Analysis of deep-space spacecraft navigation based on GNSS weak signals with lunar relay satellite signals

According to the applying needs of autonomous navigation in Earth-Moon transfer orbits in China's Lunar probe program, we study the scheme of autonomous navigation based on GNSS weak signals by taking the transfer process of ‘Chang e NO.1’ as an example. And we analyze the influence of different styles of joint-constellation on the coverage of navigation signals from the view point of engineering application. Since the effective coverage for the whole transfer process can't be achieved only based on GNSS, we further discuss the navigation scheme by introducing lunar relay satellites signals. The simulations show that effective coverage ratios for three GTO orbits in the transfer process are all above 60% based on combined signals from GNSS with fully used side lobe signals of them. The coverage property has been further improved by introducing the lunar relay signals into GNSS system.