GNSS-based navigation for lunar missions

The European Space Agency's (ESA) interest in lunar exploration has motivated research on systems which could increase the robustness of the navigation architecture of future lunar exploration missions and improve their autonomous operation capabilities. Global Navigation Satellite Systems (GNSS) are currently used in space missions, not only as a navigation sensor but also as a science instrument. Although their use has been generally limited to orbits below the GNSS constellations, recent studies have shown that GNSS-based navigation for GEO and HEO missions is feasible and with relatively good performances, demonstrating its applicability to a wide range of space missions. The LunarGNSS project (funded by ESA, contract no. 4000107785/12/NL/AF, and led by DEIMOS Engenharia in cooperation with Politecnico di Torino, Thales Alenia Space - France, DEIMOS Space and Thales Alenia Space - Italy) goes far beyond GEO, analyzing the feasibility and performance of a navigation solution based on GPS and Galileo for missions to the Moon and focusing on the investigation of the use of weak GNSS signals to provide real-time navigation capabilities to various future lunar assets. An overview of the methodology and tools used in the LunarGNSS project, along with the proposed solution and preliminary results (taking into account expected environment characteristics and considering a simple statistical model for the GNSS observables) have been presented by the authors in the past. This paper presents the final results of the LunarGNSS study, focusing on the expected environment characteristics and on the GNSS based navigation performances achievable with the proposed navigation system architectur