(rā’ dar) A system in which short electromagnetic waves are transmitted and the energy scattered back by reflecting objects is detected. Acronym for ‘‘radio detection and ranging.’’ Ships use radar to help ‘‘see’’ other ships, buoys, shorelines, etc. Beacons sometimes provide distinctive targets. Radar is used in aircraft navigation (see Doppler-radar), in positioning, and in remote sensing. The radar spectrum is sometimes subdivided: P-band, 225–390 MHz; L-band, 390–1550 MHz; S-band, 1550 to 5200 MHz; X-band, 5200–11 000 MHz; K-band, 11–36 GHz; Q-band, 36–46 GHz; V-band, 46–56 GHz. Other systems of radar designation are shown in Figure R-1.