On the Study of the Absolute On-orbit Calibration Consistency between ATMS Instruments

The Advanced Technology Microwave Sounder (ATMS) is a passive microwave radiometer for the current generation of polar-orbiting meteorological satellites operated by the National Oceanic and Atmospheric Administration (NOAA). The first two ATMS instruments are manifested onboard the Suomi National Polar-orbiting Partnership (S-NPP) and NOAA-20 satellites. With the successful launch of NOAA-21 in November, 2022, there are currently three operational ATMS instruments running in the same orbit of 1:30pm ascending node. Based on the ground Thermal Vacuum Test (T-VAC) data and the post-launch CAL/VAL test results of NOAA-21, several critical improvements have been made to optimize the ATMS on-orbit calibration algorithm, which include:

• Dynamic antenna Earth side-lobe corrections to reduce the cold calibration bias;
• 2-D lunar contamination correction algorithm to improve the lunar brightness temperature calculation accuracy;
• New algorithm to mitigate the satellite near-field contamination

The new algorithms have been tested out in MiCalPS and ADL, results show that by implementing the new algorithms, the calibration difference between the three satellite can be reduced and the TDR/SDR product quality can be further improved for operational applications.