Influence Analysis of Terrain of the Farside of the Moon on Soft-Landing

Abstract

Chang'e-4 probe is planned to land on the farside of the moon for the first time of the human being. Compared to the nearside of the moon, the terrain on the farside of the moon is rugged and complex, and there is no large flat area, so the change of the terrain will affect the soft-landing of Chang'e-4. The Chang'e-4 landing site on the South-Pole Aitken Basin is analyzed and compared wth the landing area of Chang'e-3 mission, considering the influences ofthe mission design, the lander design and the lunar working procedure. The main conclusions are as follows:1) The latitude and longitude range of the landing area is reduced from 16.4° and 3° for Chang'e-3 mission to about 4° and 2° for Chang'e-4 mission; 2) During the power descent phase, the strategy after the main deceleration phase is changed from the oblique forward motion trajectory to the vertical down trajectory, and the operation time of the distance measuring sensor is also changed; 3) The signal transmission powers and signal to noise ratios of the microwave ranging and velocity sensor will be improved; 4) The lighting of the lander and the communication by the terrain occlusion will be prediected, and the design operation strategies such as sleep mode or eclipse mode will be established. Through the modification, Chang'e-4 mission can be adapted to the changes in the topography of the farside of the moon to reduce the risk of landing and lunar mission.