side-looking airborne radar
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side-looking airborne radar (SLAR)
An airborne radar that produces an image of a portion of the earth's surface by sweeping the terrain by means of one or more antennae and at an angle to the axis of the aircraft. A SLAR can look at the ground, which can be 25 to 60 miles (40–100 km) on one side of the aircraft. A long antenna is mounted on the aircraft side. It has a very narrow beam width of 0.1° or less. Its wide vertical beam is arranged to cover a wide swath, parallel to the aircraft track. The resolution of the ground is determined by the pulse length and the horizontal beam width. The azimuth discrimination worsens with the range. It can be used for navigational purposes by providing speed and direction over the ground to a dead-reckoning computer.