LEO constellation optimization for BDS precise orbit determination in LEO enhanced BDS

LEO-enhanced GNSS (LeGNSS) has been proposed and quickly gained prominence in recent years. A high-precision orbit is imperative for achieving accuracy in LeGNSS applications. The 'One-step' method has been proven effective in optimizing orbit accuracy in precise orbit determination, especially for BDS. On one hand, the orbital accuracy of BDS GEO is constrained by poor geometry, even with globally distributed stations; on the other hand, in cases with only regional stations available, the accuracy of the entire constellation is significantly compromised. However, constrained by computational costs and the phased development of LEO constellations, the optimization of LEO constellations is crucial for achieving high-precision BDS orbit determination with limited LEO satellites. Previous research has primarily focused on optimizing LEO constellations to enhance the performance of LeGNSS PPP. In this study, our emphasis shifts towards improving BDS orbit determination accuracy. We analyze the impact of LEO constellation inclination on BDS orbit determination using simulated data. The walker parameters of the simulated LEO constellations are set at 6/6/1, with the inclination angle ranging from 5° to 90° in 5° increments. We examine the orbit accuracy of BDS GEO, IGSO, and MEO in combination with LEO constellations of varying inclinations for orbit determination at global and regional stations. The key findings are as follows: For global stations, the orbital accuracy of GEO is significantly influenced by the inclination of LEO satellites, with the worst accuracy at high inclination angles and the best at medium inclination angles. The accuracy improves from 24cm without joint LEO satellites to 0.4cm with the inclusion of joint medium-inclination satellites, while the result of polar orbit is 0.6cm. IGSO and MEO show no clear relationship with the inclination of LEO satellites. In cases where only regional stations are available, GEO and MEO are more affected by the inclination of LEO satellites. GEO achieves the highest accuracy at medium inclination angles, peaking at 0.9cm when the inclination is 55°. MEO orbit accuracy increases with the inclination angle, with a worst accuracy of 2.3cm when the inclination of LEO is 5°, and reaching the best of 1.2cm when combined with polar orbit LEO satellites. Additionally, implementing a mixed-inclination constellation comprising three 55° satellites and three 90° satellites yields optimal overall orbital accuracy for the BDS, surpassing any single-inclination constellation.