The Lunar Pathfinder PNT Experiment and Moonlight Navigation Service: The Future of Lunar Position, Navigation and Timing

The interest in Moon exploration has substantially grown in the last years, making the Moon an attractive testbed to develop the required technologies and capabilities for human Deep Space exploration. In the past decades, lunar missions have almost entirely relied on Direct-to-Earth (DTE) communications, whilst using ranging radiometric measurements from Earth for navigation. The growing trend in the number of missions to the Moon is creating demand for the deployment of a dedicated lunar communication and navigation infrastructure to support the international community. The European Space Agency’s vision, represented by the Moonlight initiative, is to stimulate the creation and development of lunar communication and navigation services that will support the next generation of institutional and private Lunar Exploration Missions, including enhancing the performance of those missions currently under definition. Within this initiative, ESA has defined a lunar navigation roadmap in 3 phases: firstly, making use of terrestrial GNSS signals (Phase 1), then adding in some limited (initial) lunar infrastructure (Phase 2) before transitioning to full lunar service capabilities (Phase 3). This contribution presents both ongoing and planned activities related with phase 1 and 2 of the roadmap. Regarding phase 1, the GNSS experiment planned with Lunar Pathfinder is described and the expected performance levels are presented: the experiment aims to demonstrate, for the first time in a lunar orbit, the use of a GNSS receiver to compute the satellite orbit on-board in real time. Regarding phase 2 of the roadmap, aiming to provide a dedicated navigation service in cis-lunar space as part of the Moonlight initiative, this contribution describes the Moonlight navigation service and analyses the potential user performance levels that can be achieved when landing on the lunar surface.