Rotor

ROTOR was a huge and elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. In order to get it operational as quickly as possible, it was initially made up primarily of WWII-era systems, notably the original Chain Home radars for early warning role, and the AMES Type 7 for plotting and interception control. The system built a network of control stations, mostly built underground, and connected with an extensive telephone and telex network.

Work also began on a new microwave frequency radar to replace Chain Home, initially known as Green Garlic. When this was first deployed in 1953 it was found to have the accuracy needed to replace the Type 7 radars for plotting, and its greatly improved range over those systems meant that far fewer radars would be needed to provide coverage over the entire United Kingdom. Much of the ROTOR systems was ultimately redundant, and many of its separate bases were replaced by single Master Radar Stations run by the AMES Type 80 radars. These stations were, in turn, replaced by the Linesman/Mediator system in the 1960s, with only five AMES Type 84 radars.

A similar expedient system in the United States was the Lashup Radar Network.

UK radar operations were wound down late in the war, and by the time the war ended were already largely unused. It was assumed that another war was at least ten years away, and the need for any improvements in the cobbled-together system seemed remote.

Thinking changed dramatically in 1949 with the Soviet test of their first atom bomb. It was known that the Soviets had made exact copies of the B-29 Superfortress as the Tu-4 Bull, and these aircraft had the performance needed to reach the UK with a nuclear payload. Studying the problem, the 1949 Cherry Report suggested that the 170 existing Royal Air Force radar stations be reduced to 66 sites and the electronics extensively upgraded.

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