Re-Evaluation of Lunar Regolith Thickness Using Relative Microwave Brightness Temperature of Chang’E-2 Microwave Radiometer

Abstract

The exploration of the Moon has never ceased. One of the most significant challenges is determining the thickness of the lunar regolith. This letter employs the relative microwave brightness temperature (TB) to invert the thickness of the lunar regolith. A multilayer parallel stratified model serves as the forward model. In the inversion process, the simulated microwave TB is derived by calculating the sum of the TB contributions from each layer. Based on the forward model, the areas where the simulated TB is sensitive to lunar regolith thickness can be identified. Subsequently, the simulated TB is compared with the measured TB by the Chang’E-2 Microwave Radiometer (MRM) at 3 GHz at midnight (24:00) of the lunar local time. The discrepancy between the observed and modeled TB at a specified location, such as the Apollo 12 landing site (A12), is regarded as a correction for the simulated TBs at other locations with the same latitude. Ultimately, the thickness of the regolith is inverted according to the corrected simulated TB. This letter compares the inverted result with the regolith thickness obtained by DEM data. It is found that regions where the model inverted results closely align with the DEM data tend to have higher FeO/TiO2 content. The uncertainty of the inversion is also discussed, which indicates that the method presented in this letter is feasible.