Analysis of LNSS satellite occlusion in the southern polar region of the Moon based on DEM

The Moon's Southern Pole region is crucial due to the unique terrain features. This study suggests using Digital Elevation Model (DEM) data to assess the positioning performance of the Lunar Navigation Satellite System (LNSS) in this area. Two LNSS constellation types, Elliptical Lunar Frozen Orbit (ELFO) and Elliptical Repeat Ground-Track Orbit, (ERGO), are evaluated based on lunar DEM data. The focus is on Number of Visible Satellites (NVS) and Position Dilution of Precision (PDOP) variations with satellite numbers and elevation mask angles. ELFO (8 satellites) shows a 69% probability of 4 + visible satellites with a 52% PDOP within 10, while ERGO (8 satellites) has 64% and 60% probabilities, respectively. Hybrid constellations involving an additional near-rectilinear halo orbit (NRHO) satellite are also explored. ELFO-NRHO (9 satellites) has a 96% probability of 4 + visible satellites and a 73% PDOP within 5, while ERGO-NRHO (9 satellites) presents probabilities of 83% and 78%, respectively. The positioning accuracy performance of hybrid constellations with NRHO is approximately 30 m.