Brightness Temperature of Lunar Surface for Calibration of Multichannel Millimeter-Wave Radiometer of Geosynchronous FY-4M

摘要

One of Chinese meteorological satellites, Feng Yun-4M (FY-4M), as one the of new generation of geosynchronous series satellites, is planning to upload multichannel millimeter-wave radiometers, e.g., from 50 to 430 GHz. Due to long-period stability and no atmospheric interference, brightness temperature (TB) of the lunar surface can be seen as a good candidate for thermal calibration of FY-4M radiometers. In this paper, the physical temperature profile of lunar regolith media is first derived by resolving 1-D heat transfer equation with validation of the measurements of the Diviner lunar radiometer experiment onboard the lunar reconnaissance orbiter. Then, the loss tangent is fit and validated using the TiO2 abundances, which is derived from Clementine five-band multispectral data and Chinese Chang'e-2 37-GHz TB data. Multichannel TB of a lunar surface region along the moon equator at certain lunar time (noon and midnight) is numerically derived for all FY-4M channels. TB of lunar equator center area (0 degrees N, 0 degrees E) is presented with variation of the lunar local time. These results can be well applied to calibration of FY-4M, with a sustainable error in the range of 1.8 (425 GHz) to 3.8 K (89 GHz).