Accurate relative positioning of Yutu lunar rover using VLBI phase-referencing mapping technology

Abstract

Real-time high-accuracy VLBI techniques played an important role in the Chinese lunar exploration mission in executing the soft landing of the ChangE-3 probe on the lunar surface. To make this possible, in-beam phase referencing was used to obtain accurate relative positioning between the Yutu rover and the lander. The visibilities outputted by the correlator software were initially converted to the uniform FITS-IDI format. Astronomical mapping software, such as AIPS and Difmap, was then used to complete the mapping and angular positioning of the Yutu antenna. A new positioning algorithm was developed to determine the three dimension positions of the rover on the lunar surface. We took advantage of the in-beam observations, for which the signals from lander and rover were received in the same digital terminal, to eliminate system errors. Theoretical analysis, null position testing, and comparisons with visual localization results show that an accuracy of about one meter is achieved in relative positioning. The in-beam phase-referencing technique has potential for use in accurate positioning, navigation, and visual location calibration in future lunar and/or planetary exploration.