Lunar trans-Earth trajectory design and practice for the Chang’e-5 mission

Abstract

<p indent=0mm>The Chang’e-5 mission is the first automatic robot Lunar sampling return mission in China. Compared with the previous Chinese Lunar exploration missions, the Lunar trans-Earth flight is a new phase and facing many challenges. Limited by the capability of launch vehicle and the high latitude of the domestic touchdown region, the flight scheme adopted in the Chang’e-5 spacecraft is quite the different from those of American Apollo mission and Soviet Union’s Luna mission. The Lunar trans-Earth scheme of Chang’e-5 mission is to escape Lunar orbit using the optimal injection time and return to the Earth with skip-entry. The design constraints, models, algorithms and practical engineering considerations of the Lunar trans-Earth trajectory design of the Chang’e-5 mission are systematically introduced in this paper. A novel optimal trans-Earth injection (TEI) guidance algorithm, which can obtain the optimal escape impulsive and accurately target the entry interface (EI) from elliptical Lunar parking orbit, is proposed. The all-target aiming guidance algorithm with separation disturbance compensation is desinged to improve the accuracy and rapidity of convergence. The results of Chang’e-5 on-orbit flight show that the Lunar trans-Earth trajectory design and corresponding guidance algorithm can acheive the mission requirements. Besides, the aiming accuracy of entry corridor is very high.