Housed in a dome 30 feet (9.1 meters) in diameter, six feet (1.8 meters) thick, and suspended 11 feet (3.3 meters) above the fuselage on two struts, the AN/APY-1/2 radar is the most notable feature of the E-3 Airborne Early Warning aircraft. Introduced in 1977, the APY-1/2 equipped Sentry aircraft have served as the primary AEW sensor for both America and NATO. When in operation, the radar turns at 6 revolutions per minute, and is capable of scanning the sea, ground, and air in a 200 mile (320km) radius around the aircraft. The APY-1 radar is sensitive enough to detect and track slow moving, low altitude air targets over any terrain, and can track both sea and air targets simultaneously. The AN/APY-1/2 can operate in a variety of modes; Pulse Doppler Non Elevation Scan for surveillance of airborne targets, Pulse Doppler Elevation Scan to determine the elevation, beyond the horizon pulse radar mode, receive only mode for passive operation, and maritime mode which uses very short pulse width for surface ship detection.