Research on Scientific and Technological Applications of Spaceborne GNSS for China’s Space Station

• Accurately quantifying the impacts of key events such as spacecraft docking/separation and extravehicular activities. • Assess the operational status of the onboard external atmospheric detector. • The estimated scale factor of the modeled aerodynamic drag effectively reflected the China’s Space Station’s frontal cross-sectional area. • Independent evaluation of the external clock’s frequency stability. • Near-real-time Precise Orbit Determination for China’s Space Station was achieved with an accuracy of 15 cm and the subsequent orbit prediction errors were 37m@3h. China’s Space Station (CSS) is equipped with a high-performance BDS/GPS receiver that enables centimeter-level Precise Orbit Determination (POD) and sub-nanosecond time synchronization to support scientific research tasks. This study investigates the scientific and technological applications of the orbital and empirical parameters estimated from the reduced-dynamic Precise Orbit Determination (RPOD) process. Analysis of in-flight data demonstrates the following practical applications: 1) The dynamic and empirical acceleration parameters allow for an independent centimeter-level determination of the CSS’s in-flight center-of-mass (CoM), while accurately quantifying the impacts of key events such as spacecraft docking/separation and extravehicular activities. 2) The aerodynamic force modeled using a detailed geometric macro-model can assess the operational status of the onboard external atmospheric detector. 3) The estimated scale factor of the modeled aerodynamic drag effectively reflects the CSS’s frontal cross-sectional area, exhibiting a strong positive correlation with the daily reference area provided by the flight control team. 4) The GNSS receiver can run with external time source, thereby, GNSS-based timing with 0.1 ns precision enables independent evaluation of the external clock’s frequency stability. 5) Leveraging rapid data downlink via China’s Tianlian geosynchronous relay satellite system and near-real-time (NRT) GNSS products, NRT-POD for CSS is achieved with an accuracy of 15 cm and the subsequent orbit prediction errors are 37m@3h and 565m@12h during high solar activity period. Overall, this study demonstrates the feasibility of using spaceborne GNSS receiver as a multi-functional ‘ sensor’ to monitor and predict the status of large space stations. These capabilities can further support space scientific activities, collision avoidance maneuvers and flight plan coordination.