Effects of time-varying relative spectral response on the calibration of MODIS reflective solar bands

Kevin A. Twedt; Amit Angal; Xiaoxiong Xiong

doi:10.1117/12.2321255

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7 September 2018 Effects of time-varying relative spectral response on the calibration of MODIS reflective solar bands

Kevin A. Twedt, Amit Angal, Xiaoxiong Xiong

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Proceedings Volume 10764, Earth Observing Systems XXIII; 1076413 (2018) https://doi.org/10.1117/12.2321255
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States

Abstract

Calibration of the on-orbit gain changes of the narrow bandwidth reflective solar bands (RSB) of Terra and Aqua MODIS is usually based on the band center wavelength. The relative spectral response (RSR) of each band is assumed to be constant on orbit and the time dependence of an overall gain factor is calculated. Any on-orbit changes to the RSR of the MODIS bands will introduce some error into the calibration and may also have an impact on the Earth scene radiance retrieval. We consider two different ways to track how the RSR of the MODIS RSB may be changing on orbit, and the effect that these changes will have on the calibration. First, we examine in-band RSR measurements from the spectro-radiometric calibration assembly (SRCA) carried on-board both MODIS instruments. Second, we study the broadband degradation of the MODIS scan mirror and how it may be changing the effective out-of-band response of the RSB. We find that RSR changes have a small effect on the radiance calibrated using the on-board solar diffuser, generally less than 0.5% in all cases at any time in the missions, with bands 1, 8, and 9 impacted the most.

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Kevin A. Twedt, Amit Angal, and Xiaoxiong Xiong "Effects of time-varying relative spectral response on the calibration of MODIS reflective solar bands", Proc. SPIE 10764, Earth Observing Systems XXIII, 1076413 (7 September 2018); https://doi.org/10.1117/12.2321255

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