Characterization and correction of stray light for NOAA-20 VIIRS day/night band

Abstract

The Day/Night Band (DNB) onboard NOAA-20 is a continuation of the heritage nighttime imaging capability on SNPP VIIRS/DNB and supports a wide range of applications such as short-term weather prediction, disaster response and numerous socioeconomic applications. Stray light was observed both in northern and southern hemisphere for SNPP VIIRS/DNB and monthly correction look-up-table has been routinely generated for operational DNB data production. For NOAA-20 VIIRS/DNB, a few changes were introduced such as using Mode 21 to aggregate CCD detectors to form pixels beyond zone 21 due to the nonlinearity in the aggregation with higher mode number. A direct consequence of such aggregation mode change is the extension of the scan angle coverage counter-clockwise beyond that of SNPP, i.e. ~ 4.22 degree into the extended Earth view zone. Evaluation of NOAA-20 DNB performance revealed the appearance of strong and rapidly rising stray light in the extended zone while the overall stray light pattern within the same scan angle range is similar to those of SNPP DNB. This paper characterizes the NOAA-20 DNB stray light. New developments in the DNB stray light correction to address the new stray light features in NOAA-20 DNB are discussed together with the evaluation of the performance of stray light correction.