Analysis and evaluation of positioning systems for lunar navigation

This work contributes to the growing field of lunar exploration: an evolving domain that positions the Moon as a crucial testbed for developing technologies essential for human deep space exploration. Recently, the interest in lunar missions has increased, necessitating the development of a dedicated lunar communications and navigation infrastructure to support the international community’s expanding initiatives. This necessity aligns with the European Space Agency’s Moonlight initiative, which aims to foster the creation of lunar communications and navigation services provided by private partners, expected to enhance the performance of both existing and future lunar exploration missions. This dissertation proposes an innovative autonomous lunar navigation system, primarily comprising a constellation of satellites in lunar orbit. Designed to provide essential navigation services to orbiters in Low Lunar Orbit, landing crafts, and surface rovers, the system addresses the challenges of lunar navigation, historically reliant on Earth-based ranging measurements, by offering a solution with higher autonomy and accuracy. The study explores various system configurations, considering factors such as service coverage, system measurement errors, and positioning accuracy, including a detailed analysis of mathematical formulations for different localization techniques. The subsequent analysis evaluates various architectures and methods, leading to the proposal of a modular architecture compatible with state-of-the-art recommendations. This includes One-Way and Two-Way ranging techniques, with Two-Way ranging demonstrating superior accuracy and availability compared to One-Way, despite some limits in capacity and latency. Moreover, integrating a local element at a fixed location on the lunar surface for differential correction significantly enhances accuracy without affecting continuity or availability. The local element can also include additional mea surements like Range and Angle of Arrival for independent localization, especially for critical landing phases. This last this method introduces coverage constraints and increases complexity and costs at the local station. Additionally, evaluations incorporating an onboard sensor like an altimeter and a DEM model, despite limitations due to high DEM errors, show potential for improving system availability and continuity, aiding in absolute positioning, particularly beneficial for users with fewer satellites in visibility. Further, the application of a Kalman filter significantly improves the system’s performance, optimally fusing information from different sources and continuously refining estimates. This proves particularly effective in various lunar cinematic scenarios such as orbiting, landing, and surface exploration. Finally, a hybrid solution is proposed, coherent with ESA plans, combining One-Way and Two-Way ranging measurements emerges as an effective solution, offering enhanced positioning accuracy and availability. In conclusion, this work provides valuable insights into the feasibility and performance of a lunar navigation satellite system. It highlights the system’s potential in enhancing the accuracy of lunar landings, enabling more precise exploration of the lunar surface, and facilitating missions to the far side of the Moon. By offering a comprehensive understanding of the complexities involved in lunar navigation, the research contributes to making lunar exploration more accessible and efficient, paving the way for future advancements in space exploration and potential lunar habitation.