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Proceedings Paper

Improvements in the on-orbit response versus scan-angle characterization for the MODIS ocean color bands
Author(s): Xu Geng; Amit Angal; Yonghong Li; Kevin Twedt; Xiaoxiong Xiong
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Paper Abstract

On-orbit characterization of the response versus scan-angle (RVS) is one of the most challenging aspects of the reflective solar band (RSB) calibration for the MODIS instruments onboard the Terra and Aqua spacecraft. The degradation of the solar diffuser, together with the lack of onboard calibrators (OBCs) to cover additional scan angles, other than the one for the lunar observations, has resulted in the use of Earth view responses from the pseudo-invariant desert sites to track the on-orbit RVS changes. This approach has been implemented in Collection 6 (C6) and C6.1 for bands 1-4, 8 and 9 of both instruments and also band 10 of Terra MODIS. As the missions continue to operate over a decade beyond their designed life and the instrument optics continue to degrade, it is expected that the OBC based RVS currently applied to other bands, specifically the high-gain ocean bands, will be inadequate to maintain the long-term calibration stability. An interband calibration approach is formulated and implemented in this paper. The proposed approach relies on the use of a spectrally matching stable reference band to evaluate the long-term calibration stability of the high-gain ocean bands that typically saturate while viewing the selected calibration deserts. Results from this approach indicate a noticeable drift for Terra MODIS bands 11 and 12 whereas the Aqua bands continue to show excellent temporal stability. These results are consistent with the corrections derived by the NASA Ocean Biology Processing Group (OBPG) and are expected to have minimum impacts on the downstream science products.

Paper Details

Date Published: 10 October 2019
PDF: 10 pages
Proc. SPIE 11151, Sensors, Systems, and Next-Generation Satellites XXIII, 1115124 (10 October 2019); doi: 10.1117/12.2532081
Show Author Affiliations
Xu Geng, Science Systems and Applications, Inc. (United States)
Amit Angal, Science Systems and Applications, Inc. (United States)
Yonghong Li, Science Systems and Applications, Inc. (United States)
Kevin Twedt, Science Systems and Applications, Inc. (United States)
Xiaoxiong Xiong, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 11151:
Sensors, Systems, and Next-Generation Satellites XXIII
Steven P. Neeck; Philippe Martimort; Toshiyoshi Kimura, Editor(s)

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