Navigation, Guidance and Control Technology of Mars Exploration Orbiter Tianwen-1

Abstract

Tianwen-1, China’s first autonomous Mars exploration mission, faced many challenges in the process of interplanetary transfer and orbiting, such as long delay of data transmission between the orbiter and the Earth, many directional constraints during flight, and high requirements for autonomy and reliability. The autonomous navigation based on Mars optical target characteristic measurement, velocity vector control based on thrust direction compensation and angular momentum management based on multi-target pointing reference optimization were proposed. By adaptive edge extraction and accurate edge fitting based on ellipsoidal model for the characteristics of Mars time-varying target, high-precision navigation observation information of the target was obtained, and the accuracy of near-Mars navigation was better than 100 km and that of Mars circumnavigation was better than 2 km. The real-time estimation of thrust direction based on accelerometer measurement and attitude feedforward compensation were used to make the braking capture control accuracy reach the order of millimeter/second. Combined with the multi-target pointing constraint, attitude reference optimization design was carried out with the goal of global optimal jamming torque, to guarantee the autonomous flight control without ground support for more than 30 days. The proposed method was applied to the GNC subsystem of Tianwen-1 surrounding device. The in-orbit flight results of Tianwen-1 show that the proposed method can meet the constraints of autonomous control and autonomous management of interstellar flight, which provides important reference for subsequent deep-space exploration model missions.

Keywords

Mars exploration / Guidance Navigation and Control (GNC) / speed increment control / optical autonomous navigation / multi-objective reference design