Miles City Air Force Station
Miles City Air Force Station (1954-1968) - A Cold War Air Force Radar Station first established in 1954 near Miles City, Custer County, Montana. Named Miles City Air Force Station after the location. The station was built on a portion of the old Fort Keogh military reservation. Initially assigned a Permanent ID of M-98 and later a Sage ID of Z-98. Abandoned in 1968.
History
Established on 1 Oct 1954 and became operational in 1955 as Miles City Air Force Station manned by the 902nd AC&W Squadron. The station initially had both a Ground-Control Intercept (GCI) and an early warning mission. The early warning mission involved tracking and identifying all aircraft entering their airspace while the GCI mission involved guiding Air Force interceptors to any identified enemy aircraft. Controllers at the station vectored fighter aircraft at the correct course and speed to intercept enemy aircraft using voice commands via ground-to-air radio.
Initial equipment included the mobile MPS-7 search radar and an MPS-14 height-finder radar. The MPS-7 search radar was replaced by an FPS-20 in 1958 and that radar was upgraded to an FPS-66 in 1961 and later to an FPS-27. The MPS-14 height-finder was replaced by an FPS-6 in 1961.
SAGE System Transition
The transition of the manual GCI system to the automated SAGE system began with the installation of the FST-2 coordinate data transmitter and search radar upgrades. The FST-2 equipment digitized the radar returns and transmitted the digital returns to the SAGE direction center. Under the SAGE System, interceptor aircraft were directed to their targets by the direction center computers and controllers, greatly reducing the need for local controllers and equipment at every radar station.
The FST-2 was a very large digital system using vacuum tube technology. Over 6900 vacuum tubes were used in each FST-2 requiring 21 air-conditioned cabinets, 40 tons of air conditioning, 43.5 kva of prime power, and usually a large new addition to the operations building. The FST-2B modification added two more cabinets but with newer solid-state (transistor) technology to process coded responses from aircraft transponders.
SAGE System Operation

| Assigned | Direction Center | Sector | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| 1 Jan 1961 - 25 Jun 1963 | Minot SAGE Direction Center DC-19 | Minot Air Defense Sector | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 25 Jun 1963 - 1 Apr 1966 | Malmstrom SAGE Direction Center DC-20 | Great Falls Air Defense Sector | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 1 Apr 1966 - 18 Jun 1968 | Malmstrom SAGE Direction Center DC-20 | 28th Air Division
The site began operation as a SAGE site on 1 Jan 1961 initially feeding the Minot SAGE Direction Center DC-19 at Minot AFB. With the closure of DC-19 in 1963, Miles City was connected to the Malmstrom SAGE Direction Center DC-20 at Malmstrom AFB and remained connected to them until the site closed in 1968. Gap FillersMiles City AFS was responsible for maintaining two remote unattended gap-filler radar sites. The gap-filler sites were placed in locations where the main search radar lacked coverage. The unattended gap filler sites were placed in locations where the main search radar lacked coverage. These sites were equipped with short range FPS-14 or FPS-18 search radars and FST-1 Coordinate Data transmitters that sent digitized radar target data to a SAGE direction center and to the main radar site. Both the radar set and the FST-1 were dual channel to increase site up time. Maintenance teams were dispatched for regularly scheduled maintenance or when fault indicators on the FSW-1 remote monitoring equipment suggested the site had problems. The FSW-1 also allowed remote operation of specific functions such as channel changes for the radar and for the FST-1, it also allowed remote operation of the diesel generators at the gap filler site. Miles City AFS was responsible for the gap-filler sites at Glendive and Brockway Montana.
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