PEGASUS—Performance Experiments in Germany on ADS-B Using Mode S Extended Squitter

Future surveillance systems have to be capable of operating worldwide and to co-exist with other systems in the same frequency band. Extended Squitter is an ADS-B system which uses the same frequencies as current SSR (Secondary Surveillance Radar) systems (also called ATCRBS = Air Traffic Control Radar Beacon System). The German CAA, Deutsche Flugsicherung GmbH (DFS), and the U.S. Department of Transportation/Federal Aviation Administration (FAA) agreed to collaborate on a measurement activity in 2000 using Extended Squitter as the ADS-B medium. The Extended Squitter frequency 1090 MHz is actively being used for replies to secondary surveillance radars and for TCAS air-to-air surveillance. Frankfurt was chosen to perform the measurements under high interference conditions. The primary objective of the tests was the Extended Squitter performance measurement in the dense interference environment of Frankfurt. Both air-to-air and air-to-ground receptions were to be tested. For a good understanding of the results and to allow estimates for future environments, measuring the interference environment, the aircraft density and distribution was another objective. Results of these background measurements as well as of Extended Squitter performance in this specific environment are presented below.