In Situ Measurements of Thermal Environment on the Moon's Surface Revealed by the Chang'E-4 And Chang'E-5 Missions

The thermal environment of the lunar surface is of crucial importance for the lander thermal design and the interpretation of scientific data. Clarifying the radiative sources and intensity on the outer surface of the lander is one of the key aspects of lander thermal design. The installation of temperature sensors on the body of the Chang'e-4 (CE-4) and Chang'e-5 (CE-5) landers has provided valuable opportunities for quantifying the influence of lunar thermal conditions on the surface temperature of the lander. In this study, we established a temperature model for the near-surface regolith and a heat transfer model based on the observations from sensors installed on the body of the lander and auxiliary pillars. By integrating factors, such as the density of the lunar regolith, the thermal conductivity of the lunar regolith, and the relative positions of the temperature measurement points to the Earth and the Sun, we conducted analyzes on the temperature measurement data for both CE-4 and CE-5, respectively. Our results indicate that during the daytime of the Moon, the temperature of the lander's surface is mainly influenced by solar radiation and the infrared thermal radiation from the lunar surface. During the nighttime of the Moon, the heat transferred outward from the inside of the lander plays a key role in the temperature of the outer surface of the lander. The lunar surface thermal environment significantly affects the temperatures of both the shaded and sunny sides of the lander, with its influence on the shaded side even surpassing that on the sunny side. The lunar surface's thermal environment directly impacts the stability and reliability of the electronic components within scientific payloads. Our results offer dependable lunar thermal environment parameters for the design of scientific instruments on future lunar landers and the deployment of instruments in their designated positions.