Update of S-NPP VIIRS On-orbit Calibration and Performance

Launched in October, 2011, the S-NPP VIIRS has successfully operated for about 5 years. The VIIRS sensor collects data in 22 spectral bands, covering wavelengths from 0.4 to 12.4 μm. It includes a day-night band (DNB) that can make observations over a very large dynamic range. The VIIRS reflective solar bands (RSB) are calibrated primarily by a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system. Its thermal emissive bands (TEB) are calibrated via an on-board blackbody (BB), nominally controlled at a constant temperature. In addition to the use of its on-board calibrators, the VIIRS makes lunar observations on a regular basis to support its RSB calibration. This paper provides an overview of S-NPP VIIRS on-orbit calibration activities, methodologies, and performance assessments. In general, VIIRS on-orbit calibration performance has met the design requirement for both RSB and TEB. Also illustrated in this paper are some recent studies undertaken to address various issues that could have potential impact on sensor calibration and characterization. Because of these efforts, the VIIRS on-orbit calibration is now made with improved SDSM screen vignetting function, reduced SD degradation uncertainty, and combined solar and lunar calibration approach for the RSB. Changes made and results derived from these studies will be discussed in this paper.