Gap-Sunlight-Intrusion Risk of a Moon Based Earth Radiation Observatory

A Moon-based Earth radiation observatory (MERO) could contribute to the better understanding of the Earth radiation budget by providing data with less nonsimultaneous sampling uncertainty and higher temporal resolution as well as better Earth polar region spatial-temporal coverage. Assessing the gap-sunlight-intrusion risk is a crucial step in the MERO protection unit design and operation planning. In this study, we proposed a new method to estimate such a risk taking into account the Earth atmosphere radiative refraction and attenuation as well as the entrance pupil irradiance of the MERO, which could find the new refracted-type risky events and eliminated the included “fake” risky incidents compared to current method solely based on Sun-Earth-Moon geometric analysis. As 18.6-years evaluation from Jan. 2021 to Sep. 2039 shows that gap-sunlight-intrusion risk annual duration ranges from 10 to 29 h. MERO-location-effect assessment exhibits that MERO location latitudinal change [from (0°E, 81°N) to (0°E, 81°S)] would result in an annual risky duration difference ranging from 0 to 5 h, and that induced by longitudinal MERO location change [from (80°E, 0°N) to (80°W, 0°S)] varied between 0 and 3 h. Total risky time occupies 0.23% in the 18.6-years evaluation period (Jan. 2021 to Sep. 2039), which is about 2.56 times larger than that of the study only with consideration of the Sun-Earth-Moon geometry.