Validation of the Calibrated Microwave Lunar Radiative Transfer Model With the ATMS 2-D Moon Observations at Different Moon Phase Angles

The NOAA-21 ATMS, launched in November 2022, collected two-dimensional lunar scan data on March 10, 2023, during its commissioning phase at a Moon phase angle of 34°. The raw data were calibrated using MiCalPS, a microwave calibration and geolocation tool developed at the University of Maryland. Analysis showed that NOAA-21’s lunar antenna gain is generally lower than NOAA-20’s due to sampling rate differences. After correcting for beam pointing errors, disk-averaged lunar brightness temperatures (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DISK</sup><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>B</i>,Moon</sub>) were derived for 23–183 GHz. These were compared to NOAA-20 data at 0° phase angle and predictions from the microwave lunar radiative transfer model (ML-RTM). The observed model differences were: −3.3 K (K band), 0.01 K (V), 2.0 K (W), −2.3 K (low-G), and 1.6 K (high-G), consistent with predicted phase delay trends. Further observations at varying Moon phases are recommended to enhance MLRTM validation.