Precise Real-Time Navigation of the LT-1A Satellite Based on New BDS-3 B1C/B2a Signals

Precise real-time navigation using the global navigation satellite system (GNSS) is a mainstream technique for low-Earth-orbiting (LEO) satellites, with increasing development opportunities due to the availability of multiple GNSS constellations and public service signals. In this study, we investigate precise real-time navigation of the LuTan-1A (LT-1A) satellite, utilizing new B1C/B2a signals from the BeiDou Global Navigation Satellite System (BDS-3). The real-time navigation accuracy of LT-1A for the 3-D position is 70.4, 63.2, and 74.7 cm, respectively, with BDS-3 B1C/B2a, global positioning system (GPS) L1/L2, and BDS-3 B1I/B3I signals under the pseudorange-based solution. The accuracy significantly improves to 15.6, 25.7, and 16.0 cm, respectively, under the carrier-phase-based solution. The slightly worse accuracy performance of new B1C/B2a signals than L1/L2 signals under the pseudorange-based solution is due to the larger clock offset error and overall signal-in-space range error (SISRE) in BDS-3 broadcast ephemeris. The better accuracy performance based on B1C/B2a signals than L1/L2 signals under the carrier-phase-based solution brings an important finding, that is, although the clock offset error of BDS-3 broadcast ephemeris is larger than that of GPS one, the change rate of clock offset error is much smaller due to the higher stability of BDS-3 atomic clocks. This results in a slower changing line-of-sight (LOS) error in BDS-3 broadcast ephemeris, in comparison to GPS, and consequently, it can be more effectively absorbed by the estimated pseudoambiguity parameters in the carrier-phase-based solution, leading to higher real-time navigation accuracy. These above findings highlight the excellent performance for real-time navigation of LEO satellites based on new B1C/B2a signals.