Geostationary autonomous trajectory determination technology based on enhanced inter-satellite links of the Beidou medium earth orbit constellation

Trajectory determination is critical for autonomous operations in Geostationary Orbit (GEO). However, the existing methods cannot satisfy the need for stability and accuracy in short-cycle scenarios. Since the emerging method based on the Ka-band Inter-Satellite Link (ISL) of the Beidou satellite navigation system medium Earth orbit constellation has the advantages of high accuracy and anti-interference, this paper applies it to the autonomous operations of GEO satellites and analyzes the feasibility and link characteristics. Different from previous ISL-related studies about long-term orbit determination, there is an issue of periodic failure of priori orbital data caused by frequent maneuvers in short-cycle autonomous operations for ISL-based applications. In this paper, by fusing the priori clock bias information and multiple ISL observation data under the constraint of a sub-hour period, we propose an ISL-based fractional steps filtering method containing rapid contraction and precise tracking, assisted by an optimized satellite selection strategy, to address the issue above. The result indicates that thanks to an average number of 12.16 visible navigation satellites for GEO users, the proposed method with dispersed and diversified satellite selection scheme gives excellent results, with convergence to sub-meter accuracy in 10 min on average that satisfies the constraint of a sub-hour period and shows a 41.1 % improvement in average convergence time efficiency compared to the traditional method. Moreover, regarding trajectory determination accuracy in short-cycle autonomous operations, the root-mean-square error achieves about 0.38 m, which is better than the result of existing applications of about 10-20 m precision, demonstrating the advantages of the proposed method.