Radar picket

A radar picket is a radar-equipped station, ship, submarine, aircraft, or vehicle used to increase the radar detection range around a nation or military (including naval) force to protect it from surprise attack, typically air attack, or from criminal activities such as smuggling.

By definition a radar picket must be some distance removed from the anticipated targets to be capable of providing early warning.

Chain Home or CH was the codename for the ring of coastal early warning radar stations built by the Royal Air Force (RAF) before and during World War II to detect and track aircraft.

In 1942 the AMES Type 7 radar began to assume the job of tracking of targets once detected, and CH moved entirely to the early warning role.

Despite encouraging results, the operational trials ended after the Luftwaffe stopped air launches by mid January 1945.

Each station consisted of a control center with a FuMG A1 Freya radar with a range of about 100 km and a directed searchlight for the night fighters.

[3] From 1943 Nazi Germany's Kriegsmarine operated several radar-equipped night fighter guide ships (Nachtjagdleitschiffe), including the NJL Togo.

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.

Deploying some distance from the force to be protected along likely directions of attack, radar pickets were the nearest ships to the Japanese airfields.

A ring of 15 radar picket stations was established around Okinawa to cover all possible approaches to the island and the attacking fleet.

Eventually, the number of destroyers and supporting ships were doubled at the most threatened stations, and combat air patrols were provided as well.

[6][7] The high casualties off Okinawa gave rise to the radar picket submarine, which had the option of diving when under attack.

During the Cold War, the Royal Canadian Air Force and the United States Air Force jointly built and operated radar picket stations to detect Soviet bombers, and the United States Navy expanded the naval radar picket concept.

The naval concepts were: 1) every carrier group would have radar pickets deployed around it for early warning of the increasing threat of Soviet air-to-surface missile attack, and 2) radar pickets would form barriers off the North American coasts, thus extending the land based lines.

The subsequent invention of the angled flight deck made it possible to install islands and radar on supercarriers, and so this role was eliminated from the Northampton conversion.

These were designed under project SCB 84 for a high surface speed with the intent of scouting in advance of carrier groups, and were equipped with large BPS-2 and BPS-3 radars.

[20] Picket stations were about 400–500 miles (640–800 km) off each coast and provided an overlapping radar or electronic barrier against approaching aircraft.

The U.S. Navy began to develop airborne early warning (AEW) aircraft in the last years of World War II under Project Cadillac.

The first U.S. AEW aircraft were the 1945 carrier based Grumman TBM-3W Avenger under Project Cadillac I, followed by the 1948 Douglas AD-3W, −4W, and −5W Skyraider and the 1950 Grumman AF-2W Guardian (not to be confused with the AGR ships of the same name); though the Skyraiders and Guardians were built in large numbers, none were very successful as they were too small to function as a full CIC, and all were used more often in the anti-submarine warfare (ASW) role.

While the 1957 carrier-compatible Sikorsky HR2S-1W helicopter with the AN/APS-20E or AN/APS-32 radar (sources differ) had room for a full CIC it also failed, largely due to excessive vibration, slow speed, and cost.

[22] Far more successful was the land based Lockheed EC-121 Warning Star, which was introduced in 1954 in both Air Force and Navy service as pickets and in other roles with the AN/APS-20 and AN/APS-45 radars, respectively under and atop the aircraft.

Starting in 1955 they successfully combined airborne early warning radar surveillance and long endurance in all possible roles, but they were fragile, too slow to quickly reach stations far from base, and expensive (their overhead costs also increased after the ASW blimps were retired, having become technically obsolete due to the introduction of higher performance nuclear submarines).

[19][24][15] By 1965, the development of over-the-horizon radar (OTH) made the barrier forces obsolete, and the DERs and the AGR Guardians were retired.

The British Royal Navy constructed or converted two types of dedicated aircraft direction ships in the late 1950s and early 1960s.

With the mid-1960s decision to phase out the fast carriers, the Battle-class ships were placed in reserve 1966–1968 and were scrapped or converted to non-combat roles by 1974.

[31][29]: 119 In 1958 the Soviet Union began development of an aircraft intended to act as an airborne early warning (AEW) radar picket in the far north along the Arctic coast, so that the expense of land stations could be avoided.

They can perform complex command and control of a battlespace in air engagements by directing fighter and attack aircraft strikes.

AEW&C units are also used to carry out surveillance, including over ground targets and frequently perform BMC2 (battle management command and control) functions.

[40] A similar system, JLENS, was developed starting in 1998 by the United States for tracking cruise missiles and other threats, but was cancelled in 2017.