The
Cold War radar station near Mill Valley was one of twenty-eight stations approved by the
United States Secretary of Defense on July 21, 1950, as part of the
Permanent System radar network (the Corps of Engineers managed construction for the USAF). Construction began at an upper location of the former
World War II Mount Tamalpais Radar Site of the
Aircraft Warning Service (the World War II information center of the AWC was located at
tbd for plotting radar tracks in the San Francisco area).
Mount Tamalpais Air Force Station Mount Tamalpais Air Force Station was the
military installation where the 666th Aircraft Control and Warning Squadron was activated on January 1, 1951. The squadron "began operating a pair of
AN/CPS-6B radars at this Bay-area site in late 1951". The
Air Defense Command Manual Control Center at the station networked
ground-controlled interception radars, and on March 10, 1952, the first Multiple Corridor System for identification of traffic arriving from overseas became operational outside San Francisco. Mount Tamalpais AFS was re
named for the nearby
Mill Valley community on December 1, 1953.
Mill Valley Air Force Station Mill Valley Air Force Station' received an
AN/FPS-8 in 1955 (subsequently converted to an
AN/GPS-3), and during 1956 an
AN/FPS-4 height-finder radar operated (superseded by an
AN/FPS-6 in 1958.) Mill Valley began operating an
AN/FPS-7 search radar in 1960 at facility built in 1959 by the General Electric company. During
SAGE deployment, a
Burroughs AN/FST-2 Coordinate Data Transmitting Set (CDTS) was installed at Mill Valley AFS and "in late 1960" began providing digitize radar tracks for telecommunication via microwave to the
Air Defense Direction Center (DC-18) at
Beale Air Force Base (the squadron was re-designated
666th Radar Squadron (SAGE) on 15 January 1961.) By 1961 the 666th added
AN/FPS-6 and AN/FPS-6B height-finder radars, and a detachment of the 666th began operating radars at the
Mather AFB P-58 radar station which, as with the
Fort Ord P-38A gap filler annex (
AN/FPS-14 at ), provided radar video to the Mill Valley CDTS for
analog-to-digital conversion.
NORAD Control Center Mill Valley AFS was the "
San Francisco Defense Area NORAD Control Center from 1961
to 1974" after the Army's "
40th Artillery Brigade Air Defense Command Post" was established in September 1961. Initially planned to use a Martin
AN/MSG-4 command, control, and coordination system (instead deployed to 2 Alaska Nike/Hawk sites),
Martin AN/GSG-5 Battery Integration and Radar Display Equipment (BIRDIE) was instead emplaced the
Project Nike "Master Direction Center" (SF-90DC). The AADCP operated by the 40th Artillery Brigade from 1959 until June 1971 (13th Air Defense Artillery Group from July 1971 to August 1974) received crosstelling from the Beale DC-18 for coordinating fire from the TBD
Nike batteries in the
San Francisco Metropolitan Area. On July 31, 1963, Mill Valley
P-38 was redesignated as NORAD ID Z-38. With the inactivation of the
San Francisco Air Defense Sector at Beale in 1963, Mill Valley CDTS data was transmitted to
Adair AFS, Oregon (DC-13). GATR R-18 was taken over by the 666th RADS as OL-A. In 1964 an
AN/FPS-26A height-finder radar replaced the AN/FPS-6 and the AN/FPS-6B was modified to an
AN/FPS-90. In 1966 the AN/FPS-26A was converted to an
AN/FSS-7 SLBM detection & warning radar operated by the
3d Missile Warning Squadron and later as Detachment 3
14th Missile Warning Squadron on 8 July 1972. After transfer to
Air Defense, Tactical Air Command (ADTAC) on October 1, 1979, the 666th Radar Squadron was inactivated on September 30, 1980 (the SLBM radar deactivated c. 1980). Most Mill Valley AFS property transferred to the
NPS (e.g., for
Mount Tamalpais State Park), and the radar facilities transferred to the FAA (the USAF retained control of the height-finder that was modified to an AN/FPS-116). In 1995 the FAA operated an AN/FPS-66A search set. In the late 1990s, the AN/FPS-66A was replaced with an ARSR-4 in the old AN/FPS-26A / AN/FSS-7 tower, the only CONUS site to place an
ARSR-4 in a tower other than a specially designed ARSR-4 tower.
Air Force squadron and assignments •
666th Aircraft Control and Warning Squadron activated at Mount Tamalpais AFS 27 Nov 1950 : Redesignated
666th Radar Squadron (SAGE), 15 January 1961 : Redesignated
666th Radar Squadron, 1 February 1974 : Inactivated on 30 September 1980 ;Squadron assignments •
542d Aircraft Control and Warning Group, 1 January 1951 •
28th Air Division, 6 February 1952 •
San Francisco Air Defense Sector, 1 July 1960 •
Portland Air Defense Sector, 1 August 1963 •
26th Air Division, 1 April 1966 •
27th Air Division, 15 September 1969 • 26th Air Division, 19 November 1969 - 30 September 1980
Ground Equipment Facility On December 23, 1980, the USAF declared
full operational capability for the 1st 7
Joint Surveillance System Regional Operations Control Centers, including the ROCC replacing the Mill Valley NCC. After 1980s turnover to the FAA, in "1995 the FAA operated an AN/FPS-66A search set" at J-33. The FAA currently operates an ARSR-4 radar at the site. ==References==