Real-Time Kinematic Orbit Determination for LEO by Integrating Broadcast Ephemerides, Galileo HAS, and BDS-3 PPP-B2b

Real-time kinematic orbit determination (KOD) based on broadcast ephemerides (BRD) enables onboard, high-rate orbit updates for Low Earth Orbit (LEO) missions but with limited accuracy. With the operational availability of the Galileo High Accuracy Service (HAS) and the BDS-3 Precise Point Positioning B2b (PPP-B2b), real-time, high-accuracy corrections have become accessible to spaceborne receivers, enhancing orbit determination performance. Nevertheless, each product exhibits distinct strengths and limitations: BRD provides global coverage at relatively low accuracy; HAS delivers global corrections but exhibits degraded performance in the Asia–Pacific; PPP-B2b achieves high accuracy but is confined to a regional service centered on China. These complementary characteristics motivate their integration to achieve both high precision and robust global performance. Using the LuTan-1A mission as a case study, we assess the quality and availability of HAS and PPP-B2b products and propose a real-time KOD method that integrates BRD, HAS and PPP-B2b. Carrier phase pseudo-ambiguities are modeled as random-walks, with noise parameters determined for each ephemeris source through a para metric search experiment. Results show that the three-dimensional orbit error decreases from 25.06 cm for the combination of GPS and BDS-3 BRD to 18.86 cm when HAS is incorporated, and further to 17.09 cm with the addition of PPP-B2b. Specially, in the Asia-Pacific region, adding PPP-B2b to BRD+HAS reduces the orbit error from 20.57 cm to 16.63 cm. Overall, these findings demonstrate the stability and adaptability of the proposed integrated method under current GNSS configurations, providing a practical pathway to higher-precision, real-time orbit determination for future LEO missions.