Fortuna Air Force Station Fortuna Air Force Station is a closed United States Air Force General Surveillance Radar station . It is located west of Fortuna , North Dakota . It was closed in 1979 as a radar station , remaining as a Long - Range Radar ( LRR ) facility until 1984 . Fortuna Air Force Station was part of the last batch of twenty - three radar stations constructed as part of the Air Defense Command permanent network . It was activated in April , and declared completely operational in late 1952 . History . The 780th Aircraft Control and Warning Squadron ( AC & W Sq ) began operations using AN / FPS - 3 search and AN / FPS - 4 height - finder radars , and initially the station functioned as a Ground - control intercept ( GCI ) and warning station . As a GCI station , the squadron ' s role was to guide interceptor aircraft toward unidentified intruder s picked up on the unit ' s radar scopes . During 1957 an AN / GPS - 3 search radar made a brief appearance . Reportedly , an AN / TPS - 10 D was also briefly used . In 1958 the 780th began operating an AN / FPS - 20 A search radar that replaced the AN / GPS - 3 . By 1960 a pair of AN / FPS - 6 , - 6A handled height - finder chores . During 1961 Fortuna AFS joined the Semi Automatic Ground Environment ( SAGE ) system , initially feeding data to DC - 20 at Malmstrom AFB , Montana . After joining , the squadron was redesignated as the 780th Radar Squadron ( SAGE ) on 1 August 1961 . The radar squadron provided information 24 / 7 the SAGE Direction Center where it was analyzed to determine range , direction altitude speed and whether or not aircraft were friendly or hostile . Fortuna was incorporated into BUIC I , a manual back - up interceptor control system implemented in 1962 . BUIC I provided limited command and control capability in the event the SAGE system was disabled . In 1963 , the AN / FPS - 20A was removed , and the makeup of the radars at Fortuna consisted of an AN / FPS - 35 search radar along with AN / FPS - 6 and AN / FPS - 90 height - finder radars . On 31 July 1963 , the site was redesignated as NORAD ID Z - 27 . In 1964 an AN / FPS - 26 A height - finder radar was installed , and the AN / FPS - 6 was retired . In the winter of 1964 , a fierce wind storm blew over the AN / FPS - 35 sail ; the sail was not replaced until the following year ( by the one formerly installed at Manassas AFS , VA , reportedly ) . For the interim , in 1965 an AN / FPS - 64 search radar was installed in the former AN / FPS - 20A tower ; it was removed in 1967 after the AN / FPS - 35 was again fully operational . The AN / FPS - 90 height - finder radar was removed in 1969 . Work proceeded on the installation of BUIC II in 1966 , after the installation of a Burroughs CSA - 51 computer system , In 1969 it became a BUIC III site . Over the years , the equipment at the station was upgraded or modified to improve the efficiency and accuracy of the information gathered by the radars . The 780th Radar Sq was inactivated and replaced by the 780th Air Defense Group in March 1970 . The upgrade to group status was done because of Fortuna AFS ' status as a Backup Interceptor Control ( BUIC ) site . BUIC sites were alternate control sites in the event that SAGE Direction Centers became disabled and unable to control interceptor aircraft . The group was inactivated and replaced by the 780th Radar Squadron . as defenses against manned bombers were reduced . The group was disbanded in 1984 . Normal operations continued until 1979 when Aerospace Defense Command was inactivated in September and the radar station was inactivated . The GATR site ( R - 27 ) was retained until the Joint Surveillance System ( JSS ) switchover , c . 1984 . The Federal Aviation Administration ( FAA ) opened an unmanned ARSR - 4 radar facility about half - way between Sidney , Montana , and Watford City , North Dakota , ( just off of Highway 68 ) before the Fortuna radars were finally decommissioned in 1984 . Current use . The station was bought by private investors that pillaged the site and stripped the site of anything of value and sold it off . After this " salvage " , the site was forfeited to Divide County over a valuation dispute , and now sits half - demolished , useless as a facility , and abandoned . An environmental impact study is currently planned as a precursor to a possible land reclamation effort . Buildings and facilities . Buildings on the station include : The Ground to Air Transmitter - Receiver ( GATR ) facility was located off - station at , roughly one mile south of the main station . References . Bibliography . Further Reading