Air Route Surveillance Radar

The Air Route Surveillance Radar is used by the United States Air Force and the Federal Aviation Administration to control airspace within and around the borders of the United States.

The ARSR-4 is the FAA's most recent (late 80s, early 90s) addition to the "Long Range" series of radars, which are search radars with a range of at least 200 nautical miles (370 km; 230 mi). The Westinghouse system is solid state and has a 250-nautical-mile (460 km; 290 mi) range. In addition, the ARSR-4 features a "look down" capability that enables the radar to detect aircraft attempting to elude detection by flying at low altitudes, advanced clutter reduction via hardware and software post-processing, and enhanced poor-weather detection of aircraft. A Beacon system, the ATCBI-6M (a monopulse system), is installed along with each ARSR-4. However, since the ARSR-4 is a 3D radar, it is capable of determining aircraft altitude independently of its associated Beacon (albeit less accurately).