BDS-3-Only Precise Orbit Determination Without External Initial Orbit and Clock Corrections

Precise orbit determination (POD) is a fundamental requirement for satellite navigation, Earth observation, and space applications. Conventional POD methods typically depend on external initial orbit states and clock corrections, which limit resilience and may introduce external biases. Here, we demonstrate a resilient POD method that depends solely on observations from the third generation BeiDou Navigation Satellite System (BDS-3) without requiring any external initial orbit and clock information. Reliable initial orbit states are internally obtained through a global network solution of double-differenced code observations with robust estimation. Using one year of data collected from about 200 BDS-3 tracking ground stations in 2024, initial orbit position and velocity accuracies reach approximately 0.5 km and 0.1 m/s, respectively. Based on these initial orbit states and a zero-mean clock constraint, a two-step scheme is then applied to realize the joint precise determination of satellite orbits and satellite clock corrections. The resulting orbits achieve an accuracy of up to 4.5 cm, in terms of the standard deviation (STD) of satellite laser ranging (SLR) residuals. These results confirm the feasibility of fully resilient BDS-3-only POD without reliance on external initial conditions, enabling independent and robust satellite navigation.