VIIRS reflective solar bands on-orbit calibration using solar diffuser and solar diffuser stability monitor

The reflective solar bands (RSB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (SNPP) satellite are primarily calibrated on-orbit by a solar diffuser (SD) panel whose performance is monitored by an accompanying solar diffuser stability monitor (SDSM). In this paper, the SD and SDSM calibration methodology is reviewed and the results from the analysis of the up-to-date three and half years of mission data are presented. With the newly derived product of the SD bidirectional reflectance factors, the vignetting functions for the screens in the SD/SDSM system and the carefully selected “sweet spots”, and the fully illumination region, the artificial seasonal patterns and noises in the derived SD degradation and the RSB calibration coefficients are removed or significantly reduced. The result shows that the SD degrades faster at short wavelengths while the RSB degrades in a much complex pattern.