NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Day-Night Band Calibration Using the Scheduled Lunar Collections

As a panchromatic band, the Day-Night Band (DNB) on National Oceanic Atmospheric Administration (NOAA)-20 Visible Infrared Imaging Radiometer Suite (VIIRS) has a unique capability of observing very low radiances down to Nano-watt [cm−1 sr−1] level, because of its three different focal planes with gain stages. The DNB radiometric calibration is based on the Solar Diffuser observations near the night to day time termination points. Besides the primary calibration source of SD, the moon provides alternative source of calibration with a specific lunar roll maneuvers. This study provides detailed methodology and results of lunar calibration for NOAA-20 VIIRS sensor and initial two year DNB radiometric calibration results from SD and scheduled lunar calibration. Over two years of NOAA-20 VIIRS operation, the Low Gain Stage (LGS) slope (inverse gain) trend showed a decreasing trend, whereas the calculated monthly lunar F-factor showed a stable response (inverse gain normalized to the lunar irradiance model) using a lunar irradiance model. These differences are monitored, compared, and applied for the best quality of NOAA-20 VIIRS DNB product.