Performance analysis of LEO augmented GNSS precise point positioning from in-orbit CENTISPACE^TM satellites

Abstract Low Earth orbit (LEO) satellites can be used to augment global navigation satellite system (GNSS) precise point positioning (PPP) for rapid convergence, which has been demonstrated by an abundance of simulation studies. In this contribution, we analyze the performance of LEO augmented GNSS PPP using real data from two in-orbit CENTISPACE TM experimental satellites launched by Beijing Future Navigation Tech Co., Ltd. The onboard GNSS observations are used to determine the precise orbits and the initial clock offsets of LEO satellites, and the clock corrections are estimated using the observations from a ground network. The RMS values of measurement residuals for dual-frequency ionosphere-free combination of LEO downlink pseudorange and phase observations are about 0.8 m and 2 cm. We select three ground tracking stations for the PPP experiment and the performance of GPS, BeiDou Navigation Satellite System (BDS)-3, GPS + BDS-3, GPS + BDS-3 + Galileo PPP with the augmentation of 1 and 2 LEO satellites is evaluated and analyzed. The results indicate that the observations from LEO satellites can significantly improve the GNSS convergence performance. Compared with GNSS-only PPP, the convergence time is shortened by more than 50% with the addition of 1 LEO satellite, while the two LEO satellites achieve an improvement of 68%–73%. In particular, to achieve a horizontal accuracy of better than 10 cm, the convergence time for the GPS + BDS-3 + Galileo PPP solutions is reduced from 10.8 min to 3–5 min with the augmentation of 1–2 LEO satellites, which reveals the excellent potential of LEO satellites for rapid PPP convergence. The correlation analysis between ambiguity parameters and other related parameters during the PPP processing also demonstrates the superior performance of the LEO satellites in accelerating the PPP convergence. Furthermore, the GNSS/LEO combined PPP improves the 3D positioning accuracy by 10%–20%.