Simulation of Combined Orbit Determination with a Small LEO Constellation and BDS‐3 Full Constellation

  Objectives  Limited by the regional distribution of ground monitoring stations and the geostatic characteristics of geostationary earth orbit (GEO) satellites, the GEO satellites of the BeiDou satellite navigation system (BDS) have poor orbit determination accuracy. The inclusion of spaceborne observation data of low-Earth orbit (LEO) satellites by processing combined precise orbit determination (CPOD) can improve the orbit determination accuracy of global navigation satellite systems (GNSS).

  Methods  This study simulates and analyzes the performance of CPOD with the BDS-3 full constellation and LEO satellites in enhancing the orbit determination accuracies of BDS satellites on the basis of a small LEO satellite constellation of 24 LEOs. With the simulated observation data, experiments of POD with ground stations only and CPOD with ground stations and LEOs are conducted. Three types of station networks, i.e. the global network, the Asia-Pacific regional network, and the Asia-Sea network, are discussed.

  Results  (1) The three dimension orbit accuracies of GEO satellites are at the decimeter magnitude in the case of POD with ground stations only. When LEO data are added, the corresponding orbit determination accuracy is at the centimeter level, with an increase of over 80%.(2) In the case of the regional station network, the three dimension root mean squares error(RMSE) of navigation satellite orbits are at the decimeter level. When LEO data are added, the orbit determination accuracies of all types of navigation satellites are several centimeters.(3) In the case of the global station network, the orbit determination accuracy of inclined GeoSynchronous orbit (IGSO) and medium Earth orbit (MEO) satellites can still be improved on an millimeter-centimeter level.

  Conclusions  Under the regional monitoring network, the addition of a small number of LEO satellites can significantly improve the orbit accuracy of GNSS satellites. When the global uniform/Asia-Sea network is deployed, the orbit accuracy of navigation satellites can still be slightly improved after the addition of LEO satellites. With the more LEO satellites added, the improvement of the orbit determination accuracy of navigation satellites is limited.