Relative position determination between Chang’E-3 lander and rover using in-beam phase referencing

Abstract

Chang’E-3 is China’s first lunar surface exploration mission, as a part of the second phase of China’s Lunar Exploration Program (CLEP). It landed successfully in the northwest of Mare Imbrium on December 14, 2013, incorporating two probes, a lander and a rover named Yutu. The execution of the cooperative science tasks required an accurate determination of the relative position between the lander and the rover. In-beam phase referencing experiments have been conducted with the Chinese VLBI Network (CVN) to accurately image the rover in reference to the stationary lander in order to obtain their offsets in Right Ascension and Declination, which were then transformed into the lunar local coordinate system to acquire their relative position on the lunar surface. The observations and the data processing procedures are described in this paper. Images of the rover in six epochs between December 15 and 21, 2013 were made, resulting in accurate positions of the rover that are consistent with the visual localization approach. Through measurement of the locations of the rover’s omnidirectional antenna with respect to the lander’s directional antenna before their separation, and the recognition of the rover’s turning actions during its exploratory moves, we demonstrate that the accuracy of relative position determined in this way could reach the meter level and the resolution is better than 1 meter.