Design Of The Earth-Moon Libration Point Navigation Satellite Constellation And Navigation Performance Analysis

Expanding human space activities have put forward higher requirements for satellite navigation technology. The current satellite navigation system can provide real-time, high-precision, and global navigation support for near-earth users, but with targets moving from the Earth into deep space, and the increasing demand for autonomous operation, the deficiencies in navigation capacity and autonomy of the current satellite navigation system are becoming more obvious. As a result, the development of a new type of satellite navigation system which can meet the requirements of deep-space navigation and operational autonomy has become an urgent research topic. Under such background, this work is intended to shed light on the value of the Earth-Moon libration point satellite navigation system.The Earth-Moon libration point satellite navigation system is a novel navigation architecture that consists of satellites located in periodic orbits around the Earth-Moon libration points. On one hand, it can rescue the current satellite navigation system from the inability to support deep-space users. On the other hand, libration point navigation satellites can use satellite-to-satellite tracking (SST) data to perform autonomous orbit determination, which will greatly improve the autonomy of the navigation system.In this work, a systematic study on the constellation design of the Earth-Moon libration point satellite navigation system is presented. Firstly, a coverage analysis is conducted for the libration point navigation satellites. After a thorough search, three kinds of candidate constellations that can achieve continuous global coverage for lunar orbits are obtained, which are, the Earth-Moon L1,2 two-satellite constellation, the Earth-Moon L2,4,5 three-satellite constellation and the Earth-Moon L1,2,4,5 four-satellite constellation. Then, the autonomy of the libration point satellite navigation system is analyzed. Based on discussions on the acceleration asymmetry and state-measurement matrix, the observability of the autonomous orbit determination method is proved. Simulation results indicate that libration point navigation satellites can achieve an orbit determination accuracy of a few meters in a 180-day period. Thereafter, navigation performances of the candidate constellations for future Lunar and Mars exploration missions are evaluated, respectively. It is indicated that the orbit of L1, navigation satellite has a significant effect on the navigation accuracy in cislunar space. When the L1, navigation satellite is located in Halo orbit or vertical Lyapunov orbit, the Earth-Moon L1,2,4,5 four-satellite constellation can always achieve a better performance, with an accuracy of 20 m for both the trans-lunar and lunar orbit phase. But for Mars navigation, the influence of constellation configuration is not significant anymore. The Earth-Moon L1,2,4,5 four-satellite constellation can achieve an accuracy better than 3 km for the Earth-Mars transfer phase, and better than 100 m for the Mars orbit phase. After that, the simplified navigation architecture, that is, the Earth-Moon L1,2 two-satellite constellation is analyzed in depth. According to the crosslink range requirement and the cislunar navigation performance, configuration parameters of the two-satellite constellation are optimized by a cooperative evolutionary algorithm. Finally, performance of the libration point satellite navigation system is verified in the real force model of the Earth-Moon system. The results indicate that the coverage, autonomy and navigation capacity of the candidate constellations can all be preserved in the real force model, which demonstrates the validity of the constellation design scheme.The candidate constellation architecture obtained in this work would be a valuable reference for future navigation system design.