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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.

With the growing threat in the last years of the 1950s from Soviet ICBMs, the problem of attaining warning of a missile attack was given high priority. On 14 January 1958, the Secretary of Defense gave initial approval for the construction of the Ballistic Missile Early Warning System (BMEWS) being developed by the Air Force. It was directed that the Thule site be operational in 1959 as a first priority, a site in Alaska as the second priority, and a site in Scotland as the third priority. Interim computer and display facilities at NORAD were to be activated for the Thule station and later expanded to provide capability for the full system. Scanning radars were designated for initial site capability pending development of tracking radars, which would later be installed to supplement the target verification and prediction capability.

On 9 May 1958, after extensive reviews of costs and system designs, the Secretary of Defense directed the Air Force to proceed with the radar stations at Thule and Alaska and a computer and display facility at NORAD. The total cost for this portion of the system was estimated at slightly over $800 million. Authorization to proceed with the station in Scotland was deferred pending negotiations with the United Kingdom for a joint venture.

On 13 October 1958, Headquarters USAF approved the BMEWS final operational plan. The total system would consist of three radar installations, associated rearward communications, and the computation and display facilities in NORAD headquarters. Operational target dates of September I960 for Thule and September 196l for Clear, Alaska, were now established.

The program remained in an unsettled state throughout 1958-59, however, largely because of funding difficulties. It became necessary for the Air Force to aim at only a limited operational capability in order to remain reasonably close to the projected target dates. The time of construction of the planned third site, to be located at Pylingdales Moor in the United Kingdom, was also thrown into doubt. 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 June 1959, after much discussion, DoD confirmed the USAF proposal for an interim BMEWS program to include all three sites and to be carried out in two phases. An interim display facility was approved for installation at the existing NORAD combat center, to be operational in September i960 and used until the hardened NORAD combat center was completed, possibly in 1963.

On 30 September 1960, the Thule BMEWS site did reach IOC, as scheduled. This constituted a major step toward a warning capability against missiles, since the Thule location covered four sections with a total azimuth scan of l60 degrees. Also in September 1960, work began on installation of a SAC display warning system, with three display consoles to be eventually installed at SAC headquarters. Plans for sending ICBM raid information directly to SAC from the BMEWS site were disapproved by Headquarters USAF, however; instead, SAC would receive data from NORAD.

In the meantime, experience was being gained with the system. On 5 October 1960, moon echoes appeared in one of the Thule fans and were mis-identified as a potential missile threat. However, impact points were not predicted, and both NORAD and SAC treated the alarm as false. Subsequent investigation showed that it was indeed radar echoes from the moon that had caused the false alarm. Improved "gating" procedures —i.e., means of filtering out interference or aurora from a radarscope or system—were later instituted in order to prevent another false moon alarm.

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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