A Lunar Surface Pseudolite Architecture for Regional Communication and Radionavigation

As the successful initial launch of the NASA Artemis program begins the process of returning astronauts to the Moon, lunar navigation remains a critical need and an important challenge. Multiple proposals for lunar navigation systems have been developed to support exploration, science, and commercial endeavors on and around the Moon, primarily focusing on Lunar Navigation Satellite architectures. However, these constellations are prohibitively expensive, require significant Earth-based ground station support, or have limited initial horizontal ranging performance, thus reducing their utility for lunar surface operations. This research proposes a lunar surface-based pseudolite architecture to provide an emergency alert broadcasting capability in addition to passive Position, Navigation, and Timing (PNT) services for regional applications. The architecture leverages the maturity of low Size, Weight, and Power (SWaP) small satellite components to deploy pseudolites across the lunar surface. This approach provides a costeffective solution for near-term surface operations around critical locations, including craters identified as likely habitat/ice water locations as well as scientific regions of interest around the lunar south pole. The system architecture, design parameters, trade offs, and concept of operations are defined herein, with comparisons in performance, coverage, and cost relative to alternative lunar navigation system concepts. Initial component selection, signal design, and system budgets are presented, demonstrating that the small volume, low-power pseudolite package can provide continuous communication and radionavigation support at ranges beyond 20 km with nominal pseudorange and time synchronization errors estimated at less than 1 m (3.3 ns) for a single pseudolite. Finally, pseudolite placement analysis for the Shackleton Crater, a candidate landing site for the Artemis 3 mission, is completed leveraging lunar terrain maps. The resulting six pseudolite architecture provides navigation capabilities across the vast majority (>98%) of the crater with an average horizontal positioning accuracy of better than 10 m, which can serve to stimulate exploration, habitation, and commercialization on the lunar surface.