VIIRS on-orbit calibration for ocean color data processing

The NASA VIIRS Ocean Science Team (VOST) has the task of evaluating Suomi NPP VIIRS ocean color data for the continuity of the NASA ocean color climate data records. The generation of science quality ocean color data products requires an instrument calibration that is stable over time. Since the VIIRS NIR Degradation Anomaly directly impacts the bands used for atmospheric correction of the ocean color data (Bands M6 and M7), the VOST has adapted the VIIRS on-orbit calibration approach to meet the ocean science requirements. The solar diffuser calibration time series and the solar diffuser stability monitor time series have been used to derive changes in the instrument response and diffuser reflectance over time for bands M1–M11. The lunar calibration observations have been used, in cooperation with the USGS ROLO Program, to derive changes in the instrument response over time for these same bands. In addition, the solar diffuser data have been used to develop detector-dependent striping and mirror side-dependent banding corrections for the ocean color data. An ocean surface reflectance model has been used to perform a preliminary vicarious calibration of the VIIRS ocean color data products. These on-orbit calibration techniques have allowed the VOST to produce an optimum timedependent radiometric calibration that is currently being used by the NASA Ocean PEATE for its VIIRS ocean color data quality evaluations. This paper provides an assessment of the current VIIRS radiometric calibration for the ocean color data products and discusses the path forward for improving the quality of the calibration.