Radar picket A radar picket is a radar - equipped station , ship , submarine , aircraft , or vehicle used to increase the radar detection range around a force to protect it from surprise attack , typically air attack . Radar picket vessels may also be equipped to direct friendly fighters to intercept the enemy . Often several detached radar units encircle a force to provide increased cover in all directions . US Navy World War II Radar Pickets . Radar picket ships first came into being in the US Navy during World War II to aid in the Allied advance to Japan . The number of radar pickets was increased significantly after the first major employment of kamikaze aircraft by the Japanese in the Battle of Leyte Gulf in October 1944 . " Fletcher " - and " Sumner " - class destroyer s were pressed into service with few modifications at first . Later , additional radars and fighter direction equipment were fitted , along with more light anti - aircraft ( AA ) guns for self - defense , usually sacrificing torpedo tubes to make room for the new equipment . Deploying some distance from the force to be protected along likely directions of attack , radar pickets were the nearest ships to the Japanese airfields . Thus , they were usually the first vessels seen by incoming waves of kamikazes , and were often heavily attacked . The radar picket system saw its ultimate development in World War II in the Battle of Okinawa . A ring of 15 radar picket stations was established around Okinawa to cover all possible approaches to the island and the attacking fleet . Initially , a typical picket station had one or two destroyers supported by two landing ships , usually Landing Craft Support ( Large ) ( LCS ( L ) ) or Landing Ship Medium ( Rocket ) ( LSM ( R ) ) for additional AA firepower . Eventually , the numbers of destroyers and supporting ships were doubled at the most threatened stations , and Combat Air Patrol s were provided as well . In early 1945 , 26 new construction Gearing - class destroyer s were ordered as radar pickets without torpedo tubes to allow for extra radar and AA equipment , but only some of these were ready in time to serve off Okinawa . Seven destroyer escort s were also completed as radar pickets . The radar picket mission was vital , but it was also costly to the ships performing it . Out of 101 destroyers assigned to radar picket stations , 10 were sunk and 32 were damaged by kamikaze attacks . The 88 LCS ( L ) s assigned to picket stations had 2 sunk and 11 damaged by kamikazes , while the 11 LSM ( R ) s had 3 sunk and 2 damaged . German and Japanese WWII radar pickets . From 1943 the German Navy ( " Kriegsmarine " ) operated several radar - equipped night fighter guide ships ( " Nachtjagdleitschiffe " ) , including NJL " Togo " . which was equipped with a FuMG A1 " Freya " radar for early warning and a " Würzburg - Riese " gun laying radar , plus night fighter communications equipment . From October 1943 the NJL " Togo " cruised the Baltic Sea under the operational control of the " Luftwaffe " . In March 1944 , after the three great Soviet bombing raids on Helsinki , she arrived in the Gulf of Finland to provide night fighter cover for Tallinn and Helsinki . Also , the Imperial Japanese Navy briefly modified two Ha - 101 class submarines as dedicated radar pickets in the first half of 1945 , but reconverted them to an even more important role as tanker submarines in June of that year . Cold War . During the Cold War , the United States Navy expanded the radar picket concept . The wartime radar picket destroyers ( DDR ) were retained , and additional DDRs , destroyer escorts ( DER ) , and submarines ( SSR ) were converted and built 1946 - 1955 . The concept was that every carrier group would have radar pickets deployed around it for early warning of the increasing threat of Soviet Air - to - surface missile attack . The 26 Gearing - class DDRs were supplemented by nine additional conversions during the early 1950s . The seven wartime DERs were not considered worth modernizing and were relegated to secondary roles . However , twelve additional DER conversions were performed 1954 - 58 . Ten of these were conversions of diesel - powered DEs , which had a longer at - sea endurance than their steam - powered equivalents . The slow DERs were used in combination with converted Liberty ships to extend the Distant Early Warning ( DEW ) line in the North Atlantic and North Pacific , to warn of Soviet bomber attacks . The high casualties off Okinawa gave rise to the radar picket submarine , which had the option of diving when under attack . It was planned to employ converted radar picket submarines should the invasion of Japan become necessary . Two submarines received rudimentary radar conversions during the war , and in 1946 two more extensive conversions were performed . The radar equipment of these diesel submarines took the place of torpedoes and their tubes in the stern torpedo rooms . By 1953 , a total of 10 SSR conversions had been performed , with radar suites called Migraine I , II , and III , the most extensive conversion adding a 24 - foot compartment as an expanded Combat Information Center ( CIC ) . Also , in 1956 two large , purpose - built diesel SSRs , the " Sailfish " class , were commissioned . These were designed for a high surface speed with the intent of scouting in advance of carrier groups . However , the SSRs did not fare well in this mission . Their maximum surfaced speed of 21 knots was too slow to effectively operate with a carrier group , although it was sufficient for amphibious group operations . It was thought that nuclear power would solve this problem . The largest , most capable , and most expensive radar picket submarine was the nuclear - powered USS Triton ( SSRN - 586 ) , commissioned in 1959 . The longest submarine built by the United States until the Ohio - class Trident missile submarines of the 1980s , " Triton " ' s two reactors allowed her to exceed 30 knots on the surface . The introduction of the Grumman E - 1 Tracer airborne early warning aircraft in 1958 doomed the radar picket as a carrier escort . Airborne radar had evolved to the point where it could warn of an incoming attack more efficiently than a surface ship . In 1961 the majority of radar pickets of all types were withdrawn . The DDRs received anti - submarine warfare conversions under the FRAM I program and were redesignated as DDs . The SSRs were converted to other roles or scrapped . " Triton " was left without a mission . Some alternatives were considered , including serving as an underwater national command post , but she eventually became the first US nuclear submarine to be decommissioned , in 1969 . The DERs stayed on the DEW Line patrols until 1965 . From 1955 - 65 , the United States Navy employed radar picket ships converted from the former Boxed Aircraft Transport version of the Liberty ship to extend the DEW Line seaward . Sixteen Liberty ships converted to Radar Picket Ships were stationed on the East Coast and West Coast , eight stationed at Treasure Island , California and eight stationed at Davisville , Rhode Island . Ship names matched the mission : " Outpost AGR 10 , Guardian , Lookout , Skywatcher , Searcher , Scanner , Locator , Picket " and the " Interceptor " on the East Coast and " Investigator , Protector , Vigil , Interdictor , Interpreter , Tracer " and " Watchman " on the West Coast . The designation of the ships was YAGR , later changed to AGR . Picket stations were spotted about 400 – 500 miles out and provided an overlapping radar or electronic barrier against approaching aircraft . While on station , the ships shifted operational control from the Navy to the Air Force and NORAD . Each ship while on station 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 standard crew consisted of 13 Officers , eight Chief Petty Officers , and 125 enlisted . Typical station duty was about 30 – 45 days out and 15 days in port . By 1965 , the development of Over - the - horizon radar made the Radar Ships obsolete . Ground - based systems then had the capability to see beyond their once state - of - the - art radar systems . The final use of the radar picket concept by the US Navy was in the Vietnam War . The Gulf of Tonkin Positive Identification Radar Advisory Zone ( PIRAZ ) guided missile frigate s ( redesignated cruisers in 1975 ) and cruiser s provided significant air control and air defense in that war .