Guardian-class radar picket ship

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USS Guardian (AGR-1).jpg
USS Guardian, the lead ship of the class
Class overview
Name: Guardian class
Operators:  United States Navy
Built: 1943-1945
In commission: 1954-1965
Completed: 16
Retired: 16
General characteristics
Type: Radar picket ship, converted Liberty ship, type Z-EC2-S-C5
Displacement: 10,760 long tons (10,930 t) full load
Length: 441 ft 6 in (134.57 m)
Beam: 56 ft 11 in (17.35 m)
Draft: 24 ft (7.3 m)
Propulsion: two 220 PSI boilers; one 3 cylinder triple-expansion steam engine; one 4-blade, 18 ft 6 in (5.64 m) propeller; 2,500 shp (1,900 kW)
Speed: 11 kn (20 km/h; 13 mph)
Complement: 13-20 officers, 138-150 enlisted
Armament: 2 × 3 in (76 mm)/50 caliber guns

The Guardian-class radar picket ships were a class of ocean radar picket ships (YAGR, later AGR), converted 1954-1958 from World War II Liberty ships acquired by the U.S. Navy. Their task was to act as part of the radar defenses of the United States in the Cold War, serving until 1965.

Ship type

The converted Liberty ships were typically the boxed aircraft transport version, type Z-EC2-S-C5. The hull classification symbol of the ships was initially YAGR, changed to AGR in 1958.


As converted, each ship carried an AN/SPS-8 height finding radar, AN/SPS-12 air/surface search radar, AN/SPS-17 long range air search radar, and AN/UPA-22 IFF sensor. The AN/SPS-8 was later replaced on some ships by the AN/SPS-30. The AN/SPS-17, purpose built for the Guardian class, could detect large aircraft such as bombers up to 220 nautical miles (410 km; 250 mi) away and small aircraft up to 102 nautical miles (189 km; 117 mi) away.[1]


The AGRs were based on both coasts at Newport, Rhode Island (later Davisville, Rhode Island) and Treasure Island, California near San Francisco, eight on the East Coast and eight on the West Coast. The assignments on the east coast were Guardian AGR-1, Lookout AGR2, Skywatcher AGR3, Searcher AGR4, Investigator AGR-9, Outpost AGR10, Protector AGR-11 and Vigil AGR-12. The west coast assignments were Scanner AGR-5, Locator AGR-6, Picket AGR-7, Interceptor AGR-8, Interdictor AGR-13, Interpreter AGR-14, Tracer AGR-15 and Watchman AGR-16. Tracer was originally named Interrupter but was changed to avoid confusion with the other ship names. They would spend 30-45 days at sea regardless of weather, alternating with 15 days in port, monitoring aircraft approaching the United States as an extension of the Distant Early Warning line under the Continental Air Defense Command. Their primary duty was to warn of a surprise Soviet bomber attack. The AGRs were augmented by twelve radar picket destroyer escorts of the Edsall and John C. Butler classes, known as DERs, and Lockheed WV-2 Warning Star. By 1965, the development of over the horizon radar had superseded their function, and the radar picket ships were decommissioned and scrapped by the early 1970s.[2]

Picket stations were about 400–500 miles (640–800 km) off each coast and provided an overlapping radar or electronic barrier against approaching aircraft. While on station, the ships' operational control shifted from the Navy to the Air Force and NORAD. While on station, each ship stayed within a specific radius of its assigned picket station, reporting and tracking all aircraft contacts. Each ship carried qualified air controllers to direct intercept aircraft sent out to engage contacts. While on station other duties such as search and rescue, weather reporting, and miscellaneous duties were assigned. The National Marine Fisheries Service even provided fishing gear so that the crew could fish for tuna during the season, and the ships sent daily reports of fish caught for research purposes.

The Guardian class spent more time at sea than any other US Navy vessels, apart from ballistic missile submarines, averaging 220-250 days per year on patrol. To make this very high amount of sea time as comfortable as possible for the crew, all sleeping quarters were air conditioned, each officer had a private stateroom, petty officers shared two-man cabins and enlisted men slept in four-man cabins (most other USN enlisted men at the time slept in hammocks).[3]


  1. Nick McCamley (2013). Cold War Secret Nuclear Bunker: The Passive Defence of the Western World During the Cold War. Pen and Sword. p. 37. ISBN 1844155080.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. Friedman, pp. 231-233
  3. Naval War College Review. Naval War College. 52: 127. 1999. Missing or empty |title= (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  • Friedman, Norman "US Destroyers: An Illustrated Design History (Revised Edition)", Naval Institute Press, Annapolis:2004, ISBN 1-55750-442-3.

This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.

See also