Real-Time Navigation of LEO Satellite Using QZSS MADOCA-PPP Signal Based on RTKLIB

Quasi-zenith satellite system (QZSS) multi-GNSS advanced orbit and clock augmentation - precise point positioning (MADOCA-PPP) is a Japanese precise positioning service by way of QZSS satellite communication links, whose PPP/PPPambiguity resolution (AR) reference software based the well-known open-source RTKLIB is developed. MADOCA-PPP has the potential to perform the precise real-time navigation of a low Earth orbit (LEO) satellite. The purpose of this study is to show and evaluate the precise orbit determination (POD) algorithm using the MADOCA-PPP approach combined with RTKLIB modifications suitable for the LEO satellite POD such as satellite dynamic models and tuning techniques in PPP filter. In several data samples of Sentinel-6A, the reduced dynamics improved the 3D root mean square (3D-RMS) position error by 9–16 % and the convergence time by 2 % compared to the kinematic PPP/PPP-AR solutions. Additionally, the fixed solution with PPP-AR reduced the position accuracy by 3–11 % and the convergence time by 5 % compared to the float solution and the average fixed ratio was 84.9 %. Overall, the position solution combining the satellite dynamic model and PPP-AR with the tuning techniques provided the best results, with an average 3D-RMS position error of 11.4 cm and convergence time of 30.7 minutes confirmed in several samples. From these results, the proposed QZSS MADOCA-PPP based on RTKLIB was found to achieve LEO POD with decimeter-level position accuracy. The availability of QZSS MADOCA-PPP would be limited in comparison with global PPP service, however, this is expected to work as the more continuous and precise real-time navigation of the LEO satellite by considering further algorithm improvement and additional GNSS equipment.