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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.

1. 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.
   
   
2. 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.
   
   
3. 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.
   
   
4. 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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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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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