AN/FPS-50

The AN/FPS-50 was an Early Warning Radar developed by General Electric (GE) in the United States as part of the Ballistic Missile Early Warning System (BMEWS) program. Operating at 425 MHz with a peak power of 10 MW, it utilized a large, fixed Torus Antenna fence system to project two beams. The lower-angled beam provided initial warning data to the North American Air Defense Command (NORAD), while the upper beam enabled trajectory computations for launch and target points. Each AN/FPS-50 detection radar comprised three 165-foot high by 400-foot long antennas, each monitoring a 40-degree azimuth sector, providing approximately 3,000 nautical miles of coverage. These antennas, parabolic in height and circular horizontally, continuously scanned fixed areas of space with radar beams at 3.5-degree and 7-degree elevation angles. The system's transmitters used six pairs of 18-inch diameter Litton klystron tubes, each providing an average power of 2.5 megawatts, routed through large waveguides to the scanners. A prototype was built in Trinidad in February 1959 to support missile tests from the U.S. Atlantic Missile Range. Lincoln Laboratory significantly contributed to its design, including the high-power Organ-Pipe Scanner, Doppler filter banks, data-processing computers, and target-threat characterization algorithms. GE's Heavy Military Electronics Department installed these systems at Clear, Alaska, and Thule, Greenland, in the early 1960s. In 1971, the sites were modernized to the AN/FPS-50(V) configuration, which employed conventional ranging and pulse-Doppler techniques to determine the range, position, and range rate of space objects.

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