Abstract: In view of the deficiency of the existing safe landing site selection method for planetary soft landing, a safe landing site selection method base on inverse pyramid is proposed in this article. Combined with the landing point accuracy, autonomous obstacle avoidance ability and terrain slope adaptability of the lander, a terrain safety analysis and quantitative search model is established based on leveling point, safe landing point, reliable obstacle avoidance point and nominal landing point. The model have a four layer inverse pyramid structure in which the results of each layer are used as the input of the next layer search, progressively converging to 100% terrain safe landing area from weak constraint to strong constraint. The flight results of Chang’e 5 show that the method can quickly determine the safe landing area and nominal landing site, and effectively guide the design of landing descent nominal flight path and the formulation of orbit control strategy.

Key words: Inverse pyramid, Safe landing site, Safe landing area, Terrain analysis