Almaden Air Force Station Almaden Air Force Station is a closed United States Air Force General Surveillance Radar station . It is located southeast of Los Gatos , California . It was closed in 1980 . History . Almaden Air Force Station was established in 1954 by Air Defense Command as one of a planned deployment of forty - four Mobile radar stations to support the permanent ADC Radar network in the United States sited around the perimeter of the country . This deployment was projected to be operational by mid - 1952 . Funding , constant site changes , construction , and equipment delivery delayed deployment . Almaden AFS was located on the summit of Mount Umunhum in the Santa Cruz Mountains , the station is a few miles south of San Jose , California and sits above Almaden Valley . Great difficulties were encountered in construction at this site . During fiscal year 1957 , the Air Defense Command held up construction due to funding shortfalls . The 682nd Aircraft Control and Warning Squadron was assigned to the new station by the 28th Air Division on September 1 , 1957 . It became operational on March 21 , 1958 , equipped with AN / FPS - 20 and twin AN / FPS - 6 radars . In 1961 , the site received an AN / FPS - 24 radar , but could test the radar only on a not - to - interfere basis with television transmissions . This radar became operational in 1962 , and the AN / FPS - 20 was removed soon afterward and its concrete foundation was re - purposed as a helipad . In 1963 , an AN / FPS - 90 replaced the second AN / FPS - 6 height - finder and the original AN / FPS - 6 was removed and replaced with an AN / MPS - 14 height finder adjacent to the AN / FPS - 24 radar tower . During 1961 , Almaden AFS joined the Semi Automatic Ground Environment ( SAGE ) system , feeding data to DC - 18 at Beale AFB , California . After joining , the squadron was re - designated as the " 682d Radar Squadron ( SAGE ) " . In 1963 , the SAGE site was switched to DC - 17 at Norton AFB , California . Also on 31 July 1963 , the site was re - designated as NORAD ID Z - 96 . In 1979 Almaden AFS came under Tactical Air Command ( TAC ) jurisdiction with the inactivation of Aerospace Defense Command and the creation of ADTAC . Operations ceased on 1 April 1980 as a result of budget restrictions , and the general phase down of air defense radar stations . The station operated a Ground - to - Air Transmitter - Receiver ( GATR ) atop the summit of Mount Umunhum until the completion of the AN / FPS - 24 radar in 1962 . To eliminate radio frequency interference from the AN / FPS - 24 radar , the GATR was then moved one mile west to the summit of Mount Thayer . The original GATR building was subsequently converted to supply storage and ultimately as a training room facility . The station today is abandoned and off - limits to the general public . It was acquired in 1986 by the Midpeninsula Regional Open Space District ( MROSD ) . The site is now a part of the Sierra Azul Open Space Preserve although it is not yet open to the public because of environmental hazards ( asbestos , black mold , and lead - based paint ) . The MROSD estimates it will take at least US $ 13 . 1 million to clean up the base for public use .