Orbit prediction and orbital parameters generation for next-generation Global Navigation Satellite Systems

To achieve higher accuracy in satellite-based navigation, the Institute of Communication and Navigation of the German Aerospace Centre is investigating innovative architectures for a future satellite system that fully exploits the benefits of Optical Inter-Satellite Links (OISLs). In such scenario, the system’s ground infrastructure is minimized and the Precise Orbit Determination of GNSS satellites is considerably improved thanks to the accurate inter-satellite ranging enabled by the OISLs. In this technical note, we address two aspects of orbit dissemination. Firstly, to make use of the estimated orbits, which refer to past epochs due to the inherent latency of the orbit determination process, it is necessary to propagate the orbits for a certain amount of time in the future, so to be able to provide final GNSS users with actual orbit data. With the intention of understanding to what extent can orbit prediction be autonomously performed onboard each satellite, it is important to simplify the propagation process which is by nature highly computationally intensive. Secondly, since the broadcast GNSS signals are characterized by low data rate, it is necessary to parametrise the propagated orbits to maximize the efficiency of the dissemination. In this work, the force models underlying the orbit propagation are investigated and simplified to find an optimal trade-off between orbit accuracy and model complexity reduction, and the process of orbit parameter generation is evaluated.