Saugatuck Gap Filler Radar Annex

Saugatuck Gap Filler Annex
Part of Air Defense Command (ADC)
Aerial view of Saugatuck Gap Filler Annex
Saugatuck Gap Filler Annex Location of the Saugatuck Gap Filler Annex
Coordinates	42°39′41″N 086°12′33″W
Type	SAGE Gap Filler Radar
Site information
Controlled by	United States Air Force
Open to the public	The site is not open to the public
Site history
Built	Construction began late 1956
In use	1958–1968
Garrison information
Garrison	781st Aircraft Control & Warning Squadron, later 781st Radar Squadron (SAGE)

781st Radar Squadron (SAGE) patch

The Saugatuck Gap Filler Annex (ADC ID: P-67C, NORAD ID: Z-67C, Z-34G) is a decommissioned radar installation that once served in the vast Cold War era Semi-Automatic Ground Environment (SAGE) air defense system. Of the hundreds of SAGE radars, Saugatuck's is one of, perhaps, two that remain nearly completely intact.

Located immediately across the Kalamazoo River from Saugatuck, Michigan, at the top of Mount Baldhead, a 230 foot dune on the shore of Lake Michigan, the annex was positioned to fill gaps in the coverage of long-range "heavy" radars sited further inland. The heavy radars searched for attacking Soviet bombers but were unable to detect aircraft flying low to the west of the dunes along Lake Michigan. Saugatuck's original AN/FPS-14 radar was commissioned in mid-1958 and operated until it was replaced with a more capable AN/FPS-18 in 1963. The FPS-18 radar served continuously until the site was decommissioned early in 1968. The city of Saugatuck purchased the building, tower, and radar equipment from the Air Force in 1969. Today, the installation appears very much as it did when operational with virtually all of the original electronic equipment still in place.

The Saugatuck Gap Filler Annex has been nominated for inclusion in the National Register of Historic Places and efforts are underway, by a work group commissioned by the city of Saugatuck, to stabilize the site and secure funding for further preservation and restoration.

The Cold War

The Strange Alliance

The United States, United Kingdom, and Union of Soviet Socialist Republics (Soviet Union) joined forces in World War II to become the key members in the Grand Alliance against the Axis Powers. It was always a "Strange Alliance," with a pronounced wariness between the United States, the world’s greatest capitalist country, and the Soviet Union, the greatest socialist country. Post war, with aggravations from both sides, the strain slowly crystallized into hostility approaching open conflict. Spanning decades, this period in history is known as the "Cold War."

Despite increasing Soviet aggression the United States felt its nuclear monopoly was an effective deterrent against attack until mid 1949 when the Soviet Union successfully tested its first atomic bomb, about four years sooner than had been anticipated. Earlier, they had unveiled the totally unexpected TU-4 bomber, a literal piece by piece copy of the United States B-29 with one-way range sufficient to carry an atomic bomb from the Soviet Union to most large cities in the continental United States.

The Lashup System

In 1949, the only vestige of a North American continental air defense system was a motley collection of surplus WWII-era radars scattered sparsely across Canada and the northern United States. These were euphemistically named the Lashup System. Previously, lacking a viable threat, there had been little incentive to invest in upgrades to this network. With the sudden advent of the Soviet atom bomb and the TU-4, however, priorities were rapidly reassessed and the US Air Force launched an aggressive program to augment radar coverage of the most likely routes of attack from the north over Canada.

By 1952, the Lashup System had been reinforced with the emerging Permanent System radars arrayed along the border between the United States and Canada, soon supplemented by the Mid-Canada radar fence. The Ground Observer Corps (GOC), disbanded at the end of World War II, had been brought back into service and greatly expanded to assist in visually identifying aircraft and estimating altitude. The GOC’s sightings and those detected by radar were reported by telephone to Manual Control Centers (MCCs) where the flight tracks of suspect aircraft and of the fighters dispatched to intercept them were plotted by hand on large plexiglass maps as controllers attempted to guide the fighter pilots by radio. But a number of exercises simulating attacking bombers revealed the MCCs were quickly overwhelmed by even modest incursions. Additionally, numerous blind spots were discovered in the coverage of the heavy radars where their ability to detect low level aircraft was obstructed by terrain.

SAGE

The solution identified to address the issues with manual control was to use massive computers to analyze radar data, assess which defenses were most appropriate for response, and direct interception, all with minimal human involvement. The system that emerged to satisfy this requirement was SAGE, the Semi-Automatic Ground Environment, a continent wide network of enormous AN/FSQ-7 computers linked to hundreds of radars.

The number of radars in the SAGE network reached a peak in 1962 with nearly 250 heavy and gap-filler radars from the Permanent System, the remnants of the Lashup System, and some semi-mobile radars, all distributed primarily across the northern United States with some in Canada. In addition, there were the Distant Early Warning (DEW) Line radars just north of the Arctic Circle, Canada’s Mid-Canada Line radar fence, and the Pine Tree Line radars across southern Canada. To these were added three ill-fated oil-rig-like Texas Tower radar installations built on the continental shelf off New England, a small number of radars carried by early warning aircraft and radar picket ships which operated off both coasts, and a few dirigibles.

To augment the Permanent System heavy radars and resolve the low-level blind spots, around 240 gap-filler radar sites were planned between 1956 and 1962. Not all of the proposed sites were actually developed and, even if the buildings were constructed, not all received the radar equipment and towers as funds were slowly diverted to address the emerging threat of missile attack, highlighted by the launch of the Soviet Union's Sputnik satellite in 1957. Ultimately, a maximum of 131 gap-fillers were in service at any one time, the Saugatuck Gap Filler Annex among them.

The Saugatuck Gap Filler Annex

History

The Air Force entered into a lease with the City of Saugatuck on June 1, 1956, for a small site at the top of Mt. Baldhead, the dune upon which the radar installation was constructed. Also included in the lease was an area at the eastern foot of the dune, below and slightly south of the radar site. This area was for ancillary equipment consisting principally of underground diesel fuel tanks and pumps used to move fuel to a storage tank at the top of the dune which supplied a generator in the annex building. There was also an easement connecting the two sites, running parallel to the stairs up the east face of the dune, to accommodate diesel fuel lines, electrical service, and telephone lines.

Construction of the equipment and generator building began on August 23, 1956, with an anticipated completion date in January 1957. Many gap-fillers were being constructed at this time and there was a delay before the radar equipment arrived. After installation and testing, the Bendix AN/FPS-14 radar became operational between April 1 and June 30, 1958, reporting to the 781st Aircraft Control and Warning (AC&W) Squadron at Custer Air Force Station (AFS), the “prime site,” near Battle Creek, Michigan, where the heavy long-range and height-finder radars were located. The 781st's prime associated interceptor squadron was the 319th Fighter Interceptor Squadron, stationed at Bunker Hill Air Force Base in Peru, Indiana.

Like the other three gap-fillers under control of Custer AFS, the Saugatuck Gap Filler Annex was designed to be unmanned and was operated remotely by the prime site. Also like the other gap-fillers, the Saugatuck annex employed an AN/FST-1 Coordinate Data Transmitter to send radar data to the immense AN/FSQ-7 computer housed at SAGE Direction Center DC-06, co-located with the 781st AC&W Squadron at Custer AFS. The AN/FST-1 was a state-of-the-art digital electronic device implemented almost entirely with vacuum tubes. It filtered spurious and fixed radar echoes from those of actual aircraft, converted the analog data into digital form, then transmitted it via leased telephone lines using the first modem employed in an actual application outside of research.

Custer AFS was known by Permanent System ID P-67, and Saugatuck, one of four subordinate gap-fillers, held site ID P-67C until July 31, 1963, when all SAGE radar squadron designations were changed to the NORAD prefix Z and Saugatuck became Z-67C. As SAGE became fully operational, the squadron title was changed to 781st Radar Squadron (SAGE) October 1, 1959.

Custer AFS operated the following AN/FPS-18 Gap Filler sites in addition to its own heavy and height-finder radars:

• Midland, MI (P-67A/P-20G) 43°38′03″N 084°25′42″W
• Richland Center, IN (P-67B/P-73J) 41°07′05″N 086°14′28″W
• Saugatuck, MI (P-67C/Z-34G) 42°39′41″N 086°12′33″W
• Shelby, MI (P-67D/Z-34H) 43°36′00″N 086°20′25″W

The AN/FPS-14 radar was removed in June, 1963, to be upgraded by an Bendix AN/FPS-18 radar. The FPS-18 was an improved design having a more refined ability to discriminate between fixed and moving targets and output power of one megawatt, a little over twice that of the FPS-14. Despite the additional power, effective range remained 48 miles due to limitations of the FST-1. A number of months lapsed between the removal of the old radar and installation of the new equipment. The AN/FPS-18 radar finally became operational on December 14, 1963, and remains in place in the equipment room today. At the same time, a rigid radome was installed to protect the new antenna at the top of the tower. This is the iconic white ball still visible for miles in all directions.

Control of the Saugatuck radar annex was transferred to the 752nd Radar Squadron (SAGE) on January 27, 1965, located at Empire Air Force Station, Z-34, near Empire, Michigan. The Saugatuck Gap Filler Annex was redesignated Z-34G and recommissioned on February 2, 1965. As the missile threat continued to gain priority, the 752nd received notice on March 31, 1968, that operation of all gap-fillers would terminate. The squadron was directed to drain and flush the transmitter coolant systems, tape the doors of the equipment cabinets, and prepare the diesel generators for storage.

On April 1, 1968, the Saugatuck Gap Filler Annex was permanently deactivated. After removing the diesel generator and all spare parts, the Air Force terminated its lease of the annex site effective December 31, 1968. Possession of the land reverted to the city of Saugatuck, which purchased the building, tower, and all the radar equipment for $250 in July 1969.

Apparently, removal of the radar antenna had been scheduled at some point prior to Saugatuck's purchasing the radar station because, very shortly after the sale, an Air Force crew appeared and began to dismantle the radome. The misunderstanding was quickly straightened out, and the crew reassembled the dome without removing any equipment.

Present Status

The process of listing the Saugatuck Gap Filler Annex on the National Register of Historic Places (NRHP) is partially complete. This will open doors for grants and funding to support additional preservation of the building, equipment, and tower.

In support of the NRHP nomination, research was conducted to determine how many of the original SAGE system radar sites remain and their present condition. The database of gap-filler sites gathered and maintained by The Air Defense Radar Veteran's Association at www.radomes.org was utilized to inspect each location via Google Maps satellite view to determine if any structures remained. Where necessary to clarify their status, physical visits were made to sites and owners or controlling agencies were contacted. The results indicate that, of the hundreds of SAGE system radars scattered across the United States when SAGE was fully implemented, only four remain with structure and antenna appearing substantially as they did during the Cold War era. Of these, the Saugatuck Gap Filler Annex is one of, at most, two which have survived almost completely intact with most of the radar equipment still in place in the radome and building, although all of the vacuum tubes and fragile equipment are currently stored off-site. The other surviving gap-filler is privately owned, and the presence of its electronic equipment has not yet been verified.

In May 2021, the Mount Baldhead Radar Station Work Group was established by the Saugatuck City Council to investigate and report on approaches for dealing with the deteriorating radar annex. Primary concerns were liability regarding trespassers being injured as they attempted to gain access to the antenna tower and the roof of the building and the elimination of unsightly graffiti on the building's walls and exterior equipment. Options to be considered ranged from complete demolition to full restoration. What emerged as the most effective immediate path was to stabilize the structure and improve security against vandalism and trespassers, basically freezing the site in its present state to buy more time for consideration of long term prospects.

The group acted quickly. First on the list, with the invaluable help of volunteers, was removal of the daunting mass of vegetation that had sprung up on the annex grounds and structures, which conveyed the sense that no one cared about the site and provided a screen behind which vandals and trespassers felt free to act. A roofing contractor was hired to temporarily address serious leakage issues threatening the roof structure and building interior. Numerous volunteers stepped up to assist in cleaning graffiti from the exterior walls, seal the more serious gaps and voids in the cement block walls, and apply a new coat of paint all around. An organization specializing in preservation and rehabilitation of historic structures was consulted to suggest methods by which deterioration of the foundation and block walls could most effectively be addressed. Security cameras were installed with signage to alert potential trespassers that the site is not open to the public and is under surveillance.

Future

Having stabilized and secured the site, the work group now turns to determining what the next steps should be in preserving the Saugatuck Gap Filler Annex, the last SAGE gap-filler in public hands where the Cold War structures and radar equipment can be examined in situ.

External links

• www.radomes.org, Information for Saugatuck, MI
• www.radomes.org, USAF CONUS Gap-Filler Radar Sites, 1957 - 1970
• www.ll.mit.edu, MIT Lincoln Laboratory SAGE site
• Searching the Skies, The Legacy of the United States Cold War Defense Radar

References

 This article incorporates public domain material from the Air Force Historical Research Agency