A Rapid, Low-Cost Path to Lunar Communication and Navigation with a Lunar Surface Station

Multiple international efforts are developing systems for position, navigation, timing, and communications (PNT+C) for the Moon. These architectures plan to implement a large lunar constellation similar to Earth-like Global Navigation Satellite Systems (GNSS) enabling high-performance PNT+C for a scalable user segment on the lunar surface. However, the collective cost and timeline of a complete infrastructure deployment could reach many billions in USD over decades before surface users can fully utilize its PNT+C capabilities. We propose the use of a lunar surface station to achieve high performance PNT+C for lunar south pole surface users during the initial deployment of a large lunar constellation. The early addition of a single station can provide the same or better PNT+C performance as a large lunar constellation while only requiring a lunar constellation with $\leq$4 orbiters. Thus, a surface-station-enhanced (SSE) PNT+C architecture significantly reduces the required timeline and overall infrastructure cost to achieve accurate and scalable PNT+C. A static lunar surface station positioned at the Connecting Ridge supplies valuable PNT+C services to future missions in nearby permanently shadowed regions. The station provides communication relay and store-and-forward capabilities between lunar relay orbiters and nearby surface users. In addition, the station receives augmented forward signals (AFS) from the LunaNet compatible constellation to generate one-way pseudorange and Doppler shift observables. The station then generates differential and Joint Doppler and Ranging corrections with these observables and broadcasts corrections, along with an additional AFS, to its target region. Both the corrections and geometric benefits from an additional surface-to-surface AFS result in significant improvements in real-time PNT performance for surface users, even amid large ephemeris and radiometric biases, drift, and noise. With a lunar constellation as small as three orbiters, this SSE PNT+C architecture can achieve $<$20 m positioning accuracy (3$\sigma$), $<$20 mm/s velocity accuracy (3$\sigma$), $<$10 ns timing distribution (3$\sigma$), and up to 300 Mbps in data throughput for nearby surface users. Along with PNT+C benefits, the station maintains a highly stable timing reference for time distribution, constellation synchronization, and lunar timekeeping. Designed to survive throughout lunar night, the station can also provide continuous scientific value with the deployment of a science payload. A lunar surface station can enable a rapid path to full PNT+C capabilities, while still providing long-term benefits after the completion of a large lunar infrastructure.