An efficient and robust GNSS/LEO joint orbit determination method based on regional ground control sources

Abstract

Abstract The precise orbit determination (POD) for Global Navigation Satellite Systems (GNSS) generally relies on numerous ground-based observations and heavily depends on the geometry of ground stations. Joint orbit determination (JOD) of GNSS satellites and low Earth orbit (LEO) satellites can largely compensate for the limitations of ground station geometry. In the common JOD, the POD of LEO satellite is mainly processed by the reduced-dynamic approach. However, this approach involves complex calculations and is susceptible to disruptions caused by orbit maneuvering. Therefore, a simplified JOD method is designed that employs kinematic approach to determine the LEO satellites orbit. To validate the effectiveness of the proposed method, the orbit and clock offset of GPS satellites and LEO satellites are jointly estimated utilizing the eight regional ground stations. Eight LEO satellites, including GRACE-C, GRACE-D, SWARM-A, SWARM-B, SWARM-C, SENTINEL-3A, SENTINEL-3B, and JASON-3, are chosen for JOD with GPS satellites. Kinematic POD (KPOD) and reduced-dynamic POD (RDPOD) are employed to determine the LEO orbits in the JOD. The comprehensive performance of JOD using different methods for LEO POD is analyzed in terms of GPS orbit accuracy, GPS clock efficiency, LEO orbit accuracy, and computation time. The results show that applying both KPOD and RDPOD methods for LEO satellites led to a substantial improvement in the quality of GPS orbit and clock offset. The adoption of RDPOD yields superior enhancement and results in higher accuracy of the LEO orbits. However, the overall computation is time-consuming and the performance of JOD declines significantly when LEO satellites undergo orbital maneuvers. Alternatively, when employing KPOD, although the accuracy of the LEO orbits in the JOD is comparatively lower, it offers a substantial reduction in the overall network computation time compared to RDPOD. Moreover, the simplified JOD mode based on LEO KPOD is nearly unaffected by orbital maneuvers of LEO satellites, presenting unique advantages in practical data processing.