Deep Space GNSS in Moon Transfer Orbit: the LuGRE Receiver

The Lunar GNSS Receiver Experiment (LuGRE) is a payload developed as part of the NASA Commercial Lunar Payload Services (CLPS) program as a partnership between the Italian Space Agency (ASI) and the National Aeronautics and Space Administration (NASA). The main objective of the project is to achieve GNSS-based Positioning, Navigation, and Timing (PNT) during the Moon Transfer Orbit (MTO) and, finally, on the Moon's Surface (MS). The project focused on the development of a GNSS Software Defined Radio (SDR) receiver, which is a Moon-customized version of the Qascom QN400-SPACE. The receiver logic has been refined with specific features that permit it to operate properly in deep-space environments. High-sensitivity acquisition and tracking techniques have been embedded to acquire and track GNSS signals at higher altitudes. Specialized Navigation plugins have been added for MTO and static MS positioning. This paper aims to present and analyze the most significant results obtained during the LuGRE receiver test campaign. The test scenarios are presented to provide a fruitful comparison between the receiver's real and expected performance.