Performance Analysis of Spatial Reference Transfer between Global Navigation Satellite System Satellites and Earth-Moon Libration Point Satellites

To elucidate the unclear mechanisms of autonomous orbit-determination accuracy and the stable maintenance of spatial reference under mutual support between Global Navigation Satellite System (GNSS) satellites and Earth–Moon Libration (EML) point satellites in an integrated cislunar-space Positioning, Navigation, and Timing (PNT) system, this paper focuses on the mutually supported autonomous orbit-determination method and the performance of GNSS and EML point satellites through intersatellite two-way link observations. Based on simulation data, the orbit-determination accuracy is analyzed under three scenarios, i.e., autonomous orbit determination of the EML point constellation, GNSS satellites anchoring EML point satellites, and EML point satellites anchoring GNSS satellites, under different orbit arc lengths and anchoring conditions. The results show that the orbit-determination accuracy of the EML point satellite constellation can reach the 10 m level under an orbit arc exceeding 5 days. Through the support of GNSS satellite anchoring, the EML point constellation achieves 10-m accuracy under a 1 day orbit arc. Additionally, when the EML point satellite constellation anchors the GNSS constellation with orbits exhibiting 12~29 m of error and 1 day arc length, the average three-dimensional position error of GNSS MEO satellites is 4.99 m, and the average orbit URE is 2.61 m. This study indicates that EML point satellites can provide an inertial spatial reference for GNSS satellites. The 1-day anchoring effect of GNSS satellites can be equivalent to the effect of autonomous orbit maintenance of EML point satellites for more than 5 days. These conclusions provide a basis for constructing an integrated PNT system of MEO/GEO/IGSO and deep-space navigation constellations as well as for supporting the construction of the cislunar-space situational-awareness system.