Design and station-keeping strategies for robust lunar navigation constellations

To support the ever-increasing number of missions planned to visit the Moon, an international effort is underway to design and deploy lunar navigation satellite constellations. This study focuses on small-scale lunar constellations based on frozen orbits and aims to ensure stable long-term navigation performance. The proposed multi-objective optimization algorithm takes into account the frozen behavior and provides solutions that are robust to changes in the orbits orientations. Numerical results highlight that the residual performance degradation is linked to a secular mean anomaly drift, which can be prevented by adjusting the initial semi-major axes. By plotting the navigation performance versus the mean anomaly offsets, a mapping between the constellation geometry and the service quality is derived, allowing the definition of orbital control boxes. Finally a station-keeping strategy based on the control of the mean anomaly drift rate is proposed to maintain the desired navigation performance with minimal fuel costs.