Ballistic Missile Early Warning System (BMEWS)
AN/FPS-50 Detection Radar
AN/FPS-92 Tracking Radar

The Ballistic Missile Early Warning System (BMEWS) became the first operational missile detection radar in 1959. The BMEWS system would provide long-range, immediate warning of a missile attack over the polar region utilizing stations in the northern hemisphere.

By 1958, a prototype of the Ballistic Missile Early Warning System (BMEWS) at the Trinidad, British West Indies, site provided surveillance and tracking of ballistic missiles, as an overall step in the BMEWS development. The Trinidad Radar Site commenced operation on 4 February 1959, gathering data on missiles fired on the Atlantic Missile Range, satellites, and meteors. In February 1962 the Radio Corporation of America (RCA) assumed responsibility for the operation of the Trinidad Radar.

In late 1959, ARPA opened the 474L System Program Office (SPO), which it tasked to develop techniques and equipment for tracking space objects and detecting incoming Soviet ICBMs. By the mid-1960s, the 474L SPO had activated three Ballistic Missile Early Warning System (BMEWS) radars located at Thule AB, Greenland (1960); Clear AFS, Alaska (1961); and RAF Fylingdales Moor, England (1963). These radars provided the capability to detect an incoming ICBM attack and provide 15 minutes warning. They also provided tracking data on most orbiting satellites. ARDC set up the Interim National Space Surveillance Control Center at Hanscom AFB in January 1960. The Air Force designated ADC the primary user of spacetrack data. BMEWS Site II is located at Clear Air Force Station, Alaska. It is 40 miles north of Mount McKinley and 80 miles south of Fairbanks. It manages and operates three AN/FPS-50 detection radars that cover 120 degrees in azimuth and approximately 3,000 nautical miles in range. It also has one AN/FPS-92 tracking radar.

Clear's Technical Site (or "Tech Site" for short) was the last mechanical Ballistic Missile Early Warning System (BMEWS) site in the world. The other two BMEWS sites, Thule AB in Greenland and Fylingdales-Moor in Great Britain, converted to phased-array systems long prior. Clear's tech site was operational for 40 years, from 1961 to 2001, when the new Solid-State Phased Array Radar System (SSPARS) became operational. The mechanical BMEWS radar located at Clear Air Station was deactivated on February 1, 2002, and replaced by the AN/FPS-120 Solid State Phased-Array (SSPAR) radar. Considerations behind the deactivation included the prohibitive costs associated with maintaining the system, its manpower needs )requiring 5 personnel to operate it) and its limitations (the system was incapable of tracking more than one object at a time)

As of October 2002, Clear's tech site was still standing and awaiting its final disposition. It is comprised of three Detection Radars (DR 1, 2, and 3), three scanner buildings (104, 105, and 106), two transmitter buildings (101 and 102), and the Tracking Radar (TR) housed in its protective dome. The power plant is also a part of the tech site. Each DR is 165 feet tall and 400 feet wide (larger than a football field) and weighs more than 2,000,000 lbs. The tracking radar, housed in a 140 foot protective dome atop building 102, has an 85 foot diameter dish capable of rotating 360 degrees.

AN/FPS-50 Detection Radar

Each AN/FPS-50 detection radar consists of three antennas and associated equipment which monitors three areas, each area is 40 degrees in azimuth, whie providing a coverage of approximately 3,000 nautical miles in range. The Detection Radar antennas are 165-feet high by 400-feet long. They continuously watch a fixed area of space for missile launches and orbiting satellites. Each of the DR areas is repetitively scanned by radar beams at two elevation angles. The upper radar fans radiate at 7-degree elevation and the lower radar fans at 3.5-degree elevation.

AN/FPS-92 Tracking Radar

In June 1965, RADC was assigned engineering control of the AN/FPS-92 tracking radar. This radar was added to the Site II BMEWS. The AN/FPS-92 tracking radar is an 84-foot diameter mechanical antenna, housed in a 140-foot high radome. Radar signals are sent out and processed for targets. This radar also performs space surveillance functions.


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