Space-based multilateration for a GNSS-independent aircraft localisation
Mauro Leonardi, Giulio Sidoretti, Edoardo Navarra, Mahsa Mohebbi · Acta Astronautica · 2026
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. For this reason, ground-based systems are currently used to validate ADS-B data, but they are unavailable in remote areas, such as the ocean. 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 synchronisation issues. To address these limitations, two possible solutions are presented and evaluated: (i) a combination of Time of Arrival (TOA) with additional measurements, such as Frequency of Arrival (FOA) and Angle of Arrival (AOA); (ii) an improved and optimised receiver antenna to obtain larger coverage of the satellites. In both cases, the proposed architecture comprises LEO satellites equipped with ADS-B phased array antennas, useful for obtaining multiple beams with different footprints on the ground. The system localisation 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 localisation accuracy that completely meets the requirements of air traffic control en-route (i.e., 350 m horizontal RMS error).