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7 September 2018 On-orbit performance of the Terra and Aqua MODIS solar diffuser stability monitor
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The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on-board the Terra and Aqua space- craft are equipped with several on-board calibrators (OBCs) and continue to operate normally since launch. One such calibrator is the solar diffuser (SD), which allows for the calibration of the 20 reflective solar bands (RSBs) with wavelengths ranging from 0.41 to 2.3 μm. In order to accurately characterize the RSBs on-orbit, the changes associated with the SD bi-directional reflectance factor (BRF) are tracked using a solar diffuser stability monitor (SDSM). The SDSM consists of nine detectors located within a spherical integration source (SIS) and covers wavelengths from 0.41 to 0.94 μm. During each calibration event, the SDSM alternately views sunlight through an attenuation screen and the sunlight reflected from the SD in order to accurately characterize the degradation of the SD at those nine wavelengths. This paper provides a brief overview of the SD/SDSM calibration and operation, with more emphasis on the recent performance of the SD degradation and the SDSM detectors. A methodology to compute the signal-to-noise ratio (SNR) for each of the SDSM detectors is formulated and the noise performance is tracked over the mission lifetime. The importance of the detector noise to the RSB calibration uncertainty and to other instruments, such as the VIIRS SDSM, is also discussed.
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Emily J. Aldoretta, Kevin A. Twedt, Amit Angal, Hongda Chen, and Xiaoxiong Xiong "On-orbit performance of the Terra and Aqua MODIS solar diffuser stability monitor", Proc. SPIE 10764, Earth Observing Systems XXIII, 107641O (7 September 2018);

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