Prototype of Real-Time Orbit Service for LEO Navigation Satellite System

With continuous deployment of Low Earth Orbit (LEO) satellites and development of inter-satellite links, LEO enhanced Global Navigation Satellite System (LeGNSS) brings new opportunities for future high-precision positioning, navigation, and timing (PNT) services. Real-time precise LEO orbit is the prerequisite for real-time precise positioning. In order to provide precise real-time LEO orbit and guarantee the normal operation of LeGNSS, a prototype of real-time orbit service for LEO navigation satellite system is proposed. We evaluate the accuracy of LEO orbit, and demonstrate the system infrastructure and working principle. In addition, two real-time LEO orbit broadcasting methods are designed: (1) using LEO orbit determined by RTS products as the fitting part to predict orbit, the prediction part is fitted by ephemeris parameters, which are injected into LEO and broadcasted to users. (2) differences between LEO orbits obtained by RTS products and the broadcast ephemeris are used to generate orbit corrections and broadcasted to users. Results show that LEO near-real-time orbit achieves centimeter-level accuracy, and the fitting errors of broadcast ephemeris are smaller than 10 cm in 20-min fitting arc. Moreover, the LEO broadcast ephemeris would obtain decimeter-level accuracy orbit, while the orbit corrections method would provide users with real-time centimeter-level LEO orbit.