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AN/FPS-85 Spacetrack Radar

Air Force Rome Air Development Center [RADC] was tasked with engineering responsibility for the development of a spacetrack radar (AN/FPS-85) and sponsored a developmental contract with the Bendix Corporation. As the initial operational application of the phased-array concept, in which a beam from several transmitters was transmitted without the movement or rotation of conventional radar, the AN/FPS-85 would be the first phased-array radar developed to track objects in space.

The Aerospace Defense Command's 14th Aerospace Force assumed operational control of the AN/FPS-85 Space Track Radar -- previously designated the Electronically Steerable Array Radar (ESAR) -- at Eglin AFB in late December 1968. This was the first phased-array radar system especially designed to detect and track objects in space. The physical structure of the system was 13 stories high, and the radar contained 5,134 transmitters and 4,660 receivers and utilized three computers.

The AN/FPS-85 covers 120 degrees in azimuth and in excess of 22,000 nautical miles in range. The transmitter array contains 5,928 transmitter antennas in a 78 x 76 square array and 5,184 transmitter modules installed in a 72 x 72 square array. The receiver array contains 19,500 receiver antennas and 4,660 receiver modules.

The AN/FPS-85 building is composed of the receiver side which is 192 feet long, 143 feet deep, and 143 feet high. The transmitter side is 126 feet long, 95 feet deep, and 95 feet high. Total floor space is 250,000 square feet, with 1,250 tons of structural steel, 1,400 cubic yards of concrete, and a total of 2,500,000 cubic feet in the building.

A fire station is on site and fire fighting equipment includes a 12.5 ton carbon dioxide storage tank, two fire vehicles, three water pumps (2 electrical, 1 diesel) which can pump 1500 gallons per minute each, two water tanks (250,000 gallons each) which can provide two gallons of water for every square foot of floor space, smoke and heat detectors, and automatic door closures.

Air conditioning equipment includes three 500-ton water chillers. Electrical prime power is available from Choctawhatchee Electric Cooperative. There are two 400 KVA uninterruptible power supplies; system power requirements are approximately 4,000 KW, and three emergency diesel generators (500 KW and two 400 KW).

The computer room houses five IBM computers used in mission performance, communication and software development and testing. Also, two radar interface control equipment (RICE) cabinets provide a means to interface the mission computers to the radar.

Communications equipment includes two Message Distribution Terminals (MDT) and one Mitron magnetic tape unit. Each MDT terminal has a 486 CPU and two medium speed printers. The Patch and Test Facility consists of the cryptographic equipment, patch panels, test equipment, secure voice equipment, Defense Information Agency Network (DISN) equipment and the Node for the Space Digital Information Network (SDIN).

Construction of the radar facilities began in October 1962, at test site C6, about 35 miles east of Eglin Air Force Base, FL. The testing was scheduled for May 1965, but four months before, the building and all the equipment were destroyed in a fire caused by arcing electrical equipment. The Air Force took ownership of the site in September 1968.

Initially charged with tracking objects in Earth's orbit, new software installed in 1975 allowed tracking of submarine launched ballistic missiles. This became the main use of the AN/FPS-85 though still used to perform space tracking.

The AN/FPS-85 played an active role in America's space program. From 1971 to 1984, the site was home of the Alternate Space Surveillance Center. It provided computational support to the Space Surveillance Center at Cheyenne Mountain AS, CO. If the need arose, the squadron operating the AN/FPS-85 could assume command and control for worldwide space track sensors. When that squadron integrated US Air Force Space Command in the early 1980's, the AN/FPS85 became the proving ground for the Air Force's phased array radars. The new technology was used in new radars specifically designed and located for early warning of SLBM attacks. These PAVE Phased Array Warning System radars assumed early warning responsibilities away from the Eglin Space Track Radar.

In 1987, the site returned to its original mission space surveillance. The site underwent a major transition, allowing Defense Department civilians to staff the majority of support and maintenance functions, while military people staffed the command section, orderly room and operations functions.


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