Preliminary analysis for the joint autonomous orbit determination of the BDS-3 MEO satellites and lunar ELFO satellites based on inter-satellite links

Abstract A fundamental limitation of Autonomous Orbit Determination (AOD) for Global Navigation Satellite Systems (GNSS) constellations using Inter-Satellite Links (ISLs) is the inherent unobservability of the overall rotational bias, leading to continuous degradation of orbit determination accuracy. To address this limitation, we propose a joint AOD framework integrating the BeiDou-3 Global Navigation Satellite System (BDS-3) constellation with lunar satellites in Elliptical Lunar Frozen Orbits (ELFO). The proposed framework exploits strong lunar gravitational dominance experienced by ELFO satellites to break the dynamical symmetry of the GNSS constellation, thereby establishing an absolute reference that effectively suppresses the systemic rotational drift. Validation using real onboard ISL measurements from BDS-3 Medium Earth Orbit (MEO) satellites, combined with simulated ELFO ISL measurements demonstrates that integrating ELFO satellites effectively suppresses the rotational bias, stabilizing the three-axis errors at 13.59, 10.27, and 4.04 mas over 60 d. Consequently, the mean Root Mean Square (RMS) User Range Error (URE) for the 24 BDS-3 MEO satellites is maintained at 0.35 m. Furthermore, the ELFO satellites achieve high-accuracy joint orbit determination, with maximum radial, along-track, and cross-track errors below 0.16 m, 1.7 m, and 1.8 m, respectively, resulting in a maximum Three Dimensional (3D) position error of less than 2.3 m.