Searchwater radar is a maritime surveillance

Surveillance

Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...

 radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 developed by Thorn-EMI under project P1149. This type of radar has been in service with the Royal Air Force

Royal Air Force

The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

 Hawker Siddeley Nimrod aboard the MR2 variant since the 1970s.
The retirement of the Royal Navy's fleet carriers in 1978 meant that the airborne early warning

Airborne Early Warning

An airborne early warning and control system is an airborne radar system designed to detect aircraft at long ranges and control and command the battle space in an air engagement by directing fighter and attack plane strikes...

 (AEW) capable Fairey Gannet

Fairey Gannet

The Fairey Gannet was a British carrier-borne anti-submarine warfare and airborne early warning aircraft of the post-Second World War era developed for the Royal Navy's Fleet Air Arm by the Fairey Aviation Company...

 was also withdrawn from service. During the Falklands War

Falklands War

The Falklands War , also called the Falklands Conflict or Falklands Crisis, was fought in 1982 between Argentina and the United Kingdom over the disputed Falkland Islands and South Georgia and the South Sandwich Islands...

, a number of warships were lost due to the lack of an indigenous AEW presence. Consequently, a greatly accelerated project was started to equip Westland Sea King

Westland Sea King

The Westland WS-61 Sea King is a British licence-built version of the American Sikorsky S-61 helicopter of the same name, built by Westland Helicopters. The aircraft differs considerably from the American version, with Rolls-Royce Gnome engines , British made anti-submarine warfare systems and a...

 helicopters with a slightly modified version of the system known as Searchwater LAST (Low Altitude Surveilance Task). The raydome was mounted in a distinctive inverted cupola on a swivel arm attached to the right side of the fuselage just aft of the main door. This arm allowed the helicopter to lower the radar below the fuselage in flight and to raise it for landing.
Searchwater radar was developed by the Royal Signals and Radar Establishment

Royal Signals and Radar Establishment

The Royal Signals and Radar Establishment was a scientific research establishment within the Ministry of Defence of the United Kingdom, located primarily at Malvern in Worcestershire. It was formed in 1976 in an amalgamation of earlier research establishments including the Royal Radar Establishment...

 and EMI

EMI

The EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...

 (later Thorn Sensors Group). Racal Radar Defence Systems acquired Searchwater in 1995. Thorn and Racal merged to form Racal-Thorn Defence.