Grand Rapids Air Force Station
Grand Rapids Air Force Station (1956-1963) - A Cold War U.S. Air Force Radar Station. Located near Grand Rapids, Itasca County, Minnesota. Initially assigned a Permanent ID of SM-138 and Sage ID of Z-138. Closed in 1963.
Established in 1956 and became operational on 1 Feb 1957 as Grand Rapids Air Force Station manned by the 707th Radar Squadron (SAGE).
Initial equipment included the FPS-3 search radar and one FPS-6 height-finder radar. The FPS-3 was upgraded to a FPS-20 in 1958 and later to updated to a FPS-20A. In 1959 a second height-finder was added, a FPS-6B. This configuration met the requirements for the transition to the SAGE System operation.
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
Grand Rapids AFS and the 707th were deactivated in 1963.
The physical plant of the site was divided into the main site, a cantonment area, a housing area and two radio sites. 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. Apart from the main site was a small 19 unit housing area for married personnel.
A separate radio site housed the radio equipment for directing aircraft intercepts. Like most early radar stations, GrandRapids originally had a radio transmitter site and a separate radio receiver site used by local controllers for voice direction of fighter interceptors to their targets. With the SAGE System, the SAGE Direction centers had the primary task of directing intercepts and the local radio sites were reconfigured, usually into a single site that was known as the Ground to Air Transmitter Receiver (GATR) site. The GATR site communicated with the interceptors from either the local site or the SAGE direction center via voice commands and/or a digital data link.
Note: Reported dates overlap and may be incorrect or reflect periods of intermittant temporary command.
The main site is overbuilt with new construction. Parts of the Radio Transmitter and Receiver site still exist. The housing area is in private owners hands. Cantonment area is overbuilt.