Effective Lunar Microwave Brightness Temperature Observed by MWHS-II Onboard FY-3C

• Published in: IEEE transactions on geoscience and remote sensing Vol. 63; pp. 1 - 9
• Main Authors: Zhou, Yu, Xie, Xinxin, Guo, Yang, He, Jieying, Han, Yong, Gu, Songyan
• Format: Journal Article
• Language: English
• Published: New York IEEE 2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Accuracy; Antennas; Brightness; Brightness temperature; Calibration; Electromagnetic heating; Identification methods; Instruments; Lunar intrusion; lunar microwave brightness temperature; Lunar phases; micro-wave humidity sounder-II (MWHS-II); Microwave integrated circuits; Microwave radiometry; Moon; Moon phases; Radiance; Satellite broadcasting; Satellites; Surface radiation temperature; Voltage measurement; Weather forecasting
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2025.3547344

Observations of the Micro-Wave Humidity Sounder-II (MWHS-II) onboard FengYun-3C (FY-3C) satellite are crucial for numerical weather prediction. Precise calibration of MWHS-II is fundamental for the accurate application. However, the Moon's presence in the deep space view (DSV) can corrupt the in-orbit calibration of MWHS-II, and thus it is necessary to quantify the Moon's influence. This study proposes a method to identify the Moon's intrusion into the DSV, which improves the accuracy of lunar identification, by taking into account the lunar phases and the detectable radiance change of the sensor. The abrupt jump in the DSV due to the lunar contamination is removed, assuming the radiometric gain of the adjacent scans barely changes. With the corrected DSV counts, the effective lunar brightness temperature (TB) is calculated. It is found that the phase of the Moon observed by the FY-3C MWHS-II is in the range of 95°-140°, and the effective lunar TB is up to 15 K at 89/118.75 GHz and 45-50 K at 150/183.31 GHz. Though the results are subject to the uncertainties of the Moon calculations and the beam pointing, this study offers unique insights into the lunar observations of MWHS-II onboard the polar-orbiting FY-3C.