Inter-Satellite Link Enhanced Orbit Determination for BeiDou-3

TLDR

BeiDou‑3 (BDS‑3) is a global navigation satellite system slated for full operation by 2020, but high‑precision orbits—essential for its accuracy—are hard to obtain because global ground monitoring stations are scarce, so Ka‑band inter‑satellite links (ISLs) on BDS‑3 satellites can extend the visible arc of medium‑earth orbit satellites and enhance ground‑based orbit determination. This study evaluates ISL‑enhanced orbit determination for eight BDS‑3 satellites using observations from ten Chinese domestic and thirteen international GNSS monitoring stations. By integrating ISL measurements with ground‑based data, the authors analyze overlapping orbit differences (OODs) to assess orbit accuracy improvements. The analysis shows that with only ten regional stations the 3‑D RMS error of OODs is about 1 m, but adding ISL data reduces it to 0.5 m and improves 24‑hour orbit prediction accuracy from 2 m to 0.7 m—better than using globally distributed stations—and the benefit is expected to grow as more ISLs are deployed.

Abstract

The third generation of the BeiDou navigation satellite system (BDS-3) is a global navigation system, and is expected to be in full operation by 2020. High-precision orbits are a precondition for BDS-3 to provide a highly accurate service, which needs a global tracking and monitoring capability for the operational satellites. However, it is difficult for BDS to construct global ground monitoring stations. Fortunately, Ka-band Inter-Satellite Link (ISL) antennae fitted to the BDS-3 satellites can be used to extend the visible arc of the Medium Earth Orbit (MEO) satellites and to enhance the ground stations for orbit determination. This paper analyses the ISL-enhanced orbit determination for eight BDS-3 satellites, using the data from ten Chinese domestic stations and 13 international Global Navigation Satellite System (GNSS) Monitoring and Assessment System (iGMAS) overseas stations. The results show that the Three-Dimensional (3D) position Root Mean Square (RMS) error of the Overlapping Orbit Differences (OODs) is approximately 1 m when only ten regional stations are used. When the ISL measurements are added, the 3D position RMS error is decreased to 0·5 m, and the accuracy of the 24-hour orbit prediction can also be improved from 2 m to 0·7 m, which is even better than that of the orbits determined using globally distributed stations. It can be expected that with the subsequent launch of BDS-3 satellites and the increasing number of ISLs, the advantage of the ISL enhanced orbit determination will become more significant.