IntroductionIn aviation, a radar system used to detect aircraft, weather formations, and terrain. The radar system uses radio waves to determine the range, altitude, direction and speed of objects. The primary surveillance radar (PSR) and secondary surveillance radar (SSR) are installed in the ground-based air traffic control (ATC) radar system. The PSR is a radar system that detects aircraft positions in the control zone and weather conditions. The SSR is a radar system that detects aircraft positions and receives additional information, for example the identity, altitude and distance of the aircraft. The PSR and SSR antennas are co-located and operate as an integral system. The Raytheon Airport Surveillance Radar (ASR-11) is a National Airspace System (NAS) certified ATC radar system deployed worldwide at more than 125 locations. The radar systema)System CapabilitiesPSR is independent surveillance, with no additional on-board equipment required for detection. PSR allows the air traffic controller to monitor aircraft in the airspace, when no aircraft can remain invisible. The PSR only determines the position of the aircraft when the energy beam hits an aircraft and is reflected in the direction the reflection came from and in the weather conditions. The position will be sent to the ATC system where it will be displayed to the air traffic controller as a radar signal. The SSR is associated with the PSR and requires the installation of a transponder on board as it is a radio receiver and transmitter operating on the radar frequency which receives n 1030. MHz and transmits on 1090MHz. The SSR will send a 1030 MHz interrogation signal from a continuously rotating antenna to aircraft flying in its sector and a transponder-equipped aircraft...... middle of paper ...... services and procedures" ,2 May 2013 http://www.iaa.ie/safe_reg/iaip/Published%20Files/AIP%20Files/ENR/EI_ENR_1_6_EN.pdfFAA, “Section 5. Surveillance systems”, March 4, 2014 http://www. faa.gov /air_traffic/publications/atpubs/aim/aim0405.htmlPhil V., "Air Traffic Services Surveillance Systems" http://www.airwaysmuseum.com/Surveillance.htmFAA, "Airport Surveillance Radar (ASR-11)", January 15, 2014 http://www.faa.gov/air_traffic/technology/asr-11/Wikipedia, "Controller-pilot data link communications" http://en.wikipedia.org/wiki/Controller%E2%80 %93pilot_data_link_communicationsVatsim UK, “Introducing RADAR” www.vatsim-uk.co.uk/download/fetch/?downloadID=00208Mail Today, “30-minute radar outage hits flight operations at Delhi's IGI Airport ", February 9, 2013 http://indiatoday.intoday.in/story/power-outage-igi-airport-leads-to-mass-scare-india-today/1/249546.html