The positioning, navigation, and timing (PNT) service of the Global Navigation Satellite System (GNSS) is developing in the direction of real time and high precision. However, there are some problems that restrict the development of real-time and high-precision PNT technology. Satellite orbit maneuvering is one of the factors that reduce the reliability of real-time navigation products, especially the high-frequency orbit maneuvering of geostationary earth orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites. The BeiDou Navigation Satellite System (BDS) constellation is designed to contain GEO, IGSO, and medium earth orbit (MEO). These orbit maneuvers bring certain difficulties for data processing, especially for BeiDou satellites, such as decreased real-time service performance, which results in real-time navigation products including unusable maneuvered satellites. Additionally, the performance of real-time navigation products will decrease because the orbit maneuvers could not be known in advance, which diminishes the real-time PNT service performance of BDS for users. Common users cannot obtain maneuvering times and strategies owing to confidentiality, which can lead to a decline in the BDS real-time service performance. Thus, we propose a method to predict orbit maneuvers. BDS data from the broadcast ephemeris were analyzed to verify the availability of the proposed method. In addition, the results of real-time positioning were analyzed by using ultra-rapid orbit products, demonstrating that their reliability is improved by removing maneuvered satellites in advance. This is vital to improve the reliability of real-time navigation products and BDS service performance.

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The precise orbit determination (POD) for Global Navigation Satellite Systems (GNSS) generally relies on numerous ground-based observations and heavily depends on the geometry of ground stations. Joint orbit determination (JOD) of GNSS satellites and low Earth orbit (LEO) satellites can largely compensate for the limitations of ground station geometry. In the common JOD, the POD of LEO satellite is mainly processed by the reduced-dynamic approach. However, this approach involves complex calculations and is susceptible to disruptions caused by orbit maneuvering. Therefore, a simplified JOD method is designed that employs kinematic approach to determine the LEO satellites orbit. To validate the effectiveness of the proposed method, the orbit and clock offset of GPS satellites and LEO satellites are jointly estimated utilizing the eight regional ground stations. Eight LEO satellites, including GRACE-C, GRACE-D, SWARM-A, SWARM-B, SWARM-C, SENTINEL-3A, SENTINEL-3B, and JASON-3, are chosen for JOD with GPS satellites. Kinematic POD (KPOD) and reduced-dynamic POD (RDPOD) are employed to determine the LEO orbits in the JOD. The comprehensive performance of JOD using different methods for LEO POD is analyzed in terms of GPS orbit accuracy, GPS clock efficiency, LEO orbit accuracy, and computation time. The results show that applying both KPOD and RDPOD methods for LEO satellites led to a substantial improvement in the quality of GPS orbit and clock offset. The adoption of RDPOD yields superior enhancement and results in higher accuracy of the LEO orbits. However, the overall computation is time-consuming and the performance of JOD declines significantly when LEO satellites undergo orbital maneuvers. Alternatively, when employing KPOD, although the accuracy of the LEO orbits in the JOD is comparatively lower, it offers a substantial reduction in the overall network computation time compared to RDPOD. Moreover, the simplified JOD mode based on LEO KPOD is nearly unaffected by orbital maneuvers of LEO satellites, presenting unique advantages in practical data processing.