The Invisible Backbone

After 20 years of leading the Marco Chamber of Commerce “Leadership Marco History Day,” I realized that little was really known about the purpose and operations of the U.S. Air Force’s Eglin Gulf Test Range. Fortunately, Clifford “Randy” Gilmore, who oversaw the Marco Missile Tracking Station in 1960 – 61 as an employee of the Vitro Corporation, and later in 1962 was in charge of the entire Eglin Gulf Test Range, extending down the entire length of the Gulf coast of Florida, reached out to me to clarify the purpose of Marco’s Missile Tracking Station and dispel myths including why the Tracking Station was eventually closed. This is the first of three articles regarding the Marco Missile Tracking Station. Some of this information may, even after 60 years, appear to be “science fiction,” but all of it was cutting-edge at the time, showing significant advancements in technology.

Why would the United States Air Force build a sophisticated missile tracking station on the isolated southwest tip of Marco Island (where the Cape Marco development is now located)? It seems like an unusual location until you realize that the station was never intended to watch Marco Island at all. Instead, its eyes were fixed nearly 400 miles to the northwest, where some of America’s most advanced missile testing was taking place.

During the height of the Cold War (being the competition between the U.S. and the Soviet Union in many areas: a nuclear arms race, a competition to dominate space, the 1962 Cuban Missile Crisis, etc.) Eglin Air Force Base in the Florida Panhandle had become the center of the Eglin Gulf Test Range, an enormous military testing area that covered 120,000 square miles of the Gulf of Mexico. From there, the Air Force tested a growing number of experimental weapons, including the BOMARC surface-to-air missile, one of the nation’s first long-range guided interceptor missiles. BOMARC A first launched on January 15, 1959, and its successor BOMARC B had its inaugural service test on April 13, 1960. The BOMARCs were the first U.S. missiles designed to carry a nuclear warhead.

The military soon discovered a problem. As missiles became capable of flying hundreds of miles, no single radar station could follow an entire flight. Because of the curvature of the Earth, the missile eventually disappeared below the radar horizon. The answer was surprisingly simple: build a chain of tracking stations along Florida’s Gulf Coast so that each station would take over where the previous one left off. This chain became the “eyes and ears” of the range. As Clifford “Randy” Gilmore, manager of the Marco Tracking Station stated: “The Marco radar site was built especially for testing the BOMARCs missiles launched from Santa Rosa Island, in Florida’s Panhandle.”

Before long, the Gulf Test Range stretched far beyond Eglin itself. Missile launches began near Santa Rosa Island at Site A-15. As the missile headed south over the Gulf, tracking responsibilities shifted to stations at Port St. Joe (Site D-3) and Anclote Point/Tarpon Springs (Site D-4). Eventually the missile entered the coverage area of Marco Island’s Site D-7 near Caxambas Pass. Depending upon the test, Cudjoe Key, in the Florida Keys (Site D-8) could continue tracking until the missile completed its flight over the Gulf before reaching the Florida Keys. This network followed a strict handoff protocol: tests began at the launch sites on Santa Rosa Island (Site A-15), were picked up mid-course by sites like Port St. Joe (D-3) and Anclote Point (D-4) and were finally monitored during their terminal phase by southernmost outposts like Marco Island (Site D-7) and Cudjoe Key (D-8).

Why Marco Island? Geography provided the answer. Located approximately 370 statute miles southeast of Eglin Main, Marco occupied exactly the position the Air Force needed to observe the final portion of many missile flights. From this location, technicians could monitor the missile’s speed, altitude, position, and flight path before it splashed harmlessly into the Gulf. Every piece of information collected on Marco was transmitted in real time back to Eglin, where engineers and Range Safety Officers evaluated the success of the test.

The designation “D-7” was not simply an arbitrary military code. The letter identified the station as part of the southeastern quadrant of the expanded Gulf Test Range, while the number distinguished it from the other down-range facilities. Although the station occupied only a small piece of land on Marco Island of approximately 20 acres, it became one link in a much larger military network that stretched hundreds of miles across the Gulf of Mexico.

The facility at Marco Island was then staffed by approximately 50 personnel, largely electronic technicians employed by the Vitro Corporation. In January of 1960, Randy Gilmore was sent down to Marco to be the Manager of the Missile Tracking Station. He was the right person for the job as his background included serving three years in the U.S. Army during the Korean War, assigned to the Army Security Agency in Okinawa working in radio intelligence. After leaving the Army as a Staff Sergeant in 1953, he enrolled at Alabama Polytechnic Institute, now Auburn University, to study Electronic Engineering. A cooperative training program brought him to Eglin Air Force Base in 1955. While still in college, Randy was assigned to help maintain the UNIVAC Scientific Computer Model 1103, a very early computer designed to process enormous amounts of mathematical information and a machine that weighed approximately 19 tons, containing 4,700 vacuum tubes and 6,000 diodes. Randy graduated from Auburn in 1957 and worked for Vitro Corporation, a private contractor responsible for much of Eglin’s Gulf Test Range equipment. Randy remained on Marco for about a year, returning to Eglin, where he advanced to being the Data System Chief, then in 1961 and 1962 Range Instrumentation Director, and in November of 1962 was promoted to being the Manager of the entire Gulf Test Range. He retired in 1984 after 33 years with Vitro. 

The hardware at the Marco site represented the cutting-edge of 1960s instrumentation:

Precision Radar: When the site first opened, it utilized two mobile radars. These were later replaced by the fixed-based FPS-16 radar built by RCA, which was more precise and easier to maintain.

Telemetry Receivers: These captured high-speed diagnostic "health data" broadcast by missiles and drones during flight, including altitude, speed, and fuel consumption.

Tropospheric Scatter ("Tropo-scatter"): The site featured massive "billboard" style antennas used for long-distance, high-bandwidth communication. This system allowed data to be "shot" over the horizon by bouncing radio signals off the upper atmosphere, connecting Marco directly to Cudjoe Key.

Microwave Links: In addition to tropo-scatter, microwave towers with repeater antennas tied the entire coastal chain together, allowing all sites to act as a single, synchronized system.

Radio Frequency (RF) Guidance Equipment: Instrumentation used specifically to communicate with and provide steering commands to the remote-controlled drone aircraft.

Atmospheric Monitoring Tools: The Marco site D-7 utilized tools like radiosondes (weather balloons) to collect refractive index data. This was necessary because radar signals could bend or distort due to humidity and temperature layers over the ocean.

Power Generation: Electricity was provided by Lee County Electric Cooperative, which provided the first generated power to Marco Island and Goodland. Electricity was essential, providing air conditioning cooling the above equipment. The site also maintained its own huge backup generators, which allowed it to return to operation quickly even after major events like Hurricane Donna.

For most Marco residents, the tracking station was simply another fenced government installation at the end of the road. Few people realized that every successful missile test depended upon a carefully coordinated chain of radar and communications sites scattered along Florida’s Gulf Coast. Remove any one of those stations, including Marco’s Site D-7, and valuable information about the missile’s performance could be lost before the flight was complete.

The Marco tracking station never launched a missile, and it never made national headlines. Yet for more than a decade, this quiet facility at Caxambas played an indispensable part in one of America’s largest Cold War testing programs, linking a small island in Southwest Florida with one of the nation’s most important military research efforts.

To be continued in Part Two: “Inside Marco’s Missile Tracking Station’s High-Tech Operations”