A Recalibration Model Based on the Statistical Regression Analysis Method to Align the Microwave Data of Chang'E-1 and Chang'E-2

The two microwave radiometers (MRMs) onboard the Chinese Lunar explorers Chang'E-1 (CE-1) and Chang'E-2 (CE-2) are considered to be identical instruments, yet the results differ, with lunar brightness temperatures obtained by CE-2 generally lower than those of CE-1 in all four frequency channels. The differences can reach over 10 K in the same local time. We propose a recalibration model that takes into account the brightness temperature constant shift of the MRM equipment and the possibility that the Chang'E calibration antennas may have inadvertently picked up some thermal radiation from the lunar surface due to its field of view cutting into the lunar surface. These effects may have negatively influenced the accuracy of the simple two-point calibration procedure and led to the difference between the available MRM level 2C data from CE-1 and CE-2. Our recalibration model determines the correction parameters through a statistical analysis that minimizes the mismatch between the two datasets. Recalibration of the level 2C data based on our recalibration model successfully realigns the microwave brightness temperatures measured by CE-1 and CE-2.