Update on SNPP and NOAA-20 VIIRS day/night band stray light correction

Abstract

The VIIRS Day/Night Band (DNB) sensors onboard NOAA-20 and SNPP satellites, being 50 minutes apart along the same orbit, provide nighttime imagery of clouds, nocturnal lights, aurora etc., and have been used for a variety of studies involving both geophysical and socio-economic activities. DNB stray light has been observed over both the Northern and the Southern Hemisphere. The monthly stray light correction look-up-table has been routinely generated for operational DNB data production. The calibration algorithm of DNB was recently improved to reduce strong striping at the end aggregation zones for both SNPP and NOAA-20. In addition, there were remnant stray light of the magnitude ~1 nW/cm2- sr in the SNPP DNB image over the southern hemisphere resulting from the use of static yearly-recycled stray light correction look-up-tables (twelve sets) generated during 2014 and 2015. To address these issues, the stray light correction algorithm was improved to support operational SNPP DNB calibration since May 2019. For NOAA-20 DNB, to synchronize with the improved DNB calibration algorithm and maintain consistency between DNB stray light correction and calibration algorithm update, monthly DNB stray light correction LUTs have been routinely generated for one additional full year until November 2019. This paper reports the updates that have been performed for SNPP and NOAA- 20 DNB stray light correction and evaluates the improvements in DNB imagery products.