Autonomous navigation scheme of lunar relay satellite based on weak GNSS signals

Lunar Relay Satellite plays a significant role in lunar science, manned lunar landing and lunar surface navigation. Compared with ground based telemetry and command methods, the approach applying GNSS (Global Navigation Satellite System) receiver to autonomous navigation system of lunar relay satellite has great application value. It can reduce the workloads of Deep Space Surveying Control Network and improve the coverage and navigation accuracy of lunar orbiter. In this paper, we investigate the autonomous navigation scheme of Lunar Polar Orbit Relay Constellation based on weak GNSS signals. The navigation accuracy of lunar orbiter exerted by GNSS constellation scale, constellation type and receiver sensitivity is discussed. The simulation result shows that lunar relay satellite has at least one-satellite visibility to GNSS constellation in 81.85% of its orbit period and has four-satellite visibility in 13.03% of its orbit period when combing the signals emitted by GPS, COMPASS, GALILEO and GLONASS and making full use of the side-lobe signals. The increase of receiver sensitivity further improves the satellite visibility. This makes contribution to the scheme of orbit control system in the subsequent series of lunar exploration satellites.