Built on strong heritage of the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, the Visible Infrared Imaging Radiometer Suite (VIIRS) carried on Suomi NPP (National Polar-orbiting Partnership) satellite (http://npp.gsfc.nasa.gov/viirs.html) has been in operation for nearly five fives. The on-board calibration of the VIIRS reflective solar bands (RSB) relies on a solar diffuser (SD) located at a fixed scan angle and a solar diffuser stability monitor (SDSM). The VIIRS response versus scan angle (RVS) was characterized prelaunch in lab ambient conditions and is currently used to determine the on orbit response for all scan angles relative to the SD scan angle. Since the RVS is vitally important to the quality of calibrated level 1B products, it is important to monitor its on-orbit stability. In this study, the RVS stability is examined based on reflectance trends collected from 16-day repeatable orbits over preselected pseudo-invariant desert sites in Northern Africa. These trends cover nearly entire Earth view scan range so that any systematic drifts in the scan angle direction would indicate a change in RVS. This study also compares VIIRS RVS on-orbit stability results with those from Aqua and Terra MODIS over the first four years of mission for a few selected bands, which provides further information on potential VIIRS RVS on-orbit changes.

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Aisheng Wu, Xiaoxiong (Jack) Xiong, and Changyong Cao, "Tracking on-orbit stability of the response versus scan angle for the S-NPP VIIRS reflective solar bands," Proc. SPIE 9972, Earth Observing Systems XXI, 99721C (Presented at SPIE Optical Engineering + Applications: September 01, 2016; Published: 19 September 2016); https://doi.org/10.1117/12.2238106.