Robust GNSS–ISL Synchronization in LEO Constellations for Space-Based Aircraft Multilateration: Assessment Using Real Data

This paper presents a secure synchronization framework for Low Earth Orbit (LEO) satellite constellations based on the combined use of Global Navigation Satellite Systems (GNSS) and the Precision Time Protocol (PTP) over intersatellite links. Accurate time synchronization among satellites is a key enabler for precise aircraft tracking in regions without radar coverage, achieved by exploiting Automatic Dependent Surveillance-Broadcast (ADS-B) signals and advanced localization algorithms based on Time of Arrival (TOA) measurements. An Extended Kalman Filter (EKF) is employed to estimate and correct onboard clock errors in real time while enhancing security against anomalies and cyber-attacks. Three integrity monitoring mechanisms are integrated into the EKF to assess innovation consistency, measurement compliance, and the presence of GNSS and PTP disruptions. The framework is evaluated under nominal and adversarial conditions, including jamming, spoofing, and denial-of-service attacks, using real data. The results demonstrate timing accuracy on the order of tens of nanoseconds under both nominal and degraded operating conditions. The proposed approach significantly enhances the security, safety, and reliability of space-based aircraft surveillance systems, supporting next-generation air traffic monitoring services in areas lacking terrestrial infrastructure.