Secondary surveillance radar

Secondary surveillance radar (SSR) is a radar system used in air traffic control (ATC), that unlike Primary Surveillance Radar (PSR) systems that measure the bearing and distance of targets using the detected reflections of radio signals, relies on targets equipped with a radar transponder, that reply the Mode that an interrogation pulse code corresponds to, by transmitting a pulse telegram containing, e.g. the identity code as 4 digit octal number in Mode A, the aircraft's altitude from the barometric pressure sensor of an aircraft in Mode C and a unique 24-bit address and further information in other Modes. SSR is based on the military Identification Friend or Foe (IFF) initially standardized in the U.S. and later adopted by NATO (North Atlantic Treaty Organization), however first IFF systems date back to World War II. SSR Mode A, C and S are compatible with IFF Mode 3A, C and S. SSR Mode B and D are not specified in ICAO Annex 10 any more for use today. Additional SSR Mode S based systems are ADS-B, TCAS, Multilateration Systems (MLAT) and satellite based surveillance using ADS-B messages.

This article is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.