Assessment of the radiometric calibration accuracy of the thermal emissive bands onboard the NOAA-21 visible infrared imaging radiometer suite and cross-comparison with S-NPP and NOAA-20

Abstract

There are currently three Visible Infrared Imaging Radiometer Suite (VIIRS) sensors in orbit onboard the S-NPP (15 years), NOAA-20 (9 years), and NOAA-21 (4 years) spacecraft; with two others, JPSS-4 and JPSS-3, planned for launch in 2027 and 2032, respectively. VIIRS provides continuous observations of the Earth’s surface and is considered the successor to the legacy left by the MODIS instruments onboard the Terra and Aqua satellites. VIIRS has 7 thermal emissive bands (TEB) whose center wavelengths range from 3.7 to 12.0 μm. Routine post-launch calibrations are performed using the sensor’s onboard blackbody and space view port, and vicarious targets that include the ocean and Dome Concordia (Dome C) in Antarctica. Maintaining the radiometric calibration accuracy of each VIIRS instrument, as well as the consistency between the satellite retrievals from the three instruments is essential in generating a reliable multi-year data record for the long-term monitoring of the Earth’s surface using the NASA Science Investigator-led Processing System (SIPS) Level 1B (L1B) data. This manuscript assesses the NOAA-21 VIIRS TEB radiometric calibration accuracy using vicarious calibration practices via measurements over Dome C and the ocean, as well as an intersensor comparison using simultaneous nadir overpasses with the Infrared Atmospheric Sounding Interferometer (IASI) sensor onboard the MetOp satellite series. The mission-long trends of the NOAA-21 VIIRS TEB are presented, and their cross-comparison with the corresponding bands onboard S-NPP and NOAA-20 is also discussed. Results show that, after 4 years of mission, the NOAA-21 VIIRS TEB time series are stable. Additionally, the cross-comparison indicates consistency between the three VIIRS sensors. This thorough assessment serves as a robust record containing a summary of the NOAA-21 VIIRS TEB calibration performance as well as the consistency between the VIIRS sensors.