A New Method for Simulation of Lunar Microwave Brightness Temperatures and Evaluation of Chang'E-2 MRM Data Using Thermal Constraints From Diviner

We used the bolometric brightness temperatures (T-Bol) derived from the Lunar Reconnaissance Orbiters Diviner Lunar Radiometer (Diviner) as an upper boundary condition in our thermal model. We then calculated temperature profiles at any local time based on our improved thermal model at low to middle latitudes (70 degrees N/S). Based on the temperature profiles, we modeled the midnight brightness temperature at 19.35 (T-B19) and 37GHz (T-B37). Comparing to the Chang'E-1 and Chang'E-2 (CE-1/2) observations, we found that CE-1 showed a better data quality than that of CE-2, especially for the T-B37 data. Assuming that the issue with the CE-2 data is caused by heat contamination of the cold-reference antennas, we performed an empirical normalization of the CE-2 microwave radiometer data near midnight following the approach of Hu et al. (2017). The results show that T-B difference (modeled values minus modified T-B) for 19.35GHz is less than 3.40K for approximate to 80% of the pixels. At 37GHz, approximate to 67% of the pixels have T-B difference less than 2.88K. Additionally, we identified some areas of low microwave temperature in our modified T-B maps. These low-T-B features can be characterized by two types: (1) low T-B spots at fresh craters with high rock abundance and bright rays and (2) high-Ti lunar mare surfaces with a low content of rock fragments. Investigating these low-T-B regions with the modified T-B data can reveal more information about subsurface thermal regime and properties and help us better understand the evolution of regolith on the Moon. Plain Language Summary We proposed a new method to simulate the microwave brightness temperature of the Moon using surface thermal constraints from Lunar Reconnaissance Orbiter Diviner data. We evaluated the Chang'E-1/2 microwave radiometer data and adjusted the midnight observations to account for its calibration uncertainties. Our results provide better constraints on the thermal regime in the subsurface. Of particular interest is microwave cold regions, the presence of which can be related to thermophysical and compositional properties of the regolith in these locations. The modified Chang'E-2 microwave data can also be applied to study the thermal evolution of the Moon