Abstract: In order to cope with the characteristics of short duration of Mars EDL process, large telemetry and telecontrol delay, large impact dynamic environment and shortage of high precision map, the entry capsule GNC system of Tianwen 1 probe is designed with autonomy and fault tolerance. The design of system level hot backup and heterogeneous hot backup of key components ensures the independent diagnosis and correction of component failure. The fault tolerance of the system is improved by the strategies of independent work mode conversion and the multi criterion backup of key work mode conversion. The autonomous impact resistance management of the components power supply as well as the autonomous fault diagnosis and correction strategy of touch down sensors ensure the effective response to the high dynamic conditions such as the initiation of initiating explosive device. Aiming at the combination of parachute backshell avoidance and terrain obstacle avoidance, a set of hazard avoidance system and its application strategy of laser imaging sensor and optical sensor are designed. Special experiments such as helicopter flight test are implemented to verify the system design. In actual flight, the entry capsule GNC system of Tianwen 1 probe successfully implemented the key actions such as unfolding the trim wing, completed the parachute backshell avoidance and terrain obstacle avoidance, and achieved the final landing accuracy of 3.1 km, which fully proved the correctness of the system design.

Key words: Mars Landing, Guidance, navigation and control (GNC), Tianwen 1 probe, Entry, descent and landing (EDL)