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Status of the MODIS spatial and spectral characterization and performance after recent SRCA operational changes

TitleStatus of the MODIS spatial and spectral characterization and performance after recent SRCA operational changes
Publication TypePresentation
Year of Publication2017
AuthorsLink, D., Z. Wang, K. A. Twedt, and X. Xiong
ProceedingsProc. SPIE - Earth Observing Systems XXII
MCST ConferenceSPIE - Earth Observing Systems XXII
KeywordsAqua; characterization; MODIS; spatial; spectral; SRCA; terra

There are two nearly identical MODIS instruments currently operating on-board the NASA EOS Terra and Aqua
spacecraft. Each MODIS is equipped with several on-board calibrators (OBCs) including a Spectro-Radiometric
Calibration Assembly (SRCA). The SRCA is a multi-configuration calibrator that aids in determining the performance
parameters of MODIS detectors on-orbit. Depending on its configuration, scheduled operations of the SRCA provide
measurements to assess the on-orbit radiometric, spatial, and spectral performance. The SRCA was designed to utilize
various combinations of three 10 Watt lamps and one 1 Watt lamp and included a spare of each type. On-orbit lamp
degradation and failures reduced the available number of 10 Watt lamps from four to two for each mission by 2006.
Over the past year, each instrument experienced an issue on-orbit. The nadir door of Terra MODIS closed as the
instrument was autonomously commanded into safe-mode after a spacecraft commanding issue. The instrument and
spacecraft operations were successfully recovered shortly after the event. For Aqua, a failure occurred for one of the two
remaining 10 Watt lamps. We investigate each issue as it relates to the SRCA’s operation and its ability to properly
characterize MODIS detector performance. For Terra MODIS, we present changes in MODIS spectral and spatial
performance due to changes in the instrument environment. In the case of Aqua MODIS, losing a lamp reduces the
output potential of the SRCA. We present the results from this impact and the adjustments made to calibration activities
to maximize the effectiveness of the remaining lamps.