Illumination and regolith temperature for China's candidate lunar landing sites with multiple scattering considerations

Abstract

Following the Chang'e-6 mission, China is planning a lunar landing and sampling mission at the Moon's South Pole, with a focus on volatile components such as water ice. To support future missions, this study combines orbital images with elevation data to reconstruct a three-dimensional (3D) model of the candidate landing region, producing a 1-m resolution digital elevation model (DEM). The DEM is then utilized to analyze the illumination conditions of the candidate landing site. A finite volume method is applied to solve the 1-dimensional (1D) heat conduction equation for the regolith, accounting for non-uniform density. Based on the high-resolution DEM and illumination data, we estimate the lunar regolith temperature at the candidate site. The main findings are as follows: (1) The high-resolution DEM accurately captures terrain details, and the simulated illumination closely matches observed image, validating the DEM and demonstrating the reliability of the illumination model for temperature simulations. (2) The candidate landing area, due to its elevation, receives sufficient illumination, enabling effective solar radiation throughout the lunar day. (3) Direct solar radiation is the primary heat source, with minor contributions from scattered solar and infrared radiation. Earth's reflected solar and longwave radiation have the least impact on the regolith temperature. (4) Surface temperatures fluctuate with short-term illumination cycles, while deeper layers (depth ≥ 0.18 m) remain more thermally stable. (5) Some regions at a depth of 0.18 m maintain temperatures below 112 K, indicating potential sites for volatile components sampling. These locations have been identified and mapped for future landing missions. This study provides insights for lunar landing site selection and regolith thermal analysis, offering essential data for future missions.