The Effects of VIIRS Spectral Response Differences between Suomi NPP and NOAA-20 for the Thermal Emissive Bands

The NOAA-20 satellite was successfully launched on November 18, 2017 into an afternoon orbit with local equator crossing time similar to 1:30pm, in the same orbital plane as that of the Suomi National Polar-orbiting Partnership (NPP) but with a time separation of half an orbit or similar to 50 minutes. The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard NOAA-20 will become the primary operational imager succeeding the VIIRS onboard Suomi NPP which has been in-orbit for more than six years. Although the VIIRS onboard Suomi NPP and NOAA-20 have identical design, there are small differences in the relative spectral response (RSR) in most bands. Previous studies have shown that minor differences in RSR can lead to a number of effects at detector level, such as striping. This study investigates the VIIRS RSR differences between Suomi NPP and NOAA-20 for the Thermal Emissive Bands (TEB) including M12-M16. The Line-By-Line radiative transfer model (LBLRTM) is used at very high spectral resolution for convolving with the RSR of VIIRS on both satellites. The impact of RSR difference between Suomi NPP and NOAA-20 are evaluated for radiometric biases and potential striping in TEB. This study will contribute to the measurement consistency for the long term observations in the thermal infrared bands, and ensure the quality of the data produced by VIIRS, such as sea surface temperature (SST), fire and other retrievals.