Radar

Radar (radio detection and ranging) measures range by timing a microwave pulse echo and bearing by antenna direction; it is required by SOLAS V/19 on ships of 300 GT and over. The 9 GHz X-band gives sharp short-range definition and shows small targets and SARTs; the 3 GHz S-band penetrates rain and sea clutter for long-range detection in heavy weather. ARPA processing tracks targets and computes CPA and TCPA for collision avoidance, the radar complement to the COLREGs lookout duty under Rule 5.