On the Performance of LCNS-Based Differential Positioning on the Moon

The development of dedicated Lunar Communication and Navigation System (LCNS) infrastructure, envisioned within the Moonlight initiative of the European Space Agency (ESA), will lay the foundations for autonomous lunar navigation of surface rovers, and orbiting and landing spacecrafts. The absence of lunar ionosphere makes the deployment of a reference station an attractive choice for significantly reducing the satellite orbit and clock errors so that improved navigational capabilities are delivered with long baselines on the lunar surface. The present contribution aims to provide insight into and analyze the relative-positioning performance of lunar surface rovers provided that a 4-satellite LCNS constellation is available and that its satellites are capable of transmitting GNSS-like signals on a single frequency. To assess the code-only (DGNSS) and code-plus-phase (RTK) expected performance, we present a formal analysis of the positioning precision and the ambiguity resolution capabilities, and demonstrate whether and under what conditions high-precision positioning can indeed be achieved on the Moon. Our sensitivity analysis shows how the rover's performance responds to several contributing factors, including the number of epochs involved, the code measurement precision, the number of visible satellites, the presence of height-constraints, and the baseline length. Finally, numerical results along a simulated traverse in the lunar surface demonstrate that sub-meter and few-dm positioning is possible with multi-epoch DGNSS and RTK solutions, respectively, with the effective uncertainty of the differential satellite orbital errors in a 500 km baseline slightly deteriorating the performance with both zero-latency and nonzero-latency corrections.