airport surface detection equipment

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A ground mapping system that uses analog radar equipment to provide surveillance of aircraft and other surface vehicles on an airport surface. It is used by air-traffic controllers in airport control towers to monitor and control the movement of aircraft and vehicles. A situation display of the targets includes a map identifying the runways and taxiways and a visual map of the airport features, created through the contrast on the radar display resulting from the absence of returns from smooth concrete surfaces and the ground-clutter returns from grassy areas. An important safety function of the airport surface detection equipment (ASDE) is to determine whether or not a runway is clear for the next departure or arrival operation. This runway clearance determination is aided by the ASDE's capability to display an image of the aircraft in which the target's extremities (nose, tails, and wing tips), especially for large aircraft, are evident to the eye.

The ASDE antenna revolves at 60 revolutions per minute, providing a rapid update of target movements. It is located on a high vantage point, typically on top of the tower cab or on a special remote tower, that provides line-of-sight coverage of the desired areas. Modern ASDEs utilize digital processing and an interrogation technique called frequency agility, which permits the transmission of up to 16 different Ku-band frequencies within a cycle. These techniques optimize target detection in the presence of ground and rain clutter and the rejection of false targets. In the digital processing, different thresholds for rejecting clutter are used on specified areas of the airport surface, such as on paved surfaces versus grassy areas. These systems are designed to detect all aircraft and vehicles having a radar cross section of 30 ft² (3 m²) or greater, and will resolve two closely spaced targets when separated by 40 ft (12 m) in range or 80 ft (24 m) in azimuth at a range of 12,000 ft (3650 m). The basic coverage is the entire airport surface out to 24,000 ft (7300 m) in range and 200 ft (60 m) in altitude. Areas where coverage is not desired are ignored for detection and blanked out on the situation display.

The digital processing in modern ASDEs also provides the basis for automation functions that process target data to provide controllers with improved information. Principal automation features include target tracking, the application of runway safety logic functions to the tracks, and automatic alerting of the controller to dangerous situations determined by the logic. The design requirements for advanced surface surveillance systems include providing data that allows determination of target identity and target intent from flight-plan information or from data-link messages between the control tower and aircraft. See also Air-traffic control; Electronic navigation systems; Moving-target indication; Radar.

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(DOD) Short-range radar displaying the airport surface. Aircraft and vehicular traffic operating on runways, taxiways, and ramps, moving or stationary, may be observed with a high degree of resolution.

Radar equipment specifically designed to detect all principal features on the surface of an airport, including aircraft and vehicular traffic, and to present the entire picture on a radar indicator console in the control tower. The equipment is used to augment the visual observation by tower personnel of aircraft and/or vehicular movements on runways and taxiways.

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