28 January 2017 Characterizing response versus scan-angle for MODIS reflective solar bands using deep convective clouds
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Abstract
MODIS consists of a cross-track, two-sided scan mirror, whose reflectance is not uniform but is a function of angle of incidence (AOI). This feature, known as response versus scan-angle (RVS), was characterized for all reflective solar bands of both MODIS instruments prior to launch. The RVS characteristic has changed on orbit, which must be tracked precisely over time to ensure the quality of MODIS products. The MODIS characterization support team utilizes the onboard calibrators and the earth view responses from multiple pseudoinvariant desert sites to track the RVS changes at different AOIs. The drawback of using deserts is the assumption that these sites are radiometrically stable during the monitoring period. In addition, the 16-day orbit repeat cycle of MODIS allows for only a limited set of AOIs over a given desert. We propose a novel and robust approach of characterizing the MODIS RVS using tropical deep convective clouds (DCC). The method tracks the monthly DCC response at specified sets of AOIs to compute the temporal RVS changes. Initial results have shown that the Aqua-MODIS collection 6 band 1 level 1B radiances show considerable residual RVS dependencies, with long-term drifts up to 2.3% at certain AOIs.
© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Rajendra Bhatt, Rajendra Bhatt, David R. Doelling, David R. Doelling, Amit Angal, Amit Angal, Xiaoxiong Xiong, Xiaoxiong Xiong, Benjamin R. Scarino, Benjamin R. Scarino, Arun Gopalan, Arun Gopalan, Conor O. Haney, Conor O. Haney, Aisheng Wu, Aisheng Wu, } "Characterizing response versus scan-angle for MODIS reflective solar bands using deep convective clouds," Journal of Applied Remote Sensing 11(1), 016014 (28 January 2017). https://doi.org/10.1117/1.JRS.11.016014 . Submission: Received: 15 July 2016; Accepted: 5 January 2017
Received: 15 July 2016; Accepted: 5 January 2017; Published: 28 January 2017
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