Robust and Resilient GNSS Synchronization of LEO Satellites for Space-based Aircraft Multilateration

This paper aims at developing a robust and resilient synchronization framework for Low Earth Orbit (LEO) satellites based on the combination of GNSS and Precision Time Protocol (PTP) via inter-satellite link. The satellite synchronization is needed to enable precise aircraft tracking in areas without radar coverage, by leveraging Automatic Dependent Surveillance-Broadcast (ADS-B) signals and advanced localization algorithms, exploiting Time Of Arrival (TOA), Frequency Of Arrival (FOA), and Angle Of Arrival (AOA). An Extended Kalman Filter (EKF) corrects onboard clock errors in real time, while detecting and mitigating anomalies or cyber-attacks like GNSS jamming, spoofing or denial of service. Nanosecond accuracy under nominal and disrupted conditions is obtained, significantly enhancing safety and reliability of the tracking system.