Simulation case study of precise orbit determination for IGSO satellites using onboard Ka/GNSS observations

Inter-satellite links (ISLs) can provide a more accurate spatial reference for inclined geosynchronous orbit satellite (IGSO) satellites than onboard global navigation satellite system (GNSS) side-lobe signals. In this study, precise orbit determination (POD) quality is analyzed based on onboard Ka/GNSS observations using a simulated IGSO satellite orbit. Considering the similar orbit altitude, we first select three IGSO satellites from BeiDou Navigation Satellite System (BDS-3) as target satellites, which have real Ka-band measurements available, along with other BDS-3 satellites and ground anchor stations, enabling us to evaluate POD performance. For the POD results using real Ka-band measurements, the root mean square of the residuals can reach 10.9 cm, and the orbit consistency in the 3D direction is better than 0.35 m. Additionally, simulations are conducted for onboard GNSS, ISL, and ground anchor-satellite link (GSL), considering the different constraints on the Ka-band resources. When only GNSS measurements are used, the 3D orbit accuracy estimated by the simulated theoretical orbit is approximately 1.5 m, and when only ISL measurements are used, the 3D orbit accuracy can reach approximately 0.35 m. However, when additional ISL and GSL measurements are included, the POD accuracy can exceed 0.28 m. These results demonstrate that incorporating Ka-band measurements can effectively enhance the POD accuracy for high-orbit satellites.