###### Abstract  
This study investigates and verifies the feasibility of the precise point positioning (PPP)-B2b enhanced real-time (RT) precise orbit determination (POD) of low Earth orbit (LEO) satellites. The principles and characteristics of matching various PPP-B2b corrections are introduced and analyzed. The performance and accuracy of broadcast ephemeris and PPP-B2b signals are compared and evaluated by referring to the precise ephemeris. The root mean square (RMS) errors in the Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS)-3 broadcast ephemeris orbits in the along direction are larger than those in the other two (radial and cross) directions, and correspondingly, the along component PPP-B2b corrections are greatest. The continuity and smoothness of the GPS and BDS-3 broadcast ephemeris orbits and clock offsets are improved with the PPP-B2b corrections. The availability of PPP-B2b corrections is comprehensively analyzed for the TJU-01 satellite. Several comparative schemes are adopted for the RT POD of the TJU-01 satellite using the broadcast ephemeris and PPP-B2b corrections. The RT POD performance is improved considerably with the broadcast ephemeris corrected by the PPP-B2b signals. The RMS of the RT orbital errors in the radial, along, and cross directions is 0.10, 0.13, and 0.09 m, respectively, using BDS-3 and GPS PPP-B2b corrections, with reference to the solutions calculated with the precise ephemeris. The accuracy is improved by 5.1%, 43.9%, and 28.7% in the three directions, respectively, relative to that achieved with the broadcast ephemeris. It is concluded that a greater proportion of received PPP-B2b satellite signals corresponds to a greater improvement in the accuracy of the RT POD of the LEO satellite. GPS; BDS-3; broadcast ephemeris; real time; PPP-B2b; precise orbit determination Article  
Real-Time Precise Orbit Determination of Low Earth Satellites Based on GPS and BDS-3 PPP B2b Service  
2024168333103390/rs1605083310390/rs1605083310390/rs1605083310390/rs1605083310390/rs1605083310390/rs1605083310390/rs160508310390/rs160508  
The global networking of the Beidou Global Navigation Satellite System (BDS) was completed in 2020. PPP-B2b is one of the services provided by the BDS-3 navigation system and is used to enhance precise point positioning (PPP). The PPP-B2b signal is used as the broadcast channel, and BDS-3 geosynchronous orbit (GEO) satellites broadcast correction information to users. This signal provides users with RT PPP services [7]. The widespread application of PPP-B2b has coincided with the study of PPP-B2b by many scholars [7; 8; 9; 10; 11; 12; 13]. [PERSON] et al. reported the physical properties of PPP-B2b including the area covered by its signal and its accuracy for PPP [14]. [PERSON] et al. found the precision of PPP enhanced by PPP-B2b products is higher than that of RT products from Wuhan University [8]. [PERSON] et al. compared the kinematics PPP accuracy when using BDS-3 PPP-B2b with that when using the GPS and an RT service (RTS) provided by the National Centre for Space Studies [11]. [PERSON] et al. evaluated the performance of RT products provided by the BDS [15]. Many scholars have studied RT corrections for the RT POD of LEO satellites. When using the high-quality RT GPS precise ephemeris and clocks from the German Space Operations Center for the RT POD of the Terra Synthetic Aperture Radar-X mission, the RMS error of orbits was 2.1 cm [16]. [PERSON] et al. (2022) explored an innovative way of controlling the receiver clock offset quality in the RT POD for the Gravity Recovery and Climate Experiment (GRACE) follow-on mission and demonstrated that the RMS error in the three orthogonal directions of the RT POD of the mission using the German Research Centre for Geosciences BeiDou multi-GNSS product is about 8 cm and that using the National Centre for Space Studies RT ephemeris is approximately 10 cm [17].