ADS-B is a surveillance technique that relies on aircraft broadcasting their identity. Space-based ADS-B systems allow aircraft to broadcast their identity and position in oceanic and remote areas where it would be difficult or impossible to install ADS-B ground stations. As a result, space-based ADS-B allows for reduced separation and increased airspace operational efficiency via more direct routing and increased availability of optimal altitudes. But spaced-based ADS-B broadcasts can get distorted and lose their integrity. The project will develop an integrity estimator for space-based ADS-B systems based on crosschecking positions reported in ADS-B messages with position estimations provided by space-based multilateration  (MLAT) systems. The aim is to deliver a prediction tool to compute the theoretical performance of a MLAT system whose receiving stations are onboard of a constellation of low-orbit satellites.