Orbit Determination Using Combined GPS + Beidou Observations for Low Earth Cubesats: Software Validation in Ground Testbed

Abstract

Nowadays, satellites in low earth orbit (LEO) can benefit from Global Navigation Satellite System (GNSS), such as Global Positioning System (GPS) of United States, to estimate positions and velocities. As China’s BeiDou Navigation Satellite System (BDS) has been formally operational since the end of 2012, standalone Beidou and combined GPS + Beidou positioning techniques tend to be applied in the future space missions. However, no LEO satellites have been operated with Beidou receivers at present. Hence Beidou-based precise orbit determination (POD) technique is required to be tested and verified on ground at first stage. This study is to test the GPS + Beidou orbit determination software in ground testbed. GNSS data collected from iGMAS (International GNSS Monitoring and Assessment Service) and MGEX (Multi-GNSS Experiment) stations are processed in both static and kinematic PPP (Precise Point Positioning) modes. Decimetre level of positioning accuracy is achieved. The inter-system biases between GPS and Beidou are estimated and analysed. Results indicate that GPS + Beidou solutions are more precise than the standalone GPS solutions.