Air Force Tracks Russian ICBMs With 12,288 Antennas
By Miriam Adler ·
Russian missile trajectories are tracked with mathematical precision by 143 civilians aboard a converted merchant ship that serves as a floating intelligence asset.
It is a structure that weighs 250 tonnes and stands over forty feet high. An octagonal S-band array, consisting of 12,288 antenna elements and measuring approximately seven meters in diameter, is housed within a mechanically rotated steel turret. This is the AN/SPQ-11 COBRA JUDY, a ship-based radar system designed for the singular purpose of detecting, tracking, and collecting intelligence on strategic ballistic missile tests over the Pacific Ocean.
According to an FAS Intelligence Resource Program page, the radar is primarily tasked with tracking ICBMs launched by Russia in their west-to-east missile range. To achieve this, the system operates in the 2900-3100 MHz band. In 1985, the government added a further layer of scrutiny: a 9-GHz X-band radar with a parabolic dish antenna, five stories high, installed aft of the ship's funnel. This upgrade was intended to provide a better degree of resolution and target separation during the terminal phase of missile tests. Together, these arrays serve as the eyes of the Ballistic Missile Defense Organization, verifying treaty compliance and supporting development tests in regions that ground-based sensors simply cannot reach.
12,288 Antenna Elements
The operation of such a massive apparatus requires a strange hybrid of military and civilian labor. The ship, the USNS Observation Island (T-AGM 23), is operated by the Military Sealift Command for the U.S. Air Force Technical Applications Center at Patrick Air Force Base, Florida. While the intelligence is for the Air Force, the ship is manned by a crew of 143 civilians under the command of a civilian master.
There is a specific visual marker for this distinction. The blue and gold bands on the ship's stack indicate that it is a "United States Naval Ship" rather than a commissioned "United States Ship." It is a floating piece of intelligence infrastructure, an asset that moves across the globe to ensure that the trajectory of a Russian missile is recorded with mathematical precision. The sheer scale of the equipment—from the tonnes of steel to the five-story dish—reflects a commitment to surveillance that dwarfs the human crew tasked with maintaining it.
Document imagery from irp.fas.org From the files: irp.fas.org
SS Empire State Mariner
The Observation Island was not born into the intelligence community. Her keel was laid on September 15, 1952, at the New York Shipbuilding Corporation in Camden, New Jersey, where she began her life as the SS Empire State Mariner. For a short time, she was a merchant vessel, a ship of commerce. But the priorities of the state shifted, and on September 10, 1956, the vessel was transferred to the Navy.
By December 1958, she was commissioned as the USS Observation Island (EAG-154). The conversion was extensive; the superstructure and holds were gutted and rebuilt to accommodate the first complete Fleet Ballistic Missile (FBM) Weapons System. The ship was no longer carrying cargo; it was carrying the blueprint for nuclear escalation. From its commissioning until August 1959, the officers and men focused on the first at-sea launch of the Polaris Missile, a milestone achieved in September 1959 off the coast of Cape Canaveral.
Document imagery from irp.fas.org From the files: irp.fas.org
November 16, 1963
Throughout the early 1960s, the ship became an essential support hub for the nuclear triad. It supported the USS George Washington and the USS Ethan Allen, facilitating the transition of Polaris missiles from test platforms to operational submarines. On March 1, 1961, the ship successfully launched the new A2 Polaris Missile.
This era of development peaked on November 16, 1963, when the ship hosted President John F. Kennedy. He came aboard to observe a Polaris A2 launch from the submerged submarine USS Andrew Jackson. It was a demonstration of submerged lethality, witnessed from the deck of a converted merchant ship. By 1964, the vessel was operating in the Pacific Missile Range, making port visits in Pearl Harbor and Hong Kong, before returning to the Atlantic to support more submerged launches. This cycle of modification and deployment continued until September 1972, when the ship was placed in reserve.
Document imagery from irp.fas.org From the files: irp.fas.org
A $11.8 Million Contract
The ship was reacquired by the Navy on August 18, 1977, and reclassified as T-AGM 23, returning to the sea as a permanent surveillance platform. The cost of maintaining this posture is significant. On May 14, 1999, Raytheon Support Services, based in Burlington, Massachusetts, was awarded a firm-fixed-price contract for $11,824,227. This contract covered the operation and maintenance of both the Cobra Judy and the Cobra Gemini radar systems for a single year.
The procurement process was tight; four firms were solicited, and three proposals were received. The contract, managed by the 668th Logistics Squadron at Kelly AFB, Texas, ensured that the massive arrays remained operational through May 13, 2000. The solicitation for this work had been issued on October 20, 1998.