Calibration Support for NASA's Earth Observing System
Overview
NASA's Earth Observing System
(EOS)
is an international, multi-instrument, multi-platform satellite remote sensing
program designed to produce long time series data on global climate change. EOS
constitutes the major component of NASA's Mission to Planet Earth (MTPE),
and data from EOS will be used as a guide for the implementation of
international environmental policies. The utility of these data in this regard
will depend on the accuracy of the calibration of the full ensemble of EOS
instruments on the multiple platforms flown over the duration of the EOS
mission. This calibration will require an unprecedented level of accuracy and
long term measurement stability.
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Statement of Work
Statement of Work with
NASA
Given the importance and technologically challenging nature of the
EOS calibration task, the National Institute of
Standards and Technology (NIST)
Optical Technology Division will
perform the following key roles in the EOS calibration from FY'95 through
FY'00.
- NIST will (1) assist the EOS project in identifying areas in the
calibration of each EOS instrument which requires the transfer of NIST
radiometric or metrological scales and (2) develop and implement
measurement methods, techniques, and instrumentation to transfer these
NIST absolute radiometric and metrological scales to those
instruments. Instrumentation developed by NIST will include
radiometers operating in the visible/near infrared (VNIR), the short
wave infrared (SWIR), and the thermal infrared (TIR).
A key activity in this regard will be the participation by the EOS
instrument teams, laboratories with direct ties to the EOS program
(e.g., vicarious calibration programs), and NIST in joint NASA/NIST
directed round-robin measurement comparisons employing NIST standards
and NIST radiance scale artifacts. Series of round-robin comparison
measurements in areas such as target reflectance, detector aperture
area, and filter transmission will be conducted prelaunch at EOS
instrument builder facilities and EOS vicarious calibration
laboratories and postlaunch at EOS vicarious calibration laboratories.
Joint NASA/NIST directed round-robin campaigns will also be held
periodically at NIST. NIST will review the optimal calibration and
recalibration schedules determined by NASA for the suite of EOS
instruments. The existing radiometric measurement facilities at NIST
and NIST facilities designed in response to EOS calibration needs will
be available to EOS instruments.
- During the EOS program, NIST will interface directly with the
instrument manufacturers and EOS scientists and engineers who are
responsible for the calibration of individual instruments. This
interaction will include participation in NASA/NIST sponsored
workshops in metrology and radiometry. It is anticipated that these
technical interactions will permit NIST to disseminate their
state-of-the-art expertise in these areas to EOS instruments.
- NIST will participate in a detailed technical review capacity in
the critical design reviews, calibration peer reviews, and calibration
critical design reviews of EOS instruments.
- The ultimate goal of this program with NIST is to establish and
maintain a radiometric and metrologic calibration capacity which will
enable NASA to calibrate and characterize current and future EOS
instruments, other
MTPE
instruments, and international instruments at the required levels of
accuracy and precision/confidence. It is anticipated that
participation by NIST in the aforementioned areas of the EOS
calibration program will enable the production by EOS instruments of
long time scale global change data sets which are not only accurate
but also on the same calibration scales as instruments on the same and
successive platforms.
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Goals and Accomplishments
In the visible and near infrared, the radiometric measurements by
the scientific community in the remote sensing of the Earth and its
environment are generally traceable to NIST through the lamp standards
of spectral irradiance, which are calibrated on FASCAL. In the
thermal infrared, the radiometric measurements are traceable to NIST using
resistance
thermometers and modeling to realize blackbody sources. However, these
links are indirect. To ensure the accuracy of the measurements, the EOS
Project Science Office and NIST has developed a program that allows for
direct comparison of spectral radiance, provides for intercomparisons
and training, and ensures that NIST personnel participate in EOS
calibration peer reviews.
For radiance comparisons in the visible and near infrared (to 870 nm), a
6-channel filter Visible Transfer Radiometer (VXR) was designed and built. The
VXR is an improved version of the SeaWiFS Transfer Radiometer
(SXR).
For radiance comparisons in the near and short wave infrared, the Short Wave
Infrared Transfer Radiometer (SWIXR) was built. It utilizes a monochromator to
cover the spectral interval from 800 nm to 2500 nm. For radiance
comparisons in the thermal infrared, a two-channel, vacuum-compatible filter
radiometer was designed and built. This instrument is named the Thermal
Infrared Transfer Radiometer
(TXR). The
VXR has been used to measure the radiance of the integrating sphere sources
used to calibrate the Moderate Resolution Imaging Spectrometer
(MODIS),
the Multi-angle Imaging Spectrometer (MISR),
and the visible radiometer in the Advanced Spaceborne Thermal Emission and
Reflection Radiometer
(ASTER).
The SWIXR has also been used to measure the spectral radiance of the MODIS
sphere source. The first deployment of the TXR is scheduled for 1998, in
support of field measurements of ASTER validation experiments such as the one in
June 1997. In addition to the portable radiometers, a NIST large area water
bath blackbody was transported to the Rosenstiel School of Marine and
Atmospheric Science for an intercomparison in support of sea surface
temperature.
Finally, an intercomparison for bi-directional reflectance distribution
function (BRDF) was carried out, with NIST, NASA's Goddard Space Flight
Center, and various EOS participants.
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EOS/NIST Publication List
Butler, J.J. and Johnson, B.C.,
"EOS radiometric measurement comparisons at NEC Corporation and
Mitsubishi Electric Corporation,"
The Earth Observer, A Bimonthly EOS Publication
9(1), 15-17 (1997).
Early, E.A. and Johnson, B.C., in E-n. Yeh, Barnes, R.A., Darzi, M.,
Kumar, L., Early, E.A., Johnson, B.C., and Mueller, J.L.,
"Calibration and characterization of the GSFC sphere,"
NASA Tech Memo. 104566
41, Hooker, S.B. and Firestone, E.R., Eds.,
NASA Goddard Space Flight Center, Greenbelt, MD, 3-17 (1997).
Butler, J.J. and Johnson, B.C.,
"Calibration in the EOS Project Part 2: Implementation,"
The Earth Observer
8
(2),
26
(1996).
Butler, J.J. and Johnson, B.C.,
"EOS radiometric measurement comparisons at Hughes Santa Barbara
remote sensing and NASA's Jet Propulsion Laboratory,"
The Earth Observer
8(5), 17 (1996).
Butler, J.J. and Johnson, B.C.,
"Organization and implementation of calibration in the EOS project
-Part 1,"
The Earth Observer 8(1), 22 (1996).
Rice, J.P. and Johnson, B.C.,
"A NIST thermal infrared transfer standard radiometer for the EOS program,"
The Earth Observer 8(3), 31 (1996).
Sakuma, F., Johnson, B.C., Biggar, S.F., Butler, J.J.,
Cooper, J.W., Hiramatsu, M., and Suzuki, K.,
"EOS AM-1 preflight radiometric measurement comparison using the
advanced spaceborne thermal emission and reflection radiometer (ASTER)
visible/near-infrared integrating sphere,"
SPIE 2820 (1996).
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Online: September 1997 - Last updated: March 2002
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