis and was employed as a laboratory standard source in spectrograph calibrations. This calibration was accomplished through the use of a standard photodiode detector obtained from the National Bureau of Standards together with onsite measurements of spectral properties of optical components used. The stability of the light source for use in the calibration of vacuum ultraviolet spectrographs and optical systems was investigated and found to be amenable to laboratory applications. The lamp was studied for a range of operating parameters; the results indicate that with appropriate peripheral instrumentation, the light source can be used as a secondary laboratory standard source when operated under preset controlled conditions. Absolute intensity measurements were recorded for the wavelengths 127.7, 158.0, 177.5, and 195.0 nm for a time period of over 1 month, and the measurements were found to be repeatable to within 11 percent.

  14. 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.

  15. Multispectral Photometry of the Moon and Absolute Calibration of the Clementine UV/Vis Camera

    NASA Astrophysics Data System (ADS)

    Hillier, John K.; Buratti, Bonnie J.; Hill, Kathryn

    1999-10-01

    We present a multispectral photometric study of the Moon between solar phase angles of 0 and 85°. Using Clementine images obtained between 0.4 and 1.0 μm, we produce a comprehensive study of the lunar surface containing the following results: (1) empirical photometric functions for the spectral range and viewing and illumination geometries mentioned, (2) photometric modeling that derives the physical properties of the upper regolith and includes a detailed study of the causes for the lunar opposition surge, (3) an absolute calibration of the Clementine UV/Vis camera. The calibration procedure given on the Clementine calibration web site produces reflectances relative to a halon standard and further appear significantly higher than those seen in groundbased observations. By comparing Clementine observations with prior groundbased observations of 15 sites on the Moon we have determined a good absolute calibration of the Clementine UV/Vis camera. A correction factor of 0.532 has been determined to convert the web site (www.planetary.brown.edu/clementine/calibration.html) reflectances to absolute values. From the calibrated data, we calculate empirical phase functions useful for performing photometric corrections to observations of the Moon between solar phase angles of 0 and 85° and in the spectral range 0.4 to 1.0μm. Finally, the calibrated data is used to fit a version of Hapke's photometric model modified to incorporate a new formulation, developed in this paper, of the lunar opposition surge which includes coherent backscatter. Recent studies of the lunar opposition effect have yielded contradictory results as to the mechanism responsible: shadow hiding, coherent backscatter, or both. We find that most of the surge can be explained by shadow hiding with a halfwidth of ˜8°. However, for the brightest regions (the highlands at 0.75-1.0μm) a small additional narrow component (halfwidth of <2°) of total amplitude ˜1/6 to 1/4 that of the shadow hiding surge is

  16. PREMOS Absolute Radiometer Calibration and Implications to on-orbit Measurements of the Total Solar Irradiance

    NASA Astrophysics Data System (ADS)

    Fehlmann, A.; Kopp, G.; Schmutz, W. K.; Winkler, R.; Finsterle, W.; Fox, N.

    2011-12-01

    On orbit measurements starting in the late 1970's, have revealed the 11 year cycle of the Total Solar Irradiance (TSI). However, the absolute results from individual experiments differ although all instrument teams claim to measure an absolute value. Especially the data from the TIM/SORCE experiment confused the community as it measures 0.3 % lower than the other instruments, e.g. VIRGO/SOHO by PMOD/WRC, which clearly exceeds the uncertainty stated for the absolute characterization of the experiments. The PREMOS package on the PICARD platform launched in June 2010 is the latest space experiment by PMOD/WRC measuring the TSI. We have put great effort in the calibration and characterization of this instrument in order to resolve the inter-instrument differences. We performed calibrations at the National Physical Laboratory (NPL) in London and the Laboratory for Atmospheric and Space Physics (LASP) in Boulder against national SI standards for radiant power using a laser beam with a diameter being smaller than the aperture of the instrument. These measurements together with the World Radiometric Reference (WRR) calibration in Davos allowed to compare the WRR and the SI radiant power scale. We found that the WRR lies 0.18 % above the SI radiant power scale which explains a part of the VIRGO-TIM difference. The Total solar irradiance Radiometer Facility (TRF) at the LASP allows to generate a beam that over fills the apertures of our instruments, giving the presently best available representation of solar irradiance in a laboratory. These irradiance calibrations revealed a stray light contribution between 0.09 and 0.3 % to the measurements which had been underestimated in the characterization of our instruments. Using the irradiance calibrations, we found that the WRR lies 0.32 % above the TRF scale which in turn explains the full VIRGO-TIM difference. The first light PREMOS measurements in space confirmed our findings. If we use the WRR calibration, PREMOS yields a TSI

  17. SIMBIOS Normalized Water-Leaving Radiance Calibration and Validation: Sensor Response, Atmospheric Corrections, Stray Light and Sun Glint. Chapter 14

    NASA Technical Reports Server (NTRS)

    Mueller, James L.

    2001-01-01

    This Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) contract supports acquisition of match up radiometric and bio-optical data for validation of Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) and other ocean color satellites, and evaluation of uncertainty budgets and protocols for in situ measurements of normalized water leaving radiances.

  18. 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.

  19. Precision evaluation of calibration factor of a superconducting gravimeter using an absolute gravimeter

    NASA Astrophysics Data System (ADS)

    Feng, Jin-yang; Wu, Shu-qing; Li, Chun-jian; Su, Duo-wu; Xu, Jin-yi; Yu, Mei

    2016-01-01

    The precision of the calibration factor of a superconducting gravimeter (SG) using an absolute gravimeter (AG) is analyzed based on linear least square fitting and error propagation theory and factors affecting the accuracy are discussed. It can improve the accuracy to choose the observation period of solid tide as a significant change or increase the calibration time. Simulation is carried out based on synthetic gravity tides calculated with T-soft at observed site from Aug. 14th to Sept. 2nd in 2014. The result indicates that the highest precision using half a day's observation data is below 0.28% and the precision exponentially increases with the increase of peak-to-peak gravity change. The comparison of results obtained from the same observation time indicated that using properly selected observation data has more beneficial on the improvement of precision. Finally, the calibration experiment of the SG iGrav-012 is introduced and the calibration factor is determined for the first time using AG FG5X-249. With 2.5 days' data properly selected from solid tide period with large tidal amplitude, the determined calibration factor of iGrav-012 is (-92.54423+/-0.13616) μGal/V (1μGal=10-8m/s2), with the relative accuracy of about 0.15%.

  20. Absolute intensity calibration of two-channel prototype ITER vacuum ultraviolet spectrometer with a collimating mirror.

    NASA Astrophysics Data System (ADS)

    Seon, Changrae; Hong, Joohwan; Cheon, Munseong; Pak, Sunil; Lee, Hyeongon; Biel, Wolfgang; Barnsley, Robin

    2012-10-01

    To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a two-channel prototype spectrometer was implemented with No. 3 (14.4 nm -- 31.8 nm) and No. 4 (29.0 nm -- 60.0 nm) among the five channels. The prototype is composed of a toroidal mirror, and two toroidal diffraction gratings and two different detectors of the back-illuminated CCD and the micro-channel plate (MCP). To verify each optical component, the absolute intensity calibration was performed using the calibrated hollow cathode lamp. Inverse sensitivities of each spectrometer were derived by dividing the incident photon numbers with the measured detector counts. The measured sensitivity values were consistent with the sensitivities calculated from the grating and the detector efficiencies. Consequently the calibration curves of the two-channel VUV spectrometer were provided, and the mirror reflectivity and the detector efficiency could be confirmed experimentally. For the application of the calibrated spectrometer, measurements of impurity lines in KSTAR plasmas were performed, and the line integrated emissivity was derived from the calibration curve during impurity injection experiments.

  1. Absolute range calibration for JASON-1 and ENVISAT using a dedicated transponder

    NASA Astrophysics Data System (ADS)

    Cristea, E.; Pesec, P.

    2003-04-01

    Altimeter waveforms are used to study absolute range calibration for the altimeters on board of JASON-1 and ENVISAT. As a uniquely defined terrestrial reflection surface, a transponder is deployed within the footprint of the altimeter. The waveforms corresponding to the transponder distinguish themselves from the other waveforms resulting from natural targets in power and shape. When a satellite-borne altimeter passes over a ground-based active transponder, it makes within 3 to 4 seconds, 3000 - 4000 measurements of the satellite to transponder separation. That distance (range) varies in a parabolic fashion so that, when a parabolic curve is fitted to the measurements, the range at the point of the closest approach, that is the vertex of this parabola, can be determined with a resolution < 1mm. The accuracy of a single measurement of this sort is limited to about 2 - 3 cm by the ability to model the propagation delay in the atmosphere. The technique of using a dedicated transponder eliminates error sources such as tides and sea state bias and resolves the unknown altimeter calibration constant. Best results are obtained when the range window of the radar altimeter is preset to a fixed value during the transponder overpass, and this has been successfully used on RA-2 on board of ENVISAT. The poster presents the concept of absolute range calibration using a transponder and will show numerical results if relevant data are available.

  2. Absolute energy calibration of the Telescope Array fluorescence detector with an electron linear accelerator

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Beitollahi, M.; Fukushima, M.; Ikeda, D.; Langely, K.; Matthews, J. N.; Sagawa, H.; Shin, B. K.; Thomas, S. B.; Thomson, G. B.

    2013-06-01

    The Electron Light Source(ELS) is a new light source for the absolute energy calibration of cosmic ray Fluorescence Detector(FD) telescopes. The ELS is a compact electron linear accelerator with a typical output of 109 electrons per pulse at 40 MeV. We fire the electron beam vertically into the air 100 m in front of the telescope. The electron beam excites the gases of the atmosphere in the same way as the charged particles of the cosmic ray induced extensive air shower. The gases give off the same light with the same wavelength dependence. The light passes through a small amount of atmosphere and is collected by the same mirror and camera with their wavelength dependence. In this way we can use the electron beam from ELS to make an end-to-end calibration of the telescope. In September 2010, we began operation of the ELS and the FD telescopes observed the fluorescence photons from the air shower which was generated by the electron beam. In this article, we will reort the status of analysis of the absolute energy calibration with data which was taken in September 2010, and beam monitor study in November 2011.

  3. Atmospheric Emitted Radiance Interferometer (AERI) Handbook

    SciTech Connect

    Demirgian, J; Dedecker, R

    2005-01-01

    The atmospheric emitted radiance interferometer (AERI) measures the absolute infrared (IR) spectral radiance (watts per square meter per steradian per wavenumber) of the sky directly above the instrument. The spectral measurement range of the instrument is 3300 to 520 wavenumbers (cm-1) or 3-19.2 microns for the normal-range instruments and 3300 to 400 cm-1 or 3-25 microns, for the extended-range polar instruments. Spectral resolution is 1.0 cm-1. Instrument field-of-view is 1.3 degrees. A calibrated sky radiance spectrum is produced every 8 minutes in normal mode and every minute in rapid sampling mode. The actual sample scan time is 20-30 sec in rapid sampling mode with periodic gaps when the instrument is looking at the blackbodies. Rapid sampling will become available in all AERIs. Rapid sampling time will eventually be reduced to data every 20 seconds. The AERI data can be used for 1) evaluating line-by-line radiative transport codes, 2) detecting/quantifying cloud effects on ground-based measurements of infrared spectral radiance (and hence is valuable for cloud property retrievals), and 3) calculating vertical atmospheric profiles of temperature and water vapor and the detection of trace gases.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1987-09-01

    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.

  7. 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.

  8. 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

  9. A reference radiance-meter system for thermodynamic temperature measurements

    NASA Astrophysics Data System (ADS)

    Salim, S. G. R.; Briaudeau, S.; Bourson, F.; Rougié, B.; Truong, D.; Kozlova, O.; Coutin, J.-M.; Sadli, M.

    2016-06-01

    This paper presents the work carried out to evaluate the radiometric performance of a radiance-meter system which has been built at the LNE-Cnam to determine the thermodynamic temperature of high-temperature fixed points. The work comes as an integral part of the ‘implementing the new Kelvin’ (INK) project in which nine National Metrology Institutes (NMIs) strive to assign the thermodynamic temperatures to the melting curve of high-temperature fixed points with the lowest possible uncertainty. The method used in this research is based on the radiance approach. It exploits a system based on a laser-illuminated integrating sphere source whose radiance is absolutely measured by a trap detector through a well-defined geometry. The trap detector is calibrated traceable to the LNE-Cnam’s cryogenic radiometer. Once the radiance of the sphere is defined, a single grating-based spectroradiometer is used to measure the radiance of the fixed point source at the laser wavelength through direct comparison with the sphere radiance. This allows the thermodynamic temperature of the fixed point to be determined using Planck’s radiation law. The work provides a thorough evaluation of the system along with a detailed study of all related systematic effects and their corresponding uncertainties.

  10. 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.

  11. 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. PMID:27199718

  12. Absolute calibration method for laser megajoule neutron yield measurement by activation diagnostics

    NASA Astrophysics Data System (ADS)

    Landoas, Olivier; Yu Glebov, Vladimir; Rossé, Bertrand; Briat, Michelle; Disdier, Laurent; Sangster, Thomas C.; Duffy, Tim; Marmouget, Jean Gabriel; Varignon, Cyril; Ledoux, Xavier; Caillaud, Tony; Thfoin, Isabelle; Bourgade, Jean-Luc

    2011-07-01

    The laser megajoule (LMJ) and the National Ignition Facility (NIF) plan to demonstrate thermonuclear ignition using inertial confinement fusion (ICF). The neutron yield is one of the most important parameters to characterize ICF experiment performance. For decades, the activation diagnostic was chosen as a reference at ICF facilities and is now planned to be the first nuclear diagnostic on LMJ, measuring both 2.45 MeV and 14.1 MeV neutron yields. Challenges for the activation diagnostic development are absolute calibration, accuracy, range requirement, and harsh environment. At this time, copper and zirconium material are identified for 14.1 MeV neutron yield measurement and indium material for 2.45 MeV neutrons. A series of calibrations were performed at Commissariat à l'Energie Atomique (CEA) on a Van de Graff facility to determine activation diagnostics efficiencies and to compare them with results from calculations. The CEA copper activation diagnostic was tested on the OMEGA facility during DT implosion. Experiments showed that CEA and Laboratory for Laser Energetics (LLE) diagnostics agree to better than 1% on the neutron yield measurement, with an independent calibration for each system. Also, experimental sensitivities are in good agreement with simulations and allow us to scale activation diagnostics for the LMJ measurement range.

  13. 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.

  14. Comb-calibrated frequency-modulated continuous-wave ladar for absolute distance measurements.

    PubMed

    Baumann, Esther; Giorgetta, Fabrizio R; Coddington, Ian; Sinclair, Laura C; Knabe, Kevin; Swann, William C; Newbury, Nathan R

    2013-06-15

    We demonstrate a comb-calibrated frequency-modulated continuous-wave laser detection and ranging (FMCW ladar) system for absolute distance measurements. The FMCW ladar uses a compact external cavity laser that is swept quasi-sinusoidally over 1 THz at a 1 kHz rate. The system simultaneously records the heterodyne FMCW ladar signal and the instantaneous laser frequency at sweep rates up to 3400 THz/s, as measured against a free-running frequency comb (femtosecond fiber laser). Demodulation of the ladar signal against the instantaneous laser frequency yields the range to the target with 1 ms update rates, bandwidth-limited 130 μm resolution and a ~100 nm accuracy that is directly linked to the counted repetition rate of the comb. The precision is <100 nm at the 1 ms update rate and reaches ~6 nm for a 100 ms average. PMID:23938965

  15. 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

  16. Absolute calibration accuracy of L4 TM and L5 TM sensor image pairs

    USGS Publications Warehouse

    Chander, G.; Micijevic, E.

    2006-01-01

    The Landsat suite of satellites has collected the longest continuous archive of multispectral data of any land-observing space program. 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. However, little attention has been paid to ensuring that the data are calibrated and comparable from mission to mission, Launched in 1982 and 1984 respectively, the Landsat 4 (L4) and Landsat 5 (L5) Thematic Mappers (TM) are the backbone of an extensive archive of moderate resolution Earth imagery. To evaluate the "current" absolute accuracy of these two sensors, image pairs from the L5 TM and L4 TM sensors were compared. The approach involves comparing image statistics derived from large common areas observed eight days apart by the two sensors. The average percent differences in reflectance estimates obtained from the L4 TM agree with those from the L5 TM to within 15 percent. Additional work to characterize the absolute differences between the two sensors over the entire mission is in progress.

  17. 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.

  18. Absolute energy calibration for relativistic electron beams with pointing instability from a laser-plasma accelerator

    SciTech Connect

    Cha, H. J.; Choi, I. W.; Kim, H. T.; Kim, I J.; Nam, K. H.; Jeong, T. M.; Lee, J.

    2012-06-15

    The pointing instability of energetic electron beams generated from a laser-driven accelerator can cause a serious error in measuring the electron spectrum with a magnetic spectrometer. In order to determine a correct electron spectrum, the pointing angle of an electron beam incident on the spectrometer should be exactly defined. Here, we present a method for absolutely calibrating the electron spectrum by monitoring the pointing angle using a scintillating screen installed in front of a permanent dipole magnet. The ambiguous electron energy due to the pointing instability is corrected by the numerical and analytical calculations based on the relativistic equation of electron motion. It is also possible to estimate the energy spread of the electron beam and determine the energy resolution of the spectrometer using the beam divergence angle that is simultaneously measured on the screen. The calibration method with direct measurement of the spatial profile of an incident electron beam has a simple experimental layout and presents the full range of spatial and spectral information of the electron beams with energies of multi-hundred MeV level, despite the limited energy resolution of the simple electron spectrometer.

  19. ABSOLUTE RADIOMETRIC CALIBRATION OF THE EUNIS-06 170-205 A CHANNEL AND CALIBRATION UPDATE FOR CORONAL DIAGNOSTIC SPECTROMETER/NORMAL-INCIDENCE SPECTROMETER

    SciTech Connect

    Wang Tongjiang; Brosius, Jeffrey W.; Thomas, Roger J.; Rabin, Douglas M.; Davila, Joseph M.

    2010-02-01

    The Extreme-Ultraviolet Normal-Incidence Spectrograph sounding-rocket payload was flown on 2006 April 12 (EUNIS-06), carrying two independent imaging spectrographs covering wavebands of 300-370 A in first order and 170-205 A in second order, respectively. The absolute radiometric response of the EUNIS-06 long-wavelength (LW) channel was directly measured in the same facility used to calibrate Coronal Diagnostic Spectrometer (CDS) prior to the Solar and Heliospheric Observatory (SOHO) launch. Because the absolute calibration of the short-wavelength (SW) channel could not be obtained from the same lab configuration, we here present a technique to derive it using a combination of solar LW spectra and density- and temperature-insensitive line intensity ratios. The first step in this procedure is to use the coordinated, cospatial EUNIS and SOHO/CDS spectra to carry out an intensity calibration update for the CDS NIS-1 waveband, which shows that its efficiency has decreased by a factor about 1.7 compared to that of the previously implemented calibration. Then, theoretical insensitive line ratios obtained from CHIANTI allow us to determine absolute intensities of emission lines within the EUNIS SW bandpass from those of cospatial CDS/NIS-1 spectra after the EUNIS LW calibration correction. A total of 12 ratios derived from intensities of 5 CDS and 12 SW emission lines from Fe X to Fe XIII yield an instrumental response curve for the EUNIS-06 SW channel that matches well to a relative calibration which relied on combining measurements of individual optical components. Taking into account all potential sources of error, we estimate that the EUNIS-06 SW absolute calibration is accurate to {+-}20%.

  20. 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...

  1. 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...

  2. Absolute Dating of Desert Varnish Using Portable X-Ray Fluorescence: Calibration and Testing

    NASA Astrophysics Data System (ADS)

    Pingitore, N. E.; Lytle, F. W.; Rowley, P. D.; Ferris, D. E.

    2004-12-01

    Desert varnish, also called rock varnish, is a thin biogenic layer of Mn-oxides, Fe-oxides, and clays that coats rock surfaces in arid and semi-arid regions. The mass of these metals in the varnish registers cumulative biologic activity over time and presents a possible dating mechanism, subject to appropriate assumptions and restrictions. We have used a portable x-ray fluorescence (PXRF) unit to measure Mn and Fe in numerous desert varnishes, both in the field and laboratory; the anticipated relationship between age and mass emerges from these data. Our attempts to refine the PXRF technique for absolute dating of desert varnish are confounded by the limited number of "dated" varnishes available to calibrate and test the method. Although there is no current method to directly ascertain the age of desert varnish, our search for "dated" varnishes has yielded three suitable types of test materials: (1) The ages of young basalt flows dated by various K/Ar radiometric techniques represent the maximum age of varnish developed on those surfaces. Such rocks are useful in the time range of perhaps 250,000 to 10,000 years; surface spalling with loss of varnish presents an upper time limit and difficulty in dating Holocene basalts presents a lower limit. Basalt flows typically provide horizontal surfaces that are ideal for PXRF measurements because, as a biogenic process, varnish development even at a single site varies with solar orientation. (2) Petroglyphs are the rock art that native peoples produced by pecking away varnish to expose fresh rock. This process restarts varnish development and the pecked surface gradually repatinates over time. At some locales, certain figures, symbols, and stylistic elements can be associated with an archaeological culture of known antiquity and duration, thus providing an age range for such glyphs. In the desert Southwest and Great Basin of the United States, appropriate glyphs are known from the present to at least 7000 years BP. Many of

  3. Absolute radiometric calibration of Als intensity data: effects on accuracy and target classification.

    PubMed

    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.

  4. Absolute radiometric calibration of Als intensity data: effects on accuracy and target classification.

    PubMed

    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

  5. 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.

  6. Generalized Effective Radiance Temperature

    NASA Astrophysics Data System (ADS)

    Yuan, Z.

    2015-12-01

    Radiance temperature is one of the most important and widely used concepts in radiation thermometry. The usual definition of radiance temperature does not strictly apply for complex situations, such as when surrounding radiation is non-negligible or when corrections are applied to measurements made using an inappropriate emissivity setting. A novel concept, generalized effective radiance temperature (GERT), that adopts a graybody as the reference radiator is proposed in this study to express and explain the actual measurands that exist extensively in practical radiation thermometry applications; for example, a measurement result by a spectral-band radiation thermometer whose instrumental emissivity setting is less than 1. An effective wavelength approach has been developed to elucidate the relationship between a thermometer-dependent temperature (reading from an actual spectral-band radiation thermometer) and the object-side parameter GERT. The characteristics of GERT and the effective wavelength of a GERT measurement are discussed. Choosing an arbitrary emissivity setting to correct for the emissivity of a real target is equivalent to using this value as the emissivity of the reference graybody of the GERT. The GERT can be used in calibrations of both sources and thermometers.

  7. Absolute calibration of optical power for PDT: report of AAPM TG140.

    PubMed

    Zhu, Timothy C; Bonnerup, Chris; Colussi, Valdir C; Dowell, Marla L; Finlay, Jarod C; Lilge, Lothar; Slowey, Thomas W; Sibata, Claudio

    2013-08-01

    This report is primarily concerned with methods for optical calibration of laser power for continuous wave (CW) light sources, predominantly used in photodynamic therapy (PDT). Light power calibration is very important for PDT, however, no clear standard has been established for the calibration procedure nor the requirements of power meters suitable for optical power calibration. The purposes of the report are to provide guidance for establishing calibration procedures for thermopile type power meters and establish calibration uncertainties for most commercially available detectors and readout assemblies. The authors have also provided a review of the use of various power meters for CW and pulsed optical sources, and provided recommended temporal frequencies for optical power meter calibrations and guidance for routine quality assurance procedure.

  8. 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

  9. 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.

  10. Establishing the moon as a spectral radiance standard

    USGS Publications Warehouse

    Kieffer, H.H.; Wildey, R.L.

    1996-01-01

    A new automated observatory dedicated to the radiometry of the moon has been constructed to provide new radiance information for calibration of earth-orbiting imaging instruments, particularly Earth Observing System instruments. Instrumentation includes an imaging photometer with 4.5-in. resolution on a fully digital mount and a full-aperture radiance calibration source. Interference filters within 0.35-0.95 ??m correspond to standard stellar magnitude systems, accommodate wavelengths of lunar spectral contrast, and approximate some band-passes of planned earth-orbiting instruments (ASTER, Landsat-7 ETM, MISR, MODIS, and SeaWIFS). The same equipment is used for lunar and stellar observations, with the use of an aperture stop in lunar imaging to comply with Nyquist's theorem and lengthen exposure times to avoid scintillation effects. A typical robotic night run involves observation of about 60 photometric standard stars and the moon; about 10 of the standard stars are observed repeatedly to determine atmospheric extinction, and the moon is observed several times. Observations are to be made on every photometric night during the bright half of the month for at least 4.5 years to adequately cover phase and libration variation. Each lunar image is reduced to absolute exoatmospheric radiance and reprojected to a fixed selenographic grid system. The collection of these images at various librations and phase angles will be reduced to photometric models for each of the approximately 120 000 points in the lunar grid for each filter. Radiance models of the moon can then be produced for the precise geometry of an orbiting instrument observation. Expected errors are under 1% relative and 2.5% absolute. A second telescope operating from 1.0 to 2.5 ??m is planned.

  11. Telescope Spectrophotometric and Absolute Flux Calibration, and National Security Applications, Using a Turntable Laser on a Satellite

    NASA Astrophysics Data System (ADS)

    Albert, J.; Burgett, W.; Rhodes, J.

    We propose a tunable laser-based satellite-mounted spectrophotometric and absolute flux calibration system, to be utilized by ground- and space-based telescopes. As uncertainties on the photometry, due to imperfect knowledge of both telescope optics and the atmosphere, will in the near future begin to dominate the uncertainties on fundamental cosmological parameters such as WL (Omega_Lambda) and w in measurements from SNIa, weak gravitational lensing, and baryon oscillations, a method for reducing such uncertainties is needed. We propose to improve spectrophotometric calibration, currently obtained using standard stars, by placing a tunable laser and a wide-angle light source on a satellite by early next decade (perhaps included in the upgrade to the GPS satellite network) to improve absolute flux calibration to 0.1% and relative spectrophotometric calibration to better than 0.001% across the visible and near-infrared spectrum. As well as fundamental astrophysical applications, the system proposed here potentially has broad utility for defense and national security applications such as ground target illumination and space communication. For further details please see http://www.arxiv.org/abs/astro-ph/0604339.

  12. 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.

  13. Absolute calibration of photostimulable image plate detectors used as (0.5-20 MeV) high-energy proton detectors.

    PubMed

    Mancić, A; Fuchs, J; Antici, P; Gaillard, S A; Audebert, P

    2008-07-01

    In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5-20 MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband laser-accelerated protons, which are spectrally resolved. The final result is a calibration curve that enables retrieving the proton number from the IP signal. PMID:18681694

  14. 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

  15. Absolutely calibrated, time-resolved measurements of soft x rays using transmission grating spectrometers at the Nike Laser Facility

    NASA Astrophysics Data System (ADS)

    Weaver, J. L.; Feldman, U.; Seely, J. F.; Holland, G.; Serlin, V.; Klapisch, M.; Columbant, D.; Mostovych, A.

    2001-12-01

    Accurate simulation of pellet implosions for direct drive inertial confinement fusion requires benchmarking the codes with experimental data. The Naval Research Laboratory (NRL) has begun to measure the absolute intensity of radiation from laser irradiated targets to provide critical information for the radiatively preheated pellet designs developed by the Nike laser group. Two main diagnostics for this effort are two spectrometers incorporating three detection systems. While both spectrometers use 2500 lines/mm transmission gratings, one instrument is coupled to a soft x-ray streak camera and the other is coupled to both an absolutely calibrated Si photodiode array and a charge coupled device (CCD) camera. Absolute calibration of spectrometer components has been undertaken at the National Synchrotron Light Source at Brookhaven National Laboratories. Currently, the system has been used to measure the spatially integrated soft x-ray flux as a function of target material, laser power, and laser spot size. A comparison between measured and calculated flux for Au and CH targets shows reasonable agreement to one-dimensional modeling for two laser power densities.

  16. 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.

  17. 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.

  18. Absolute calibration of OH density in a nanosecond pulsed plasma filament in atmospheric pressure He-H2O: comparison of independent calibration methods

    NASA Astrophysics Data System (ADS)

    Verreycken, T.; van der Horst, R. M.; Sadeghi, N.; Bruggeman, P. J.

    2013-11-01

    The absolute density of OH radicals generated in a nanosecond pulsed filamentary discharge in atmospheric pressure He +0.84% H2O is measured independently by UV absorption and laser induced fluorescence (LIF) calibrated with Rayleigh scattering. For the calibration of LIF with Rayleigh scattering, two LIF models, with six levels and four levels, are studied to investigate the influence of the rotational and vibrational energy transfers. In addition, a chemical model is used to deduce the OH density in the afterglow from the relative LIF intensity as function of time. The different models show good correspondence and by comparing these different methods, the accuracy and the effect of assumptions on the obtained OH density are discussed in detail. This analysis includes an analysis of the sensitivity to parameters used in the LIF models.

  19. 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.

  20. 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.

  1. Calibration of a Solar Absolute Cavity Radiometer with Traceability to the World Radiometric Reference

    SciTech Connect

    Reda, I.

    1996-01-01

    This report describes the present method of establishing traceability of absolute cavity radiometers to the World Radiometric Reference (WRR) through the process employed in the International Pyrheliometer Comparisons (IPC). This method derives the WRR reduction factor for each of the participating cavity radiometers. An alternative method is proposed, described, and evaluated as a way to reduce the uncertainty in the comparison process. The two methods are compared using a sample of data from the recent IPC-VIII conducted from September 25th to October 13th, 1995 at the World Radiation Center in Davos, Switzerland. A description of absolute cavity radiometers is also included, using a PMO-6 as an example of active cavity radiometers, and a HF as an example of passive cavity radiometers.

  2. Radiance Data Products at the GES DAAC

    NASA Technical Reports Server (NTRS)

    Savtchenko, A.; Ouzounov, D.; Acker, J.; Johnson, J.; Leptoukh, G.; Qin, J.; Rui, H.; Smith, P.; Teng, W.

    2004-01-01

    The Goddard Earth Sciences Distributed Active Archive Center (GES DAAC) has been archiving and distributing Radiance data, and serving science and application users of these data, for over 10 years now. The user-focused stewardship of the Radiance data from the AIRS, AVHRR, MODIS, SeaWiFS, SORCE, TOMS, TOVS, TRMM, and UARS instruments exemplifies the GES DAAC tradition and experience. Radiance data include raw radiance counts, onboard calibration data, geolocation products, radiometric calibrated and geolocated-calibrated radiance/reflectance. The number of science products archived at the GES DAAC is steadily increasing, as a result of more sophisticated sensors and new science algorithms. Thus, the main challenge for the GES DAAC is to guide users through the variety of Radiance data sets, provide tools to visualize and reduce the volume of the data, and provide uninterrupted access to the data. This presentation will describe the effort at the GES DAAC to build a bridge between multi-sensor data and the effective scientific use of the data, with an emphasis on the heritage of the science products. The intent is to inform users of the existence of this large collection of Radiance data; suggest starting points for cross-platform science projects and data mining activities; provide data services and tools information; and to give expert help in the science data formats and applications.

  3. Absolute gauge block calibration using ultra-precise optical frequency synthesizer locked to a femtosecond comb.

    PubMed

    Hussein, Hatem; Farid, Niveen; Terra, Osama

    2015-02-01

    In this paper, we report a gauge block (GB) calibration that is traceable to the SI unit of time, the second. Four ultra-stable optical telecommunication wavelengths near 1556 nm are obtained by locking a narrow-tuning-range fiber laser to a fiber-based femtosecond frequency comb. Since the GB calibration system does not operate at this region of spectrum, the superior frequency stability of the laser is transferred to the 778 nm region by using a waveguide periodically poled lithium niobate crystal. After applying the locking scheme, the stability and accuracy of the laser become better than 8×10(-12). The frequency-doubled light is sent through 30 m optical fiber to a GB interferometer, which is installed at a different laboratory in the same building. Using this calibration scheme, a GB with a nominal length of 100 mm is calibrated with an uncertainty of ±52  nm. This uncertainty value is still comparable to or even better than other metrology laboratories for a similar block length.

  4. Comparison of Two Methodologies for Calibrating Satellite Instruments in the Visible and Near Infrared

    NASA Technical Reports Server (NTRS)

    Barnes, Robert A.; Brown, Steven W.; Lykke, Keith R.; Guenther, Bruce; Xiong, Xiaoxiong (Jack); Butler, James J.

    2010-01-01

    Traditionally, satellite instruments that measure Earth-reflected solar radiation in the visible and near infrared wavelength regions have been calibrated for radiance response in a two-step method. In the first step, the spectral response of the instrument is determined using a nearly monochromatic light source, such a lamp-illuminated monochromator. Such sources only provide a relative spectral response (RSR) for the instrument, since they do not act as calibrated sources of light nor do they typically fill the field-of-view of the instrument. In the second step, the instrument views a calibrated source of broadband light, such as lamp-illuminated integrating sphere. In the traditional method, the RSR and the sphere spectral radiance are combined and, with the instrument's response, determine the absolute spectral radiance responsivity of the instrument. More recently, an absolute calibration system using widely tunable monochromatic laser systems has been developed, Using these sources, the absolute spectral responsivity (ASR) of an instrument can be determined on a wavelength-hy-wavelength basis. From these monochromatic ASRs. the responses of the instrument bands to broadband radiance sources can be calculated directly, eliminating the need for calibrated broadband light sources such as integrating spheres. Here we describe the laser-based calibration and the traditional broad-band source-based calibration of the NPP VIIRS sensor, and compare the derived calibration coefficients for the instrument. Finally, we evaluate the impact of the new calibration approach on the on-orbit performance of the sensor.

  5. 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

  6. Absolute calibration method for fast-streaked, fiber optic light collection, spectroscopy systems.

    SciTech Connect

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

    2010-04-01

    This report outlines a convenient method to calibrate fast (<1ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such a system is used to collect spectral data on plasmas generated in the A-K gap of electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA). On RITS, light is collected through a small diameter (200 micron) optical fiber and recorded on a fast streak camera at the output of 1 meter Czerny-Turner monochromator (F/7 optics). To calibrate such a system, it is necessary to efficiently couple light from a spectral lamp into a 200 micron diameter fiber, split it into its spectral components, with 10 Angstroms or less resolution, and record it on a streak camera with 1ns or less temporal resolution.

  7. Absolute energy calibration of FD by an electron linear accelerator for Telescope Array

    SciTech Connect

    Shibata, T.; Fukushima, M.; Ikeda, D.; Enomoto, A.; Fukuda, S.; Furukawa, K.; Ikeda, M.; Iwase, H.; Kakihara, K.; Kamitani, T.; Kondo, Y.; Ohsawa, S.; Sagawa, H.; Sanami, T.; Satoh, M.; Shidara, T.; Sugimura, T.; Yoshida, M.; Matthews, J. N.; Ogio, S.

    2011-09-22

    The primary energy of the ultra-high energy cosmic rays(UHECR) are measured with the number of fluorescence photons which are detected with fluorescence detectors(FD) in the Telescope Array experiment(TA). Howevery since there is large uncertinty as 19% in the measurement of the energy scale, the most important theme is improvement of the energy calibration. The electron light source(ELS) is a small electron linear accelerator for new energy calibration. The ELS is located 100 m far from the FD station, and injects electron beam which is accelerated to 40 MeV energy into the sky. We can calibrate the FD energy scale by detection the air shower directly which is generated by the electron beam. The ELS was developed in KEK Japan, and moved to the TA site in March 2009. We started the beam operation in September 2010, in consequence we detected the air shower which was generated by electron beam in the air. The output kinetic energy of the electron beam was 41.1 MeV, we adjusted the output charge from 40 to 140 pC/pulse. We expect that we can improve the uncertinty of the energy scale to about 10% with the ELS, futhermore ELS will be a very useful apparatus for R and D of future UHECR observation.

  8. First preliminary results for the absolute calibration of the Chinese HY-2 altimetric mission using the CRS1 calibration facilities in West Crete, Greece

    NASA Astrophysics Data System (ADS)

    Mertikas, Stelios P.; Zhou, Xinghua; Qiao, Fangli; Daskalakis, Antonis; Lin, Mingsen; Peng, Hailong; Tziavos, Ilias N.; Vergos, George; Tripolitsiotis, Achilleas; Frantzis, Xenophon

    2016-01-01

    In this work, absolute calibration of the Chinese HY-2 satellite altimetry mission is carried out, employing Pass No. 280 and the calibration facility, CRS1, located in the Southwest end of the island of Crete, Greece. Satellite Pass No. 280 is descending and follows a ground track almost parallel to the west coast of Crete. It comes close to the coast, at a distance of about 9 km from the CRS1 calibration site, and finally goes away south of Crete. The HY-2 sensor geophysical data records (S-GDR) have been incorporated into the calibration procedures and processing has taken place for cycles No. 54-62, at 20 Hz data rate. Some peculiarities in the HY-2 satellite altimeter data, as delivered and depicted in the I-GDR and S-GDR data, have also been noticed. All calibration results have been determined using a regional, precise and detailed geoid, along with a good knowledge of local ocean circulation and site characteristics and a well-defined sea-surface calibration methodology. The first preliminary results for the HY-2 altimeter calibration have shown that the initial cycles, up to No. 51, display an erratic behavior. After those cycles, the altimeter range bias values seem to be stable and reach a value of B = -45.6 cm ± 4.4 cm, when applying the net instrument corrections as provided in the GDR. If the relativistic effects of the satellite clocks are properly applied for the net instrument corrections, then the altimeter range bias goes down to B = -27 cm ± 3 cm. Also, preliminary cross-over analysis with the SARAL/AliKa and Jason-2 satellites show a bias of B = -23 cm, and B = -28.5 cm, respectively. The performance of the HY-2 on-board radiometer has also been examined in terms of the wet troposphere corrections and shows a mean difference of -1 cm ± 0.1 cm with respect to in-situ GNSS-derived corrections. Finally, the ionosphere path corrections of the HY-2 satellite show a difference of +1 cm ± 1.1 cm, when compared against the GNSS-derived ionosphere

  9. 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.

  10. Absolutely calibrated CCD images of Saturn at methane band and continuum wavelengths during its 1991 opposition

    NASA Astrophysics Data System (ADS)

    Ortiz, J. L.; Moreno, F.; Molina, A.

    1993-02-01

    Ground-based charge-coupled device images of Saturn were obtained at the Cassegrain focus of the 1.52-m telescope at the Calar Alto Observatory (Andalucia, Spain) during the 1991 opposition. The images were obtained in and out of the absorption methane bands at 6190, 7250, and 8900A under very good seeing conditions. A Bayesian deconvolution technique was employed in the restoration procedure. The derived absolute reflectivities and band depths at some locations of the disk are provided in tables appropriate for analysis in terms of scattering models. Possible temporal variations between the reflectivities found here and those reported by West et al. (1982) are discussed. No longitudinal variations in reflectivity larger than a 4 percent level were found. Some images showed bright spot activity at the equatorial region.

  11. Validation of short-pulse-laser-based measurement setup for absolute spectral irradiance responsivity calibration.

    PubMed

    Schuster, Michaela; Nevas, Saulius; Sperling, Armin

    2014-05-01

    This paper describes the validation process of mode-locked lasers in the "tunable lasers in photometry" (TULIP) setup at Physikalisch-Technische Bundesanstalt (PTB) regarding spectral irradiance responsivity calibrations. Validation has been carried out in the visible spectral range, 400-700 nm, with two different photometer heads and in the long wavelength range, 690-780 nm, with a filtered radiometer. A comparison of the results against those from two different validated measurement setups has been carried out for validation. For the visible spectral range, the comparison is conducted against the data obtained from a lamp-based monochromator setup for spectral irradiance responsivity calibrations and against the photometric values (integral quantity) measured at the photometric bench setup of PTB. For the long wavelength range, comparisons against results from two different lamp-based monochromator measurement setups were made. Additionally, the effect of different radiation bandwidths on interference oscillations has been determined for a filter radiometer without a diffuser. A procedure for the determination of the optimum bandwidth of the setup for the respective measurement device is presented. PMID:24921865

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

    NASA Astrophysics Data System (ADS)

    Chander, Gyanesh; Markham, Brian L.; Micijevic, Esad; Teillet, Philippe M.; Helder, Dennis L.

    2005-08-01

    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.

  13. 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.

  14. SU-E-J-85: Leave-One-Out Perturbation (LOOP) Fitting Algorithm for Absolute Dose Film Calibration

    SciTech Connect

    Chu, A; Ahmad, M; Chen, Z; Nath, R

    2014-06-01

    Purpose: To introduce an outliers-recognition fitting routine for film dosimetry. It cannot only be flexible with any linear and non-linear regression but also can provide information for the minimal number of sampling points, critical sampling distributions and evaluating analytical functions for absolute film-dose calibration. Methods: The technique, leave-one-out (LOO) cross validation, is often used for statistical analyses on model performance. We used LOO analyses with perturbed bootstrap fitting called leave-one-out perturbation (LOOP) for film-dose calibration . Given a threshold, the LOO process detects unfit points (“outliers”) compared to other cohorts, and a bootstrap fitting process follows to seek any possibilities of using perturbations for further improvement. After that outliers were reconfirmed by a traditional t-test statistics and eliminated, then another LOOP feedback resulted in the final. An over-sampled film-dose- calibration dataset was collected as a reference (dose range: 0-800cGy), and various simulated conditions for outliers and sampling distributions were derived from the reference. Comparisons over the various conditions were made, and the performance of fitting functions, polynomial and rational functions, were evaluated. Results: (1) LOOP can prove its sensitive outlier-recognition by its statistical correlation to an exceptional better goodness-of-fit as outliers being left-out. (2) With sufficient statistical information, the LOOP can correct outliers under some low-sampling conditions that other “robust fits”, e.g. Least Absolute Residuals, cannot. (3) Complete cross-validated analyses of LOOP indicate that the function of rational type demonstrates a much superior performance compared to the polynomial. Even with 5 data points including one outlier, using LOOP with rational function can restore more than a 95% value back to its reference values, while the polynomial fitting completely failed under the same conditions

  15. Improved entrance optics design for ground-based solar spectral ultraviolet irradiance measurements and system absolute calibration

    NASA Astrophysics Data System (ADS)

    Dai, Caihong; Yu, Jialin; Huang, Bo; Tian, Yan

    2009-07-01

    The angular response of entrance optics is an important parameter for solar spectral UV measurements, and ideal cosine entrance optics is required to measure ground-based global solar spectral UV irradiance including direct and diffuse radiation over a solid angle of 2π sr. Early international comparisons have shown that deviations from the ideal cosine response lead to uncertainties in solar measurements of more than 10%. A special spectroradiometer used for solar spectral UV measurements was developed at National Institute of Metrology (NIM). Based on Polytetrafluoroethylene (PTFE) integrating sphere, seven kinds of cosine-entrance system were designed and compared. A special cosine measurement apparatus was developed to measure the angular response of the entrance optics. Experimental results show that, the integral cosine error is 1.41% for a novel combination entrance optics, which is composed by a PTFE integrating sphere, a spherical ground quartz diffuser and a special correction ring, and the cosine error is 0.08% for an incidence angle of θ=+/-30°, 0.84% at θ=+/-45°, -0.47% at θ=+/-60°, -0.74% at θ=+/-70°, and 5.47% at θ=+/-80°. With the new non-plane entrance optics, the angular response of the solar UV spectroradiometer is improved evidently, but on the other side, the system's absolute calibration becomes more difficult owing to the curved geometry of the new diffuser. The calibration source is a 1000W tungsten halogen lamp, but the measurement object is the global radiation of the solar, so a small error of the calibration distance will lead to an enormous measurement error of solar spectral UV irradiance. When the calibration distance is 500mm, for an actual diffuser with spherical radius 32.5mm and spherical height 20mm, the calibration error will be up to 3%~10% on the assumption that the starting point was calculated just from the acme or the bottom of the half-spherical diffuser. It was investigated that which point inside the

  16. Calibration and absolute normalization procedure of a new Deep Inelastic Neutron Scattering spectrometer

    NASA Astrophysics Data System (ADS)

    Rodríguez Palomino, L. A.; Blostein, J. J.; Dawidowski, J.

    2011-08-01

    We describe the calibration process of a new Deep Inelastic Neutron Scattering (DINS) spectrometer, recently implemented at the Bariloche Electron LINAC (Argentina), consisting in the determination of the incident neutron spectrum, dead-time and electronic delay of the data acquisition line, and detector bank efficiency. For this purpose, samples of lead, polyethylene and graphite of different sizes were employed. Their measured spectra were corrected by multiple scattering, attenuation and detector efficiency effects, by means of an ad hoc Monte Carlo code. We show that the corrected spectra are correctly scaled with respect to the scattering power of the tested materials within a 2% of experimental error, thus allowing us to define an experimental constant that links the arbitrary experimental scale (number of recorded counts per monitor counts) with the involved cross-sections. The present work also serves to analyze the existence of possible sources of systematic errors.

  17. New method to remove the electronic noise for absolutely calibrating low gain photomultiplier tubes with a higher precision

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Hayward, Jason P.; Laubach, Mitchell A.

    2014-08-01

    A new method to remove the electronic noise in order to absolutely calibrate low gain photomultiplier tubes with a higher precision is proposed and validated with experiments using a digitizer-based data acquisition system. This method utilizes the fall time difference between the electronic noise (about 0.5 ns) and the real PMT signal (about 2.4 ns for Hamamatsu H10570 PMT assembly). Using this technique along with a convolution algorithm, the electronic noise and the real signals are separated very well, even including the very small signals heavily influenced by the electronic noise. One application that this method allows is for us to explore the energy relationship for gamma sensing in Cherenkov radiators while maintaining the fastest possible timing performance and high dynamic range.

  18. In-flight calibration of the experimental Absolute Scalar Magnetometer vector mode on board the Swarm satellites

    NASA Astrophysics Data System (ADS)

    Leger, J. M.; Jager, T.; Bertrand, F.; Cattin, V.; Fratter, I.; Brocco, L.; Vigneron, P.; Lalanne, X.; Hulot, G.

    2014-12-01

    While the role of the ASM is to provide absolute measurements of the magnetic field's strength for the in-flight calibration of the Vector Fluxgate Magnetometer, it can also deliver simultaneously vector measurements with no impact on its scalar performance. Since these scalar and vector measurements are both perfectly synchronous and spatially coherent, their comparison can be directly used to assess the ASM performances at instrument level with no need to correct for the various magnetic perturbations generated by the satellites. This presentation will detail the ASM vector calibration process, with an emphasis on its susceptibility to the ASM operational conditions (primarily the sensor temperature and attitude, but also sun exposition parameters). The evolution of the instrument's performances during the first year of the Swarm mission will then be discussed, with a particular interest in the long term scalar residuals behaviour. These results will be analyzed to demonstrate both the noise performances of the ASM scalar and vector measurements and their excellent long term stability.

  19. Determining the Absolute Concentration of Nanoparticles without Calibration Factor by Visualizing the Dynamic Processes of Interfacial Adsorption.

    PubMed

    Wo, Xiang; Li, Zhimin; Jiang, Yingyan; Li, Minghe; Su, Yu-Wen; Wang, Wei; Tao, Nongjian

    2016-02-16

    Previous approaches of determining the molar concentration of nanoparticles often relied on the calibration factors extracted from standard samples or required prior knowledge regarding the geometry, optical, or chemical properties. In the present work, we proposed an absolute quantification method that determined the molar concentration of nano-objects without any calibration factor or prior knowledge. It was realized by monitoring the dynamic adsorption processes of individual nanoparticles with a high-speed surface plasmon resonance microscopy. In this case, diffusing nano-objects stochastically collided onto an adsorption interface and stayed there ("hit-n-stay" scenario), resulting in a semi-infinite diffusion system. The dynamic processes were analyzed with a theoretical model consisting of Fick's laws of diffusion and random-walk assumption. The quantification of molar concentration was achieved on the basis of an analytical expression, which involved only physical constants and experimental parameters. By using spherical polystyrene nanoparticles as a model, the present approach provided a molar concentration with excellent accuracy. PMID:26781326

  20. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors.

    PubMed

    Waugh, C J; Rosenberg, M J; Zylstra, A B; Frenje, J A; Séguin, F H; Petrasso, R D; Glebov, V Yu; Sangster, T C; Stoeckl, C

    2015-05-01

    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. PMID:26026524

  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. 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.

  2. 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.; 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,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

  3. 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.

  4. Experimental and Metrological Basis for SI-Traceable Infrared Radiance Measurements From Space

    NASA Astrophysics Data System (ADS)

    Gero, P. J.; Dykema, J. A.; Anderson, J. G.; Leroy, S. S.

    2007-12-01

    In order to establish a climate benchmark record and to be useful in interdecadal climate forecast testing, satellite measurements of high spectral resolution infrared radiance must have uncertainty estimates that can be proven beyond a doubt. An uncertainty in radiance of about 1 part in 1000 is required for climate applications. This can be accomplished by appealing to the best measurement practices of the metrology community. The International System of Units (SI) are linked to fundamental physical properties of matter, and can be realized anywhere in the world without bias. By doing so, one can make an accurate observation to within a specified uncertainty. Achieving SI-traceable radiance measurements from space is a novel requirement, and requires specialized sensor design and a disciplined experimental approach. Infrared remote sensing satellite instruments typically employ blackbody calibration targets, which are tied to the SI through Planck's law and the definition of the Kelvin. The blackbody temperature and emissivity, however, must be determined accurately on- orbit, in order for the blackbody emission scale to be SI-traceable. We outline a methodology of instrument design, pre-flight calibration and on-orbit diagnostics for realizing SI- traceable infrared radiance measurements. This instrument is intended as a component of the Climate Absolute Radiance and Refractivity Earth Observatory (CLARREO), a high priority recommendation of the National Research Council decadal survey. Calibration blackbodies for remote sensing differ from a perfect Planckian blackbody; thus the component uncertainties must be evaluated in order to confer traceability. We have performed traceability experiments in the laboratory to verify blackbody temperature, emissivity and the end-to-end radiance scale. We discuss the design of the Harvard standard blackbody and an intercomparison campaign that will be conducted with the GIFTS blackbody (University of Wisconsin, Madison) and

  5. 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.

  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. High-resolution imaging spectrometer for recording absolutely calibrated far ultraviolet spectra from laser-produced plasmas.

    PubMed

    Brown, Charles M; Seely, John F; Feldman, Uri; Holland, Glenn E; Weaver, James L; Obenschain, Steven P; Kjornrattanawanich, Benjawan; Fielding, Drew

    2008-10-01

    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 23 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(2) square silicon photodiodes with 0.4 ns rise time. The telescope mirrors, spectrometer gratings, and 1 mm(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(-7) J/nm from a plasma source area of 0.37 mm(2) and with 0.4 ns time resolution.

  8. (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).

  9. (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). PMID:26774395

  10. 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.

  11. Thematic Mapper, band 6, radiometric calibration and assessment

    NASA Astrophysics Data System (ADS)

    Schott, John R.

    1988-01-01

    A technique is presented for absolute radiometric calibration of longwave infrared satellite systems. The technique involves a combination underflight technique and radiometric models to estimate the radiance field reaching a satellite sensor. The radiance field can then be compared to the radiance observed at the satellite to evaluate the sensor's post launch calibration. The technique was applied to the Thematic Mapper band 6 sensor on board Landsat 5. Results are presented for three underflight dates. These results indicate that the TM band 6 sensor can be calibrated to yield an expected error (1 standard deviation) in surface temperature of 0.9K. The radiometric propagation models used to achieve these results are presented along with estimates of potential sensor calibration errors. The final radiometric propagation models developed can be applied independent of underflight requirements and represent a general approach to computation of kinetic surface temperatures. The parameters included in the analysis encompass internal calibration, sensor spectral response, atmospheric transmission, upwelled radiance, downwelled radiance, and sample emissivity.

  12. Progress in obtaining an absolute calibration of a total deuterium-tritium neutron yield diagnostic based on copper activationa)

    NASA Astrophysics Data System (ADS)

    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 63Cu(n,2n)62Cu(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)4He 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 62Cu 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.

  13. 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.

  14. Absolutely calibrated radio polarimetry of the inner Galaxy at 2.3 and 4.8 GHz

    NASA Astrophysics Data System (ADS)

    Sun, X. H.; Gaensler, B. M.; Carretti, E.; Purcell, C. R.; Staveley-Smith, L.; Bernardi, G.; Haverkorn, M.

    2014-01-01

    We present high-sensitivity and absolutely calibrated images of diffuse radio polarization at a resolution of about 10 arcmin covering the range 10° < l < 34° and |b| < 5° at 2.3 GHz from the S-band Polarization All Sky Survey and at 4.8 GHz from the Sino-German λ6 cm polarization survey of the Galactic plane. Strong depolarization near the Galactic plane is seen at 2.3 GHz, which correlates with strong Hα emission. We ascribe the depolarization to spatial Faraday rotation measure fluctuations of about 65 rad m-2 on scales smaller than 6-9 pc. We argue that most (about 90 per cent) of the polarized emission seen at 4.8 GHz originates from a distance of 3-4 kpc in the Scutum arm and that the random magnetic field dominates the regular field there. A branch extending from the North Polar Spur towards lower latitudes can be identified from the polarization image at 4.8 GHz but only partly from the polarization image at 2.3 GHz, implying that the branch is at a distance larger than 2-3 kpc. We show that comparison of structure functions of complex polarized intensity with those of polarized intensity can indicate whether the observed polarized structures are intrinsic or caused by Faraday screens. The probability distribution function of gradients from the polarization images at 2.3 GHz indicates that the turbulence in the warm ionized medium is transonic.

  15. A New Measurement of the Absolute Spectral Reflectance of the Moon

    NASA Technical Reports Server (NTRS)

    Lawrence, S. J.; Lau, E.; Steutel, D.; Stopar, J. D.; Wilcox, B. B.; Lucey, P. G.

    2003-01-01

    The spectral reflectance of the Moon is an important property for studies of lunar geology, quantitative physical modeling of the moon, and in-flight calibration of spacecraft sensors. Previous studies have claimed that telescopic absolute reflectance values for the Moon are greater than laboratory reflectance measurements by a factor of two. In order to confirm these results, we performed ground-based observations of the lunar surface using a visible/near-infrared spectroradiometer and compared the measured lunar surface radiance to solar radiance corrected for atmospheric scattering and absorption. These data were compared to previously obtained laboratory reflectance measurements from Apollo soil samples.

  16. 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

  17. 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

  18. 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

  19. Revised Landsat-5 TM Radiometrie Calibration Procedures and Postcalibration Dynamic Ranges

    USGS Publications Warehouse

    Chander, G.; Markham, B.

    2003-01-01

    Effective May 5, 2003, Landsat-5 (L5) Thematic Mapper (TM) data processed and distributed by the U.S. Geological Survey (USGS) Earth Resources Observation System (EROS) Data Center (EDC) will be radiometrically calibrated using a new procedure and revised calibration parameters. This change will improve absolute calibration accuracy, consistency over time, and consistency with Landsat-7 (L7) Enhanced Thematic Mapper Plus (ETM+) data. Users will need to use new parameters to convert the calibrated data products to radiance. The new procedure for the reflective bands (1-5,7) is based on a lifetime radiometric calibration curve for the instrument derived from the instrument's internal calibrator, cross-calibration with the ETM+, and vicarious measurements. The thermal band will continue to be calibrated using the internal calibrator. Further updates to improve the relative detector-to-detector calibration and thermal band calibration are being investigated, as is the calibration of the Landsat-4 (L4) TM.

  20. 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. PMID:23262612

  1. 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.

  2. 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

  3. 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

  4. Comparison of two methodologies for calibrating satellite instruments in the visible and near-infrared.

    PubMed

    Barnes, Robert A; Brown, Steven W; Lykke, Keith R; Guenther, Bruce; Butler, James J; Schwarting, Thomas; Turpie, Kevin; Moyer, David; DeLuccia, Frank; Moeller, Christopher

    2015-12-10

    Traditionally, satellite instruments that measure Earth-reflected solar radiation in the visible and near infrared wavelength regions have been calibrated for radiance responsivity in a two-step method. In the first step, the relative spectral response (RSR) of the instrument is determined using a nearly monochromatic light source such as a lamp-illuminated monochromator. These sources do not typically fill the field of view of the instrument nor act as calibrated sources of light. Consequently, they only provide a relative (not absolute) spectral response for the instrument. In the second step, the instrument views a calibrated source of broadband light, such as a lamp-illuminated integrating sphere. The RSR and the sphere's absolute spectral radiance are combined to determine the absolute spectral radiance responsivity (ASR) of the instrument. More recently, a full-aperture absolute calibration approach using widely tunable monochromatic lasers has been developed. Using these sources, the ASR of an instrument can be determined in a single step on a wavelength-by-wavelength basis. From these monochromatic ASRs, the responses of the instrument bands to broadband radiance sources can be calculated directly, eliminating the need for calibrated broadband light sources such as lamp-illuminated integrating spheres. In this work, the traditional broadband source-based calibration of the Suomi National Preparatory Project Visible Infrared Imaging Radiometer Suite sensor is compared with the laser-based calibration of the sensor. Finally, the impact of the new full-aperture laser-based calibration approach on the on-orbit performance of the sensor is considered. PMID:26836861

  5. 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

  6. 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.

  7. 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.

  8. Infrared cloud radiance.

    PubMed

    Kattawar, G W; Plass, G N

    1969-06-01

    The radiance of clouds is calculated at nine wavelengths in the ir. The single scattering function is obtained by Mie theory from the measured values of the complex index of refraction and with two different drop size distributions. Multiple scattering is taken into account by a Monte Carlo technique which computes the exact three-dimensional paths of the photons. The upward and downward radiance is obtained as a function of optical thickness, angle of observation, drop size distribution, and incident solar angle. The mean optical path of the photon, the cloud albedo, and the flux at the lower and upper boundaries are also given.

  9. Update to the Cosmic Origins Spectrograph FUV Calibration: Improved Characterization Below 1150 Angstroms and Improved Absolute Flux Calibration at all Wavelengths

    NASA Astrophysics Data System (ADS)

    Sonnentrucker, Paule; Bostroem, K. A.; Ely, J.; Debes, J. H.; DiFelice, A.; Hernandez, S.; Hodge, P. E.; Lindsay, K.; Lockwood, S. A.; Massa, D.; Oliveira, C. M.; Roman-Duval, J.; Penton, S. V.; Proffitt, C. R.; Taylor, J. M.

    2014-01-01

    As of Cycle 20, the three COS/FUV "Blue Mode" wavelength settings at G130M/1055, 1096 and 1222, have become available as regular observing modes. We provide updates on the wavelength and flux calibration of these new Blue Mode settings, which allow medium-resolution spectroscopy down to 900A with effective areas comparable to those of FUSE. We discuss also recent improvements to the COS/FUV flux and flat-field calibrations and present the most recent time-dependent sensitivity trends of the FUV and NUV channels.

  10. Radiance Measurement for Low Density Mars Entry

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.

    2012-01-01

    We report measurements of radiance behind a shock wave in Martian simulant (96% CO2, 4% N2) atmosphere at conditions relevant for aerodynamic decelerators. Shock waves are generated in the NASA Ames Electric Arc Shock Tube (EAST) facility at velocities from 6-8 km/s and freestream densities from 1.2-5.9 x 10(exp -4) kilograms per cubic meter (0.05-0.25 Torr, corresponding to 35-50 km altitude). Absolute radiance is measured as a function of wavelength and position in the shock. Radiance measurements extend from the vacuum ultraviolet to near infrared (120-1650 nm). As at higher density/velocity, radiation is dominate by CO 4th positive radiation in the vacuum ultraviolet, though CN contribution is also significant. At most low density conditions, the shock does not relax to equilibrium over several centimeters. A small number of measurements in the mid-infrared were performed to quantify radiation from the fundamental vibrational transition in CO, and this is found to be a minor contributor to the overall radiance at these speeds. Efforts to extend test time and reliability in the 60 cm (24) shock tube will be discussed in the full paper.

  11. 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%.

  12. 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.

  13. Absolute calibration of Kodak Biomax-MS film response to x rays in the 1.5- to 8-keV energy range

    NASA Astrophysics Data System (ADS)

    Marshall, F. J.; Knauer, J. P.; Anderson, D.; Schmitt, B. L.

    2006-10-01

    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 3keV but has reduced sensitivity above 3keV (˜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.

  14. Snow Radiance Assimilation Studies

    NASA Astrophysics Data System (ADS)

    Kim, E. J.; Durand, M. T.; Toure, A.; Margulis, S. A.; Goita, K.; Royer, A.; Lu, H.

    2009-12-01

    Passive microwave-based retrievals of terrestrial snow parameters from satellite observations form a 30-year global record which will continue for the forseeable future. So far, these snow retrievals have been generated primarily by regression-based empirical “inversion” methods based on snapshots in time, and are limited to footprints around 25 km in diameter. Assimilation of microwave radiances into physical land surface models may be used to create a retrieval framework that is inherently self-consistent with respect to model physics as well as a more physically-based approach vs. legacy retrieval/inversion methods. This radiance assimilation approach has been used for years for atmospheric parameters by the operational weather forecasting community with great success, and represents one motivation for our work. A radiance assimilation scheme for snow requires a snowpack land surface model (LSM) coupled to a radiative transfer model (RTM). In previous local-scale studies, Durand, Kim, & Margulis (2008) explored the requirements on LSM model fidelity (i.e., snowpack state information) required in order for the RTM to produce brightness temperatures suitable for radiance assimilation purposes at a local scale, using the well-known Microwave Emission Model for Layered Snowpacks (MEMLS) as the RTM and a combination of Simple SIB (SSiB) and Snow Atmosphere (SAST) as the LSM. They also demonstrated improvement of simulated snow depth through the use of an ensemble Kalman filter scheme at this local scale (2009). This modeling framework reflects another motivation—namely, possibilities for downscaling. Our focus at this stage has been at the local scale where high-quality ground truth data is available in order to evaluate radiance assimilation under a “best case scenario.” The quantitative results then form a benchmark for future assessment of effects such as sparse forcing data, upscaling/downscaling, forest attenuation, and model details. Field data from

  15. 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.

  16. 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. PMID:26628164

  17. 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.

  18. 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.

  19. Temporal radiance caching.

    PubMed

    Gautron, Pascal; Bouatouch, Kadi; Pattanaik, Sumanta

    2007-01-01

    We present a novel method for fast, high quality computation of glossy global illumination in animated environments. Building on the irradiance caching and radiance caching algorithms, our method leverages temporal coherence by sparse temporal sampling and interpolation of the indirect lighting. In our approach, part of the global illumination solution computed in previous frames is reused in the current frame. Our reusing scheme adapts to the change of incoming radiance by updating the indirect lighting only where there is a significant change. By reusing data in several frames, our method removes the flickering artifacts and yields a significant speedup compared to classical computation in which a new cache is computed for every frame. We also define temporal gradients for smooth temporal interpolation. A key aspect of our method is the absence of any additional complex data structure, making the implementation into any existing renderer based on irradiance and radiance caching straightforward. We describe the implementation of our method using graphics hardware for improved performance.

  20. 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.

  1. 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

  2. Absorption by ground-state lead atoms of the 283. 3-nm resonant line from a lead hollow cathode lamp. An absolute number density calibration

    SciTech Connect

    Simons, J.W. ); Oldenborg, R.C.; Baughcum, S.L. )

    1989-10-19

    An accurate absolute number density calibration curve for absorption by gaseous lead atoms of the 283.3-nm resonant line from a typical lead hollow cathode lamp is reported. This calibration shows the usual curvature in the Beer-Lambert plot for atomic absorption at moderate to high absorbances that is commonly attributed to self-absorption leading to line reversal in the source and/or preferential absorption at the line center when the absorber temperature is not much greater than the source Doppler temperature. A theoretical calculation utilizing a Doppler-limited Fourier transform spectrum of the 283.3-nm emission from the lamp and a tabulated value of the absorption cross section and accounting for the isotopic and nuclear hyperfine components in both the emission and absorption due to naturally occurring lead quantitatively reproduces the experimental calibration curve without any parameter adjustments. It is found that the curvature in the Beer-Lambert plot has more to do with the fact that the absorbing and emitting atoms are a mixture of isotopes giving several isotopic and nuclear hyperfine transitions at slightly different frequencies than it does with preferential absorption at line centers.

  3. 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.

  4. Radiometric modeling and calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) ground based measurement experiment

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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

  5. Sea-based Infrared Radiance Measurements of Ocean and Atmosphere from the ACAPEX/CalWater2 Campaign

    NASA Astrophysics Data System (ADS)

    Gero, P. J.; Knuteson, R.; Hackel, D.; Phillips, C.; Westphall, M.

    2015-12-01

    The ARM Cloud Aerosol Precipitation Experiment (ACAPEX) / CalWater2 was a joint DOE/NOAA field campaign in early 2015 to study atmospheric rivers in the Pacific Ocean and their impacts on the western United States. The campaign goals were to improve understanding and modeling of large-scale dynamics and cloud and precipitation processes associated with atmospheric rivers and aerosol-cloud interactions that influence precipitation variability and extremes in the western United States. Coordinated measurements were made from ground-, aircraft- and sea-based platforms. The second ARM mobile facility (AMF-2) was deployed on board the NOAA Ship Ronald H. Brown for this campaign, which included a new Marine Atmospheric Emitted Radiance Interferometer (M-AERI) to measure the atmospheric downwelling and reflected infrared radiance spectrum at the Earth's surface with high absolute accuracy. The M-AERI measures spectral infrared radiance between 520-3020 cm-1 (3.3-19 μm) at a resolution of 0.5 cm-1. The M-AERI can selectively view the atmospheric scene at zenith, and ocean/atmospheric scenes over a range of ±45° from the horizon. The AERI uses two high-emissivity blackbodies for radiometric calibration, which in conjunction with the instrument design and a suite of rigorous laboratory diagnostics, ensures the radiometric accuracy to be better than 1% (3σ) of the ambient radiance. The M-AERI radiance spectra can be used to retrieve profiles of temperature and water vapor in the troposphere, as well as measurements of trace gases, cloud properties, surface emissivity and ocean skin temperature. We present preliminary results on measurements of ocean skin temperature, ocean emissivity properties as a function of view angle and wind speed, as well as comparisons with radiosondes and satellite observations.

  6. CO{sub 2} laser light scattering by bare soils for emissivity measurements: Absolute calibration and correlation with backscattering and composition

    SciTech Connect

    Kologo, N.; Stoll, M.P.

    1996-07-01

    Measurements of the scattering cross section of a number of bare soils have been made with CO{sub 2} laser illumination at 10.59 {micro}m. The primary focus was on absolute calibration of the measurements. First, comparison of emissivity values resulting from the application of Kirchhoff`s relation after angular integration of the bidirectional measurements, with emissivity values obtained from the analysis of the emitted radiation show excellent agreement to within less than 0.3%. Second, it was found that a simple formula holds for a relationship between the emissivity and co- and cross-polarized backscattering cross section at an angle of 30{degree}. Third, a clear correlation was observed between emissivity and composition (in this case % Al + Fe oxides; % SiO{sub 2}) for a homogeneous series of samples from the same area in Niger. These results emphasize the importance of calibrated experimental data. The implications of the research give evidence of the advantage of obtaining emissivity from remote reflectivity measurements and possibly only backscattering measurements, and remotely estimating mineral composition.

  7. Use of the Moon for spacecraft calibration over 350-2500 nm

    USGS Publications Warehouse

    Kieffer, H.H.; Anderson, J.M.

    1998-01-01

    The Moon is the only natural object outside the Earth's atmosphere that is within the dynamic range of most imaging instruments on Earth-orbiting spacecraft. The excellent photometric stability of the Lunar surface will allow its use as a long-term instrument calibration source once the dependence of Lunar spectral radiance on phase and libration angles are well characterized. A program to provide this characterization is underway. Observations are being made in 23 bands within 350-950 nm, 7 of which correspond closely with spacecraft instrument bands. Observations in nine bands within 950-2500 nm began recently. Although at this time the absolute Lunar radiance model is preliminary and uncertainties are larger than most instrument calibration goals, changes in spacecraft instrument sensitivity can be precisely monitored and absolute calibration can be applied retroactively as the accuracy of the Lunar spectral radiance model improves. Several space-based imaging systems have already begun using the Moon for calibration and the EOS AM-1 platform will make periodic attitude maneuvers for Lunar and space calibration.

  8. 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

  9. Radiance Covariance and Climate Models

    NASA Technical Reports Server (NTRS)

    Haskins, R.; Goody, R.; Chen, L.

    1998-01-01

    Spectral Empirical Orhtogonal Functions (EOFs) derived from the covariance of satellite radiance spectra may be interpreted in terms of the vertical distribution of the covariance of temperature, water vapor, and clouds. The purpose of the investigation is to demonstrate the important constraints that resolved spectral radiances can place upon climate models.

  10. A New Instrument for Measurement of the Solar Aureole Radiance Distribution from Unstable Platforms

    NASA Technical Reports Server (NTRS)

    Ritter, Joseph M.; Voss, Kenneth J.

    1999-01-01

    A novel imaging solar aureole radiometer, which can obtain absolute radiometric measurements of the solar aureole when operated on an unstable platform is described. A CCD array is used to image the aureole, while a neutral density occulter on a long pole blocks the direct solar radiation. This ensures accurate direction registration as the sun appears in acquired images, and the total circumsolar region is measured simultaneously. The imaging nature of this instrument along with a special triggering device permit acquisition of the circumsolar sky radiance within 7.5 degrees of the center of the solar disk, and within 1 degree of the edge of the solar disk. This innovation makes possible for the first time, reliable and accurate radiometric measurements of the solar aureole from unstable mobile platforms such as ships. This allows determination small angle atmospheric scattering. The instrument has been used in field studies of atmospheric aerosols and will be used in satellite validation and calibration campaigns.

  11. Analysis of Reference Sources for the Characterization and Calibration of Infrared Cameras

    NASA Astrophysics Data System (ADS)

    Gutschwager, B.; Taubert, D.; Hollandt, J.

    2015-03-01

    This paper gives an analysis of the radiometric properties of different types of reference sources applied for the characterization and calibration of infrared cameras. For the absolute radiance measurement with an infrared camera, a metrological characterization and calibration of the instrument are essential. Similar to the calibration of radiation thermometers, this calibration is generally performed with reference sources of known radiance. As infrared cameras are optically and electronically more complex than radiation thermometers, which are equipped with a single element detector, the applied reference sources have to be carefully characterized and limitations in their performance have to be considered. Each pixel of the image measured with an infrared camera should depict correctly the desired physical quantity value of the projected object area. This should be achieved for all relevant conditions of observation, e.g., at different distances or at different incident angles. The performance of cavity radiators and plate radiators is analyzed based on ray-tracing calculations and spatially and angularly resolved radiance measurements with radiation thermometers and cameras. Relevant components of a calibration facility for infrared cameras at PTB are presented with their specifications. A first analysis of the relevant characteristics of the applied infrared calibration sources and infrared cameras is presented as the essential basic information for the realization of the calibration of infrared cameras.

  12. 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…

  13. 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%).

  14. 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.

  15. Absolute intensity calibration of flat-field space-resolved extreme ultraviolet spectrometer using radial profiles of visible and extreme ultraviolet bremsstrahlung continuum emitted from high-density plasmas in Large Helical Device

    SciTech Connect

    Dong Chunfeng; Wang Erhui; Morita, Shigeru; Goto, Motoshi

    2011-11-15

    A precise absolute intensity calibration of a flat-field space-resolved extreme ultraviolet (EUV) spectrometer working in wavelength range of 60-400 A is carried out using a new calibration technique based on radial profile measurement of the bremsstrahlung continuum in Large Helical Device. A peaked vertical profile of the EUV bremsstrahlung continuum has been successfully observed in high-density plasmas (n{sub e}{>=} 10{sup 14} cm{sup -3}) with hydrogen ice pellet injection. The absolute calibration can be done by comparing the EUV bremsstrahlung profile with the visible bremsstrahlung profile of which the absolute value has been already calibrated using a standard lamp. The line-integrated profile of measured visible bremsstrahlung continuum is firstly converted into the local emissivity profile by considering a magnetic surface distortion due to the plasma pressure, and the local emissivity profile of EUV bremsstrahlung is secondly calculated by taking into account the electron temperature profile and free-free gaunt factor. The line-integrated profile of the EUV bremsstrahlung continuum is finally calculated from the local emissivity profile in order to compare with measured EUV bremsstrahlung profile. The absolute intensity calibration can be done by comparing measured and calculated EUV bremsstrahlung profiles. The calibration factor is thus obtained as a function of wavelength with excellent accuracy. It is also found in the profile analysis that the grating reflectivity of EUV emissions is constant along the direction perpendicular to the wavelength dispersion. Uncertainties on the calibration factor determined with the present method are discussed including charge-coupled device operation modes.

  16. Absolute number density calibration of the absorption by ground-state lead atoms of the 283. 3-nm resonance line from a high-intensity lead hollow cathode lamp and the calculated effect of argon pressures

    SciTech Connect

    Simons, J.W.; McClean, R.E. ); Oldenborg, R.C. )

    1991-03-21

    The absolute number density calibration for the absorption by ground-state lead atoms of the 283.3-nm resonance line from a high-intensity lead hollow cathode lamp (Photron superlamp) is determined and found to be the same as that of a standard hollow cathode lamp. Comparisons of the calibrations to theoretical calculations are found to be quite satisfactory. The effects of argon pressures in the absorption cell on the calibration are examined theoretically by using a simple Lorentzian broadening and shifting model. These calculations show the expected reduction in sensitivity and increasing linearity of Beer-Lambert plots with increasing argon pressure.

  17. 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

  18. 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.

  19. A New Marine Atmospheric Emitted Radiance Interferometer (M-AERI) for Shipboard Atmospheric and Oceanic Observations

    NASA Astrophysics Data System (ADS)

    Gero, P. J.; Knuteson, R. O.; Hackel, D.; Best, F. A.; Garcia, R.; Phillips, C.; Revercomb, H. E.; Smith, W. L.; Verret, E.; Lantagne, S. M.; Roy, C. B.

    2014-12-01

    A new ship-based Fourier transform spectrometer has been developed to measure the atmospheric downwelling and reflected infrared radiance spectrum at the Earth's surface with high absolute accuracy. This instrument was designed and built by ABB (Québec, Canada) based on the heritage of the Atmospheric Emitted Radiance Interferometer (AERI) designed by the University of Wisconsin Space Science and Engineering Center (UW-SSEC) for the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program. Prior versions of the M-AERI have been operated by the University of Miami for over a decade on research ships transiting the Atlantic and Pacific in support of NASA and NOAA satellite validation. The M-AERI measures infrared radiance between 520-3020 cm-1 (3.3-19 μm), at a resolution of 1 cm-1, using two detectors cooled to cryogenic temperatures with a Stirling cycle cooler. A gold-coated rotating scene mirror allows the M-AERI to selectively view the atmospheric scene at zenith, and ocean/atmospheric scenes over a range of +/- 45° from the horizon. The AERI uses two high-emissivity blackbodies for radiometric calibration, which in conjunction with the instrument design and a suite of rigorous laboratory diagnostics, ensures the radiometric accuracy to be better than 1% (3σ) of the ambient radiance. The M-AERI radiance spectra can be used to retrieve profiles of temperature and water vapor in the troposphere, as well as measurements of trace gases, cloud properties, and ocean skin temperature. The M-AERI measurement of ocean skin temperature has a demonstrated accuracy of better than 0.1 K. The first marine deployment of the new M-AERI will be as part of the second ARM mobile facility (AMF-2) during the ARM Cloud Aerosol Precipitation Experiment (ACAPEX) on board the NOAA Ship Ronald H. Brown in early 2015, occurring jointly with the NOAA CalWater 2 experiment. This field campaign aims to improve understanding and modeling of large-scale dynamics and cloud

  20. Assessment of the first radiances received from the VSSR Atmospheric Sounder (VAS) instrument

    NASA Technical Reports Server (NTRS)

    Chesters, D.; Uccellini, L. W.; Montgomery, H.; Mostek, A.; Robinson, W.

    1981-01-01

    The first orderly, calibrated radiances from the VAS-D instrument on the GOES-4 satellite are examined for: image quality, radiometric precision, radiation transfer verification at clear air radiosonde sites, regression retrieval accuracy, and mesoscale analysis features. Postlaunch problems involving calibration and data processing irregularities of scientific or operational significance are included. The radiances provide good visual and relative radiometric data for empirically conditioned retrievals of mesoscale temperature and moisture fields in clear air.

  1. Absolute calibration and atmospheric versus mineralogic origin of absorption features in 2.0 to 2.5 micron Mars spectra obtained during 1993

    NASA Technical Reports Server (NTRS)

    Bell, James F., III; Pollack, James B.; Geballe, Thomas R.; Cruikshank, Dale P.; Freedman, Richard

    1994-01-01

    We obtained new high resolution reflectance spectra of Mars during the 1993 opposition from Mauna Kea Observatory using the UKIRT CGS4 spectrometer. Fifty spectra of 1600-2000 km surface regions and a number of standard star spectra were obtained in the 2.04 to 2.44 micron wavelength region on 4 February 1993 UT. Near-simultaneous observations of bright standard stars were used to perform terrestrial atmospheric corrections and an absolute flux calibration. Using the known magnitude of the stars and assuming blackbody continuum behavior, the flux from Mars could be derived. A radiative transfer model and the HITRAN spectral line data base were used to compute atmospheric transmission spectra for Mars and the Earth in order to simulate the contributions of these atmospheres to our observed data. Also, we examined the ATMOS solar spectrum in the near-IR to try to identify absorption features in the spectrum of the Sun that could be misinterpreted as Mars features. Eleven absorption features were detected in our Mars spectra. Our data provide no conclusive identification of the mineralogy responsible for the absorption features we detected. However, examination of terrestrial spectral libraries and previous high spectral resolution mineral studies indicates that the most likely origin of these features is either CO3(sup 2-), HCO3(-), or HSO4(-) anions in framework silicates or possibly (Fe, Mg)-OH bonds in sheet silicates.

  2. 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.

  3. MODIS Radiances for Earth System Science Studies

    NASA Astrophysics Data System (ADS)

    Ahmad, S. P.; Salomonson, V. V.; Barnes, W. L.; Xiong, X.; Leptoukh, G. G.; Serafino, G. N.

    2002-05-01

    MODIS, a major NASA's Earth Observing System (EOS) instrument, was launched aboard the Terra satellite on December 18, 1999 (10:30 am equator crossing time) for global monitoring of the atmosphere, the terrestrial ecosystems and oceans, to develop better understanding of the 'Total Earth System', and to study the effects of natural and human-induced changes on the global environment. MODIS with its 2330 km viewing swath width provides almost daily global coverage. It acquires data in 36 high spectral resolution bands between 0.415 and 14.235 micron with spatial resolutions of 250 m (2 bands), 500 m (5 bands), and 1000 m (29 bands). This year a similar instrument will be flown on the EOS-Aqua satellite (1:30 pm equator crossing time). This will enable us to study diurnal variation of the rapidly varying systems. The radiance data measured by MODIS at high spatial resolution with some new channels (never used before for remote sensing from space) provides improved and valuable information about the physical structure of the Earth system, such as vertical distribution of temperature and humidity, cloud and aerosol characteristics, sources and sinks of trace gases, surface emissivity, land and sea surface temperature, land cover and primary productivity, snow cover and sea ice concentration, glacier and polar ice sheets, ocean currents, ocean color, and phytoplankton. Almost all key climate and environmental parameters are available as standard MODIS products and are derived from MODIS high spatial resolution radiances. However, these radiometrically corrected and geolocated high spatial resolution radiance data (referred as Level 1B product) are much in demand by the science user community. These radiances are needed to enhance existing algorithms, to test new algorithms for the retrieval of existing or new parameters, and for developing simulation datasets for characterization of new sensors. MODIS radiance counts, calibrated radiance/reflectance, geolocation

  4. The Pathfinder Mission for Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Baize, R. R.; Boyer, C.; Cageao, R.; Currey, C.; Fleming, G. A.; Jackson, T.; Johnson, D. G.; Leckey, J.; Liu, X.; Lukashin, C.; McCorkel, J.; Mlynczak, M. G.; Shea, Y.; Thome, K. J.; Wielicki, B. A.; Sun, W.

    2016-01-01

    Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.

  5. 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.

  6. 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.

  7. Vicarious calibration of the Geostationary Ocean Color Imager.

    PubMed

    Ahn, Jae-Hyun; Park, Young-Je; Kim, Wonkook; Lee, Boram; Oh, Im Sang

    2015-09-01

    Measurements of ocean color from Geostationary Ocean Color Imager (GOCI) with a moderate spatial resolution and a high temporal frequency demonstrate high value for a number of oceanographic applications. This study aims to propose and evaluate the calibration of GOCI as needed to achieve the level of radiometric accuracy desired for ocean color studies. Previous studies reported that the GOCI retrievals of normalized water-leaving radiances (nLw) are biased high for all visible bands due to the lack of vicarious calibration. The vicarious calibration approach described here relies on the assumed constant aerosol characteristics over the open-ocean sites to accurately estimate atmospheric radiances for the two near-infrared (NIR) bands. The vicarious calibration of visible bands is performed using in situ nLw measurements and the satellite-estimated atmospheric radiance using two NIR bands over the case-1 waters. Prior to this analysis, the in situ nLw spectra in the NIR are corrected by the spectrum optimization technique based on the NIR similarity spectrum assumption. The vicarious calibration gain factors derived for all GOCI bands (except 865nm) significantly improve agreement in retrieved remote-sensing reflectance (Rrs) relative to in situ measurements. These gain factors are independent of angular geometry and possible temporal variability. To further increase the confidence in the calibration gain factors, a large data set from shipboard measurements and AERONET-OC is used in the validation process. It is shown that the absolute percentage difference of the atmospheric correction results from the vicariously calibrated GOCI system is reduced by ~6.8%.

  8. 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

  9. Requirements of a solar diffuser and measurements of some candidate materials. [for calibration of satellite sensors

    NASA Technical Reports Server (NTRS)

    Guzman, Carmen T.; Palmer, James M.; Slater, Philip N.; Bruegge, Carol J.; Miller, Edward A.

    1991-01-01

    If the solar spectral irradiance and the orientation and directional reflectance of a solar diffuser are known, then the spectral radiance of the diffuser is readily calculated and it can be used for the accurate absolute calibration of a satellite sensor. However, the solar diffuser is exposed during in-flight satellite sensor calibration to high-energy ultraviolet irradiance, particle impacts and atomic oxygen effects. This paper describes desirable solar diffuser characteristics and the results of proton and UV irradiation on the directional-hemispheric spectral reflectance, the bidirectional spectral reflectance factor and the polarization properties of candidate diffuser materials.

  10. 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.

  11. Hyperspectral radiance simulator: cloudy radiance modeling and beyond

    NASA Astrophysics Data System (ADS)

    Huang, Hung-Lung; Tobin, David C.; Li, Jun; Olson, Erik R.; Baggett, Kevin; Huang, Bormin; Mecikalski, John; Knuteson, Robert O.; Osborne, Brian; Posselt, Derek; Antonelli, Paolo B.; Revercomb, Henry E.; Smith, William L.; Yang, Ping

    2003-04-01

    Current and future advanced atmospheric profile sounding and imaging instruments are evolving to enable global or hemispherical hyperspectral resolution measurements from space. The NASA/Navy/NOAA Geosynchronous Imaging FTS (GIFTS) for EO-3, NOAA Hyperspectral Environmental Sounder (HES) for GOES-R, and the currently operational Atmospheric Infrared Sounder (AIRS) on the NASA's Aqua Spacecraft will collect infrared high-spectral resolution/hyperspectral radiance spectra for remote sensing of the atmosphere, clouds, land, and ocean surfaces. These semi-continuous infrared high spectral- resolution/hyperspectral radiances will provide unprecedented information in the infrared region that is highly sensitive to absorption and emission of clouds. For sounding the atmospheric profiles one must perform cloud clearing or model the radiative effects of cloud explicitly if sounding is desired under cloud-contaminated conditions. We will describe the approach for modeling cloud attenuation in a fast-parameterized forward model that treats clouds as an additional absorber. Together with the usual clear forward model spectroscopic inputs, cloud altitude, effective particle size and shape and its ice or liquid water content are required input variables. Based on this efficient cloudy radiative transfer model, the simulation of the spatial and temporal coherent radiance images in three dimensions becomes possible. We will further explain how these 3-D GIFTS radiance cubes are used as test bed for a variety of trade studies.

  12. The MISR Calibration Program

    NASA Technical Reports Server (NTRS)

    Bruegge, Carol J.; Diner, David J.; Duval, Valerie G.

    1996-01-01

    The Multiangle Imaging SpectroRadiometer (MISR) is currently under development for NASA's Earth Observing System. The instrument consists of nine pushbroom cameras, each with four spectral bands in the visible and near-infrared. The cameras point in different view directions to provide measurements from nadir to highly oblique view angles in the along-track plane. Multiple view-angle observations provide a unique resource for studies of clouds, aerosols, and the surface. MISR is built to challenging radiometric and geometric performance specifications. Radiometric accuracy, for example, must be within +/- 3%/ 1 sigma, and polarization insensitivity must be better than +/- 1 %. An onboard calibrator (OBC) provides monthly updates to the instrument gain coefficients. Spectralon diffuse panels are used within the OBC to provide a uniform target for the cameras to view. The absolute radiometric scale is established both preflight and in orbit through the use of detector standards. During the mission, ground data processing to accomplish radiometric calibration, geometric rectification and registration of the nine view-angle imagery, and geophysical retrievals will proceed in an automated fashion. A global dataset is produced every 9 days. This paper details the preflight characterization of the MISR instrument, the design of the OBC, and the radiance product processing.

  13. 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.

  14. Asteroid 951 Gaspra Near Infrared Mapping Spectrometer Radiance Data

    NASA Astrophysics Data System (ADS)

    Granahan, J. C., Jr.

    2015-12-01

    Five radiance spectra of asteroid 951 Gaspra have been archived in the Small Bodies Node of the NASA Planetary Data System [Granahan, 2014]. The radiance spectra were created from uncalibrated Galileo spacecraft Near Infrared Mapping Spectrometer files archived in the Imaging Node of the NASA Planetary Data System. The NASA Galileo spacecraft observed asteroid 951 Gaspra on October 29, 1991 with the Near Infrared Mapping Spectrometer (NIMS) at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. The five radiance spectra consist of two 17, two 100, and one 329 spectral channel data sets. They record data that was acquired by NIMS at ranges between 27232.6 to 14723.8 kilometers from asteroid 951 Gaspra. The uncalibrated NIMS data were converted into radiance spectra using calibration coefficients obtained during the Galileo mission's first Earth encounter on December 8, 1990. The archived radiance spectral data is located at the URL (Universal Record Locator): http://sbn.psi.edu/pds/resource/gaspraspec.html and contains radiance, solar, incidence over flux, and data documentation. This archived data set contains a variety of spectral signatures. These signatures include absorptions near 1.0, 2.0, 2.8, 3.4, and 4.5 micrometers. The 1.0 and 2.0 micrometer features are indicators of olivine and pyroxene on the asteroid surface. The 2.8 micrometer feature has a shape similar to the combined spectra of multiple iron bearing phyllosilicates. The 3.4 micrometer feature is in the same location as absorptions created by a carbon-hydrogen bond. The 4.5 micrometer feature, present only in the 329 channel data set, corresponds in position to absorptions detected in sulfate minerals. Carlson, R. W., et al. (1992) Bull. of the A.A.S., 24, 932. Granahan, J. C. (2014), GO-A-NIMS-3-GASPRASPEC-V1.0, NASA Planetary Data System.

  15. Atmospheric radiance profile codes. Technical report

    SciTech Connect

    Yap, B.K.

    1986-09-17

    This report presents and describes the computer codes developed to generate atmospheric radiance profiles for various molecules, species, and rotational bands. Researchers extracted radiance profiles from the standard NLTE program output files and transferred them from the Cyber system to the Apollo system. Efforts include a routine to plot the radiance profiles sum total and SPIRE program measured data.

  16. 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+.

  17. Detection of 15 dB Squeezed States of Light and their Application for the Absolute Calibration of Photoelectric Quantum Efficiency.

    PubMed

    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 10^{17}  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. PMID:27661673

  18. 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.

  19. Overview of the radiometric calibration of MOBY

    NASA Astrophysics Data System (ADS)

    Clark, Dennis K.; Feinholz, Michael; Yarbrough, Mark; Johnson, B. Carol; Brown, Steven W.; Kim, Yong S.; Barnes, Robert A.

    2002-01-01

    The Marine Optical Buoy (MOBY) provides values of water- leaving radiance for the calibration and validation of satellite ocean color instruments. Located in clear, deep ocean waters near the Hawaiian Island of Lanai, MOBY measures the upwelling radiance and downwelling irradiance at three levels below the ocean surface plus the incident solar irradiance just above the surface. The radiance standards for MOBY are two integrating spheres with calibrations based on standards traceable to the National Institute of Standards and Technology (NIST). For irradiance, the MOBY project uses standard lamps that are routinely calibrated at NIST. Wavelength calibrations are conducted with a series of emission lines observed from a set of low pressure lamps. Each MOBY instrument views these standards before and after its deployment to provide system responses (calibration coefficients). During each deployment, the stability of the MOBY spectrographs and internal optics are monitored using three internal reference sources. In addition, the collection optics for the instrument are cleaned and checked on a monthly basis while the buoy is deployed. Divers place lamps over the optics before and after each cleaning to monitor changes at the system level. As a hyperspectral instrument, MOBY uses absorption lines in the solar spectrum to monitor its wavelength stability. When logistically feasible during each deployment, coincident measurements are made with the predecessor buoy before that buoy's recovery. Measurements of the underwater light fields from the deployment vessel are compared with those from the buoy. Based on this set of absolute calibrations and the suite of stability reference measurements, a calibration history is created for each buoy. These calibration histories link the measurement time series from the set of MOBY buoys. In general, the differences between the pre- and post-deployment radiance calibrations of the buoys range from +1% to -6% with a definitive bias to

  20. 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

  1. 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.

  2. Tree canopy radiance measurement system

    NASA Technical Reports Server (NTRS)

    Caldwell, William; Vanderbilt, V. C.

    1989-01-01

    A system is described for obtaining both an estimate of the spatial mean bidirectional reflectance factor (BRF) for a tree canopy (displaying a horizontally heterogeneous foliage distribution) and the statistical significance of that estimate. The system includes a manlift supporting a horizontal beam 7 m long on which are mounted four radiometers. These radiometers may be pointed, and radiance data acquired, in any of 11 view directions in the principal plane of the sun. A total of 80 data points, acquired in 3 min, were used to estimate the BRF of a walnut orchard 5 m tall and detect true differences of 12 percent of the mean approximately 90 percent of the time.

  3. Absolute calibration of the colour index and O4 absorption derived from Multi AXis (MAX-)DOAS measurements and their application to a standardised cloud classification algorithm

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas; Beirle, Steffen; Remmers, Julia; Shaiganfar, Reza; Wang, Yang

    2016-09-01

    A method is developed for the calibration of the colour index (CI) and the O4 absorption derived from differential optical absorption spectroscopy (DOAS) measurements of scattered sunlight. The method is based on the comparison of measurements and radiative transfer simulations for well-defined atmospheric conditions and viewing geometries. Calibrated measurements of the CI and the O4 absorption are important for the detection and classification of clouds from MAX-DOAS observations. Such information is needed for the identification and correction of the cloud influence on Multi AXis (MAX-)DOAS profile inversion results, but might be also be of interest on their own, e.g. for meteorological applications. The calibration algorithm was successfully applied to measurements at two locations: Cabauw in the Netherlands and Wuxi in China. We used CI and O4 observations calibrated by the new method as input for our recently developed cloud classification scheme and also adapted the corresponding threshold values accordingly. For the observations at Cabauw, good agreement is found with the results of the original algorithm. Together with the calibration procedure of the CI and O4 absorption, the cloud classification scheme, which has been tuned to specific locations/conditions so far, can now be applied consistently to MAX-DOAS measurements at different locations. In addition to the new threshold values, further improvements were introduced to the cloud classification algorithm, namely a better description of the SZA (solar zenith angle) dependence of the threshold values and a new set of wavelengths for the determination of the CI. We also indicate specific areas for future research to further improve the cloud classification scheme.

  4. A comparison of measured radiances from AIRS and HIRS across different cloud types

    NASA Astrophysics Data System (ADS)

    Schreier, M. M.; Kahn, B. H.; Staten, P.

    2015-12-01

    The observation of Earth's atmosphere with passive remote sensing instruments is ongoing for decades and resulting in a long-term global dataset. Two prominent examples are operational satellite platforms from the National Oceanic and Atmospheric Administration (NOAA) or research platforms like NASA's Earth Observing System (EOS). The observed spectral ranges of these observations are often similar among the different platforms, but have large differences when it comes to resolution, accuracy and quality control. Our approach is to combine different kinds of instruments at the pixel-scale to improve the characterization of infrared radiances. We focus on data from the High-resolution Infrared Radiation Sounder (HIRS) and compare the observations to radiances from the Atmospheric Infrared Sounder (AIRS) on Aqua. The high spectral resolution of AIRS is used to characterize and possibly recalibrate the observed radiances from HIRS. Our approach is unique in that we use additional information from other passive instruments on the same platforms including the Advanced Very High Resolution Radiometer (AVHRR) and the MODerate resolution Imaging Spectroradiometer (MODIS). We will present comparisons of radiances from HIRS and AIRS within different types of clouds that are determined from the imagers. In this way, we can analyze and select the most homogeneous conditions for radiance comparisons and a possible re-calibration of HIRS. We hope to achieve a cloud-type-dependent calibration and quality control for HIRS, which can be extrapolated into the past via inter-calibration of the different HIRS instruments beyond the time of AIRS.

  5. Absolute and relative quantification and calibration for sectioning fluorescence microscopy using standardized uniform fluorescent layers and SIPchart-based correction procedures

    NASA Astrophysics Data System (ADS)

    Zwier, J. M.; Oomen, L.; Brocks, L.; Jalink, K.; Brakenhoff, G. J.

    2007-02-01

    The total or integrated fluorescence intensity of a through-focus series of a thin standardized uniform fluorescent or calibration layer is shown to be suitable for image intensity correction and calibration in sectioning microscopy. This integrated intensity can be derived from the earlier introduced SectionedImagingProperty or SIPcharts, derived from the 3D layer datasets. By correcting the 3D image of an object with the 3D image of the standardized uniform fluorescent layer obtained under identical conditions one is able to express the object fluorescence in units fluorescence of the calibration layer. With object fluorescence intensities in fluorescence layer unit's or FLU's the object image intensities becomes independent of microscope system and imaging conditions. A direct result is that the often-appreciable lateral intensity variations present in confocal microscopy are eliminated (shading correction). Of more general value is that images obtained with different objectives, magnifications or from different microscope systems can be quantitatively related to each other. The effectiveness of shading correction and relating images obtained under various microscope conditions is demonstrated on images of standard fluorocent beads. Expressing the object fluorescence in FLU units seems to be a promising approach for general quantification of sectioning imaging enabling cross-correlation of imaging results over time and between imaging systems.

  6. Absolute Energy Calibration with the Neutron-Activated Liquid-Source System at BaBar's CsI(Tl) Calorimeter

    SciTech Connect

    Bauer, J

    2004-01-05

    The electro-magnetic calorimeter at the BABAR detector, part of the asymmetric B Factory at SLAC, measures photons in the energy range from 20 MeV to 8 GeV with good resolution. The calorimeter is calibrated at the low energy end with 6.13 MeV photons obtained from a liquid source system. During the calibration, a fluorine-rich liquid is activated via a neutron generator and pumped past the front of the calorimeter's crystals. Decays that occur in front of the crystals emit photons of well-defined energy, which are detected in the crystals with the regular data acquisition system. The liquid source system adds only very little material in front of the calorimeter, needs nearly no maintenance, and allows operation at the switch of a key with minimal safety hazards. The report describes the system, presents calibration results obtained from its operation since 1999, shows the crystals' loss of light yield due to radiation damage, and shares experiences gained over the years.

  7. NIMS Radiance Point Spectra of Gaspra V1.0

    NASA Astrophysics Data System (ADS)

    Granahan, J. C.

    2014-10-01

    This data volume contains radiometrically corrected point spectra of asteroid 951 as acquired by the Galileo spacecraft Near Infrared Mapping Spectrometer (NIMS) on October 29, 1991. They record the spectra collected as the Galileo spacecraft approached the target asteroid. These data are products of the calibration of the raw data number files gap015tn.qub, gap035tn.qub, gap036tn.qub, gap037tn.qub, and gap038tn.qub (DATA SET ID ='GO-A-NIMS-3 TUBE-V1.0') with calibration factors acquired during the first Earth/Moon encounter of the Galileo mission. These raw data .qub files are archived in the Imaging Node of the NASA Planetary Data System (PDS). The calibrated spectra consist of radiance measurements for wavelengths between 0.7 - 5.2 micrometers.

  8. 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.

  9. 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.

  10. Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Hires, Drew V.; Johansen, Craig T.; Bathel, Brett F.; Jones, Stephen B.; Gragg, Jeffrey G.; Splinter, Scott C.

    2012-01-01

    Calibrated spectral radiance measurements of gaseous emission spectra have been obtained from the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. A fiber-optic coupled spectrometer collected natural luminosity from the flow. Spectral radiance measurements are reported between 340 and 1000 nm. Both Silicon Carbide (SiC) and Phenolic Impregnated Carbon Ablator (PICA) samples were placed in the flow. Test gases studied included a mostly-N2 atmosphere (95% nitrogen, 5% argon), a simulated Earth Air atmosphere (75% nitrogen, 20% oxygen, 5% argon) and a simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon). The bulk enthalpy of the flow was varied as was the location of the measurement. For the intermediate flow enthalpy tested (20 MJ/kg), emission from the Mars simulant gas was about 10 times higher than the Air flow and 15 times higher than the mostly-N2 atmosphere. Shock standoff distances were estimated from the spectral radiance measurements. Within-run, run-to-run and day-to-day repeatability of the emission were studied, with significant variations (15-100%) noted.

  11. Calibration of a photomultiplier array spectrometer

    NASA Technical Reports Server (NTRS)

    Bailey, Steven A.; Wright, C. Wayne; Piazza, Charles R.

    1989-01-01

    A systematic approach to the calibration of a photomultiplier array spectrometer is presented. Through this approach, incident light radiance derivation is made by recognizing and tracing gain characteristics for each photomultiplier tube.

  12. Three Years of Atmospheric Infrared Sounder Radiometric Calibration Validation using Sea Surface Temperatures

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    This paper evaluates the absolute accuracy and stability of the radiometric calibration of the Atmospheric Infrared Sounder (AIRS) by analyzing the difference between the brightness temperatures measured at 2616 cm(exp -1) and those calculated at the top of the atmosphere (TOA), using the Real-Time Global Sea Surface Temperature (RTGSST) for cloud-free night tropical oceans between +/- 30 degrees latitude. The TOA correction is based on radiative transfer. The analysis of the first 3 years of AIRS radiances verifies the absolute calibration at 2616 cm(exp -1) to better than 200 mK, with better than 16 mK/yr stability. The AIRS radiometric calibration uses an internal full aperture wedge blackbody with the National Institute of Standards and Technology (NIST) traceable prelaunch calibration coefficients. The calibration coefficients have been unchanged since launch. The analysis uses very tight cloud filtering, which selects about 7000 cloud-free tropical ocean spectra per day, about 0.5% of the data. The absolute accuracy and stability of the radiometry demonstrated at 2616 cm(sup -1) are direct consequences of the implementation of AIRS as a thermally controlled, cooled grating-array spectrometer and meticulous attention to details. Comparable radiometric performance is inferred from the AIRS design for all 2378 channels. AIRS performance sets the benchmark for what can be achieved with a state-of-the-art hyperspectral radiometer from polar orbit and what is expected from future hyperspectral sounders. AIRS was launched into a 705 km altitude polar orbit on NASA's Earth Observation System (EOS) Aqua spacecraft on 4 May 2002. AIRS covers the 3.7-15.4 micron region of the thermal infrared spectrum with a spectral resolution of nu/Delta nu = 1200 and has returned 3.7 million spectra of the upwelling radiance each day since the start of routine data gathering in September 2002.

  13. Ground Calibrations of the Clouds and the Earth's Radiant Energy System (CERES) Tropical Rainfall Measuring Mission Spacecraft Thermistor Bolometers

    NASA Technical Reports Server (NTRS)

    Lee, Robert B., III; Smith, G. Lou; Barkstrom, Bruce R.; Priestley, Kory J.; Thomas, Susan; Paden, Jack; Pandey, Direndra K.; Thornhill, K. Lee; Bolden, William C.; Wilson, Robert S.

    1997-01-01

    The Clouds and the Earth's Radiant Energy System (CERES) spacecraft scanning thermistor bolometers will measure earth-reflected solar and earth-emmitted,longwave radiances, at the top-of-the-atmosphere. The measurements are performed in the broadband shortwave (0.3-5.0 micron) and longwave (5.0 - >100 micron) spectral regions as well as in the 8 -12 micron water vapor window over geographical footprints as small as 10 kilometers at the nadir. The CERES measurements are designed to improve our knowledge of the earth's natural climate processes, in particular those related to clouds, and man's impact upon climate as indicated by atmospheric temperature. November 1997, the first set of CERES bolometers is scheduled for launch on the Tropical Rainfall Measuring Mission (TRMM) Spacecraft. The CERES bolometers were calibrated radiometrically in a vacuum ground facility using absolute reference sources, tied to the International Temperature Scale of 1990. Accurate bolometer calibrations are dependent upon the derivations of the radiances from the spectral properties [reflectance, transmittance, emittance, etc.] of both the sources and bolometers. In this paper, the overall calibration approaches are discussed for the longwave and shortwave calibrations. The spectral responses for the TRMM bolometer units are presented and applied to the bolometer ground calibrations in order to determine pre-launch calibration gains.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. Spectroradiometric calibration of the thematic mapper and multispectral scanner system

    NASA Technical Reports Server (NTRS)

    Slater, P. N. (Principal Investigator); Palmer, J. M.

    1983-01-01

    The design of a spectroradiometer under construction for atmosheric and surface measurements at White Sands, New Mexico is described. The instrument's observation capability encompasses (1) measuring the solar radiance at a number of wavelengths as a function of air mass for Langley plot analysis in order to generate the optical depth; (2) measuring the ground radiance to determine the absolute ground reflectance; and (3) measuring the sky radiance as a method of checking the accuracy of the radiative transfer program.

  19. Constrained adaptive bias correction for satellite radiances assimilation in the ECMWF 4D-Var

    NASA Astrophysics Data System (ADS)

    Han, Wei; Bormann, Niels

    2016-04-01

    Satellite radiance observations are typically affected by biases that arise from uncertainties in the absolute calibration, the radiative transfer modeling, or other aspects. These biases have to be removed for the successful assimilation of the data in NWP systems. Two key problems have been identified in bias correction: Firstly, bias corrections can drift towards unrealistic values in regions where there is strong model error and relatively few "anchor" observations, ie, observations that have little systematic error and therefore allow the separation between model and observation bias. Examples where this has been particularly problematic are channels sensitive to ozone or stratospheric temperature. Secondly, there is undesired interaction between the quality control and bias correction for observations where bias-corrected observation departures are used for quality control and where these departures show skewed distributions (e.g., in case of cloud detection). In the study, we investigated potential solutions to these problems by providing further constraints using potential available information, such as constraints on the size of the bias correction and innovative bias correction metrics using uncertainty estimation from calibration and radiative transfer. This has been studied in the full ECMWF global 4D-Var system, using data from microwave sounders which are sensitive to stratospheric temperature. The resulting enhanced bias corrections was assessed in the context of other assimilated observations (in particular radiosondes and GPS radio occultation measurements), and through comparisons of MLS temperature retrieval data in stratosphere and mesosphere. The constrained adaptive bias correction of AMSU-A stratospheric sounding channels reduces the biases in stratosphere and improves the medium range forecasts in both stratosphere and troposphere.

  20. Reflectance-based calibration of SeaWiFS. I. Calibration coefficients.

    PubMed

    Barnes, Robert A; Zalewski, Edward F

    2003-03-20

    We present a calibration approach for the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) based on the reflectance properties of the instrument's onboard diffuser. This technique uses SeaWiFS as a reflectometer, measuring the reflected solar irradiance from the Earth and from the onboard diffuser. Because the Sun is the common source of light for both measurements, the ratio of the SeaWiFS-measured radiances from the Earth and the diffuser provide the ratio for the reflectances of the two samples. The reflectance characterization of the onboard diffuser is the calibration reference for this approach. Knowledge of the value of the solar irradiance is not required for these measurements because it falls out of the ratio. Knowledge of the absolute calibration coefficient for the SeaWiFS measurements of each of the two samples is not required either. Instead, the result of the ratioing technique is based on the linearity of the instrument's response to the intensity of the input light. The calibration requires knowledge, however, of the reflectance of the onboard diffuser at the start of the SeaWiFS mission and the response of the instrument bands, in digital numbers, for measurements of the diffuser at that time.

  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. 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.

  3. 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

  4. The Intercalibration of Geostationary Visible Imagers Using Operational Hyperspectral SCIAMACHY Radiances

    NASA Technical Reports Server (NTRS)

    Doelling, David R.; Scarino, Benjamin R.; Morstad, Daniel; Gopalan, Arun; Bhatt, Rajendra; Lukashin, Constantine; Minnis, Patrick

    2013-01-01

    Spectral band differences between sensors can complicate the process of intercalibration of a visible sensor against a reference sensor. This can be best addressed by using a hyperspectral reference sensor whenever possible because they can be used to accurately mitigate the band differences. This paper demonstrates the feasibility of using operational Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) large-footprint hyperspectral radiances to calibrate geostationary Earth-observing (GEO) sensors. Near simultaneous nadir overpass measurements were used to compare the temporal calibration of SCIAMACHY with Aqua Moderate Resolution Imaging Spectroradiometer band radiances, which were found to be consistent to within 0.44% over seven years. An operational SCIAMACHY/GEO ray-matching technique was presented, along with enhancements to improve radiance pair sampling. These enhancements did not bias the underlying intercalibration and provided enough sampling to allow up to monthly monitoring of the GEO sensor degradation. The results of the SCIAMACHY/GEO intercalibration were compared with other operational four-year Meteosat-9 0.65-µm calibration coefficients and were found to be within 1% of the gain, and more importantly, it had one of the lowest temporal standard errors of all the methods. This is more than likely that the GEO spectral response function could be directly applied to the SCIAMACHY radiances, whereas the other operational methods inferred a spectral correction factor. This method allows the validation of the spectral corrections required by other methods.

  5. Radiometric Calibration of Earth-Observing Sensors Using the Radiometric Calibration Test Site (RadCaTS)

    NASA Astrophysics Data System (ADS)

    Czapla-Myers, J.; Anderson, N. J.; Thome, K. J.; Biggar, S. F.

    2014-12-01

    The Remote Sensing Group (RSG) of the College of Optical Sciences at the University of Arizona uses the reflectance-based approach to perform the absolute radiometric calibration of such sensors as Landsat 5 TM, Landsat 7 ETM+, Landsat 8 OLI, Terra and Aqua MODIS, ASTER, RapidEye, and others. The reflectance-based approach requires that personnel be present at a test site during the sensor overpass, so the Radiometric Calibration Test Site (RadCaTS) was developed in order to capture data during every possible overpass, which assists in the temporal trending of the radiometric calibration of earth-observing sensors. The number of earth-observing sensors is rapidly increasing in recent years, and RadCaTS provides the ability to radiometrically calibrate them without the requirement of frequent field campaigns. The 2013 launch of Landsat 8 provides a unique opportunity for RadCaTS in that it is being used to supplement the in situ measurements by RSG ground personnel, and it will be used throughout the lifetime of the Landsat 8 mission. This allows more data to be collected throughout the year, and it also allows the accuracy and uncertainty of RadCaTS to be analyzed. The current top-of-atmosphere (TOA) spectral radiance uncertainty of the reflectance-based approach is ~2.6% in the mid-visible region of the spectrum, and current work indicates that the uncertainty of RadCaTS in TOA spectral radiance is ~3-4%. This work presents the radiometric calibration results of RadCaTS for a variety of sensors such as Landsat 7 ETM+, Landsat 8 OLI, Terra and Aqua MODIS, MISR, ASTER, and Suomi NPP VIIRS.

  6. Modeling and Assimilating Ocean Color Radiances

    NASA Technical Reports Server (NTRS)

    Gregg, Watson

    2012-01-01

    Radiances are the source of information from ocean color sensors to produce estimates of biological and geochemical constituents. They potentially provide information on various other aspects of global biological and chemical systems, and there is considerable work involved in deriving new information from these signals. Each derived product, however, contains errors that are derived from the application of the radiances, above and beyond the radiance errors. A global biogeochemical model with an explicit spectral radiative transfer model is used to investigate the potential of assimilating radiances. The results indicate gaps in our understanding of radiative processes in the oceans and their relationships with biogeochemical variables. Most important, detritus optical properties are not well characterized and produce important effects of the simulated radiances. Specifically, there does not appear to be a relationship between detrital biomass and its optical properties, as there is for chlorophyll. Approximations are necessary to get beyond this problem. In this reprt we will discuss the challenges in modeling and assimilation water-leaving radiances and the prospects for improving our understanding of biogeochemical process by utilizing these signals.

  7. Status of use of lunar irradiance for on-orbit calibration

    USGS Publications Warehouse

    Stone, T.C.; Kieffer, H.H.; Anderson, J.M.; ,

    2002-01-01

    Routine observations of the Moon have been acquired by the Robotic Lunar Observatory (ROLO) for over four years. The ROLO instruments measure lunar radiance in 23 VNIR (Moon diameter ???500 pixels) and 9 SWIR (???250 pixels) passbands every month when the Moon is at phase angle less than 90 degrees. These are converted to exoatmospheric values at standard distances using an atmospheric extinction model based on observations of standard stars and a NIST-traceable absolute calibration source. Reduction of the stellar images also provides an independent pathway for absolute calibration. Comparison of stellar-based and lamp-based absolute calibrations of the lunar images currently shows unacceptably large differences. An analytic model of lunar irradiance as a function of phase angle and viewing geometry is derived from the calibrated lunar images. Residuals from models which fit hundreds of observations at each wavelength average less than 2%. Comparison with SeaWiFS observations over three years reveals a small quasi-periodic change in SeaWiFS responsivity that correlates with distance from the Sun for the first two years, then departs from this correlation.

  8. 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.

  9. Effects of Nighttime Light Radiance on the Sleep of the General Population

    NASA Technical Reports Server (NTRS)

    Ohayon, Maurice M.; Milesi, Cristina

    2015-01-01

    The objectives of this study is to verify if the exposure to greater nighttime radiance is associated with changes in the sleep/wake schedule and with greater sleep disturbances. Methods: The target population was the adults (18 years and older) living in California, USA. This represents 24 million of inhabitants. A total of 3,104 subjects participated in the survey (participation rate 85.6%). The participants were interviewed by telephone using the Sleep-EVAL system. The interviews covered several topics including sleeping habits, sleep quality, sleep disturbances, physical symptoms related to menopause. Chronic insomnia was defined as difficulty initiating or maintaining sleep for at least 3 months. Global nighttime light emissions have been collected by the Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS) sensors. We extracted the radiance calibrated nighttime lights corresponding to the date of the interviews for a three by three window centered on each coordinate corresponding to an interview address. Results: Dissatisfaction with sleep quantity and/or quality was associated with an increased nighttime radiance (p=0.02). Similarly, excessive sleepiness accompanied with impaired functioning was significantly associated with an increased nighttime radiance (p (is) less than 0.0001). The association remained significant after controlling for age, gender and use of a night lamp in the bedroom. Confusional arousals were also significantly associated with an increased nighttime radiance (p (is) less than 0.0001). Bedtime hour was linearly increasing with the intensity of nighttime radiance: the later the bedtime, the greater the nighttime radiance (p (is) less than 0.0001). Similarly, wakeup time became progressively later as the nighttime radiance increased (p (is) less than 0.0001). Both associations remained significant after controlling for age, gender and use of a night lamp in the bedroom. Circadian Rhythm Disorders were the

  10. [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

  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. Comparison of methods for calibrating AVIRIS data to ground reflectance

    NASA Technical Reports Server (NTRS)

    Clark, Roger N.; Swayze, Gregg; Heidebrecht, Kathy; Goetz, Alexander F. H.; Green, Robert O.

    1993-01-01

    We are comparing three basic methods of calibrating AVIRIS data to ground reflectance: (1) atmospheric radiative transfer models with the solar flux can be used to calibrate AVIRIS radiance data (Specific methods include the University of Colorado CSES ARP and ATREM algorithms); (2) Robert Green's modified MODTRAN and AVIRIS radiance model (This method is similar to 1 but differs in that the solar radiance is bypassed, so any errors in the solar flux are canceled, too); and (3) ground calibration using known sites in the AVIRIS scene. We are using 1992AVIRIS data over Cuprite, Nevada, and Blackhawk Island, Wisconsin, as our test scenes. Both these sites have extensive field measurements. The Cuprite site had a very clear atmosphere, thus path radiance was dominated by Rayleigh scattering with little or no flux beyond 1 micron. The Blackhawk site has more aerosols, with significant path radiance flux beyond 2 micron.

  13. Radiometric calibration of Landsat Thematic Mapper

    SciTech Connect

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

    1988-08-01

    Absolute calibration of satellite-acquired data is essential for quantification of scientific studies and a variety of image- processing applications. This paper describes a multiyear, on-orbit radiometric calibration of the Landsat Thematic Mapper (TM). Primary emphasis was placed on TM band 6 (thermal) calibration, but selected reflectance-band calibration measurements were also made. Twenty-five Landsat TM coverages were acquired, and included day, night, and seasonal scenes at several geographical locations. Concurrent with Landsat overpasses, thermal and reflectance field and local meteorological (surface and radiosonde) measurements were collected. At-satellite (uncorrected) radiances and temperatures for water and non-water 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 well-characterized water features, TM band 6 average corrected temperature determinations using local radiosonde data for atmospheric adjustments are within less than or equal to0.6/degree/C of GT temperature determinations. For non-water features, TM band 6 derived temperatures are within 1/degree/C of GT temperature determinations, if appropriate emissivity adjustments are made. Corrections using non-local radiosonde data resulted in errors as large as 12/degree/C. Corrections using the US Standard atmosphere gave temperature values within 1 to 2/degree/C of GT. The average uncertainty for field instruments was +-0.2/degree/C; average uncertainty for Landsat TM corrected temperature determinations was +-0.4/degree/C. A cross-calibration of TM band 6 and the Advanced Very High Resolution Radiometer (AVHRR) for a Landsat overpass gave similar temperature results. 15 refs., 3 figs., 5 tabs.

  14. The NBS scale of radiance temperature

    NASA Technical Reports Server (NTRS)

    Waters, William R.; Walker, James H.; Hattenburg, Albert T.

    1988-01-01

    The measurement methods and instrumentation used in the realization and transfer of the International Practical Temperature Scale (IPTS-68) above the temperature of freezing gold are described. The determination of the ratios of spectral radiance of tungsten-strip lamps to a gold-point blackbody at a wavelength of 654.6 nm is detailed. The response linearity, spectral responsivity, scattering error, and polarization properties of the instrumentation are described. The analysis of the sources of error and estimates of uncertainty are presented. The assigned uncertainties (three standard deviations) in radiance temperature range from + or - 2 K at 2573 K to + or - 0.5 K at 1073 K.

  15. Radiance from an ice contaminated surface

    NASA Astrophysics Data System (ADS)

    Arenberg, J.; Adamson, J.; Harpole, G.; Niedner, M.; Bowers, C.; Mehalick, K.; Lightsey, P.

    2016-07-01

    The formation of water ice on key thermal and optical surfaces is a factor in the design of the James Webb Space Telescope. Many of these concerns are related to the mid-infrared stray light performance of the system. In this paper, an expression for the radiance of a contaminated surface is formulated, including directional, film thickness and cooling effects. The resulting formula is then evaluated to show how radiance emanating from the surface changes for various thicknesses of the ice layer as a function wavelength and the local thermal environment. This paper concludes with an analysis and discussion of this complex behavior.

  16. Atmospheric emitted radiance interferometer (AERI): Status and the aerosol explanation for extra window region emissions

    SciTech Connect

    Revercomb, H.E.; Knuteson, R.O.; Best, F.A.; Dirkx, T.P.

    1996-04-01

    High spectral resolution observations of downwelling emission from 3 to 19 microns have been made by the Atmospheric Emitted Radiance Interferometer (AERI) Prototype at the Southern Great Plains (SGP) Cloud and Radiative Testbed (CART) site for over two years. The spectral data set from AERI provides a basis for improving clear sky radiative transfer; determining the radiative impact of clouds, including the derivation of cloud radiative properties; defining the influences of aerosols in the window regions; and retrieving boundary layer state properties, including temperature, water vapor, and other trace gases. The data stream of radiometrically and spectrally calibrated radiances is routinely provided by Pacific Northwest Laboratory (PNL) to those science teams requesting it, and further information on the instrument and data characteristics is available in the ARM Science Team proceedings for 1993 and 1994 and in several conference publications. This paper describes the AERI status, calibration, field experiment wit a new AERI-01 and schedule, window region emissions, and future AERI plans.

  17. Methods for LWIR Radiometric Calibration and Characterization

    NASA Technical Reports Server (NTRS)

    Ryan, Robert; Harrington, Gary; Howell, Dane; Pagnutti, Mary; Zanoni, Vicki

    2002-01-01

    The utility of a remote sensing system increases with its ability to retrieve surface temperature or radiance accurately. Research applications, such as sea temperature and power plant discharge, require a 0.2 C resolution or better for absolute temperature retrievals. Other applications, including agriculture water stress detection, require at least a 1 C resolution. To achieve these levels of accuracy routinely, scientists must perform laboratory and onboard calibration, as well as in-flight vicarious radiometric characterization. A common approach used for in-flight radiometric characterization incorporates a well-calibrated infrared radiometer that is mounted on a bouy and placed on a uniform water body. The radiometer monitors radiant temperature along with pressure, humidity, and temperature measurements of an associated column of atmosphere. On very still waters, however, a buoy can significantly distrub these measurements. Researchers at NASA's Stennis Space Center (SSC) have developed a novel approach of using an uncooled infrared camera mounted on a boom to quantify buoy effects. Another critical aspect of using buoy-mounted infrared radiometers is the need for extensive laboratory characterization of the instruments' radiometric sensitivity, field of view, and spectral response. Proper surface temperature retrieval also requires detailed knowledge of both the upward emission and the reflected sky emission. Recent work at SSC has demonstrated that the use of a polarization-based radiometer operating at the Brewster angle can greatly simplify temperature retrieval as well as improve overall accuracy.

  18. 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

  19. Inter-Satellite Calibration Linkages for the Visible and Near-Infrared Channels of the Advanced Very High Resolution Radiometer on the NOAA-7, -9, and -11 Spacecraft. Revised

    NASA Technical Reports Server (NTRS)

    NagarajaRao, C. R.; Chen, J.

    1996-01-01

    The post-launch degradation of the visible (channel 1: 0.58- 068 microns) and near-infrared (channel 2: approx. 0.72 - l.l microns) channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-7, -9, and -11 Polar-orbiting Operational Environmental Satellites (POES) was estimated using the south-eastern part of the Libyan Desert as a radiometrically stable calibration target. The relative annual degradation rates, in per cent, for the two channels are, respectively: 3.6 and 4.3 (NOAA-7); 5.9 and 3.5 (NOAA-9); and 1.2 and 2.0 (NOAA-11). Using the relative degradation rates thus determined, in conjunction with absolute calibrations based on congruent path aircraft/satellite radiance measurements over White Sands, New Mexico (USA), the variation in time of the absolute gain or slope of the AVHRR on NOAA-9 was evaluated. Inter-satellite calibration linkages were established, using the AVHRR on NOAA-9 as a normalization standard. Formulae for the calculation of calibrated radiances and albedos (AVHRR usage), based on these interlinkages, are given for the three AVHRRs.

  20. Assimilation of the Microwave Limb Sounder Radiances

    NASA Technical Reports Server (NTRS)

    Wargan, K.; Read, W.; Livesey, N.; Wagner, P.; Nguyen. H.; Pawson, S.

    2012-01-01

    It has been shown that the assimilation of limb-sounder data can significantly improve the representation of ozone in NASA's GEOS Data Assimilation Systems (GEOS-DAS), particularly in the stratosphere. The studies conducted so far utilized retrieved data from the MIPAS, POAM, ILAS and EOS Microwave Limb Sounder (EOS MLS) instruments. Direct assimilation of the radiance data can be seen as the natural next step to those studies. The motivation behind working with radiances is twofold. First, retrieval algorithms use a priori data which are either climatological or are obtained from previous analyses. This introduces additional uncertainty and, in some cases, may lead to "self-contamination"- when the a priori is taken from the same assimilation system in which subsequently ingests the retrieved observations. Second, radiances can be available in near real time thus providing an opportunity for operational assimilation, which could help improve the use of infrared radiance instruments from operational satellite instruments. In this presentation we summarize our ongoing work on an implementation of the assimilation of EOS MLS radiances into the GEOS-5 DAS. This work focuses on assimilation of band 7 brightness temperatures which are sensitive to ozone. Our implementation uses the MLS Callable Forward Model developed by the MLS team at NASA JPL as the observation operator. We will describe our approach and recent results which are not yet final. In particular, we will demonstrate that this approach has a potential to improve the vertical structure of ozone in the lower tropical stratosphere as compared with the retrieved MLS product. We will discuss the computational efficiency of this implementation.

  1. Thematic Mapper thermal infrared calibration

    NASA Astrophysics Data System (ADS)

    Schott, J. R.; Volchok, W. J.

    1985-09-01

    TM band 6 data from Landsat-4 and Landsat-5 are analyzed by correcting the observed radiance for the spectral characteristics of the sensor, along with atmospheric propagation parameters derived from LOWTRAN models. The resultant surface radiance values or surface temperatures are compared to surface temperatures derived from underflight and ground truth data. Correlation of these data indicate that significant systematic error is evident in the satellite-derived surface temperatures. Evaluation of the expected error introduced by the LOWTRAN modeling technique results in compensation of some of this systematic error. The remaining error indicates that the satellite internal calibration, specifically the sensor gain, corrections are not completely compensating for gain shifts.

  2. Infrared transfer radiometer for broadband and spectral calibration of space chambers

    NASA Astrophysics Data System (ADS)

    Jung, Timothy M.; Carter, Adriaan C.; Woods, Solomon I.; Kaplan, Simon G.; Datla, Raju U.

    2010-04-01

    The Low-Background Infrared (LBIR) facility at NIST has recently completed construction of an infrared transfer radiometer with an integrated cryogenic Fourier transform spectrometer (Cryo-FTS). This mobile system can be deployed to customer sites for broadband and spectral calibrations of space chambers and low-background HWIL testbeds. The Missile Defense Transfer Radiometer (MDXR) has many of the capabilities of a complete IR calibration facility and will replace our existing filter-based transfer radiometer (BXR) as the NIST standard detector deployed to MDA facilities. The MDXR features numerous improvements over the BXR, including: a cryogenic Fourier transform spectrometer, an on-board absolute cryogenic radiometer (ACR), an internal blackbody reference, and an integrated collimator. The Cryo-FTS can be used to measure high resolution spectra from 4 to 20 micrometers, using a Si:As blocked-impurity-band (BIB) detector. The on-board ACR can be used for self-calibration of the MDXR BIB as well as for absolute measurements of infrared sources. A set of filter wheels and a rotating polarizer within the MDXR allow for filter-based and polarization-sensitive measurements. The optical design of the MDXR makes both radiance and irradiance measurements possible and enables calibration of both divergent and collimated sources. Details of the various MDXR components will be presented as well as initial testing data on their performance.

  3. 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.

  4. Determination of the responsivity non-uniformity of an infrared camera with regard to the measurement of radiance temperatures

    NASA Astrophysics Data System (ADS)

    Gutschwager, Berndt; Cárdenas-García, Daniel; Hollandt, Jörg

    2015-11-01

    This paper presents a method to accurately determine the responsivity non-uniformity of the pixels of an infrared camera. Mandatory for the use of infrared cameras for measurements of radiance temperatures with small uncertainties is the knowledge of this responsivity non-uniformity and the resulting ability to correct the responsivity non-uniformity of the measured image. Infrared cameras are optically and electronically more complex than radiation thermometers. For the calibration of infrared cameras a large-area source with a known radiance distribution is required. Practical implementations of such large-area sources are plate radiators, which generally have a non-homogeneous distribution of the radiance and of the radiance temperature over their surface. The determination of the non-uniformity of the radiance temperature of a plate radiator is mandatory for the accurate calibration of infrared cameras, i.e. for the determination and adequate consideration of the responsivity non-uniformity of all pixels of an infrared camera.

  5. Service Oriented Gridded Atmospheric Radiances (SOAR)

    NASA Astrophysics Data System (ADS)

    Halem, M.; Goldberg, M. D.; Tilmes, C.; Zhou, L.; Shen, S.; Yesha, Y.

    2005-12-01

    We are developing a scalable web service tool that can provide complex griding services on-demand for atmospheric radiance data sets from multiple temperature and moisture sounding sensors on the NASA and NOAA polar orbiting satellites collected over the past three decades. This server-to-server middle ware tool will provide the framework for transforming user requests for an arbitrary spatial/temporal/spectral gridded radiance data set from one or more instruments into an action to invoke a griding process from a set of scientifically validated application programs that have been developed to perform such functions. The invoked web service agents will access, subset, concatenate, convolve, perform statistical and physically based griding operations and present the data as specified level 3 gridded fields for analysis and visualization in multiple formats. Examples of the griding operations consist of spatial-temporal radiance averaging accounting for the field of view instrument response function, first footprint in grid bin, selecting min/max brightness temperatures within a grid element, ratios of channels, filtering, convolving high resolution spectral radiances to match broader band spectral radiances, limb adjustments, calculating variances of radiances falling in grid box and creating visual displays of these fields. The gridded web services tool will support both human input through a WWW GUI as well as a direct computer request through a W3C SOAP/XML web service interface. It will generate regional and global gridded data sets on demand. A second effort will demonstrate the ability to locate, access, subset and grid radiance data for any time period and resolution from remote archives of NOAA and NASA data. The system will queue the work flow requests, stage processing and delivery of arbitrary gridded data sets in a data base and notify the users when the request is completed. This tool will greatly expand satellite sounding data utilization by

  6. In-Situ Transfer Standard and Coincident-View Intercomparisons for Sensor Cross-Calibration

    NASA Technical Reports Server (NTRS)

    Thome, Kurt; McCorkel, Joel; Czapla-Myers, Jeff

    2013-01-01

    There exist numerous methods for accomplishing on-orbit calibration. Methods include the reflectance-based approach relying on measurements of surface and atmospheric properties at the time of a sensor overpass as well as invariant scene approaches relying on knowledge of the temporal characteristics of the site. The current work examines typical cross-calibration methods and discusses the expected uncertainties of the methods. Data from the Advanced Land Imager (ALI), Advanced Spaceborne Thermal Emission and Reflection and Radiometer (ASTER), Enhanced Thematic Mapper Plus (ETM+), Moderate Resolution Imaging Spectroradiometer (MODIS), and Thematic Mapper (TM) are used to demonstrate the limits of relative sensor-to-sensor calibration as applied to current sensors while Landsat-5 TM and Landsat-7 ETM+ are used to evaluate the limits of in situ site characterizations for SI-traceable cross calibration. The current work examines the difficulties in trending of results from cross-calibration approaches taking into account sampling issues, site-to-site variability, and accuracy of the method. Special attention is given to the differences caused in the cross-comparison of sensors in radiance space as opposed to reflectance space. The results show that cross calibrations with absolute uncertainties lesser than 1.5 percent (1 sigma) are currently achievable even for sensors without coincident views.

  7. Calibration of longwavelength exotech model 20-C spectroradiometer

    NASA Technical Reports Server (NTRS)

    Kumar, R.; Robinson, B.; Silva, L.

    1978-01-01

    A brief description of the Exotech model 20-C field spectroradiometer which measures the spectral radiance of a target in the wavelength ranges 0.37 to 2.5 microns (short wavelength unit), 2.8 to 5.6 microns and 7.0 to 14 microns (long wavelength unit) is given. Wavelength calibration of long wavelength unit was done by knowing the strong, sharp and accurately known absorption bands of polystyrene, atmospheric carbon dioxide and methyl cyclohexane (liquid) in the infrared wavelength region. The spectral radiance calibration was done by recording spectral scans of the hot and the cold blackbodies and assuming that spectral radiance varies linearly with the signal.

  8. 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.

  9. Solar spectral radiance and irradiance at 225.2-319.6 nanometers

    NASA Astrophysics Data System (ADS)

    Kohl, J. L.; Parkinson, W. H.; Zapata, C. A.

    1980-11-01

    Mean absolute intensities (spectral radiance) over 0.1 nm intervals between 225.2 nm and 319.6 nm at disk center and near the limb of the sun (mu = 0.23 + or - 0.04) are derived from the high spectral resolution measurements published by Kohl, Parkinson, and Kurucz. The corresponding limb-to-center ratios and spectral irradiance values are provided. A comparison with existing measurements of solar spectral radiance and spectral irradiance for the most part shows agreement within the estimated error limits, although some narrow band variations may be outside experimental errors. The contribution to the solar constant of the 230-305 nm band is derived to be 19.7 W/square m + or - 12%.

  10. Estimation of evapotranspiration using satellite TOA radiances

    NASA Astrophysics Data System (ADS)

    Peng, J.; Loew, A.

    2013-12-01

    ET (Evapotranspiration) is an important variable in the water and energy balance on the Earth's surface. Accurate estimation of the temporal and spatial pattern of ET is of great significance for hydrological, agricultural and meteorological studies. A simplified single-source energy balance parameterization scheme, known as the LST/NDVI (Land Surface Temperature/Normalized Difference Vegetation Index) feature space method, has been applied successfully to estimate clear sky ET in many studies. Based on the LST/NDVI feature space method, a new method is proposed in this study to estimate ET directly using the TOA (Top of Atmosphere) radiances without performing atmospheric correction and associated complex processes. Firstly, the feasibility and uncertainties in estimating NDTI (Normalized Difference Temperature Index, a key parameter in EF (evaporative fraction) estimation) from TOA radiances are investigated. Through a physical understanding of the Planck radiation law and radiative transfer equation, together with a detailed sensitivity analysis of NDTI on surface and atmosphere variability, it is found that the NDTI can be estimated from TOA radiances with an accuracy of 90% if the spatial variabilities of atmospheric parameters (water vapor, effective atmospheric temperature) and surface emissivity are below 10%, 4 K, and 0.05, respectively. Then the applicability and robustness of the MODIS TOA radiances based EF estimation scheme are investigated using FLUXNET (a global network of eddy covariance stations) observations. From direct comparison with measured EF at different FLUXNET sites, the estimated EF from TOA radiances perform mostly well across a wide variety of climate and biome types. The accuracy level is also comparable with published results in the literature. Furthermore, the FLUXNET measurements are used to examine the assumption of EF self preservation, and the conditions under which it can hold. It is found that the instantaneous EF can

  11. Spectral Dimensionality and Scale of Urban Radiance

    NASA Technical Reports Server (NTRS)

    Small, Christopher

    2001-01-01

    Characterization of urban radiance and reflectance is important for understanding the effects of solar energy flux on the urban environment as well as for satellite mapping of urban settlement patterns. Spectral mixture analyses of Landsat and Ikonos imagery suggest that the urban radiance field can very often be described with combinations of three or four spectral endmembers. Dimensionality estimates of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) radiance measurements of urban areas reveal the existence of 30 to 60 spectral dimensions. The extent to which broadband imagery collected by operational satellites can represent the higher dimensional mixing space is a function of both the spatial and spectral resolution of the sensor. AVIRIS imagery offers the spatial and spectral resolution necessary to investigate the scale dependence of the spectral dimensionality. Dimensionality estimates derived from Minimum Noise Fraction (MNF) eigenvalue distributions show a distinct scale dependence for AVIRIS radiance measurements of Milpitas, California. Apparent dimensionality diminishes from almost 40 to less than 10 spectral dimensions between scales of 8000 m and 300 m. The 10 to 30 m scale of most features in urban mosaics results in substantial spectral mixing at the 20 m scale of high altitude AVIRIS pixels. Much of the variance at pixel scales is therefore likely to result from actual differences in surface reflectance at pixel scales. Spatial smoothing and spectral subsampling of AVIRIS spectra both result in substantial loss of information and reduction of apparent dimensionality, but the primary spectral endmembers in all cases are analogous to those found in global analyses of Landsat and Ikonos imagery of other urban areas.

  12. Cloud altitude determination from infrared spectral radiances

    NASA Technical Reports Server (NTRS)

    Smith, William L.; Frey, Richard

    1990-01-01

    The CO2 slicing method is generally recognized as the most accurate means of inferring cloud altitude from passive infrared radiance observations. The method is applicable to semi-transparent and broken clouds. During the cirrus FIRE and COHMEX field experiments, CO2 channel radiance data suitable for cloud altitude specification were achieved from moderate spectral resolution satellite sounders (NOAA-TOVS and GOES-VAS) and from a High spectral resolution Interferometer Spectrometer (HIS) flown on the NASA U2/ER2 aircraft. Also aboard the ER2 was a down-looking active lidar unit capable of providing cloud top pressure verifications with high accuracy. A third instrument, the Multispectral Atmospheric Mapping Sensor (MAMS) provided 50 meter resolution infrared window data which is used wtih radiosonde data to verify the heights of middle and low level clouds. Comparisons of lidar and MAMS/radiosonde ground truth cloud heights are made with those determined from: high resolution (0.5/cm) HIS spectra, HIS spectra degraded to the moderate resolution (15/cm) of the VAS/TOVS instruments, and spectrally averaged HIS radiances for individual pairs of VAS spectral channels. The results show that the best results are achieved from high resolution spectra; the RMS difference with the ground truth is 23 mb. The RMS differences between the infrared radiance determination and ground truth increase by 35 percent when the spectral resolution is degraded to the moderate spectral resolution of the VAS/TOVS instruments and by 52 to 183 percent, depending upon channel combinations, when only two spectral channels at VAS/TOVS spectral resolution are used.

  13. Extraction of Profile Information from Cloud Contaminated Radiances. Appendixes 2

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Zhou, D. K.; Huang, H.-L.; Li, Jun; Liu, X.; Larar, A. M.

    2003-01-01

    Clouds act to reduce the signal level and may produce noise dependence on the complexity of the cloud properties and the manner in which they are treated in the profile retrieval process. There are essentially three ways to extract profile information from cloud contaminated radiances: (1) cloud-clearing using spatially adjacent cloud contaminated radiance measurements, (2) retrieval based upon the assumption of opaque cloud conditions, and (3) retrieval or radiance assimilation using a physically correct cloud radiative transfer model which accounts for the absorption and scattering of the radiance observed. Cloud clearing extracts the radiance arising from the clear air portion of partly clouded fields of view permitting soundings to the surface or the assimilation of radiances as in the clear field of view case. However, the accuracy of the clear air radiance signal depends upon the cloud height and optical property uniformity across the two fields of view used in the cloud clearing process. The assumption of opaque clouds within the field of view permits relatively accurate profiles to be retrieved down to near cloud top levels, the accuracy near the cloud top level being dependent upon the actual microphysical properties of the cloud. The use of a physically correct cloud radiative transfer model enables accurate retrievals down to cloud top levels and below semi-transparent cloud layers (e.g., cirrus). It should also be possible to assimilate cloudy radiances directly into the model given a physically correct cloud radiative transfer model using geometric and microphysical cloud parameters retrieved from the radiance spectra as initial cloud variables in the radiance assimilation process. This presentation reviews the above three ways to extract profile information from cloud contaminated radiances. NPOESS Airborne Sounder Testbed-Interferometer radiance spectra and Aqua satellite AIRS radiance spectra are used to illustrate how cloudy radiances can be used

  14. Infrared Spectral Radiance Intercomparisons With Satellite and Aircraft Sensors

    NASA Technical Reports Server (NTRS)

    Larar, Allen M.; Zhou, Daniel K.; Liu, Xu; Smith, William L.

    2014-01-01

    Measurement system validation is critical for advanced satellite sounders to reach their full potential of improving observations of the Earth's atmosphere, clouds, and surface for enabling enhancements in weather prediction, climate monitoring capability, and environmental change detection. Experimental field campaigns, focusing on satellite under-flights with well-calibrated FTS sensors aboard high-altitude aircraft, are an essential part of the validation task. Airborne FTS systems can enable an independent, SI-traceable measurement system validation by directly measuring the same level-1 parameters spatially and temporally coincident with the satellite sensor of interest. Continuation of aircraft under-flights for multiple satellites during multiple field campaigns enables long-term monitoring of system performance and inter-satellite cross-validation. The NASA / NPOESS Airborne Sounder Testbed - Interferometer (NAST-I) has been a significant contributor in this area by providing coincident high spectral/spatial resolution observations of infrared spectral radiances along with independently-retrieved geophysical products for comparison with like products from satellite sensors being validated. This presentation gives an overview of benefits achieved using airborne sensors such as NAST-I utilizing examples from recent field campaigns. The methodology implemented is not only beneficial to new sensors such as the Cross-track Infrared Sounder (CrIS) flying aboard the Suomi NPP and future JPSS satellites but also of significant benefit to sensors of longer flight heritage such as the Atmospheric InfraRed Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI) on the AQUA and METOP-A platforms, respectively, to ensure data quality continuity important for climate and other applications. Infrared spectral radiance inter-comparisons are discussed with a particular focus on usage of NAST-I data for enabling inter-platform cross-validation.

  15. 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…

  16. Sand dune ridge alignment effects on surface BRF over the Libya-4 CEOS calibration site.

    PubMed

    Govaerts, Yves M

    2015-01-01

    The Libya-4 desert area, located in the Great Sand Sea, is one of the most important bright desert CEOS pseudo-invariant calibration sites by its size and radiometric stability. This site is intensively used for radiometer drift monitoring, sensor intercalibration and as an absolute calibration reference based on simulated radiances traceable to the SI standard. The Libya-4 morphology is composed of oriented sand dunes shaped by dominant winds. The effects of sand dune spatial organization on the surface bidirectional reflectance factor is analyzed in this paper using Raytran, a 3D radiative transfer model. The topography is characterized with the 30 m resolution ASTER digital elevation model. Four different regions-of-interest sizes, ranging from 10 km up to 100 km, are analyzed. Results show that sand dunes generate more backscattering than forward scattering at the surface. The mean surface reflectance averaged over different viewing and illumination angles is pretty much independent of the size of the selected area, though the standard deviation differs. Sun azimuth position has an effect on the surface reflectance field, which is more pronounced for high Sun zenith angles. Such 3D azimuthal effects should be taken into account to decrease the simulated radiance uncertainty over Libya-4 below 3% for wavelengths larger than 600 nm. PMID:25654721

  17. Sand dune ridge alignment effects on surface BRF over the Libya-4 CEOS calibration site.

    PubMed

    Govaerts, Yves M

    2015-02-03

    The Libya-4 desert area, located in the Great Sand Sea, is one of the most important bright desert CEOS pseudo-invariant calibration sites by its size and radiometric stability. This site is intensively used for radiometer drift monitoring, sensor intercalibration and as an absolute calibration reference based on simulated radiances traceable to the SI standard. The Libya-4 morphology is composed of oriented sand dunes shaped by dominant winds. The effects of sand dune spatial organization on the surface bidirectional reflectance factor is analyzed in this paper using Raytran, a 3D radiative transfer model. The topography is characterized with the 30 m resolution ASTER digital elevation model. Four different regions-of-interest sizes, ranging from 10 km up to 100 km, are analyzed. Results show that sand dunes generate more backscattering than forward scattering at the surface. The mean surface reflectance averaged over different viewing and illumination angles is pretty much independent of the size of the selected area, though the standard deviation differs. Sun azimuth position has an effect on the surface reflectance field, which is more pronounced for high Sun zenith angles. Such 3D azimuthal effects should be taken into account to decrease the simulated radiance uncertainty over Libya-4 below 3% for wavelengths larger than 600 nm.

  18. Sand Dune Ridge Alignment Effects on Surface BRF over the Libya-4 CEOS Calibration Site

    PubMed Central

    Govaerts, Yves M.

    2015-01-01

    The Libya-4 desert area, located in the Great Sand Sea, is one of the most important bright desert CEOS pseudo-invariant calibration sites by its size and radiometric stability. This site is intensively used for radiometer drift monitoring, sensor intercalibration and as an absolute calibration reference based on simulated radiances traceable to the SI standard. The Libya-4 morphology is composed of oriented sand dunes shaped by dominant winds. The effects of sand dune spatial organization on the surface bidirectional reflectance factor is analyzed in this paper using Raytran, a 3D radiative transfer model. The topography is characterized with the 30 m resolution ASTER digital elevation model. Four different regions-of-interest sizes, ranging from 10 km up to 100 km, are analyzed. Results show that sand dunes generate more backscattering than forward scattering at the surface. The mean surface reflectance averaged over different viewing and illumination angles is pretty much independent of the size of the selected area, though the standard deviation differs. Sun azimuth position has an effect on the surface reflectance field, which is more pronounced for high Sun zenith angles. Such 3D azimuthal effects should be taken into account to decrease the simulated radiance uncertainty over Libya-4 below 3% for wavelengths larger than 600 nm. PMID:25654721

  19. Sand Dune Ridge Alignment Effects on Surface BRF over Libya-4 Calibration Site

    NASA Astrophysics Data System (ADS)

    Govaerts, Yves

    2015-12-01

    The Libya-4 desert area, located in the Great Sand Sea, is one of the most important bright desert CEOS pseudo-invariant calibration sites by its size and radiometric stability. This site is intensively used for radiometer drift monitoring, sensor intercalibration and as an absolute calibration reference based on simulated radiances traceable to the SI standard. The Libya-4 morphology is composed of oriented sand dunes shaped by dominant winds. The effects of sand dune spatial organization on the surface bidirectional reflectance factor is analyzed in this paper using Raytran, a 3D radiative transfer model. The topography is characterized with the 30 m resolution ASTER digital elevation model. Four different regions-of-interest sizes, ranging from 10 km up to 100 km, are analyzed. Results show that sand dunes generate more backscattering than forward scattering at the surface. The mean surface reflectance averaged over different viewing and illumination angles is pretty much independent of the size of the selected area, though the standard deviation differs. Sun azimuth position has an effect on the surface reflectance field, which is more pronounced for high Sun zenith angles. Such 3D azimuthal effects should be taken into account to decrease the simulated radiance uncertainty over Libya-4 below 3% for wavelengths larger than 600 nm..

  20. Polarization impacts on the water-leaving radiance retrieval from above-water radiometric measurements.

    PubMed

    Harmel, Tristan; Gilerson, Alexander; Tonizzo, Alberto; Chowdhary, Jacek; Weidemann, Alan; Arnone, Robert; Ahmed, Sam

    2012-12-10

    Above-water measurements of water-leaving radiance are widely used for water-quality monitoring and ocean-color satellite data validation. Reflected skylight in above-water radiometry needs to be accurately estimated prior to derivation of water-leaving radiance. Up-to-date methods to estimate reflection of diffuse skylight on rough sea surfaces are based on radiative transfer simulations and sky radiance measurements. But these methods neglect the polarization state of the incident skylight, which is generally highly polarized. In this paper, the effects of polarization on the sea surface reflectance and the subsequent water-leaving radiance estimation are investigated. We show that knowledge of the polarization field of the diffuse skylight significantly improves above-water radiometry estimates, in particular in the blue part of the spectrum where the reflected skylight is dominant. A newly developed algorithm based on radiative transfer simulations including polarization is described. Its application to the standard Aerosol Robotic Network-Ocean Color and hyperspectral radiometric measurements of the 1.5-year dataset acquired at the Long Island Sound site demonstrates the noticeable importance of considering polarization for water-leaving radiance estimation. In particular it is shown, based on time series of collocated data acquired in coastal waters, that the azimuth range of measurements leading to good-quality data is significantly increased, and that these estimates are improved by more than 12% at 413 nm. Full consideration of polarization effects is expected to significantly improve the quality of the field data utilized for satellite data validation or potential vicarious calibration purposes.

  1. Assessing the contribution from different parts of Canary islands to the hemispheric spectral sky radiance levels over European Northern Observatories

    NASA Astrophysics Data System (ADS)

    Aubé, Martin

    2015-03-01

    In this paper, we suggest to use a sky radiance model which accounts for heterogeneous distribution of light fixtures, their photometry, the ground reflectance and topography, to infer the point to point contribution of Canary Islands to the artificial sky radiance at Observatorio del Teide (Tenerife) and Observatorio Roque de los Muchachos (La Palma). In-situ hyperspectral sky radiance measurements, acquired on site in 2010, have been used to calibrate the model and to evaluate its inherent error. We aim to identify and characterize zones at which any lighting level increase or decrease may have a larger impact on light pollution at both European Northern Observatory sites, and then help to control and/or reduce their light pollution levels. This innovative methodology, can then be seen as a high level decision tool to help local authorities to restrict or reduce light pollution with the objective of protecting research class astronomical sites.

  2. Improved dewpoint-probe calibration

    NASA Technical Reports Server (NTRS)

    Stephenson, J. G.; Theodore, E. A.

    1978-01-01

    Relatively-simple pressure-control apparatus calibrates dewpoint probes considerably faster than conventional methods, with no loss of accuracy. Technique requires only pressure measurement at each calibration point and single absolute-humidity measurement at beginning of run. Several probes can be calibrated simultaneously and points can be checked above room temperature.

  3. Calibration Systems Final Report

    SciTech Connect

    Myers, Tanya L.; Broocks, Bryan T.; Phillips, Mark C.

    2006-02-01

    The Calibration Systems project at Pacific Northwest National Laboratory (PNNL) is aimed towards developing and demonstrating compact Quantum Cascade (QC) laser-based calibration systems for infrared imaging systems. These on-board systems will improve the calibration technology for passive sensors, which enable stand-off detection for the proliferation or use of weapons of mass destruction, by replacing on-board blackbodies with QC laser-based systems. This alternative technology can minimize the impact on instrument size and weight while improving the quality of instruments for a variety of missions. The potential of replacing flight blackbodies is made feasible by the high output, stability, and repeatability of the QC laser spectral radiance.

  4. 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.

  5. Initial Radiometric Calibration of the AWiFS using Vicarious Calibration Techniques

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Thome, Kurtis; Aaron, David; Leigh, Larry

    2006-01-01

    NASA SSC maintains four ASD FieldSpec FR spectroradiometers: 1) Laboratory transfer radiometers; 2) Ground surface reflectance for V&V field collection activities. Radiometric Calibration consists of a NIST-calibrated integrating sphere which serves as a source with known spectral radiance. Spectral Calibration consists of a laser and pen lamp illumination of integrating sphere. Environmental Testing includes temperature stability tests performed in environmental chamber.

  6. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  7. AVIRIS calibration and application in coastal oceanic environments

    NASA Technical Reports Server (NTRS)

    Carder, Kendall L.

    1992-01-01

    The Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) is a test-bed for future spacecraft sensors such as the High-Resolution Imaging Spectrometer and the Moderate-Resolution Imaging Spectrometers planned for the Earth Observing System. To use this sensor for ocean applications, S/N was increased by spatial averaging of images. Post-flight recalibration was accomplished using in situ the water-leaving radiance measured at flight time, modeling radiance transmission to the aircraft, and adding modeled atmospheric radiance to that value. The preflight calibration curve was then adjusted until aircraft and modeled total radiance values matched. Water-leaving radiance values from the recalibrated AVIRIS imagery were consistent with in situ data supporting the validity of the approach. Imagery of the absorption coefficient at 415 nm and backscattering coefficient at 671 nm were used to depict the dissolved and particulate constituents of an ebb-tidal esturance plume on the East coast of Florida.

  8. 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).

  9. 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).

  10. The Science of Calibration

    NASA Astrophysics Data System (ADS)

    Kent, S. M.

    2016-05-01

    This paper presents a broad overview of the many issues involved in calibrating astronomical data, covering the full electromagnetic spectrum from radio waves to gamma rays, and considering both ground-based and space-based missions. These issues include the science drivers for absolute and relative calibration, the physics behind calibration and the mechanisms used to transfer it from the laboratory to an astronomical source, the need for networks of calibrated astronomical standards, and some of the challenges faced by large surveys and missions.

  11. Atmospheric Emitted Radiance Interferometer (AERI) Handbook

    DOE Data Explorer

    Gero, Jonathan; Hackel, Denny; Garcia, Raymond

    2005-01-01

    The atmospheric emitted radiance interferometer (AERI) is a ground-based instrument that measures the downwelling infrared radiance from the Earth’s atmosphere. The observations have broad spectral content and sufficient spectral resolution to discriminate among gaseous emitters (e.g., carbon dioxide and water vapor) and suspended matter (e.g., aerosols, water droplets, and ice crystals). These upward-looking surface observations can be used to obtain vertical profiles of tropospheric temperature and water vapor, as well as measurements of trace gases (e.g., ozone, carbon monoxide, and methane) and downwelling infrared spectral signatures of clouds and aerosols.The AERI is a passive remote sounding instrument, employing a Fourier transform spectrometer operating in the spectral range 3.3–19.2 μm (520–3020 cm-1) at an unapodized resolution of 0.5 cm-1 (max optical path difference of 1 cm). The extended-range AERI (ER-AERI) deployed in dry climates, like in Alaska, have a spectral range of 3.3–25.0 μm (400–3020 cm-1) that allow measurements in the far-infrared region. Typically, the AERI averages views of the sky over a 16-second interval and operates continuously.

  12. Scientific applications of the Marine-Atmospheric Emitted Radiance Interferometer

    NASA Astrophysics Data System (ADS)

    Minnett, P. J.; Hanafin, J.; Szczodrak, M.; Key, E. L.; Izaguirre, M.; Brown, O. B.

    2006-12-01

    The Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) is a well-calibrated, ship-based Fourier Transform Infrared spectroradiometer. Its development by the University of Wisconsin SSEC in the mid- 90's was founded on a land-based analog, the AERI, which has been in continuous operation at several ARM (Atmospheric Radiation Measurement) sites around the world. The primary objective of the M-AERI was to provide accurate skin sea-surface temperatures (SST) for the validation of satellite retrievals, specifically those from MODIS (MODerate-resolution Imaging Spectroradiometer on the NASA satellites Terra and Aqua). Over the past decade, the measured spectra from the oceanic and atmospheric emission have found a wide range of applications beyond SST retrievals. Just a few topics that have been addressed using M-AERI spectra include the study of the physical behavior of the oceanic skin layer, the oceanic infrared emissivity, and the near-surface air temperature and air-sea temperature differences, and in deriving profiles of temperature and humidity in the lower marine troposphere. Here we present an overview of such applications and results.

  13. GOME Calibration and Validation Using Backscatter UV Techniques

    NASA Technical Reports Server (NTRS)

    Hilsenrath, E.; Gleason, J.; Janz, S.; Gu, X.-y.; Cebula, R. P.; Chance, K. V.; Hoekstra, R.

    1996-01-01

    GOME radiance, irradiance, and ozone products were validated by NASA Goddard Space Flight Center through three tasks which included, pre-launch calibration comparisons with SBUV and TOMS radiometric standards, validation of GOME Level-1 irradiance and radiance and Level 2 total ozone data products using SBUV/2 and TOMS algorithms and data, and studies of GOME data using the Goddard radiative transfer code. The prelaunch calibration using the NASA large aperture integrating sphere was checked against that provided by TPD. Agreement in the calibration constants, derived in air, between the Goddard and TPD system were better than 3%. Validation of Level-1 irradiance data included comparison of GOME and SSBUV and the UARS solar irradiances measurements. Large wavelength dependent differences, as high as 10%, were noted between GOME and the US instruments. This discrepancy has now been attributed to radiometric sensitivity changes experienced by GOME when operating in a vacuum. GOME Earth radiance data were then compared to the NOAA-14 SBUV/2 radiances. These results show that between 340 and 400 nm the differences in GOME and SBUV/2 data are less than 5% with some wavelength dependence. At wavelengths shorter than 300 nm, differences are of the order of 10% or more where the GOME radiances are larger. To test GOME DOAS retrieved total ozone values, these values were compared with ozone amounts retrieved using GOME radiances in the TOMS version-7 algorithm. The differences showed a solar zenith angle dependence ranging from 0 to 10% where the TOMS algorithm values were higher. GOME radiances below 300 nm were further validated by selecting radiances at wavelengths normally used by SBUV and processing them through the SBUV ozone profile algorithm and then compared to climatological values. The GOME ozone profiles ranged from 10-30% lower over altitude compared to climatological values. This is consistent with the offsets detected in the SBUV/2 radiance comparisons at

  14. Transmittance and Radiance Computations for Rocket Engine Plume Environments

    NASA Technical Reports Server (NTRS)

    Tejwani, Gopal D.

    2003-01-01

    Emission and absorption characteristics of several atmospheric and combustion species have been studied and are presented with reference to rocket engine plume environments. The effects of clous, rain, and fog on plume radiance/transmittance has also been studied.Preliminary results for the radiance from the exhaust plume of the space shuttle main engine are shown and discussed.

  15. Use of Radiometrically Calibrated Flat-Plate Calibrators in Calibration of Radiation Thermometers

    NASA Astrophysics Data System (ADS)

    Cárdenas-García, D.; Méndez-Lango, E.

    2015-08-01

    Most commonly used, low-temperature, infrared thermometers have large fields of view sizes that make them difficult to be calibrated with narrow aperture blackbodies. Flat-plate calibrators with large emitting surfaces have been proposed for calibrating these infrared thermometers. Because the emissivity of the flat plate is not unity, its radiance temperature is wavelength dependent. For calibration, the wavelength pass band of the device under test should match that of the reference infrared thermometer. If the device under test and reference radiometer have different pass bands, then it is possible to calculate the corresponding correction if the emissivity of the flat plate is known. For example, a correction of at is required when calibrating a infrared thermometer with a "" radiometrically calibrated flat-plate calibrator. A method is described for using a radiometrically calibrated flat-plate calibrator that covers both cases of match and mismatch working wavelength ranges of a reference infrared thermometer and infrared thermometers to be calibrated with the flat-plate calibrator. Also, an application example is included in this paper.

  16. FY2008 Calibration Systems Final Report

    SciTech Connect

    Cannon, Bret D.; Myers, Tanya L.; Broocks, Bryan T.

    2009-01-01

    The Calibrations project has been exploring alternative technologies for calibration of passive sensors in the infrared (IR) spectral region. In particular, we have investigated using quantum cascade lasers (QCLs) because these devices offer several advantages over conventional blackbodies such as reductions in size and weight while providing a spectral source in the IR with high output power. These devices can provide a rapid, multi-level radiance scheme to fit any nonlinear behavior as well as a spectral calibration that includes the fore-optics, which is currently not available for on-board calibration systems.

  17. A SWIR radiance model for cockpit instrumentation

    NASA Astrophysics Data System (ADS)

    Green, John; Robinson, Tim

    2013-06-01

    Night Vision Imaging Systems technology is advancing at a rapid pace. These advances can be broadly divided in two distinct categories; performance and data management. There is an encouraging trend towards higher sensitivity, better resolution, and lower power consuming devices. These improvements, coupled with the shift from analog to digital data output, promise to provide a powerful night vision device. Given a digital system, the data can be managed to enhance the pilot's view (image processing), overlay data from multiple sensors (image fusion), and send data to remote locations for analysis (image sharing). The US Air Force Research Laboratory (AFRL) has an active program to introduce a helmet mounted digital imaging system that extends the detection range from the near infrared (NIR) band to the short-wave infrared (SWIR) band. Aside from the digital output, part of the motivation to develop a SWIR imaging system includes the desire to exploit the SWIR ambient night glow spectrum, see through some levels of fog and haze, and use a robust sensor technology suitable for 24 hours per day imaging. Integrating this advanced SWIR imaging system into a cockpit presents some human factor issues. Light emitted from illuminated instruments may hinder the performance of the imaging system, reducing the pilot's ability to detect lowvisible objects at night. The transmission of light through cockpit transparencies and through the atmosphere may also impact performance. In this paper we propose a model that establishes cockpit lighting SWIR radiance limits, much like MIL-STD-3009 specifies NVIS radiance limits for NVGs. This model is the culmination of a two year program sponsored by AFRL.

  18. Consistency of CERES Radiances and Fluxes from Aqua and Suomi-NPP

    NASA Technical Reports Server (NTRS)

    Su, Wenying; Liang, Lusheng; Miller, Walter; Loeb, Norman

    2015-01-01

    The Clouds and Earth's Radiant Energy System (CERES) instruments on board Terra, Aqua, and Suomi-NPP have been providing data products critical to advancing our understanding of the effects of clouds and aerosols on radiative energy within the Earth-atmosphere system. The CERES instrument consists of a threechannel broadband scanning radiometer. The scanning radiometer measures radiances in shortwave (SW, 0.3-5 micron), window (WN, 8-12 micron), and total (0.3-200 micron) channels. The longwave (LW) component is derived as the difference between total and SW channels. These measured radiances at a given sun-Earthsatellite geometry are converted to outgoing reflected solar and emitted thermal TOA radiative fluxes by using CERES scene-type dependent angular distribution models (ADMs). The CERES instruments must remain radiometrically stable and correctly inter-calibrated to accurately capture changes in Earth"s radiation budget from interannual to decadal timescales. This presentation will focus on comparisons between collocated radiance measurements from CERES instruments on Aqua and on Suomi-NPP. As we do not have a set of ADMs that is constructed specifically for the CERES instrument on Suomi-NPP, CERES Aqua ADMs are used to invert fluxes from radiance measurements on Suomi-NPP. But the CERES Aqua footprint size is smaller than the CERES Suomi-NPP footprint size and the scene identifications provided by MODIS and VIIRS can also be different from each other. Will using Aqua ADMs for Suomi-NPP flux inversion increase the flux uncertainty? We will examine the deseasonalized flux anomaly time series using Aqua data alone and using combined Aqua and Suomi-NPP data. We will also present a simulation study to assess the Suomi-NPP flux uncertainty from using Aqua ADMs for the flux inversion.

  19. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  20. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  1. The Calibration of AVHRR Visible Dual Gain using Meteosat-8 for NOAA-16 to 18

    NASA Technical Reports Server (NTRS)

    Doelling, David R.; Garber, Donald P.; Avey, L. A.; Nguyen, Louis; Minnis, Patrick

    2007-01-01

    The NOAA AVHRR program has given the remote sensing community over 25 years of imager radiances to retrieve global cloud, vegetation, and aerosol properties. This dataset can be used for long-term climate research, if the AVHRR instrument is well calibrated. Unfortunately, the AVHRR instrument does not have onboard visible calibration and does degrade over time. Vicarious post-launch calibration is necessary to obtain cloud properties that are not biased over time. The recent AVHRR-3 instrument has a dual gain in the visible channels in order to achieve greater radiance resolution in the clear-sky. This has made vicarious calibration of the AVHRR-3 more difficult to unravel. Reference satellite radiances from well-calibrated instruments, usually equipped with solar diffusers, such as MODIS, have been used to successfully vicariously calibrate other visible instruments. Transfer of calibration from one satellite to another using co-angled, collocated, coincident radiances has been well validated. Terra or Aqua MODIS and AVHRR comparisons can only be performed over the poles during summer. However, geostationary satellites offer a transfer medium that captures both parts of the dual gain. This AVHRR-3 calibration strategy uses, calibrated with MODIS, Meteosat-8 radiances simultaneously to determine the dual gains using 50km regions. The dual gain coefficients will be compared with the nominal coefficients. Results will be shown for all visible channels for NOAA-17.

  2. Influence of high altitude clouds on upper tropospheric radiance measurements.

    PubMed

    Schmidt, E O; Patterson, E M; Williams, W J

    1990-10-01

    Altitude profiles of atmospheric window radiance measured with upward-looking sensors frequently show a rapid decrease in radiance with increasing height over a narrow altitude region in the upper troposphere. This region of rapid decrease is termed a radiometric knee in the altitude profile. The top of this knee defines a radiometric tropopause with a latitudinal height dependence similar to that of the usually defined barometric tropopause. Atmospheric window (10-12-microm) radiance at these altitudes can be associated with the presence of ice particulates. Comparison of the measurements with predicted altitude profiles of atmospheric radiance from the LOWTRAN 7 atmospheric model code shows that a well-defined knee occurs when there is a cloud layer (liquid or ice) such as a subvisual cirrus cloud present. The rate and magnitude of the radiance decrease depend on the optical depth and, therefore, the water content of the layer. Atmospheric background radiance values for near horizontal (large zenith angle) viewing with upward-looking sensors can be as much as a factor of 100 lower above the knee than below it. Comparisons between calculated and observed radiance profiles were used to estimate the vertical extent, total optical depth, and water content of the clouds.

  3. Calibration and characterization of a low-background chamber in support of hardware-in-the-loop testing and modeling of infrared seekers

    NASA Astrophysics Data System (ADS)

    Tschiegg, Richard D.; Conard, Steven J.; Thompson, Patrick L.; Carter, Adriaan

    2006-05-01

    The authors have worked in the past year on integration, characterization, and calibration of The Johns Hopkins University Applied Physics Laboratory's (JHU/APL's) Infrared Seeker Space Calibration and Test facility, a cryogenic-vacuum chamber designed to test infrared seekers that detect targets against low-radiance backgrounds. The facility includes target-like infrared sources with well-known and controllable radiometric attributes and well-known and controllable size, position, and motion. This paper summarizes the basic facility design, capabilities, concept of operations, current and projected uses, challenges, and lessons learned. It describes the chamber calibration and characterization activities conducted jointly by JHU/APL and the National Institute of Standards and Technology (NIST). In particular, this includes a description of the calibration and characterization methodology, modeling of the chamber optical path from the chamber target source module to the unit-under-test entrance aperture, ongoing calibration of the target source module at NIST with an absolute cryogenic radiometer, and planned end-to-end calibration of the chamber at JHU/APL using NIST's transfer radiometer and JHU/APL's field spectroradiometer.

  4. Retrieval of the columnar aerosol phase function and single-scattering albedo from sky radiance over the ocean - Simulations

    NASA Technical Reports Server (NTRS)

    Wang, Menghua; Gordon, Howard R.

    1993-01-01

    Based on the fact that the part of downward radiance that depends on the optical properties of the aerosol in the atmosphere can be extracted from the measured sky radiance, a new scheme for retrieval of the aerosol phase function and the single-scattering albedo over the ocean is developed. This retrieval algorithm is tested with simulations for several cases. It is found that the retrieved aerosol phase function and the single-scattering albedo are virtually error-free if the vertical structure of the atmosphere is known and if the sky radiance and the aerosol optical thickness can be measured accurately. The robustness of the algorithm in realistic situations, in which the measurements are contaminated by calibration errors or noise, is examined. It is found that the retrieved value of omega(0) is usually in error by less than about 10 percent, and the phase function is accurately retrieved for theta less than about 90 deg. However, as the aerosol optical thickness becomes small, e.g., less than about 0.1, errors in the sky radiance measurement can lead to serious problems with the retrieval algorithm, especially in the blue. The use of the retrieval scheme should be limited to the red and near IR when the aerosol optical thickness is small.

  5. View-Angle Dependent AIRS Cloud Radiances and Fluctuations: Implications of Organized Cloud Structures for Tropical Circulations

    NASA Technical Reports Server (NTRS)

    Wu, Dong L.; Gong, Jie

    2012-01-01

    Interactions between wave dynamics and moisture generate clouds in a wide range of scales. Organized cloud structures produce statistically asymmetric radiances and perturbations in AIRS and AMSU-B measurements. With high resolution (approx.14 km beamwidth) and high-sensitivity instruments, these wave-modulated cloud structures can be readily detected from calibrated Levell radiance data. In this study we analyzed eight-year (2003 - 2010) statistics of AIRS cloud-induced radiances and found that in tropical convective regions the ascending (13:30 LST) measurements reveal higher view-angle asymmetry in cloud radiance than the descending (1:30 LST). The daytime asymmetry suggests 10% more cloudiness when the instrument views east, implying tilted and banded structures in most of the anvil clouds to which AIRS is sensitive. Such banded cloud structures are likely a manifestation of embedded westward propagating gravity waves in tropical convective systems. More importantly, organized cloud structures carry asymmetric momentum fluxes in addition to energy fluxes, which must be taken into account for modeling wave-wave and wave-mean flow interactions in tropical circulations.

  6. Operational calibration of Geostationary Operational Environmental Satellite-8 and-9 imagers and sounders.

    PubMed

    Weinreb, M; Jamieson, M; Fulton, N; Chen, Y; Johnson, J X; Bremer, J; Smith, C; Baucom, J

    1997-09-20

    We describe the operational in-orbit calibration of the Geostationary Operational Environmental Satellite (GOES)-8 and-9 imagers and sounders. In the infrared channels the calibration is based on observations of space and an onboard blackbody. The calibration equation expresses radiance as a quadratic in instrument output. To suppress noise in the blackbody sequences, we filter the calibration slopes. The calibration equation also accounts for an unwanted variation of the reflectances of the instruments' scan mirrors with east-west scan position, which was not discovered until the instruments were in orbit. The visible channels are not calibrated, but the observations are provided relative to the level of space and are normalized to minimize east-west striping in the images. Users receive scaled radiances in a GOES variable format (GVAR) data stream. We describe the procedure users can apply to transform GVAR counts into radiances, temperatures, and mode-A counts.

  7. Validation of SCIAMACHY Radiances and Ozone Products Using Ground and Space Observations

    NASA Technical Reports Server (NTRS)

    Hilsenrath, E.; Bhartia, P. K.; Bojkov, B. R.; Kowalewski, M.; Labow, G.; Ahmad, Z.

    2004-01-01

    Validation of SCIAMACHY data products are is key element for the detecting a stratospheric ozone recovery, which is a high priority for environmental research and environmental policy. Models predict an ozone recovery at a much lower rate than the measured depletion rate observed to date. Therefore improved precision of the satellite and ground ozone observing systems are required over the long term to verify its recovery. We show that validation of satellite radiances from space and from the ground can be an effective means for correcting long term drifts of backscatter type satellite measurements such as SCIAMACHY and can be used to cross calibrate all BUV instruments in orbit (TOMS, SBUV/2, GOME, OMI, GOME-2, OMPS). This method bypasses the retrieval algorithms used for both satellite and ground based measurements that are normally used to validate and correct the satellite data. This approach however requires well calibrated instruments and an accurate radiative transfer model that accounts for aerosols. In addition to comparing radiances, validation of SCIAMACHY ozone products will conducted by comparing total and profile ozone with TOMS and SBUV/2.

  8. Time domain scattering of travelling wave radiance

    NASA Astrophysics Data System (ADS)

    Berger, Henry; Rand, Robert S.

    2002-12-01

    I present, apparently, a new description of radiative transfer problems in the time domain. It appears that for the first time a simple physical picture emerges of the underlying essence of scattered radiance when dealing with isotropic axially-symmetric scattering in nonconservative linear media as attenuated travelling waves was by analogy. The method used a new differential equation approach. Initially its accuracy in the frequency domain was demonstrated by applying it to a solved problem, where in the literature it is dealt with using the conventional 95-year-old integro-differential equation description. Confidence in the differential equation method was bolstered by showing how this new method produces the same analytical answer. The new technique converts the integro-differential equation formulation of radiative transfer into a "pure" differential equation formulation, consisting here in a mixture of ordinary and partial derivatives, and solves that. This paper analyzes the situation in the time domain using the differential equation description and again yields a travelling wave description. However, this time it is not simply by analogy that such a description is obtained. It is exact. This result of attenuated travelling waves was demonstrated in a prior paper by solving the integro-differential equation for the classic problem of axially-symmetric scalar isotropic scattering in a nonconservative linear medium. In this paper we revisit the problem, this time solving it by the differential equation method and obtain the identical result, once again confirming the method.

  9. ISCCP reduced resolution satellite radiance data

    NASA Technical Reports Server (NTRS)

    Rossow, W.

    1986-01-01

    The International Satellite Cloud Climatology Project (ISCCP) is the first active project of the World Climate Research Program. It is a multinational data collection project focused on collecting a data set that will improve the ability to predict and/or simulate the radiative effects of clouds on climate. For specified cloud parameters, the goals are to archieve values for 3-hour periods over the whole globe for 5 years at 30 km resolution. The task of collecting and processing radiance data from both geosynchronous and polar orbiting satellites began in July 1983. A diagram was shown illustrating the flow of data from the transmitting satellites to the various receiving institutions that handle it. The various stages of processing were then explained in detail, emphasizing Level B3-normalized, reformatted, reduced raw satellite data. The reduction of data by sampling is an essential step in the flow. By the time the ISCCP data reaches the Global Processing Center at Goddard Institute for Space Studies (GISS), the volume has been reduced by a factor of 1000. The Pilot Climate Data System (PLDS) will provide access to the ISCCP data set. It should prove to be one of the cleanest satellite data sets because it will have been through three filters--that of the operational agency, the Global Processing Center, and the PCDS. The ISCCP data set also includes other correlative data sets delivered in compatible format.

  10. Software For Calibration Of Polarimetric SAR Data

    NASA Technical Reports Server (NTRS)

    Van Zyl, Jakob; Zebker, Howard; Freeman, Anthony; Holt, John; Dubois, Pascale; Chapman, Bruce

    1994-01-01

    POLCAL (Polarimetric Radar Calibration) software tool intended to assist in calibration of synthetic-aperture radar (SAR) systems. In particular, calibrates Stokes-matrix-format data produced as standard product by NASA/Jet Propulsion Laboratory (JPL) airborne imaging synthetic aperture radar (AIRSAR). Version 4.0 of POLCAL is upgrade of version 2.0. New options include automatic absolute calibration of 89/90 data, distributed-target analysis, calibration of nearby scenes with corner reflectors, altitude or roll-angle corrections, and calibration of errors introduced by known topography. Reduces crosstalk and corrects phase calibration without use of ground calibration equipment. Written in FORTRAN 77.

  11. Theory of spectral radiance of pollutants at sea

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Remote measurement of soluble pollutants that change the color of the water in the sea is reported. The sensor is a spectral radiometer that flies over the polluted area and compares its spectral radiance to that of surrounding clean seawater. A quantitative analysis of the concentration of pollutants using the measured radiance of the sea compared to laboratory measurements of reflection and transmission spectra of the pollutants is presented. The quantities involved are defined and means for measuring them are described. The equations for remote sensing with a low-flying aircraft, in which case the absorption and radiance of intervening air is negligible are derived. High-flying aircraft and satellites, in which case the radiance of intervening air is the major problem are applied.

  12. Theory of spectral radiance of pollutants at sea, volume 1

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Remote measurement of pollutants dumped in the sea, not oil slicks, but soluble pollutants that change the color of the water, is addressed. The sensor is a spectral radiometer that flies over the polluted area and compares its spectral radiance (color) to that of surrounding clean seawater. The goal is to infer the concentration of pollutants using the measured radiance of the sea compared to laboratory measurements of reflection and transmission spectra of the pollutants. The subject is treated in three steps: (1) the quantities involved are defined and means for measuring them are described; (2) the equations for remote sensing with a low-flying aircraft are derived, in which wase the absorption and radiance of intervening air is negligible; and (3) high-flying aircraft and satellites are applied, in which case the radiance of intervening air is the major problem.

  13. Directional radiance measurements: Challenges in the sampling of landscapes

    NASA Technical Reports Server (NTRS)

    Deering, D. W.

    1994-01-01

    Most earth surfaces, particularly those supporting natural vegetation ecosystems, constitute structurally and spectrally complex surfaces that are distinctly non-Lambertian reflectors. Obtaining meaningful measurements of the directional radiances of landscapes and obtaining estimates of the complete bidirectional reflectance distribution functions of ground targets with complex and variable landscape and radiometric features are challenging tasks. Reasons for the increased interest in directional radiance measurements are presented, and the issues that must be addressed when trying to acquire directional radiances for vegetated land surfaces from different types of remote sensing platforms are discussed. Priority research emphases are suggested, concerning field measurements of directional surface radiances and reflectances for future research. Primarily, emphasis must be given to the acquisition of more complete and directly associated radiometric and biometric parameter data sets that will empower the exploitation of the 'angular dimension' in remote sensing of vegetation through enabling the further development and rigorous validation of state of the art plant canopy models.

  14. Radiance-ratio algorithm wavelengths for remote oceanic chlorophyll determination

    NASA Technical Reports Server (NTRS)

    Hoge, Frank E.; Wright, C. Wayne; Swift, Robert N.

    1987-01-01

    Two-band radiance-ratio in-water algorithms in the visible spectrum have been evaluated for remote oceanic chlorophyll determination. Airborne active-passive (laser-solar) data from coastal, shelf-slope, and blue-water regions were used to generate two-dimensional chlorophyll-fluorescence and radiance-ratio statistical correlation matrices containing all possible two-band ratio combinations from the thirty-two available contiguous 11.25-nm passive bands. The principal finding was that closely spaced radiance-ratio bands yield chlorophyll estimates which are highly correlated with laser-induced chlorophyll fluorescence within several distinct regions of the ocean color spectrum. Band combinations in the yellow, orange-red, spectral regions showed considerable promise for satisfactory chlorophyll pigment estimation in near-coastal Case II waters. Pigment recovery in Case I waters was best accomplished using blue-green radiance ratios in the 490/500-nm region.

  15. Plane parallel radiance transport for global illumination in vegetation

    SciTech Connect

    Max, N.; Mobley, C.; Keating, B.; Wu, E.H.

    1997-01-05

    This paper applies plane parallel radiance transport techniques to scattering from vegetation. The leaves, stems, and branches are represented as a volume density of scattering surfaces, depending only on height and the vertical component of the surface normal. Ordinary differential equations are written for the multiply scattered radiance as a function of the height above the ground, with the sky radiance and ground reflectance as boundary conditions. They are solved using a two-pass integration scheme to unify the two-point boundary conditions, and Fourier series for the dependence on the azimuthal angle. The resulting radiance distribution is used to precompute diffuse and specular `ambient` shading tables, as a function of height and surface normal, to be used in rendering, together with a z-buffer shadow algorithm for direct solar illumination.

  16. Spectroradiometric calibration of the Thematic Mapper and Multispectral Scanner system

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Palmer, J. M. (Principal Investigator)

    1985-01-01

    The results of analyses of Thematic Mapper (TM) images acquired on July 8 and October 28, 1984, and of a check of the calibration of the 1.22-m integrating sphere at Santa Barbara Research Center (SBRC) are described. The results obtained from the in-flight calibration attempts disagree with the pre-flight calibrations for bands 2 and 4. Considerable effort was expended in an attempt to explain the disagreement. The difficult point to explain is that the difference between the radiances predicted by the radiative transfer code (the code radiances) and the radiances predicted by the preflight calibration (the pre-flight radiances) fluctuate with spectral band. Because the spectral quantities measured at White Sands show little change with spectral band, these fluctuations are not anticipated. Analyses of other targets at White Sands such as clouds, cloud shadows, and water surfaces tend to support the pre-flight and internal calibrator calibrations. The source of the disagreement has not been identified. It could be due to: (1) a computational error in the data reduction; (2) an incorrect assumption in the input to the radiative transfer code; or (3) incorrect operation of the field equipment.

  17. Radiometric validation of NASA's Ames Research Center's Sensor Calibration Laboratory.

    PubMed

    Brown, Steven W; Johnson, B Carol; Biggar, Stuart F; Zalewski, Edward F; Cooper, John; Hajek, Pavel; Hildum, Edward; Grant, Patrick; Barnes, Robert A; Butler, James J

    2005-10-20

    The National Aeronautics and Space Administration's (NASA's) Ames Research Center's Airborne Sensor Facility (ASF) is responsible for the calibration of several airborne Earth-viewing sensor systems in support of NASA Earth Observing System (EOS) investigations. The primary artifact used to calibrate these sensors in the reflective solar region from 400 to 2500 nm is a lamp-illuminated integrating sphere source. In September 1999, a measurement comparison was made at the Ames ASF Sensor Calibration Facility to validate the radiometric scale, establish the uncertainties assigned to the radiance of this source, and examine its day-to-day repeatability. The comparison was one of a series of validation activities overseen by the EOS Calibration Program to ensure the radiometric calibration accuracy of sensors used in long-term, global, remote-sensing studies. Results of the comparison, including an evaluation of the Ames Sensor Calibration Laboratory (SCL) measurement procedures and assigned radiometric uncertainties, provide a validation of their radiometric scale at the time of the comparison. Additionally, the maintenance of the radiance scale was evaluated by use of independent, long-term, multiyear radiance validation measurements of the Ames sphere source. This series of measurements provided an independent assessment of the radiance values assigned to integrating sphere sources by the Ames SCF. Together, the measurements validate the SCF radiometric scale and assigned uncertainties over the time period from September 1999 through July 2003.

  18. Radiometric validation of NASA's Ames Research Center's Sensor Calibration Laboratory

    SciTech Connect

    Brown, Steven W.; Johnson, B. Carol; Biggar, Stuart F.; Zalewski, Edward F.; Cooper, John; Hajek, Pavel; Hildum, Edward; Grant, Patrick; Barnes, Robert A.; Butler, James J

    2005-10-20

    The National Aeronautics and Space Administration's (NASA's) Ames Research Center's Airborne Sensor Facility (ASF) is responsible for the calibration of several airborne Earth-viewing sensor systems in support of NASA Earth Observing System (EOS) investigations. The primary artifact used to calibrate these sensors in the reflective solar region from 400 to 2500 nm is a lamp-illuminated integrating sphere source. In September 1999, a measurement comparison was made at the Ames ASF Sensor Calibration Facility to validate the radiometric scale, establish the uncertainties assigned to the radiance of this source, and examine its day-to-day repeatability. The comparison was one of a series of validation activities overseen by the EOS Calibration Program to ensure the radiometric calibration accuracy of sensors used in long-term, global, remote-sensing studies. Results of the comparison, including an evaluation of the Ames Sensor Calibration Laboratory (SCL) measurement procedures and assigned radiometric uncertainties, provide a validation of their radiometric scale at the time of the comparison. Additionally, the maintenance of the radiance scale was evaluated by use of independent, long-term, multiyear radiance validation measurements of the Ames sphere source. This series of measurements provided an independent assessment of the radiance values assigned to integrating sphere sources by the Ames SCF. Together, the measurements validate the SCF radiometric scale and assigned uncertainties over the time period from September 1999 through July 2003.

  19. In-flight radiometric calibration of AVIRIS in 1994

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Conel, James E.; Helmlinger, Mark; Vandenbosch, Jeannette; Hajek, Pavel

    1995-01-01

    The AVIRIS sensor must be calibrated at the time it measures spectra from the ER-2 airborne platform in order to achieve research and application objectives that are both quantitative and physically based. However, the operational environment inside the Q-bay of the ER-2 at 20 km altitude differs from that in the AVIRIS laboratory with respect to temperature, pressure, vibration, and high-frequency electromagnetic fields. Experiments at surface calibration targets are used in each flight season to confirm the accuracy of AVIRIS in-flight radiometric calibrations. For these experiments, the MODTRAN radiative transfer code is constrained by using in situ measurements to independently predict the upwelling spectral radiance arriving at AVIRIS for a specific calibration target. AVIRIS calibration is validated in flight by comparing the MODTRAN-predicted radiance to the laboratory-calibrated radiance measured by the AVIRIS sensor for the same time over the calibration target. We present radiometric calibration results for the AVIRIS in-flight calibration experiment held at the beginning of the 1994 flight season.

  20. SeaWiFS calibration and algorithm validation

    NASA Technical Reports Server (NTRS)

    Parada, Robert J., Jr.; Slater, Philip N.

    1995-01-01

    A substantial amount of field research has been completed during this period (1 October 1994 - 31 October 1995). The applicability of different in-flight calibration methods was studied. In addition, various field instruments and new equipment were tested to appraise their usefulness during such calibration activities. The purposes and (expected) results of these field experiments are detailed in separate sections of this report. One section contains a synopsis of calibrations conducted over both land and water targets. A second section contains the results of an experiment conducted to determine the spatial uniformity of surface reflectance at Lake Tahoe, the chosen water calibration site. Advances were also made in the area of radiative transfer software development. An existing exact radiative transfer code, Successive Orders (SO), was modified to provide outputs of the radiance distribution at arbitrary altitudes above a selected calibration target. These modifications were needed to utilize the SO software in radiance-based sensor calibrations. Serious thought was given to the general applicability of various calibration techniques to calibrations conducted over water surfaces. In particular, the practicality of the radiance-based and reflectance-based methods of in-flight radiometric calibration was evaluated.

  1. Equivalent Sensor Radiance Generation and Remote Sensing from Model Parameters. Part 1; Equivalent Sensor Radiance Formulation

    NASA Technical Reports Server (NTRS)

    Wind, Galina; DaSilva, Arlindo M.; Norris, Peter M.; Platnick, Steven E.

    2013-01-01

    In this paper we describe a general procedure for calculating equivalent sensor radiances from variables output from a global atmospheric forecast model. In order to take proper account of the discrepancies between model resolution and sensor footprint the algorithm takes explicit account of the model subgrid variability, in particular its description of the probably density function of total water (vapor and cloud condensate.) The equivalent sensor radiances are then substituted into an operational remote sensing algorithm processing chain to produce a variety of remote sensing products that would normally be produced from actual sensor output. This output can then be used for a wide variety of purposes such as model parameter verification, remote sensing algorithm validation, testing of new retrieval methods and future sensor studies. We show a specific implementation using the GEOS-5 model, the MODIS instrument and the MODIS Adaptive Processing System (MODAPS) Data Collection 5.1 operational remote sensing cloud algorithm processing chain (including the cloud mask, cloud top properties and cloud optical and microphysical properties products.) We focus on clouds and cloud/aerosol interactions, because they are very important to model development and improvement.

  2. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876

  3. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses.

  4. Advances in simulating radiance signatures for dynamic air/water interfaces

    NASA Astrophysics Data System (ADS)

    Goodenough, Adam A.; Brown, Scott D.; Gerace, Aaron

    2015-05-01

    The air-water interface poses a number of problems for both collecting and simulating imagery. At the surface, the magnitude of observed radiance can change by multiple orders of magnitude at high spatiotemporal frequency due to glinting effects. In the volume, similarly high frequency focusing of photons by a dynamic wave surface significantly changes the reflected radiance of in-water objects and the scattered return of the volume itself. These phenomena are often manifest as saturated pixels and artifacts in collected imagery (often enhanced by time delays between neighboring pixels or interpolation between adjacent filters) and as noise and greater required computation times in simulated imagery. This paper describes recent advances made to the Digital Image and Remote Sensing Image Generation (DIRSIG) model to address the simulation issues to better facilitate an understanding of a multi/hyper-spectral collection. Glint effects are simulated using a dynamic height field that can be driven by wave frequency models and generates a sea state at arbitrary time scales. The volume scattering problem is handled by coupling the geometry representing the surface (facetization by the height field) with the single scattering contribution at any point in the water. The problem is constrained somewhat by assuming that contributions come from a Snell's window above the scattering point and by assuming a direct source (sun). Diffuse single scattered and multiple scattered energy contributions are handled by Monte Carlo techniques employed previously. The model is compared to existing radiative transfer codes where possible, with the objective of providing a robust movel of time-dependent absolute radiance at many wavelengths.

  5. AVIRIS calibration and application in coastal oceanic environments

    NASA Technical Reports Server (NTRS)

    Carder, Kendall L.; Reinersman, Phillip; Chen, Robert F.; Muller-Karger, Frank; Davis, Curtiss O.; Hamilton, Michael

    1993-01-01

    The Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) is a test-bed for future spacecraft sensors such as the High-Resolution Imaging Spectrometer and the Moderate-Resolution Imaging Spectrometers planned for the Earth Observing System. To use this sensor for ocean applications, S/N was increased by spatial averaging of images. Post-flight recalibration was accomplished by measuring in situ the water-leaving radiance at flight time, modeling its transmission to the aircraft, and adding modeled atmospheric radiance to that value. The preflight calibration curve was then adjusted until aircraft and modeled total radiance values matched. Water-leaving radiance values from the recalibrated AVIRIS imagery were consistent with in situ data supporting the validity of the approach. Imagery of the absorption coefficient at 415 nm and backscattering coefficient at 671 nm were used to depict the dissolved and particulate constituents of the Tampa Bay plume during late, ebb-tidal conditions.

  6. User's guide: Nimbus-7 Earth radiation budget narrow-field-of-view products. Scene radiance tape products, sorting into angular bins products, and maximum likelihood cloud estimation products

    NASA Technical Reports Server (NTRS)

    Kyle, H. Lee; Hucek, Richard R.; Groveman, Brian; Frey, Richard

    1990-01-01

    The archived Earth radiation budget (ERB) products produced from the Nimbus-7 ERB narrow field-of-view scanner are described. The principal products are broadband outgoing longwave radiation (4.5 to 50 microns), reflected solar radiation (0.2 to 4.8 microns), and the net radiation. Daily and monthly averages are presented on a fixed global equal area (500 sq km), grid for the period May 1979 to May 1980. Two independent algorithms are used to estimate the outgoing fluxes from the observed radiances. The algorithms are described and the results compared. The products are divided into three subsets: the Scene Radiance Tapes (SRT) contain the calibrated radiances; the Sorting into Angular Bins (SAB) tape contains the SAB produced shortwave, longwave, and net radiation products; and the Maximum Likelihood Cloud Estimation (MLCE) tapes contain the MLCE products. The tape formats are described in detail.

  7. Suomi NPP/JPSS Cross-track Infrared Sounder (CrIS): Calibration Validation With The Aircraft Based Scanning High-resolution Interferometer Sounder (S-HIS)

    NASA Astrophysics Data System (ADS)

    Taylor, J. K.; Revercomb, H. E.; Tobin, D.; Knuteson, R. O.; Best, F. A.; Adler, D. A.; Pettersen, C.; Garcia, R. K.; Gero, P.

    2013-12-01

    To better accommodate climate change monitoring and improved weather forecasting, there is an established need for higher accuracy and more refined error characterization of radiance measurements from space and the corresponding geophysical products. This need has led to emphasizing direct tests of on-orbit performance, referred to as validation. Currently, validation typically involves (1) collecting high quality reference data from airborne and/or ground-based instruments during the satellite overpass, and (2) a detailed comparison between the satellite-based radiance measurements and the corresponding high quality reference data. Additionally, for future missions technology advancements at the University of Wisconsin Space Science and Engineering Center (UW-SSEC) have led to the development of an on-orbit absolute radiance reference utilizing miniature phase change cells to provide direct on-orbit traceability to International Standards (SI). The detailed comparison between the satellite-based radiance measurements and the corresponding measurements made from a high-altitude aircraft must account for instrument noise and scene variations, as well as differences in instrument observation altitudes, view angles, spatial footprints, and spectral response. Most importantly, for the calibration validation process to be both accurate and repeatable the reference data instrument must be extremely well characterized and understood, carefully maintained, and accurately calibrated, with traceability to absolute standards. The Scanning High-resolution Interferometer Sounder (S-HIS) meets and exceeds these requirements and has proven to do so on multiple airborne platforms, each with significantly different instrument operating environments. The Cross-track Infrared Sounder (CrIS) on Suomi NPP, launched 28 October 2011, is designed to give scientists more refined information about Earth's atmosphere and improve weather forecasts and our understanding of climate. CrIS is an

  8. Release path temperatures of shock-compressed tin from dynamic reflectance and radiance measurements

    SciTech Connect

    La Lone, B. M. Stevens, G. D.; Turley, W. D.; Holtkamp, D. B.; Iverson, A. J.; Hixson, R. S.; Veeser, L. R.

    2013-08-14

    Dynamic reflectance and radiance measurements were conducted for tin samples shock compressed to 35 GPa and released to 15 GPa using high explosives. We determined the reflectance of the tin samples glued to lithium fluoride windows using an integrating sphere with an internal xenon flashlamp as an illumination source. The dynamic reflectance (R) was determined at near normal incidence in four spectral bands with coverage in visible and near-infrared spectra. Uncertainties in R/R{sub 0} are <2%, and uncertainties in absolute reflectance are <5%. In complementary experiments, thermal radiance from the tin/glue/lithium fluoride interface was recorded with similar shock stress and spectral coverage as the reflectance measurements. The two sets of experiments were combined to obtain the temperature history of the tin surface with an uncertainty of <2%. The stress at the interface was determined from photonic Doppler velocimetry and combined with the temperatures to obtain temperature-stress release paths for tin. We discuss the relationship between the experimental release paths and release isentropes that begin on the principal shock Hugoniot.

  9. Release Path Temperatures of Shock-Compressed Tin from Dynamic Reflectance and Radiance Measurements

    SciTech Connect

    La Lone, B. M.; Stevens, G. D.; Turley, W. D.; Holtkamp, D. B.; Iverson, A. J.; Hixson, R. S.; Veeser, L. R.

    2013-08-01

    Dynamic reflectance and radiance measurements were conducted for tin samples shock compressed to 35 GPa and released to 15 GPa using high explosives. We determined the reflectance of the tin samples glued to lithium fluoride windows using an integrating sphere with an internal xenon flashlamp as an illumination source. The dynamic reflectance (R) was determined at near normal incidence in four spectral bands with coverage in visible and near-infrared spectra. Uncertainties in R/R0 are < 2%, and uncertainties in absolute reflectance are < 5%. In complementary experiments, thermal radiance from the tin/glue/lithium fluoride interface was recorded with similar shock stress and spectral coverage as the reflectance measurements. The two sets of experiments were combined to obtain the temperature history of the tin surface with an uncertainty of < 2%. The stress at the interface was determined from photonic Doppler velocimetry and combined with the temperatures to obtain temperature-stress release paths for tin. We discuss the relationship between the experimental release paths and release isentropes that begin on the principal shock Hugoniot.

  10. Photometric calibration of the International Ultraviolet Explorer /IUE/ - Low dispersion

    NASA Technical Reports Server (NTRS)

    Bohlin, R. C.; Sparks, W. M.; Holm, A. V.; Savage, B. D.; Snijders, M. A. J.

    1980-01-01

    Absolute sensitivity curves for IUE low-resolution spectra are obtained by comparing IUE measurements of hot stars with the absolute energy distributions established for these objects by previous satellite and rocket experiments. The differences between these earlier experiments are discussed quantitatively, and a common absolute flux scale is proposed as the basis for the absolute calibration of IUE.

  11. Calibration of the NOAA 11 solar backscatter ultraviolet (SBUV/2) ozone data set from 1989 to 1993 using in-flight calibration data and SSBUV

    NASA Technical Reports Server (NTRS)

    Hilsenrath, E.; Cebula, R. P.; Deland, M. T.; Laamann, K.; Taylor, S.; Wellemeyer, C.; Bhartia, P. K.

    1995-01-01

    Total ozone and ozone profiles are currently being measured by solar backscatter ultraviolet (SBUV/2) instruments onboard NOAA polar orbiting spacecraft using the backscattered ultraviolet technique. The NOAA 11 SBUV/2 operational data set, reprocessed from January 1989 to May 1993 (version 6), includes an updated algorithm and revised prelaunch and postlaunch calibrations of the geometrical albedo observations used to derive ozone values. The postlaunch calibration revisions remove time dependent errors in the ozone amounts due to instrument drift, while the revised prelaunch calibration corrects the absolute value of retrieved ozone. The prelaunch corrections are a result of calibration checks from in-orbit comparisons of ultraviolet geometric albedos measured by shuttle SBUV (SSBUV) and the NOAA 11 SBUV/2. Geometric albedo comparison data are further corrected using a radiative transfer code to account for the small difference in observing conditions between the two spacecraft. The postlaunch corrections rely on in-flight calibration and solar irradiance data to account for time dependent changes in instrument gain, thermal response, and instrument diffuser degradation over time. Comparison of data from three SSBUV flights, which occurred about one year apart, with concurrent SBUV/2 data provided an independent check of the time dependent change derived from the in-flight calibration data. Time independent corrections result in an increase of about 1% for total ozone, 5% for ozone at 1 mbar, and near 0% at 15 mbar. The time dependent corrections amount to an increase of 2% for total ozone, 10% for ozone near 1 mbar, and 3% at 15 mbar at the end of the current record in May 1993. Recent laboratory studies indicate that the absolute radiance calibrations may still be in error by a few percent which results in ozone profile values that are too low. The SBUV/2 total and ozone profile data are compared to the Nimbus SBUV data during the period when the data

  12. Mid-infrared absolute spectral responsivity scale based on an absolute cryogenic radiometer and an optical parametric oscillator laser

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Shi, Xueshun; Chen, Haidong; Liu, Yulong; Liu, Changming; Chen, Kunfeng; Li, Ligong; Gan, Haiyong; Ma, Chong

    2016-06-01

    We are reporting on a laser-based absolute spectral responsivity scale in the mid-infrared spectral range. By using a mid-infrared tunable optical parametric oscillator as the laser source, the absolute responsivity scale has been established by calibrating thin-film thermopile detectors against an absolute cryogenic radiometer. The thin-film thermopile detectors can be then used as transfer standard detectors. The extended uncertainty of the absolute spectral responsivity measurement has been analyzed to be 0.58%–0.68% (k  =  2).

  13. Mid-infrared absolute spectral responsivity scale based on an absolute cryogenic radiometer and an optical parametric oscillator laser

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Shi, Xueshun; Chen, Haidong; Liu, Yulong; Liu, Changming; Chen, Kunfeng; Li, Ligong; Gan, Haiyong; Ma, Chong

    2016-06-01

    We are reporting on a laser-based absolute spectral responsivity scale in the mid-infrared spectral range. By using a mid-infrared tunable optical parametric oscillator as the laser source, the absolute responsivity scale has been established by calibrating thin-film thermopile detectors against an absolute cryogenic radiometer. The thin-film thermopile detectors can be then used as transfer standard detectors. The extended uncertainty of the absolute spectral responsivity measurement has been analyzed to be 0.58%-0.68% (k  =  2).

  14. The absolute path command

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the absolute path to a relative directory from the current working directory.« less

  15. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  16. A 35 Year Earth Science Data Record of Gridded IR Atmospheric Radiances

    NASA Astrophysics Data System (ADS)

    Halem, M.; Chapman, D.; Nguyen, P.

    2008-12-01

    We present the generation of a 35 year Earth Science Data Record (ESDR) of gridded level 1B atmospheric radiances at a 250 km spatial resolution from sources of satellite data including the Vertical Temperature Profiler Radiometer (VTPR), High Resolution Infrared Sounder (HIRS2/3/4), and Atmospheric Infrared Sounder (AIRS). We use the MODIS long wave channels to validate the calibration of the AIRS and HIRS data. VTPR is an operational 8-spectral channel infrared sounding system with an IFOV around 55km at nadir that operated from 1972 to 1979. The HIRS/2 sensor is a 20 spectral channel instrument with an IFOV approx. 20km, that flew from 1979 to 2001 forming a 22 year record. HIRS/3, is an advanced HIRS sounder that flew on NOAA 15-17 from 1998 to the present. HIRS/4, essentially the same as HIRS/3 except for an IFOV of 10 km has flown on the ESA Met 0p A from 2006 to present. AIRS on Aqua satellite launched on May 2002 has 2374 spectral channels from 3.7 μm to 15 μm and is well calibrated as compared with MODIS channels on the same satellite. Based on the Aqua Senior Project Review of available flight fuel, power and orbital maneuvers, the assessed life span of the satellite Aqua is estimated to be 2013. No such gridded data products of just the observed IR radiances are available since the emphasis for these sensors was the inference of temperature profiles from the observations for use in weather analysis and prediction. We have developed a system, SOAR, that provides gridded radiance data for AIRS and MODIS radiances that can meet the precision and accuracy required for a Fundamental Data Record (FDR). We are exploiting the IBM Cell blade cluster (at UMBC) of 250 processors to geolocate and grid the entire data volume of AIRS and MODIS instruments employing a data intensive raycasting algorithm. The Observation Coverage (obscov) based geolocation significantly improves gridded accuracy by 1 Kelvin Brightness Temperature over most regions on Earth, when

  17. A Systematic Error Correction Method for TOVS Radiances

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Rokke, Laurie; Einaudi, Franco (Technical Monitor)

    2000-01-01

    Treatment of systematic errors is crucial for the successful use of satellite data in a data assimilation system. Systematic errors in TOVS radiance measurements and radiative transfer calculations can be as large or larger than random instrument errors. The usual assumption in data assimilation is that observational errors are unbiased. If biases are not effectively removed prior to assimilation, the impact of satellite data will be lessened and can even be detrimental. Treatment of systematic errors is important for short-term forecast skill as well as the creation of climate data sets. A systematic error correction algorithm has been developed as part of a 1D radiance assimilation. This scheme corrects for spectroscopic errors, errors in the instrument response function, and other biases in the forward radiance calculation for TOVS. Such algorithms are often referred to as tuning of the radiances. The scheme is able to account for the complex, air-mass dependent biases that are seen in the differences between TOVS radiance observations and forward model calculations. We will show results of systematic error correction applied to the NOAA 15 Advanced TOVS as well as its predecessors. We will also discuss the ramifications of inter-instrument bias with a focus on stratospheric measurements.

  18. 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.

  19. MODIS On-orbit Calibration Uncertainty Assessment

    NASA Technical Reports Server (NTRS)

    Chiang, Vincent; Sun, Junqiang; Wu, Aisheng

    2011-01-01

    MODIS has 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). Compared to its heritage sensors, MODIS was developed with very stringent calibration uncertainty requirements. As a result, MODIS was designed and built with a set of on-board calibrators (OBC), which allow key sensor performance parameters and on-orbit calibration coefficients to be monitored and updated. 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 an in-depth analysis of its on-orbit calibration uncertainties. Also discussed in this paper are uncertainty contributions from individual components and differences due to Terra and Aqua MODIS instrument characteristics and on-orbit performance.

  20. Thermal radiance observations of an active lava flow during the June 1984 eruption of Mount Etna

    SciTech Connect

    Pieri, D.C.; Glaze, L.S.; Abrams, M.J. )

    1990-10-01

    The thermal budget of an active lava flow observed on 20 June 1984 from the Southeast crater of Mount Etna, Sicily, Italy, was analyzed from data taken by the Landsat Thematic Mapper. The Thematic Mapper images constitute one of the few satellite data sets of sufficient spatial and spectral resolution to allow calibrated measurements on the distribution and intensity of thermal radiation from active lava flows. Using radiance data from two reflective infrared channels, we can estimate the temperature and areas of the hottest parts of the active flow, which correspond to hot (>500{degree}C) fractures or zones at the flow surface. Using this techniques, we estimate that only 10%-20% of the total radiated thermal power output is emitted by hot zones or fractures, which constitute less than 1% of the observed surface area. Generally, it seems that only where hot fractures or zones constitute greater than about 1% of the surface area of the flow will losses from such features significantly reduce internal flow temperatures. Using our radiance observations as boundary conditions for a multicomponent thermal model of flow interior temperature, we infer that, for the parts of this flow subject to analysis, the boundary layer and flow thickness effects dominate over radiant zones in controlling the depression of core temperature.

  1. Extension of the absolute flux density scale to 22.285 GHz. [radio astronomy

    NASA Technical Reports Server (NTRS)

    Janssen, M. A.; Golden, L. M.; Welch, W. J.

    1974-01-01

    Extending the absolute flux density scale at microwave wavelengths, the absolute flux densities at 22.285 GHz of several standard sources were determined using the absolute calibrations of the 6.1 meter antenna of the Hat Creek Observatory. Interpolation formulas for each nonthermal standard source have been derived by combining these data with those determined at lower frequencies. The suitability of employing the standard sources for calibrating other antennas is discussed.

  2. Comparing sources of variability in cloud-characterized HIRS radiances

    NASA Astrophysics Data System (ADS)

    Staten, P.; Kahn, B. H.; Schreier, M. M.; Heidinger, A. K.

    2014-12-01

    The difficulty of modeling and observing cloud processes continue to stymie efforts at tracking and projecting cloud behavior in a changing climate. While robust determination of the global cloud feedback remains elusive, the ~30-year radiance record from High Resolution Infrared Radiation Sounders (HIRS) and the corresponding visible imagery database may enable the constraint of individual components of the cloud feedback. Specifically, signals in region- and cloud-type-specific infrared radiances may be detectable with some significance. Using nearly simultaneous nadir cloud type information from the Clouds from AVHRR Extended (CLAVR-x) dataset, we analyze sources of variability in cloud-characterized HIRS radiances. Inter-satellite biases are large enough to hamper the determination not just of long-term trends, but also of diurnal and interannual variability. However, changes in variability, rather than the mean, may be detectable with the current state of instrumentation. Characterizing cloud variability is expected to shed light on physical climate processes.

  3. Solar radiance models for determination of ERBE scanner filter factor

    NASA Technical Reports Server (NTRS)

    Arduini, R. F.

    1985-01-01

    Shortwave spectral radiance models for use in the spectral correction algorithms for the ERBE Scanner Instrument are provided. The required data base was delivered to the ERBe Data Reduction Group in October 1984. It consisted of two sets of data files: (1) the spectral bidirectional angular models and (2) the spectral flux modes. The bidirectional models employ the angular characteristics of reflection by the Earth-atmosphere system and were derived from detailed radiance calculations using a finite difference model of the radiative transfer process. The spectral flux models were created through the use of a delta-Eddington model to economically simulate the effects of atmospheric variability. By combining these data sets, a wide range of radiances may be approximated for a number of scene types.

  4. A generic fast airbreathing first stage TSTO vehicle - RADIANCE

    NASA Astrophysics Data System (ADS)

    Wagner, Alain; Dufour, Alain

    1992-12-01

    A concept is considered that reducing the delta V to be provided by the second stage reduces its mass and, hence, may allow a down scaling of the first stage despite the higher staging Mach number. The concept is based on a two-stage-to-orbit vehicle called RADIANCE that stages at Mach 12 with an airbreathing first stage and a rocket-powered second stage. A fairing is provided to avoid aerodynamic interactions between the stages. RADIANCE takes off horizontally using an integral landing gear. The booster lands horizontally on a conventional runway. After having completed its orbital mission the orbiter returns through the atmosphere for an unpowered landing to the launch base. It is noted that RADIANCE hampered by the high drag losses inherently coupled with its booster size.

  5. Modeling directional thermal radiance from a forest canopy

    NASA Technical Reports Server (NTRS)

    Mcguire, M. J.; Balick, L. K.; Smith, J. A.; Hutchison, B. A.

    1989-01-01

    The thermal vegetation canopy radiance model of Smith et al. (1981) is extended to account for the geometrically rough structure of a forest canopy. Fourier series expansion of a canopy height profile is used to calculate improved view facts which partially account for directional variations in canopy thermal radiance transfers. Predictions from the Smith model and the modified model are compared with experimental data obtained over a deciduous forest site in Tennessee. The results show that thermal radiance from a forest canopy depends on sensor viewing angle, solar position, and the degree of geometric roughness of the canopy surface. The maximum off-nadir angle variation in the original model was 1.6 deg C, compared with 4.4 C for the modified model.

  6. Summary of OARE flight calibration measurements

    NASA Astrophysics Data System (ADS)

    Blanchard, Robert C.; Nicholson, John Y.

    1995-01-01

    To date, the Orbital Acceleration Research Experiment (OARE) has flown on the shuttle orbiter for five missions; namely, STS-40, STS-50, STS-58, STS-62, and STS-65. The OARE instrument system contains a three-axis accelerometer which can resolve accelerations to the nano-g (10(exp -9) g) level and a full calibration station to permit in situ bias and scale factor calibration measurements. This calibration capability eliminates the large uncertainty encountered with accelerometers flown in the past on the orbiter which use ground-based calibrations to provide absolute acceleration measurements. A detailed flight data report presentation is given for the OARE calibration measurements from all missions, along with an estimate of the calibration errors. The main aim is to collect, process, and present the calibration data in one archival report. These calibration data are the necessary key ingredient to produce the absolute acceleration levels from the OARE acceleration flight data.

  7. Radiance limits of ceramic phosphors under high excitation fluxes

    NASA Astrophysics Data System (ADS)

    Lenef, Alan; Kelso, John; Zheng, Yi; Tchoul, Maxim

    2013-09-01

    Ceramic phosphors, excited by high radiance pump sources, offer considerable potential for high radiance conversion. Interestingly, thermodynamic arguments suggest that the radiance of the luminescent spot can even exceed that of the incoming light source. In practice, however, thermal quenching and (non-thermal) optical saturation limit the maximum attainable radiance of the luminescent source. We present experimental data for Ce:YAG and Ce:GdYAG ceramics in which these limits have been investigated. High excitation fluxes are achieved using laser pumping. Optical pumping intensities exceeding 100W/mm2 have been shown to produce only modest efficiency depreciation at low overall pump powers because of the short Ce3+ lifetime, although additional limitations exist. When pump powers are higher, heat-transfer bottlenecks within the ceramic and heat-sink interfaces limit maximum pump intensities. We find that surface temperatures of these laser-pumped ceramics can reach well over 150°C, causing thermal-quenching losses. We also find that in some cases, the loss of quantum efficiency with increasing temperature can cause a thermal run-away effect, resulting in a rapid loss in converted light, possibly over-heating the sample or surrounding structures. While one can still obtain radiances on the order of many W/mm2/sr, temperature quenching effects ultimately limit converted light radiance. Finally, we use the diffusion-approximation radiation transport models and rate equation models to simulate some of these nonlinear optical pumping and heating effects in high-scattering ceramics.

  8. Satellite radiance bias estimation with ensemble filters: Investigations with a simple model

    NASA Astrophysics Data System (ADS)

    Hacker, J.; Auligne, T.; Anderson, J. L.; Snyder, C.

    2011-12-01

    It is well known that satellite radiance observations are contaminated with errors owing to approximations in the radiative transfer calculation and the pre-processing of the observations, representativeness error, uncertainty in the instrument spectral response function, and drift in the instrument calibration. These errors can be treated as systematic errors (biases) in the observations, but vary in time and space. Biases are typically parameterized as a series expansion consisting of two terms with parameters (β0, β1) representing the mean error and the linear bias dependence on error predictors, respectively. Those parameters, if known, appear in the forward operator for the radiances. Methods to estimate the βs on-line while assimilating satellite radiances are well established for variational data assimilation, and are somewhat less mature for ensemble data assimilation. Parameters are often estimated in a separate, but concurrent, estimation step that out of necessity assumes the correlations between the parameters and the state elements are zero. The assumption of no correlation between observation parameters and state has proven useful, but ignores the fact that correlations are non-zero in an analysis produced by increments from observations containing parameters. Correlation surviving a model advance to the next assimilation cycle then violates the assumptions in the estimation procedure. In the case of forward operators that are functions of space, as weighting functions are in radiance operators, a single bias value can introduce correlations at a scale corresponding to the spatial function. We argue that an assumption of zero correlation between parameters and state is unnecessary, allowing straightforward estimation via state augmentation in an ensemble filter. State augmentation requires non-zero correlations to update the parameters. We investigate the viability of state augmentation for observation bias parameters using the 960-variable, two

  9. MODIS airborne simulator visible and near-infrared calibration, 1992 ASTEX field experiment. Calibration version: ASTEX King 1.0

    NASA Technical Reports Server (NTRS)

    Arnold, G. Thomas; Fitzgerald, Michael; Grant, Patrick S.; King, Michael D.

    1994-01-01

    Calibration of the visible and near-infrared (near-IR) channels of the MODIS Airborne Simulator (MAS) is derived from observations of a calibrated light source. For the 1992 Atlantic Stratocumulus Transition Experiment (ASTEX) field deployment, the calibrated light source was the NASA Goddard 48-inch integrating hemisphere. Tests during the ASTEX deployment were conducted to calibrate the hemisphere and then the MAS. This report summarizes the ASTEX hemisphere calibration, and then describes how the MAS was calibrated from the hemisphere data. All MAS calibration measurements are presented and determination of the MAS calibration coefficients (raw counts to radiance conversion) is discussed. In addition, comparisons to an independent MAS calibration by Ames personnel using their 30-inch integrating sphere is discussed.

  10. Strategy for the absolute neutron emission measurement on ITER.

    PubMed

    Sasao, M; Bertalot, L; Ishikawa, M; Popovichev, S

    2010-10-01

    Accuracy of 10% is demanded to the absolute fusion measurement on ITER. To achieve this accuracy, a functional combination of several types of neutron measurement subsystem, cross calibration among them, and in situ calibration are needed. Neutron transport calculation shows the suitable calibration source is a DT/DD neutron generator of source strength higher than 10(10) n/s (neutron/second) for DT and 10(8) n/s for DD. It will take eight weeks at the minimum with this source to calibrate flux monitors, profile monitors, and the activation system.

  11. Strategy for the absolute neutron emission measurement on ITER

    SciTech Connect

    Sasao, M.; Bertalot, L.; Ishikawa, M.; Popovichev, S.

    2010-10-15

    Accuracy of 10% is demanded to the absolute fusion measurement on ITER. To achieve this accuracy, a functional combination of several types of neutron measurement subsystem, cross calibration among them, and in situ calibration are needed. Neutron transport calculation shows the suitable calibration source is a DT/DD neutron generator of source strength higher than 10{sup 10} n/s (neutron/second) for DT and 10{sup 8} n/s for DD. It will take eight weeks at the minimum with this source to calibrate flux monitors, profile monitors, and the activation system.

  12. Another Technique For Calibration Of Polarimetric Radar

    NASA Technical Reports Server (NTRS)

    Van Zyl, Jakob J.

    1992-01-01

    Inexpensive technique involves four-stage procedure where different aspects of radar system calibrated at each stage. Provides calibration of relative phase, crosstalk, relative amplitude, and absolute amplitude. Only artificial target(s) required is at least one trihedral corner reflector. Advantage of four-step calibration procedure is that one does not have to perform entire procedure if one does not need full calibration.

  13. Studies of the net surface radiative flux from satellite radiances during FIFE

    NASA Technical Reports Server (NTRS)

    Frouin, Robert

    1993-01-01

    Studies of the net surface radiative flux from satellite radiances during First ISLSCP Field Experiment (FIFE) are presented. Topics covered include: radiative transfer model validation; calibration of VISSR and AVHRR solar channels; development and refinement of algorithms to estimate downward solar and terrestrial irradiances at the surface, including photosynthetically available radiation (PAR) and surface albedo; verification of these algorithms using in situ measurements; production of maps of shortwave irradiance, surface albedo, and related products; analysis of the temporal variability of shortwave irradiance over the FIFE site; development of a spectroscopy technique to estimate atmospheric total water vapor amount; and study of optimum linear combinations of visible and near-infrared reflectances for estimating the fraction of PAR absorbed by plants.

  14. NIST Infrared Blackbody Calibration Support for Climate Change Research

    NASA Astrophysics Data System (ADS)

    Hanssen, L. M.; Zeng, J.; Mekhontsev, S.; Khromchenko, V.

    2012-12-01

    The National Institute of Technology (NIST) Sensor Science Division has established measurement capabilities in support of various existing and planned satellite programs, which monitor key parameters for the study of climate change, such as solar irradiance, earth radiance, and atmospheric effects. These capabilities include the characterization of infrared reference blackbody sources and cavity radiometers, as well as the materials used to coat the cavity surfaces. In order to accurately measure high levels of effective emissivity and absorptance of cavities, NIST has developed a laser- and integrating-sphere-based facility (the Complete Hemispherical Infrared Laser-based Reflectometer (CHILR)). The system is used for both radiometer and blackbody cavity characterization. Multiple laser sources with wavelengths ranging from 1.5 μm to 23 μm are used to perform reflectance (1 - emissivity (or absorptance)) measurements of radiometer cavities. Measurements have been performed for numerous instruments including the Internal Calibration Target (ICT)) blackbody source used for calibration of the Cross track Infrared Sounder (CrIS), and the Total Irradiance Monitor (TIM) instrument on the Solar Radiation and Climate Experiment (SORCE), both for the Joint Polar Satellite System (JPSS), as well as the Active Cavity Radiometer Irradiance Monitor (ACRIM) instrument, and blackbodies constructed for prototyping of an infrared instrument on the Climate Absolute Radiance and Refractivity Observatory (CLARREO). For a more comprehensive understanding of the measurement results, NIST has also measured samples of the coated surfaces of the cavities and associated baffles. This includes several types of reflectance measurements: specular, directional-hemispherical (diffuse), and bi-directional distribution function (BRDF). The first two are performed spectrally and provide information that enables estimation of the cavity performance where laser sources for CHILR are not available

  15. Cross calibration of ocean-color bands from moderate resolution imaging spectroradiometer on Terra platform.

    PubMed

    Kwiatkowska, Ewa J; Franz, Bryan A; Meister, Gerhard; McClain, Charles R; Xiong, Xiaoxiong

    2008-12-20

    Ocean-color applications require maximum uncertainties in blue-wavelength water-leaving radiances in oligotrophic ocean of approximately 5%. Water-leaving radiances from Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite, however, exhibit temporal drift of the order of 15% as well as sensor changes in response versus scan and polarization sensitivity, which cannot be tracked by onboard calibrators. This paper introduces an instrument characterization approach that uses Earth-view data as a calibration source. The approach models the top of the atmosphere signal over ocean that the instrument is expected to measure, including its polarization, with water-leaving radiances coming from another well-calibrated global sensor. The cross calibration allows for significant improvement in derived MODIS-Terra ocean-color products, with largest changes in the blue wavelengths.

  16. Primary Radiometry for the mise-en-pratique: The Laser-Based Radiance Method Applied to a Pyrometer

    NASA Astrophysics Data System (ADS)

    Briaudeau, S.; Sadli, M.; Bourson, F.; Rougi, B.; Rihan, A.; Zondy, J.-J.

    2011-12-01

    A new setup has been implemented at LCM-LNE-CNAM for the determination "of the spectral responsivity of radiation thermometers for the determination" of the thermodynamic temperature of high-temperature blackbodies at the temperature of a metal-carbon eutectic phase transition. In this new setup, an innovative acoustic-optic modulator feedback loop is used to stabilize the radiance of a wavelength tunable laser. The effect of residual optical interferences on the calibration of a test pyrometer is analyzed. The full uncertainty budget is presented.

  17. Aerosol, Cloud and Trace Gas Observations Derived from Airborne Hyperspectral Radiance and Direct Beam Measurements in Recent Field Campaigns

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Flynn, C. J.; Shinozuka, Y.; Kacenelenbogen, M.; Segal-Rosenheimer, M.; LeBlanc, S.; Russell, P. B.; Livingston, J. M.; Schmid, B.; Dunagan, S. E.; Johnson, R. R.

    2014-01-01

    The AERONET (AErosol RObotic NETwork) ground-based suite of sunphotometers provides measurements of spectral aerosol optical depth (AOD), precipitable water and spectral sky radiance, which can be inverted to retrieve aerosol microphysical properties that are critical to assessments of aerosol-climate interactions. Because of data quality criteria and sampling constraints, there are significant limitations to the temporal and spatial coverage of AERONET data and their representativeness for global aerosol conditions. The 4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research) instrument, jointly developed by NASA Ames and PNNL with NASA Goddard collaboration, combines airborne sun tracking and AERONET-like sky scanning with spectroscopic detection. Being an airborne instrument, 4STAR has the potential to fill gaps in the AERONET data set. Dunagan et al. [2013] present results establishing the performance of the instrument, along with calibration, engineering flight test, and preliminary scientific field data. The 4STAR instrument operated successfully in the SEAC4RS [Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys] experiment in Aug./Sep. 2013 aboard the NASA DC-8 and in the DoE [Department of Energy]-sponsored TCAP [Two Column Aerosol Project, July 2012 & Feb. 2013] experiment aboard the DoE G-1 aircraft (Shinozuka et al., 2013), and acquired a wealth of data in support of mission objectives on all SEAC4RS and TCAP research flights. 4STAR provided direct beam measurements of hyperspectral AOD, columnar trace gas retrievals (H2O, O3, NO2; Segal-Rosenheimer et al., 2014), and the first ever airborne hyperspectral sky radiance scans, which can be inverted to yield the same products as AERONET ground-based observations. In addition, 4STAR measured zenith radiances underneath cloud decks for retrievals of cloud optical depth and effective diameter. In this presentation, we provide an overview of the new

  18. NIMS Radiance Point Spectra of Ida and Dactyl V1.0

    NASA Astrophysics Data System (ADS)

    Granahan, J. C.

    2013-08-01

    This data volume contains radiometrically corrected point spectra of asteroid 243 Ida and a spectrum of the asteroid satellite Dactyl (Ida I) as acquired by the Galileo spacecraft Near Infrared Mapping Spectrometer (NIMS) on August 28, 1993. They record the spectra collected as the Galileo spacecraft approached the 243 Ida system. These data are products of the calibration of the raw data number files idu002tn.qub, idu005tn.qub, idu006tn.qub, idu007tn.qub, idu019tn.qub, idu020tn.qub, idu022tn.qub, idu028tn.qub, idu032tn.qub, idu033tn.qub, and idu035tn.qub (DATA SET ID ='GO-A-NIMS-3-TUBE-V1.0') with calibration factors acquired during the Jovian tour of the Galileo mission. These raw data .qub files are archived in the Imaging Node of the NASA Planetary Data System (PDS). The calibrated spectra consist of radiance and incidence/flux measurements for wavelengths between 0.7 - 5.2 micrometers.

  19. Influence of sky radiance measurement errors on inversion-retrieved aerosol properties

    SciTech Connect

    Torres, B.; Toledano, C.; Cachorro, V. E.; Bennouna, Y. S.; Fuertes, D.; Gonzalez, R.; Frutos, A. M. de; Berjon, A. J.; Dubovik, O.; Goloub, P.; Podvin, T.; Blarel, L.

    2013-05-10

    Remote sensing of the atmospheric aerosol is a well-established technique that is currently used for routine monitoring of this atmospheric component, both from ground-based and satellite. The AERONET program, initiated in the 90's, is the most extended network and the data provided are currently used by a wide community of users for aerosol characterization, satellite and model validation and synergetic use with other instrumentation (lidar, in-situ, etc.). Aerosol properties are derived within the network from measurements made by ground-based Sun-sky scanning radiometers. Sky radiances are acquired in two geometries: almucantar and principal plane. Discrepancies in the products obtained following both geometries have been observed and the main aim of this work is to determine if they could be justified by measurement errors. Three systematic errors have been analyzed in order to quantify the effects on the inversion-derived aerosol properties: calibration, pointing accuracy and finite field of view. Simulations have shown that typical uncertainty in the analyzed quantities (5% in calibration, 0.2 Degree-Sign in pointing and 1.2 Degree-Sign field of view) yields to errors in the retrieved parameters that vary depending on the aerosol type and geometry. While calibration and pointing errors have relevant impact on the products, the finite field of view does not produce notable differences.

  20. 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.

  1. Determination of the in-flight spectral calibration of AVIRIS using atmospheric absorption features

    NASA Technical Reports Server (NTRS)

    Green, Robert O.

    1995-01-01

    Spectral calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) as data are acquired in flight is essential to quantitative analysis of the measured upwelling spectral radiance. In each spectrum measured by AVIRIS in flight, there are numerous atmospheric gas absorption bands that drive this requirement for accurate spectral calibration. If the surface and atmospheric properties are measured independently, these atmospheric absorption bands may be used to deduce the in-flight spectral calibration of an imaging spectrometer. Both the surface and atmospheric characteristics were measured for a calibration target during an in-flight calibration experiment held at Lunar Lake, Nevada on April 5, 1994. This paper uses upwelling spectral radiance predicted for the calibration target with the MODTRAN radiative transfer code to validate the spectral calibration of AVIRIS in flight.

  2. Measurement and modeling of radiance reflectance in Garda Lake

    NASA Astrophysics Data System (ADS)

    Ferratini, Silvia; Giardino, Claudia; Pierson, Donald C.; Stroembeck, Niklas; Zilioli, Eugenio

    2000-12-01

    A simple model which predicts radiance reflectance below the water surface as a function of the concentrations of chlorophyll, colored dissolved organic matter (CDOM), and suspended particulate material (SPIM) was applied in Garda lake, the largest freshwater basin in Italy and one of the most important of the European Union. The model is similar to others developed for oceanic and coastal waters predicting the radiance reflectance as a function of two inherent optical properties of water: the absorption coefficient and the backscattering coefficient. Three stations were sampled in January '98 in the southern part of Garda lake. Samples of water were collected just below the water surface to extract the optically active substances. Two underwater radiometers assembled on the same probe provided the measurement of downwelling irradiance and up welling radiance, respectively. At the same time the apparent optical properties were collected above the water volume by using a spectro radiometer. The simulated radiance reflectance spectra were compared to the ones measured and significant correlations were retrieved.

  3. Spectral reflectance and radiance characteristics of water pollutants

    NASA Technical Reports Server (NTRS)

    Wezernak, C. T.; Turner, R. E.; Lyzenga, D. R.

    1976-01-01

    Spectral reflectance characteristics of water pollutants and water bodies were compiled using the existing literature. Radiance calculations were performed at satellite altitude for selected illumination angles and atmospheric conditions. The work described in this report was limited to the reflective portion of the spectrum between 0.40 micrometer to 1.0 micrometer.

  4. The Nature of the Radiance and Polarization in Deep Oceans

    NASA Astrophysics Data System (ADS)

    You, Y.; Kattawar, G. W.; Yang, P.

    2007-12-01

    We studied the asymptotic nature of the radiance and polarization in the underwater light field in an atmosphere- ocean system. We used a vector radiative transfer code to solve for the total Stokes vector and found that the radiance of the light field becomes asymptotic more quickly than the polarization does. Our simulations imply that for a homogeneous water body described by a Petzold phase function, a single scattering albedo of ω_0 ≥ 0.8 is required to reach the asymptotic regime practically, otherwise, the radiance in the asymptotic regime becomes too small to be detected. For the asymptotic regime to be realized physically, a water body with a less anisotropic phase function and/or a larger ω0 is necessary. For a real water body described by a Case 1 water model, the asymptotic regime could be reached at wavelengths 400 nm <λ< 500 nm. The effects of Raman scattering have also been included, and it turns out that for wavelengths λ < 540 nm, the contribution from Raman scattering can be reasonably neglected in the study of the asymptotic radiance.

  5. Modeling directional thermal radiance from a forest canopy

    SciTech Connect

    McGuire, M.J.; Balick, L.K.; Smith, J.A.; Hutchinson, B.A.

    1989-12-31

    This paper describes an extension of an existing thermal vegetation canopy radiance model which has been modified to partially account for the geometrically rough structure of a forest canopy. Fourier series expansion of a canopy height profile is used to calculate view factors which partially account for the directional variations in canopy thermal radiance transfer. A modification of a previously developed thermal vegetation canopy model is presented, along with the measurements used to drive and verify the model. The evidence indicates that thermal radiance from a forest canopy depends on sensor viewing angle, solar position, and the degree of geometric roughness of the canopy surface. For the above canopy, hand-held IRT`s were not useful for investigating the nadir angle variations due to the averaging technique used. These data did show some azimuthal variations, but it is difficult to precisely interpret the trends because of the averaging employed. Comparisons were made between the ORIG and ROUGH thermal models. The data analysis and model comparisons suggest that thermal radiance from a forest canopy does depend on sensor view angle and that the variation can be partially explained by the position of the sun and the geometrically rough structure of the canopy surface.

  6. Black hole radiance, short distances, and TeV gravity.

    PubMed

    Agulló, Iván; Navarro-Salas, José; Olmo, Gonzalo J

    2006-07-28

    Using a derivation of black hole radiance in terms of two-point functions one can provide a quantitative estimate of the contribution of short distances to the spectrum. Thermality is preserved for black holes with kappalp<1. However, deviations from the Planckian spectrum can be found for mini black holes in TeV gravity scenarios, even before reaching the Planck phase.

  7. Surface Emissivity Effects on Thermodynamic Retrieval of IR Spectral Radiance

    NASA Technical Reports Server (NTRS)

    Zhou, Daniel K.; Larar, Allen M.; Smith, William L.; Liu, Xu

    2006-01-01

    The surface emissivity effect on the thermodynamic parameters (e.g., the surface skin temperature, atmospheric temperature, and moisture) retrieved from satellite infrared (IR) spectral radiance is studied. Simulation analysis demonstrates that surface emissivity plays an important role in retrieval of surface skin temperature and terrestrial boundary layer (TBL) moisture. NAST-I ultraspectral data collected during the CLAMS field campaign are used to retrieve thermodynamic properties of the atmosphere and surface. The retrievals are then validated by coincident in-situ measurements, such as sea surface temperature, radiosonde temperature and moisture profiles. Retrieved surface emissivity is also validated by that computed from the observed radiance and calculated emissions based on the retrievals of surface temperature and atmospheric profiles. In addition, retrieved surface skin temperature and emissivity are validated together by radiance comparison between the observation and retrieval-based calculation in the window region where atmospheric contribution is minimized. Both simulation and validation results have lead to the conclusion that variable surface emissivity in the inversion process is needed to obtain accurate retrievals from satellite IR spectral radiance measurements. Retrieval examples are presented to reveal that surface emissivity plays a significant role in retrieving accurate surface skin temperature and TBL thermodynamic parameters.

  8. Solar-Reflectance-Based Calibration of Spectral Radiometers

    NASA Technical Reports Server (NTRS)

    Cattrall, Christopher; Carder, Kendall L.; Thome, Kurtis J.; Gordon, Howard R.

    2001-01-01

    A method by which to calibrate a spectral radiometer using the sun as the illumination source is discussed. Solar-based calibrations eliminate several uncertainties associated with applying a lamp-based calibration to field measurements. The procedure requires only a calibrated reflectance panel, relatively low aerosol optical depth, and measurements of atmospheric transmittance. Further, a solar-reflectance-based calibration (SRBC), by eliminating the need for extraterrestrial irradiance spectra, reduces calibration uncertainty to approximately 2.2% across the solar-reflective spectrum, significantly reducing uncertainty in measurements used to deduce the optical properties of a system illuminated by the sun (e.g., sky radiance). The procedure is very suitable for on-site calibration of long-term field instruments, thereby reducing the logistics and costs associated with transporting a radiometer to a calibration facility.

  9. Thermal Targets for Satellite Calibration

    SciTech Connect

    Villa-Aleman, E.

    2001-01-10

    The Savannah River Technology Center (SRTC) is currently calibrating the Multispectral Thermal Imager (MTI) satellite sponsored by the Department of Energy. The MTI imager is a research and development project with 15 wavebands in the visible, near-infrared, short-wave infrared, mid-wave infrared and long-wave infrared spectral regions. A plethora of targets with known temperatures such as power plant heated lakes, volcano lava vents, desert playas and aluminized Mylar tarps are being used in the validation of the five thermal bands of the MTI satellite. SRTC efforts in the production of ''cold targets'' with aluminized Mylar tarps will be described. Visible and thermal imagery and wavelength dependent radiance measurements of the calibration targets will be presented.

  10. Characterization of the DARA solar absolute radiometer

    NASA Astrophysics Data System (ADS)

    Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.

    2011-12-01

    The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).

  11. ABSOLUTE POLARIMETRY AT RHIC.

    SciTech Connect

    OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.

    2007-09-10

    Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.

  12. Swarm's Absolute Scalar Magnetometer metrological performances

    NASA Astrophysics Data System (ADS)

    Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.

    2012-12-01

    The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.

  13. Lambertian nature of tissue phantoms for use as calibrators in near infrared fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Litorja, Maritoni; Lorenzo, Simón; Zhu, Banghe; Sevick Muraca, Eva

    2016-03-01

    The use of tissue phantoms as calibrators to transfer SI-referenced scale to an imager offers convenience, compared to other methods of calibration. The tissue phantoms are calibrated separately for radiance at emission wavelength per irradiance at excitation wavelength. This calibration is only performed at a single geometric configuration, typically with the detector normal to the sample. In the clinic however, the imager can be moved around, resulting in a geometric configuration different from the calibration configuration. In this study, radiometric measurements are made at different sample-imager angles to test whether the tissue phantoms are Lambertian and the angular limits to which the calibration values hold true.

  14. UNDERFLIGHT CALIBRATION OF SOHO/CDS AND HINODE/EIS WITH EUNIS-07

    SciTech Connect

    Wang Tongjiang; Brosius, Jeffrey W.; Thomas, Roger J.; Rabin, Douglas M.; Davila, Joseph M.; Young, Peter R.; Del Zanna, Giulio

    2011-12-01

    Flights of Goddard Space Flight Center's Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket in 2006 and 2007 provided updated radiometric calibrations for Solar and Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS) and Hinode/Extreme Ultraviolet Imaging Spectrometer (Hinode/EIS). EUNIS carried two independent imaging spectrographs covering wavebands of 300-370 A in first order and 170-205 A in second order. After each flight, end-to-end radiometric calibrations of the rocket payload were carried out in the same facility used for pre-launch calibrations of CDS and EIS. During the 2007 flight, EUNIS, SOHO/CDS, and Hinode/EIS observed the same solar locations, allowing the EUNIS calibrations to be directly applied to both CDS and EIS. The measured CDS NIS 1 line intensities calibrated with the standard (version 4) responsivities with the standard long-term corrections are found to be too low by a factor of 1.5 due to the decrease in responsivity. The EIS calibration update is performed in two ways. One uses the direct calibration transfer of the calibrated EUNIS-07 short wavelength (SW) channel. The other uses the insensitive line pairs, in which one member was observed by the EUNIS-07 long wavelength (LW) channel and the other by EIS in either the LW or SW waveband. Measurements from both methods are in good agreement, and confirm (within the measurement uncertainties) the EIS responsivity measured directly before the instrument's launch. The measurements also suggest that the EIS responsivity decreased by a factor of about 1.2 after the first year of operation (although the size of the measurement uncertainties is comparable to this decrease). The shape of the EIS SW response curve obtained by EUNIS-07 is consistent with the one measured in laboratory prior to launch. The absolute value of the quiet-Sun He II 304 A intensity measured by EUNIS-07 is consistent with the radiance measured by CDS NIS in quiet regions near the

  15. Ground-based determination of atmospheric radiance for correction of ERTS-1 data

    NASA Technical Reports Server (NTRS)

    Peacock, K.

    1974-01-01

    A technique is described for estimating the atmospheric radiance observed by a downward sensor (ERTS) using ground-based measurements. A formula is obtained for the sky radiance at the time of the ERTS overpass from the radiometric measurement of the sky radiance made at a particular solar zenith angle and air mass. A graph illustrates ground-based sky radiance measurements as a function of the scattering angle for a range of solar air masses. Typical values for sky radiance at a solar zenith angle of 48 degrees are given.

  16. 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.

  17. Calibration of the Microwave Limb Sounder on the Upper Atmosphere Research Satellite

    NASA Technical Reports Server (NTRS)

    Jarnot, R. F.; Cofield, R. E.; Waters, J. W.; Flower, D. A.; Peckham, G. E.

    1996-01-01

    The Microwave Limb Sounder (MLS) is a three-radiometer, passive, limb emission instrument onboard the Upper Atmosphere Research Satellite (UARS). Radiometric, spectral and field-of-view calibrations of the MLS instrument are described in this paper. In-orbit noise performance, gain stability, spectral baseline and dynamic range are described, as well as use of in-flight data for validation and refinement of prelaunch calibrations. Estimated systematic scaling uncertainties (3 sigma) on calibrated limb radiances from prelaunch calibrations are 2.6% in bands 1 through 3, 3.4% in band 4, and 6% in band 5. The observed systematic errors in band 6 are about 15%, consistent with prelaunch calibration uncertainties. Random uncertainties on individual limb radiance measurements are very close to the levels predicted from measured radiometer noise temperature, with negligible contribution from noise and drifts on the regular in-flight gain calibration measurements.

  18. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  19. Radiance and polarization of light reflected from optically thick clouds.

    PubMed

    Kattawar, G W; Plass, G N

    1971-01-01

    The reflected radiance and polarization are calculated for clouds with optical thicknesses from 10 to 100. The results are presented for both the haze C and nimbostratus model. The peak in the single scattered polarization at 140 degrees for the nimbostratus model persists even with all the multiple scattering events that occur for the largest optical thicknesses considered here. The calculations are made by a Monte Carlo technique, which includes the effect of multiple scattering through all orders and a realistic anisotropic phase function for single scattering appropriate for the distribution of particle sizes in the cloud. The effect of the surface albedo is included in the calculations for the optical thickness of 10. The variation of the radiance and polarization with both the nadir and azimuthal angle is given for several solar zenith angles.

  20. Fluorescence lidar detection with shot noise and sky radiance.

    PubMed

    Rosen, D L; Gillespie, J B

    1992-07-20

    Rank annihilation-factor analysis is potentially the best method of analyzing fluorescence lidar returns because of the following capability. Rank annihilation can recognize a fluorescence signal of a component that is hidden by a large fluorescence background without a spectrum of that background. Theoretical models were developed to analyze the effectiveness of rank annihilation-factor analysis in the interpretation of lidar returns. Interferents such as background fluorescence, photon-counting noise, sky radiance, and atmospheric extinction degraded the lidar-return spectra in numerical simulations. The rank annihilation-factor analysis detection algorithm was most severely biased by the combination of photon-counting noise and sky radiance. Rank annihilation calculations were also compared with calculations done by two other detection algorithms: finding peak wavelengths and the least-squares technique. Rank annihilation is better than both techniques.

  1. Physical Retrieval of Surface Emissivity Spectrum from Hyperspectral Infrared Radiances

    NASA Technical Reports Server (NTRS)

    Li, Jun; Weisz, Elisabeth; Zhou, Daniel K.

    2007-01-01

    Retrieval of temperature, moisture profiles and surface skin temperature from hyperspectral infrared (IR) radiances requires spectral information about the surface emissivity. Using constant or inaccurate surface emissivities typically results in large retrieval errors, particularly over semi-arid or arid areas where the variation in emissivity spectrum is large both spectrally and spatially. In this study, a physically based algorithm has been developed to retrieve a hyperspectral IR emissivity spectrum simultaneously with the temperature and moisture profiles, as well as the surface skin temperature. To make the solution stable and efficient, the hyperspectral emissivity spectrum is represented by eigenvectors, derived from the laboratory measured hyperspectral emissivity database, in the retrieval process. Experience with AIRS (Atmospheric InfraRed Sounder) radiances shows that a simultaneous retrieval of the emissivity spectrum and the sounding improves the surface skin temperature as well as temperature and moisture profiles, particularly in the near surface layer.

  2. Method for calibration of plutonium NDA

    SciTech Connect

    Lemming, J.F.; Campbell, A.R.; Rodenburg, W.W.

    1980-01-01

    Calibration materials characterized by calorimetric assay can be a practical alternative to synthetic standards for the calibration of plutonium nondestructive assay. Calorimetric assay is an effective measurement system for the characterization because: it can give an absolute assay from first principles when the isotopic composition is known, it is insensitive to most matrix effects, and its traceability to international measurement systems has been demonstrated.

  3. 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.

  4. Measurement of mechanoluminescence radiance of ZnS:Mn

    NASA Astrophysics Data System (ADS)

    Persits, Nili; Aharoni, Abraham; Tur, Moshe

    2015-07-01

    Mechanoluminescence (ML), the emission of light from certain crystals induced by mechanical stress, is being considered for structural health monitoring (SHM), potentially offering passive and real-time distributed detection systems. We measured the mechanoluminescent radiance of ZnS:Mn, a crystal with a relatively strong ML emission, embedded in a matrix of transparent polyurethane under different loading and fracture. This data is invaluable for the design and performance evaluation of ML sensor systems.

  5. Patterns of reflected radiance associated with geobotanical anomalies

    NASA Technical Reports Server (NTRS)

    Birnie, R. W.; Stone, T. A.; Francica, J. R.

    1985-01-01

    This paper summarizes three remote sensing experiments in which changes in remotely measured reflected radiance patterns of vegetation correlated with changes in geology. In two cases using airborne spectroradiometer data, changes in the physical properties of a uniform species correlated with zones of porphyry copper mineralization. In another case using Landsat digital data, changes were detected in the distribution and density of a number of species and combined with soil brightness data to produce a composite index useful for distinguishing lithologies.

  6. Community Radiative Transfer Model for Aerosol Radiance Assimilation in Global and Regional Models

    NASA Astrophysics Data System (ADS)

    Liu, Q.; van Delst, P. F.; Groff, D.; Collard, A.; Boukabara, S. A.; Weng, F.; Derber, J.

    2013-12-01

    Community Radiative Transfer Model (CRTM), developed at the Joint Center for Satellite Data Assimilation, has being operationally supporting satellite radiance assimilation for weather forecasting in NOAA and NASA. The CRTM is also supporting the MODIS, GOES-R and JPSS/NPP missions for instrument calibration, validation, monitoring long-term trending, and satellite products using a retrieval approach. The CRTM development is contributed to by multiple U.S. government agencies, universities as well as private companies. This paper will present the latest CRTM version 2.1, which is applicable for passive microwave, infrared and visible sensors. It supports all NOAA satellite instruments, NASA MODIS, and many foreign meteorological satellites. In this study, we will describe the CRTM functionalities and capabilities in the new release of version 2.1. The following are the highlights of the CRTM version: 1. Dual Transmittance models, ODAS and ODPS, 2. Sensor Specific Transmittance models: Fast Transmittance Model for Stratospheric Sounding Unit to take account for CO2 cell pressure variation, Fast Transmittance Model for SSMIS Upper Atmospheric Sounding (UAS) Channels including Zeeman-splitting. 3. Non-local Thermodynamic Equilibrium (NLTE) Radiative Transfer 4. Surface Emissivity/Reflectivity Models 5. Aerosol, Cloud, and Molecular Scattering Models Pre-computed look-up tables for extinction, scattering coefficients and phase functions 6. Dual Radiative Transfer Solver, Adding Double-Adding method [1][2], Adding Matrix Operator method, and SOI method. The CRTM is flexible for users' applications, for example one can simulate aircraft measurements, turn scattering off for fast calculations, use an aerosol optical depth (AOD) module for aerosol optical depth calculation, use an emissivity interface to input your own emissivity data base, and use a channel selection function for specified channel radiance calculations. In this presentation, we focus on aerosol product

  7. 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.

  8. A Microwave Radiance Assimilation Study for a Tundra Snowpack

    NASA Technical Reports Server (NTRS)

    Kim, Edward; Durand, Michael; Margulis, Steve; England, Anthony

    2010-01-01

    Recent studies have begun exploring the assimilation of microwave radiances for the modeling and retrieval of snow properties. At a point scale, and for short durations (i week), radiance assimilation (RA) results are encouraging. However, in order to determine how practical RA might be for snow retrievals when applied over longer durations, larger spatial scales, and/or different snow types, we must expand the scope of the tests. In this paper we use coincident microwave radiance measurements and station data from a tundra site on the North Slope of Alaska. The field data are from the 3rd Radio-brightness Energy Balance Experiment (REBEX-3) carried out in 1994-95 by the University of Michigan. This dataset will provide a test of RA over months instead of one week, and for a very different type of snow than previous snow RA studies. We will address the following questions: flow well can a snowpack physical model (SM), forced with local weather, match measured conditions for a tundra snowpack?; How well can a microwave emission model, driven by the snowpack model, match measured microwave brightnesses for a tundra snowpack?; How well does RA increase or decrease the fidelity of estimates of snow depth and temperatures for a tundra snowpack?

  9. Calibrating X-ray Imaging Devices for Accurate Intensity Measurement

    SciTech Connect

    Haugh, M. J.

    2011-07-28

    The purpose of the project presented is to develop methods to accurately calibrate X-ray imaging devices. The approach was to develop X-ray source systems suitable for this endeavor and to develop methods to calibrate solid state detectors to measure source intensity. NSTec X-ray sources used for the absolute calibration of cameras are described, as well as the method of calibrating the source by calibrating the detectors. The work resulted in calibration measurements for several types of X-ray cameras. X-ray camera calibration measured efficiency and efficiency variation over the CCD. Camera types calibrated include: CCD, CID, back thinned (back illuminated), front illuminated.

  10. Absolute cavity pyrgeometer

    DOEpatents

    Reda, Ibrahim

    2013-10-29

    Implementations of the present disclosure involve an apparatus and method to measure the long-wave irradiance of the atmosphere or long-wave source. The apparatus may involve a thermopile, a concentrator and temperature controller. The incoming long-wave irradiance may be reflected from the concentrator to a thermopile receiver located at the bottom of the concentrator to receive the reflected long-wave irradiance. In addition, the thermopile may be thermally connected to a temperature controller to control the device temperature. Through use of the apparatus, the long-wave irradiance of the atmosphere may be calculated from several measurements provided by the apparatus. In addition, the apparatus may provide an international standard of pyrgeometers' calibration that is traceable back to the International System of Units (SI) rather than to a blackbody atmospheric simulator.

  11. Calibrations of the LHD Thomson scattering system

    NASA Astrophysics Data System (ADS)

    Yamada, I.; Funaba, H.; Yasuhara, R.; Hayashi, H.; Kenmochi, N.; Minami, T.; Yoshikawa, M.; Ohta, K.; Lee, J. H.; Lee, S. H.

    2016-11-01

    The Thomson scattering diagnostic systems are widely used for the measurements of absolute local electron temperatures and densities of fusion plasmas. In order to obtain accurate and reliable temperature and density data, careful calibrations of the system are required. We have tried several calibration methods since the second LHD experiment campaign in 1998. We summarize the current status of the calibration methods for the electron temperature and density measurements by the LHD Thomson scattering diagnostic system. Future plans are briefly discussed.

  12. 1987 calibration of the TFTR neutron spectrometers

    SciTech Connect

    Barnes, C.W.; Strachan, J.D.; Princeton Univ., NJ . Plasma Physics Lab.)

    1989-12-01

    The {sup 3}He neutron spectrometer used for measuring ion temperatures and the NE213 proton recoil spectrometer used for triton burnup measurements were absolutely calibrated with DT and DD neutron generators placed inside the TFTR vacuum vessel. The details of the detector response and calibration are presented. Comparisons are made to the neutron source strengths measured from other calibrated systems. 23 refs., 19 figs., 6 tabs.

  13. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  14. 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.

  15. Use of INSAT-3D sounder and imager radiances in the 4D-VAR data assimilation system and its implications in the analyses and forecasts

    NASA Astrophysics Data System (ADS)

    Indira Rani, S.; Taylor, Ruth; George, John P.; Rajagopal, E. N.

    2016-05-01

    INSAT-3D, the first Indian geostationary satellite with sounding capability, provides valuable information over India and the surrounding oceanic regions which are pivotal to Numerical Weather Prediction. In collaboration with UK Met Office, NCMRWF developed the assimilation capability of INSAT-3D Clear Sky Brightness Temperature (CSBT), both from the sounder and imager, in the 4D-Var assimilation system being used at NCMRWF. Out of the 18 sounder channels, radiances from 9 channels are selected for assimilation depending on relevance of the information in each channel. The first three high peaking channels, the CO2 absorption channels and the three water vapor channels (channel no. 10, 11, and 12) are assimilated both over land and Ocean, whereas the window channels (channel no. 6, 7, and 8) are assimilated only over the Ocean. Measured satellite radiances are compared with that from short range forecasts to monitor the data quality. This is based on the assumption that the observed satellite radiances are free from calibration errors and the short range forecast provided by NWP model is free from systematic errors. Innovations (Observation - Forecast) before and after the bias correction are indicative of how well the bias correction works. Since the biases vary with air-masses, time, scan angle and also due to instrument degradation, an accurate bias correction algorithm for the assimilation of INSAT-3D sounder radiance is important. This paper discusses the bias correction methods and other quality controls used for the selected INSAT-3D sounder channels and the impact of bias corrected radiance in the data assimilation system particularly over India and surrounding oceanic regions.

  16. Modeling Seasonal Thermal Radiance Cycles for Change Detection at Volcanic / Geothermal Areas

    NASA Astrophysics Data System (ADS)

    Vaughan, R.; Beuttel, B. S.

    2013-12-01

    Remote sensing observations of thermal features associated with (and often preceding) volcanic activity have been used for decades to detect and monitor volcanism. However, anomalous thermal precursors to volcanic eruptions are usually only recognized retrospectively. One of the reasons for this is that precursor thermal activity is often too subtle in magnitude (spatially, temporally, or in absolute temperature) to be unambiguously detected in time to issue warnings or forecasts. Part of the reason for this is the trade-off between high spatial and high temporal resolution associated with satellite imaging systems. Thus, the goal of this work has been to develop some techniques for using high-temporal-resolution, coarse-spatial-resolution imagery to try to detect subtle thermal anomalies. To identify anomalies, background thermal activity must first be characterized. Every active, or potentially active, volcano has a unique thermal history that provides information about normal background thermal activity due to seasonal or diurnal variations. Understanding these normal variations allows recognition of anomalous activity that may be due to volcanic / hydrothermal processes - ultimately with a lead time that may be sufficient to issue eruption warnings or forecasts. Archived MODIS data, acquired ~daily from 2000 to 2012, were used to investigate seasonal thermal cycles at three volcanic areas with different types of thermal features: Mount St. Helens, which had a dacite dome-building eruption from 2004-2008; Mount Ruapehu, which has a 500-m diameter active summit crater lake; and Yellowstone, which is a large active geothermal system that has hundreds of hot springs and fumarole fields spread out over a very large area. The focus has been on using MODIS 1-km sensor radiance data in the MIR and TIR wavelength regions that are sensitive to thermal emission from features that range in temperature from hundreds of °C, down to tens of °C (below the boiling temperature

  17. Downwelling and upwelling radiance distributions sampled under cloudless conditions in Antarctica.

    PubMed

    Cordero, Raul R; Damiani, Alessandro; Ferrer, Jorge; Rayas, Juan; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Laroze, David

    2013-09-01

    We have sampled both the downwelling and upwelling radiance distributions at a camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46' S, 82° 52' W). The measurements (at 320-440 nm wavelength range) were carried out under cloudless conditions by using a sky scanner system, during a campaign (in December, 2012) meant to assess the effects of the high albedo on the radiance distribution. The angular variations observed in both the downwelling and upwelling radiance distributions increase with the wavelength. However, these variations were considerably greater in the case of the downwelling radiance than in the case of the upwelling radiance. Indeed, we found that downwelling radiance tends to be less isotropic than the corresponding upwelling radiance. Regardless of the solar zenith angle and the wavelength, the minima of the downwelling and the upwelling radiance distributions were measured close to the zenith and to the nadir, respectively. The downwelling (upwelling) radiance increased nearly monotonically toward the horizon and peaked at zenith (nadir) angles that ranged from 75° to 90°. Comparisons with the UVSPEC radiative transfer model were used to weight up the response of the downwelling radiance distribution to changes in the albedo. PMID:24085089

  18. POLCAL - POLARIMETRIC RADAR CALIBRATION

    NASA Technical Reports Server (NTRS)

    Vanzyl, J.

    1994-01-01

    Calibration of polarimetric radar systems is a field of research in which great progress has been made over the last few years. POLCAL (Polarimetric Radar Calibration) is a software tool intended to assist in the calibration of Synthetic Aperture Radar (SAR) systems. In particular, POLCAL calibrates Stokes matrix format data produced as the standard product by the NASA/Jet Propulsion Laboratory (JPL) airborne imaging synthetic aperture radar (AIRSAR). POLCAL was designed to be used in conjunction with data collected by the NASA/JPL AIRSAR system. AIRSAR is a multifrequency (6 cm, 24 cm, and 68 cm wavelength), fully polarimetric SAR system which produces 12 x 12 km imagery at 10 m resolution. AIRSTAR was designed as a testbed for NASA's Spaceborne Imaging Radar program. While the images produced after 1991 are thought to be calibrated (phase calibrated, cross-talk removed, channel imbalance removed, and absolutely calibrated), POLCAL can and should still be used to check the accuracy of the calibration and to correct it if necessary. Version 4.0 of POLCAL is an upgrade of POLCAL version 2.0 released to AIRSAR investigators in June, 1990. New options in version 4.0 include automatic absolute calibration of 89/90 data, distributed target analysis, calibration of nearby scenes with calibration parameters from a scene with corner reflectors, altitude or roll angle corrections, and calibration of errors introduced by known topography. Many sources of error can lead to false conclusions about the nature of scatterers on the surface. Errors in the phase relationship between polarization channels result in incorrect synthesis of polarization states. Cross-talk, caused by imperfections in the radar antenna itself, can also lead to error. POLCAL reduces cross-talk and corrects phase calibration without the use of ground calibration equipment. Removing the antenna patterns during SAR processing also forms a very important part of the calibration of SAR data. Errors in the

  19. Calibration of X-Ray Observatories

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.; L'Dell, Stephen L.

    2011-01-01

    Accurate calibration of x-ray observatories has proved an elusive goal. Inaccuracies and inconsistencies amongst on-ground measurements, differences between on-ground and in-space performance, in-space performance changes, and the absence of cosmic calibration standards whose physics we truly understand have precluded absolute calibration better than several percent and relative spectral calibration better than a few percent. The philosophy "the model is the calibration" relies upon a complete high-fidelity model of performance and an accurate verification and calibration of this model. As high-resolution x-ray spectroscopy begins to play a more important role in astrophysics, additional issues in accurately calibrating at high spectral resolution become more evident. Here we review the challenges of accurately calibrating the absolute and relative response of x-ray observatories. On-ground x-ray testing by itself is unlikely to achieve a high-accuracy calibration of in-space performance, especially when the performance changes with time. Nonetheless, it remains an essential tool in verifying functionality and in characterizing and verifying the performance model. In the absence of verified cosmic calibration sources, we also discuss the notion of an artificial, in-space x-ray calibration standard. 6th

  20. Redetermining CEBAF's Absolute Energy

    NASA Astrophysics Data System (ADS)

    Su, Tong; Jlab Marathon Collaboration

    2015-04-01

    With the upgrade of the Jefferson Lab accelerator (CEBAF) from 6 GeV max energy to 12 GeV, all the dipole magnets in the machine were refurbished. Most of them were switched from open c-shaped to closed h-shaped by adding extra iron. With these upgraded magnets, the energy calibration of the accelerator needed to be redetermined. We will show how an extra external dipole, which is run in series with those in the machine, helps us cross check the current in the magnets as well as precisely map out the integral field for any machine setting. Using knowledge of the relative performance of the dipoles as well as the bend angle into the Hall, has allowed us to already determine a 4th pass 7 GeV beam to better than 7 MeV. In the future, we will use g-2 spin precession as a second independent energy determination. This work is supported by Kent State University, NSF Grant PHY-1405814, and DOE Contract DE-AC05-06OR23177 (JLab).

  1. Method to obtain absolute impurity density profiles combining charge exchange and beam emission spectroscopy without absolute intensity calibrationa)

    NASA Astrophysics Data System (ADS)

    Kappatou, A.; Jaspers, R. J. E.; Delabie, E.; Marchuk, O.; Biel, W.; Jakobs, M. A.

    2012-10-01

    Investigation of impurity transport properties in tokamak plasmas is essential and a diagnostic that can provide information on the impurity content is required. Combining charge exchange recombination spectroscopy (CXRS) and beam emission spectroscopy (BES), absolute radial profiles of impurity densities can be obtained from the CXRS and BES intensities, electron density and CXRS and BES emission rates, without requiring any absolute calibration of the spectra. The technique is demonstrated here with absolute impurity density radial profiles obtained in TEXTOR plasmas, using a high efficiency charge exchange spectrometer with high etendue, that measures the CXRS and BES spectra along the same lines-of-sight, offering an additional advantage for the determination of absolute impurity densities.

  2. [Spectral radiometric calibration research of Quick Bird digital image].

    PubMed

    Zhang, Guo-Kun; Chen, Chun; Xing, Fu; Zhang, Hong-Yan; Zhao, Yun-Sheng

    2008-03-01

    The present article uses the basic operation of the digital remote image radiometric calibration of the Quickbird with high distinguishing rate, including the physical attribute and the mathematical basement of digital images, the annotation as well as the format of image data. The study makes use of information of spectral radiance from the ground-atmosphere system, which is recorded by the digital remote image of Quick Bird in Honghe area. This dissertation offered the calculation means of radiometric calibration, and changed the pixel digital number into band-integrated radiance. Then, the spectral radiance was calculated. After the radiometric calibration, the Quick Bird image showed the quantitative information of spectral feature from various ground items. Only through the calibration can the Quick Bird image be quantitatively compared and analyzed with other remote sensor images. Thus, the inversion image has the value of application. The significance consists in offering important basic condition for the image amalgamation and better disposal of the special inforation pick-up. This effort also offered spectral information of the ground items for the inversion of the remote image. Therefore, the authors can combine the research of the spectral character of ground items with the establishment of the remote application model in order to quantitatively analyze the ground items.

  3. Colorimetric calibration of coupled infrared simulation system

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Fei, Jindong; Gao, Yang; Du, Jian

    2015-10-01

    In order to test 2-color infrared sensors, a coupled infrared simulation system can generate radiometric outputs with wavelengths that range from less than 3 microns to more than 12 microns. There are two channels in the coupled simulation system, optically combined by a diachronic beam combiner. Each channel has an infrared blackbody, a filter, a diaphragm, and diaphragm-motors. The system is projected to the sensor under testing by a collimator. This makes it difficult to calibrate the system with only one-band thermal imager. Errors will be caused in the radiance levels measured by the narrow band thermal imager. This paper describes colorimetric temperature measurement techniques that have been developed to perform radiometric calibrations of these infrared simulation systems above. The calibration system consists of two infrared thermal imagers; one is operated at the wavelength range of MW-IR, and the other at the range of LW-IR.

  4. Absolute Identification by Relative Judgment

    ERIC Educational Resources Information Center

    Stewart, Neil; Brown, Gordon D. A.; Chater, Nick

    2005-01-01

    In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…

  5. Be Resolute about Absolute Value

    ERIC Educational Resources Information Center

    Kidd, Margaret L.

    2007-01-01

    This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…

  6. RADIANCE AND PHOTON NOISE: Imaging in geometrical optics, physical optics, quantum optics and radiology

    PubMed Central

    Barrett, Harrison H.; Myers, Kyle J.; Caucci, Luca

    2016-01-01

    A fundamental way of describing a photon-limited imaging system is in terms of a Poisson random process in spatial, angular and wavelength variables. The mean of this random process is the spectral radiance. The principle of conservation of radiance then allows a full characterization of the noise in the image (conditional on viewing a specified object). To elucidate these connections, we first review the definitions and basic properties of radiance as defined in terms of geometrical optics, radiology, physical optics and quantum optics. The propagation and conservation laws for radiance in each of these domains are reviewed. Then we distinguish four categories of imaging detectors that all respond in some way to the incident radiance, including the new category of photon-processing detectors. The relation between the radiance and the statistical properties of the detector output is discussed and related to task-based measures of image quality and the information content of a single detected photon. PMID:27478293

  7. The thermal infrared radiance properties of dust aerosol over ocean

    NASA Astrophysics Data System (ADS)

    Hao, Zengzhou; Pan, Delu; Tu, Qianguang; Gong, Fang; Chen, Jianyu

    2015-10-01

    Asian dust storms, which can long-range transport to ocean, often occur on spring. The present of Asian dust aerosols over ocean makes some difficult for other studies, such as cloud detection, and also take some advantage for ocean, such as take nutrition into the ocean by dry or wet deposition. Therefore, it is important to study the dust aerosol and retrieve the properties of dust from satellite observations that is mainly from the thermal infrared radiance. In this paper, the thermal infrared radiance properties of dust aerosol over ocean are analyzed from MODIS and MTSAT2 observations and Streamer model simulations. By analyzing some line samples and a series of dust aerosol region, it shows that the dust aerosol brightness temperature at 12μm (BT12) is always greater than BT11 and BT8.5, and BT8.5 is general greater than BT11. The brightness temperature different between 11μm and 12μm (BTD11-12) increases with the dust intensity. And the BTD11-12 will become positive when the atmospheric relative humidity is greater than 70%. The BTD11-12 increases gradually with the surface temperature while the effect on BTD11-12 of dust layer temperature is not evident. Those are caused by the transmission of the dust aerosol is different at the two thermal infrared channels. During daytime, dust infrared brightness temperature at mid-infrared bands should reduce the visual radiance, which takes about 25K or less. In general, BT3.7 is greater than BT11 for dust aerosol. Those results are helpful to monitor or retrieve dust aerosol physical properties over ocean from satellite.

  8. Miniature High Stability High Temperature Space Rated Blackbody Radiance Source

    NASA Astrophysics Data System (ADS)

    Jones, J. A.; Beswick, A. G.

    1987-09-01

    This paper presents the design and test performance of a conical cavity type blackbody radiance source that will meet the requirements of the Halogen Occultation Experiment (HALOE) on the NASA Upper Atmospheric Research Satellite program (UARS). Since a radiance source meeting the requirements of this experiment was unavailable in the commercial market, a development effort was undertaken by the HALOE Project. The blackbody radiance source operates in vacuum at 1300 K + 0.5 K over any 15-minute interval, uses less than 7.5 watts of power, maintains a 49°C outer case temperature, and fits within the 2.5 x 2.5 x 3.0 inch envelope allocated inside the HALOE instrument. Also, the unit operates in air, during ground testing of the HALOE instrument, where it uses 17 watts of power with an outer case temperature of 66°C. The thrust of this design effort was to minimize the heat losses, in order to keep the power usage under 7.5 watts, and to minimize the amount of silica in the materials. Silica in the presence of the platinum heater winding used in this design would cause the platinum to erode, changing the operating temperature set-point. The design required the development of fabrication techniques which would provide very small, close tolerance parts from extremely difficult-to-machine materials. Also, a space rated ceramic core and unique, low thermal conductance, ceramic-to-metal joint was developed, tested and incorporated in this design. The completed flight qualification hardware has undergone performance, environmental and life testing. The design configuration and test results are discussed in detail in this paper.

  9. Active fire detection using a peat fire radiance model

    NASA Astrophysics Data System (ADS)

    Kushida, K.; Honma, T.; Kaku, K.; Fukuda, M.

    2011-12-01

    The fire fractional area and radiances at 4 and 11 μm of active fires in Indonesia were estimated using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. Based on these fire information, a stochastic fire model was used for evaluating two fire detection algorithms of Moderate Resolution Imaging Spectroradiometer (MODIS). One is single-image stochastic fire detection, and the other is multitemporal stochastic fire detection (Kushida, 2010 - IEEE Geosci. Remote Sens. Lett.). The average fire fractional area per one 1 km2 ×1 km2 pixel was 1.7%; this value corresponds to 32% of that of Siberian and Mongolian boreal forest fires. The average radiances at 4 and 11 μm of active fires were 7.2 W/(m2.sr.μm) and 11.1 W/(m2.sr.μm); these values correspond to 47% and 91% of those of Siberian and Mongolian boreal forest fires, respectively. In order to get false alarms less than 20 points per 106 km2 area, for the Siberian and Mongolian boreal forest fires, omission errors (OE) of 50-60% and about 40% were expected for the detections by using the single and multitemporal images, respectively. For Indonesian peat fires, OE of 80-90% was expected for the detections by using the single images. For the peat-fire detections by using the multitemporal images, OE of about 40% was expected, provided that the background radiances were estimated from past multitemporal images with less than the standard deviation of 1K. The analyses indicated that it was difficult to obtain sufficient active-fire information of Indonesian peat fires from single MODIS images for the fire fighting, and that the use of the multitemporal images was important.

  10. An improved retrieval of tropospheric NO2 from space over polluted regions using an Earth radiance reference

    NASA Astrophysics Data System (ADS)

    Anand, J. S.; Monks, P. S.; Leigh, R. J.

    2015-03-01

    A novel tropospheric NO2 DOAS retrieval algorithm optimised for a nadir-viewing satellite instrument imaging polluted areas is proposed in this work. Current satellite DOAS retrievals have relied on using a solar reference spectrum to derive a total slant column, then using either model assimilation or spatial filtering to derive the tropospheric component. In the ERrs-DOAS (Earth radiance reference sector DOAS) algorithm, tropospheric NO2 slant columns are derived using spectra averaged from measurements over unpolluted regions, thus removing the need for post-hoc separation techniques, though some residual stratospheric biases may still remain. To validate the ERrs-DOAS algorithm, DOAS retrievals were performed on modelled spectra created by the radiative transfer model SCIATRAN, as well as L1B Earth radiance data measured by the NASA/KNMI Ozone Monitoring Instrument (OMI). It was found that retrievals using an Earth radiance reference produce spatial distributions of tropospheric NO2 over eastern China during June 2005 that highly correlate with those derived using existing retrieval algorithms. Comparisons with slant columns retrieved by the operational NO2 retrieval algorithm for OMI (OMNO2A) show that the ERrs-DOAS algorithm greatly reduces the presence of artificial across-track biases (stripes) caused by calibration errors, as well as the removal of path length enhancement in off-nadir pixels. Analysis of Pacific SCDs suggests that the algorithm also produces a 27% reduction in retrieval uncertainty, though this may be partially due to biases introduced by differences in the retrieval algorithm settings. The ERrs-DOAS technique also reveals absorption features over the Sahara and similar regions characteristic of sand and liquid H2O absorption, as first discovered in the analysis of GOME-2 NO2 retrievals.

  11. On the Use of Deep Convective Clouds to Calibrate AVHRR Data

    NASA Technical Reports Server (NTRS)

    Doelling, David R.; Nguyen, Louis; Minnis, Patrick

    2004-01-01

    Remote sensing of cloud and radiation properties from National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) satellites requires constant monitoring of the visible sensors. NOAA satellites do not have onboard visible calibration and need to be calibrated vicariously in order to determine the calibration and the degradation rate. Deep convective clouds are extremely bright and cold, are at the tropopause, have nearly a Lambertian reflectance, and provide predictable albedos. The use of deep convective clouds as calibration targets is developed into a calibration technique and applied to NOAA-16 and NOAA-17. The technique computes the relative gain drift over the life-span of the satellite. This technique is validated by comparing the gain drifts derived from inter-calibration of coincident AVHRR and Moderate-Resolution Imaging Spectroradiometer (MODIS) radiances. A ray-matched technique, which uses collocated, coincident, and co-angled pixel satellite radiance pairs is used to intercalibrate MODIS and AVHRR. The deep convective cloud calibration technique was found to be independent of solar zenith angle, by using well calibrated Visible Infrared Scanner (VIRS) radiances onboard the Tropical Rainfall Measuring Mission (TRMM) satellite, which precesses through all solar zenith angles in 23 days.

  12. Stratospheric thickness determined directly from satellite radiance measurements.

    NASA Technical Reports Server (NTRS)

    Quiroz, R. S.; Gelman, M. E.

    1972-01-01

    Discussion of the use of satellite radiance data for determining the thickness of deep stratospheric layers. Empirical regression equations are shown to provide better estimates of stratospheric thickness than do mean weighted temperatures obtained from the Planck equation. The best regression equations were found for thick layers emitting a substantial portion of the CO2-band infrared radiation measured by satellites. By adding the layer thickness to the observed height field for the lower boundary, it is possible to construct constant-pressure maps at very high altitudes.

  13. Mesoscale Gravity Wave Variances from AMSU-A Radiances

    NASA Technical Reports Server (NTRS)

    Wu, Dong L.

    2004-01-01

    A variance analysis technique is developed here to extract gravity wave (GW) induced temperature fluctuations from NOAA AMSU-A (Advanced Microwave Sounding Unit-A) radiance measurements. By carefully removing the instrument/measurement noise, the algorithm can produce reliable GW variances with the minimum detectable value as small as 0.1 K2. Preliminary analyses with AMSU-A data show GW variance maps in the stratosphere have very similar distributions to those found with the UARS MLS (Upper Atmosphere Research Satellite Microwave Limb Sounder). However, the AMSU-A offers better horizontal and temporal resolution for observing regional GW variability, such as activity over sub-Antarctic islands.

  14. The Clouds and the Earth's Radiant Energy System (CERES) Sensors and Preflight Calibration Plans

    NASA Technical Reports Server (NTRS)

    Lee, Robert B., III; Barkstrom, Bruce R.; Smith, G. Louis; Cooper, John E.; Kopia, Leonard P.; Lawrence, R. Wes; Thomas, Susan; Pandey, Dhirendra K.; Crommel