Caswell Air Force Station

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Caswell Air Force Station (1952-1980) - A Cold War Air Force Radar Station first established in 1952 near Caswell, Aroostook County, Maine. Named Caswell Air Force Station after the location. Initially assigned a Permanent ID of P-80 and later a Sage ID of Z-80. Abandoned in 1980.


Established in 1952 as site LP-80 replacing Lashup Radar Site L-50 at Limestone ME. Became operational in 1952 as Caswell Air Force Station manned by the 766th 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 two FPS-10 combination search/height-finder radars. The two FPS-10s were replaced with FPS-8/GPS-3 search radar in 1955-1956 and two FPS-6A height-finder radars in 1957-1958.

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

The site began operation as a SAGE site in February 1959 initially feeding the Topsham SAGE Direction Center DC-05. The search radar was upgraded to an FPS-7C in 1961. An FPS-26A height-finder radar was also installed. With the closure of Topsham SAGE Direction Center DC-05 in 1969 records indicate that the site switched to the Hancock SAGE Direction Center DC-03 but newspaper accounts indicate that the site was feeding the North Bay SAGE Direction Center DC-31.

NIKE Missile System

In 1957, four Nike Ajax missile sites were placed around nearby Loring Air Force Base for protection of the USAF Strategic Air Command B-52 bombers and their nuclear weapons. Army NIKE Headquarters facilities were located at Loring Air Force Base along with a NIKE manual AADCP command post. Caswell Air Force Station provided long-range search and height-finder radar data to the AADCP where it was plotted manually on a plotting board with tracks allocated to the individual NIKE batteries. With the SAGE System implementation, the manual plotting and assignment of tracks to the individual NIKE Batteries was eliminated and the functions were taken over by the AADCP SAGE System console operators at the Topsham SAGE Direction Center DC-05.

In 1958-1959, NIKE sites L-13 and L-58 were converted from the conventionally armed Ajax to nuclear-armed Hercules missiles. These sites remained operational until 1966. NIKE sites L-31 and L-85 were not selected for upgrade and site L31 was closed. The remaining NIKE sites were closed in June 1966.

Gap Fillers

Caswell AFS was responsible for the maintenance of one remote unattended gap-filler radar site. 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. The Caswell AFS gap-filler radar was located at Bridgewater, Maine. Other sites were planned but never built.

Caswell AFS Gap Filler Radar Sites (edit list)
ADC NORAD Location State Type From To GPS Notes
P-80B Z-80B Bridgewater ME FPS-18A, FST-1 1959-03 1967-12 46.42104,
Structures and antenna still in place


Caswell AFS and the 766th were deactivated on 1 Jul 1980.

Physical Plant

The physical plant of the site was divided into the main site, a cantonment area, a housing area, and a radio site. The main site housed the operations buildings, the radar towers, and the backup generators. The cantonment area housed the enlisted barracks, the bachelor officer's quarters, the orderly room, the dining hall, the motor pool, and other support buildings. A small 18 unit housing area was located adjacent to the cantonment area. A separate Ground to Air Transmitter/Receiver (GATR) radio site housed the radio equipment for directing aircraft intercepts.

Caswell AFS Major Equipment List
Search Radar HF Radar Data Systems
Unit Designations
  • 766th Aircraft Control & Warning (AC&W) Squadron (1952-1959)
  • 766th Radar Squadron (SAGE) (1959-1974)
  • 766th Radar Squadron (1974-1980)
766th Assignments
  • Note that articles about this site in 1977-1978 indicate that the site was connected to the 22nd NORAD Region (North Bay SAGE Direction Center DC-31) and do not mention the 21st AD Hancock SAGE Direction Center DC-03. The 22nd NORAD Region Control Center at North Bay, Ontario Canada analyzes radar data from Caswell AFS and nine Canadian sites and also 24 search radars of the Distant Early Warning (DEW) line in the Canadian Arctic."

Caswell: Eyes & Ears of Defense - Loring Limelite, 8 Aug 1978 Caswell Radar Aids National Defense - Loring Limelite, 14 Jul 1977

Caswell Air Force Station Partial Commanders List (edit list)
Assumed Relieved Rank Name Cullum Notes
1955~ 1958~ Major Simmons, Austin W. N/A Daughter confirmed years
Major Williams, Charles E. Jr. N/A
1975~ Major Arneson, Dwynne C. N/A
1976 1980 Major Reitinger, John P. N/A

Current Status

Abandoned in Caswell, Aroostook County, Maine.

Location: Caswell in Aroostook County, Maine.

Maps & Images

Lat: 46.97083 Long: -67.83444

  • Multi Maps from ACME
  • Maps from Bing
  • Maps from Google
  • Elevation: 830'

GPS Locations:

See Also:


  • Cornett, Lloyd H. & Johnson, Mildred W., A Handbook of Aerospace Defense Organization (1946-1980), Office of History ADC, Peterson AFB, Colorado, 31 Dec 1980, 179 pages, Pdf, page 166.
  • Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf, page 120.
  • USGS Geographic Names Information System (GNIS) Database Entry: 2086957


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