Space-Based Multilateration System for a GNSS-Independent Aircraft Localization

Modern Air Traffic Control (ATC) relies on the Automatic Dependent Surveillance-Broadcast (ADS-B) system, which transmits GNSS-based aircraft positions computed onboard to the ground. While ADS-B is key to future Air Traffic Management (ATM), its dependence on GNSS makes it vulnerable to failures and cyber-attacks. Ground-based systems are currently used to validate ADS-B data, but they are unavailable over remote areas, such as oceans. This paper proposes a Low Earth Orbit (LEO) satellite constellation performing multilateration (MLAT) on ADS-B signals to provide GNSS-independent position estimates. Unlike classical ground-based multilateration, the space context introduces challenges such as limited visibility, poor geometry, ill-conditioning, and synchronization issues. To address these, the evaluation of a combination of Time of Arrival (TOA), Frequency of Arrival (FOA) and Angle of Arrival (AOA) measurements is presented. The proposed architecture comprises LEO satellites equipped with ADS-B receivers and phased array antennas. Performance is evaluated using the Cramér-Rao Lower Bound (CRLB). Simulations over the Atlantic Ocean assess different measurement combinations and constellation configurations. The results show that, with the appropriate design, the system achieves a localization accuracy that is compliant with the requirements of the air traffic control in route (ie, 350 m horizontal rms error).