Radiometric Measurement Comparisons Using Transfer Radiometers in Support of the Calibration of NASA

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Radiometric Measurement Comparisons Using
Transfer Radiometers in Support of the
Calibration of NASAs Earth Observing System
(EOS) SensorsEOS/SPIE Symposium on Remote
SensingFlorence, ItalySeptember 22, 1999
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James J. Butler-NASAs Goddard Space Flight
CenterB. Carol Johnson-National Institute for
Standards and TechnologySteven W. Brown-National
Institute for Standards and TechnologyHoward Y.
Yoon-National Institute for Standards and
TechnologyBrian L. Markham-NASAs Goddard Space
Flight CenterRobert. A. Barnes-SAIC General
Sciences CorporationStuart F. Biggar-U. of
Arizona Optical Sciences CenterEdward F.
Zalewski-U. of Arizona Optical Sciences
CenterPaul R. Spyak-U. of Arizona Optical
Sciences CenterJohn W. Cooper-Raytheon
STXFumihiro Sakuma-National Research Laboratory
of Metrology
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The Earth Observing System and Calibration

• EOS is an 8 year, multi-satellite,
  multi-instrument program in remote sensing of the
  Earth.
• EOS, in its entirety, includes satellite
  instruments making global measurements and
  ground-based and airborne instruments involved in
  vicarious calibration.
• An on-going, radiometric, calibration challenge
  in EOS is to ensure all remote sensing
  instruments are placed on a common scale.
• In the visible through shortwave infrared
  wavelength regions, stable, transfer radiometers
  are being used to validate the calibration of
  integrating sphere sources employed in the
  calibration of EOS satellite, ground-based, and
  airborne instruments.

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EOS Radiometric Measurement Comparison Goals

• To validate the calibration of integrating
  spheres over the output radiance ranges utilized
  when the spheres are used to calibrate EOS
  satellite, ground-based, and airborne
  instruments.
• To measure the stability of the radiance obtained
  from the integrating spheres using the transfer
  radiometers as sphere monitors.
• To measure the repeatability of the radiance
  obtained from the integrating spheres.
• To review the overall operation, measurement
  procedures, and documentation of the operation of
  the integrating spheres by the EOS instrument
  calibration institutions (i. e. the sphere
  owners).

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The Visible/Near Infrared Transfer Radiometers
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The Shortwave Infrared Transfer Radiometers
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EOS Radiometric Measurement Comparisons
1995-1999  
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EOS Radiometric Measurement Comparison
Preliminary Results

• The preliminary results presented are those
  reported at by the participants at the end of
  each measurement day (a.k.a. rapid results).
• Data are presented in the following areas
• Typical agreement of radiance measurements at
  441nm and 661nm
• Short-time stability of the UA integrating sphere
  as measured by a sphere monitor detector and a
  transfer radiometer
• Day to day repeatability of the SBRS integrating
  sphere as determined using a transfer radiometer

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EOS Radiometric Measurement Comparison On-going
Work

• Standardization of the methods of reporting,
  analyzing, comparing, and archiving data from
  measurement comparisons.
• Augmentation of the number of comparisons between
  the shortwave infrared radiometers to better
  assess their overall level of agreement.

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EOS Radiometric Measurement Comparison Conclusions

• The good agreement between the transfer
  radiometers (within ?2.5 in the blue and within
  ?1.7 in the red) lends confidence in the use of
  transfer radiometers to validate the radiance
  scales assigned to integrating sphere sources
  used in the calibration of EOS instruments.
• In order to validate sphere radiance to better
  than 3-5 (i.e. typical EOS instrument
  radiometric calibration accuracy requirements),
  sphere repeatability and stability must be
  measured and archived and sphere operation must
  be fully documented over the time of the
  radiometric measurement comparison.