Design of Navigation Satellite Constellation for Global Lunar PNT

This study presents the design of a lunar navigation satellite constellation to provide global Positioning, Navigation, and Timing (PNT) services, beginning with coverage at the lunar South Pole and gradually expanding to the entire Moon. Building upon an initial Phase 1 constellation that ensures reliable PNT at the South Pole, Phase 2 extends this coverage globally, addressing the challenges of providing continuous navigation services across the lunar surface. The proposed Hybrid Frozen Constellation combines Elliptical Lunar Frozen Orbits (ELFOs) and Circular Frozen Orbits to offer a cost-effective and efficient solution, leveraging the stable South Pole-oriented orbits while minimizing the number of satellites required. The study explores various satellite configurations to achieve best Position Dilution of Precision (PDOP) across the entire lunar surface. By carefully analyzing the geometry and phasing of the orbits, the design aims to maximize navigation performance while reducing the satellite volume. Simulation results confirm that the full constellation achieves over 98% PDOP availability, ensuring PDOP values remain below 6, meeting the GPS standards for reliable navigation. This performance guarantees accurate positioning, even in challenging regions of the lunar surface, and supports both robotic and crewed exploration missions.