Performance Assessment of Onboard Time-Synchronization for LEO Satellites

Kurzfassung

Future Low Earth Orbit (LEO) Positioning, Navigation and Timing (PNT) systems will require accurate real-time Orbit Determination and Time Synchronization (ODTS) to meet performance and scalability demands. This paper evaluates the achievable real-time ODTS performance using flight data from three Sentinel satellites equipped with GPS/Galileo receivers. The analysis uses a ten-day dataset and assesses synchronization accuracy when relying on broadcast navigation messages and when applying Galileo High Accuracy Service (HAS) corrections, representing realistic operational conditions for future LEO-PNT architectures. Reference solutions are derived from the Navigation Support Office of the European Space Agency (ESA) Precise Orbit Determination products, aligned to Galileo System Time (GST). The results show that sub-nanosecond synchronization to GST is achievable in orbit. These findings confirm the feasibility of autonomous onboard ODTS for large-scale LEO constellations and highlight key design drivers for next-generation LEO-PNT systems.