Application of a high-precision calibration technology for lunar liftoff and verification using Chang’E-5 mission

Abstract

<p indent=0mm>Chang’E-5 explorer landed on the lunar surface on December 1, 2020, Beijing time, completed China’s first lunar surface sampling, lunar surface liftoff, and lunar orbital rendezvous and docking, and then returned to the Earth successfully. Accurate positioning of the lander and ascending vehicle assembly are the key to the success of lunar liftoff and as well as lunar orbital rendezvous and docking. Aiming at fulfilling the requirement of high-precision calibration of lunar liftoff of the lander and ascending vehicle assembly of Chang’E-5 mission, the method of using a “three-way ranging and Doppler system + VLBI interferometry system” to realize high precision of a landing position is proposed herein. Then, a high-precision determination algorithm for the lunar liftoff datum mark is provided. Using 20-min observables of Chang’E-5 mission after landing, the landing location of the lander and ascending vehicle assembly could be calculated rapidly, which was 43.0595°N and −51.9214°E, having a −2446-m elevation. Results showed that the difference between the positioning results obtained using the tracking data only <sc>20 min</sc> after landing and the lunar reconnaissance orbiter (LRO) image data provided by NASA was <sc>180 m.</sc> When only longitude and latitude were calculated and elevation was obtained from the lunar digital elevation model, the difference between the positioning result and LRO image data was<sc>97 m,</sc> which could be effectively used as the lunar surface liftoff datum mark. Using <sc>48-h</sc> observables after landing, the landing location of the lander and ascending vehicle assembly was 43.0594°N and −51.9167°E, having a −2550-m elevation, with a difference of only <sc>60 m</sc> compared with the results of LRO.