ROTOR

ROTOR was an 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 the early warning role, and the AMES Type 7 for plotting and interception control. The system had a network of control stations, mostly built underground, and connected with an extensive telephone and telex network.

Entrance bungalow to former ROTOR station at Kelvedon Hatch

Work also began on a new microwave frequency radar to replace Chain Home in the 1957 time-frame. However, an experimental system known as Green Garlic was so successful that it began replacing Chain Home starting in 1954. In service, these proved so accurate that they could replace the Type 7 radars as well, and their greatly improved range meant that far fewer radars would be needed to provide coverage over the entire United Kingdom. This led to the Master Radar Stations that filled both early warning and ground controlled interception roles. The original ROTOR plans for 66 radars was repeatedly reduced, ultimately only requiring half that number of stations.

ROTOR called for the continual upgrading of the network over time, both the radars and the command and control systems. The introduction of the carcinotron radar jammer in the mid-1950s was a serious blow to these plans; a single aircraft carrying a carcinotron could jam the ROTOR radars so completely that they were rendered useless. At the same time, the introduction of the hydrogen bomb and ballistic missile greatly changed the nature of the strategic threat, and over time the idea of whole-country defence became untenable; the only way to defend against missile attacks was deterrence, and if that failed, interceptor aircraft and missiles would have no measurable effect on the eventual outcome.

ROTOR was initially to be replaced by a new network dedicated largely to defending the V-bomber force, the "1958 Plan". But even this role was eventually abandoned, leaving only the task of locating aircraft carrying jammers in order to keep the BMEWS radars free from interference and prevent a successful sneak attack. Such a system did not require a large number of radars nor country-wide coverage. To reduce the cost of this much smaller network, studies on integrating the military radars with civilian air traffic control led to the Linesman/Mediator system of only five primary stations. The original ROTOR was replaced by Linesman in stages, starting in 1967.

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

Post-war situation

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.

Most of the new network would be made up of 28 rebuilt Chain Home systems, while the rest were taken from the existing selection of Chain Home Low, Chain Home Extra Low and the various Ground-controlled interception (GCI) radars that had formerly served special purposes. This was, in part, a stop-gap measure anticipating the availability of the dramatically improved Type 80 Green Garlic radar which would replace the various early warning radars with a single system of much greater performance. Interception guidance would still be handled by existing systems in either case.

All of the radars were to be improved in terms of siting, with the addition of hardened control bunkers to protect the operators from a conventional attack. On the east coast, the coast toward which a Soviet attack would be most likely, the bunkers were underground in the 'R' series (R1, R2, R3 and R4 etc.), while those on the western side of the UK were generally semi-sunken hardened structures ('R6') or above ground 'Secco' type huts (Hartland Point etc.). The R-series bunkers themselves were otherwise similar, featuring 10-foot-thick (3.0 m) concrete walls with all equipment, operations generators and air conditioning located inside.

Additionally, ROTOR re-arranged the existing RAF Fighter Command structure into six "Sector Operational Commands" (SOC) with their own command bunkers (three level 'R4' protected accommodation). Only four of these were built. Additional "Anti-Aircraft Operations Rooms" were built to coordinate the British Army's AA defences in the same overall system. The entire network of bunkers, radars, fighter control and command centres used up 350,000 tons of concrete, 20,000 tons of steel and thousands of miles of telephone and telex connections.

The work was mainly carried out by the Marconi Wireless and Telegraph Company in several phases, called ROTOR 1, ROTOR 2 and ROTOR 3.

Post-ROTOR

As the anticipated Type 80 "Green Garlic" radar started testing shortly after ROTOR came online, it became clear that it could fill both early warning and interception guidance from a single site. This dramatically decreased the complexity of the ROTOR system, which otherwise required sightings from the early warning radars to be telephoned to the fighter control GCI stations for local plotting. By concentrating all of this complexity at a single site the total number of operators was greatly reduced.

As a result of the introduction of the Type 80, many of the existing ROTOR sites were rationalized into Master Radar Stations (MRS), while the rest were made redundant, some only two years after opening, and all of the AAOR sites were closed. A few of these were re-used for Regional Seats of Government or local authority wartime headquarters. In the mid-1960s the MRSs themselves were replaced with a new system called Linesman/Mediator.

Until the end of the Cold War, many of the sites were retained by the government. They were later sold to private buyers, converted into museums (for example Hack Green) or transferred to the National Air Traffic Control Centre.

List of sites

Site NameSite DesignatorGrid ReferenceSite Purpose
Aird UigWIUNB 047390R10 CEW Type 80
AnstrutherFATNO 568808R3 Type 80
Barnton QuarryMHANT 203748R4 SOC Caledonian Sector
BawburghWRKTG 165080R4 SOC Eastern Sector
BawdseyPKDTM 347388R3 GCI(E)
Beachy HeadHEBTV 590959R1 CEW Type 80
BemptonRMFTA 192736R1 CEW
BoulmerEZSNU 240125R3 GCI Type 80
BoxXOBST 850690SOC Southern Sector
BuchanGBUNK 113408R3 GCI Type 80
CalvoCALNY 144545R8 GCI
Charmy DownCHAST 768702R8 GCI
CheniesHAMTQ 015997R8 GCI
Cold HesledonIDWNZ 417468R1 CEW/CHEL
CombertonCOBSO 968461R8 GCI
CrosslawHCVNT 880680R2 CHEL
Danby BeaconNZ 732097CH
Douglas WoodNO 488415CH
Drone HillNT 845665CH
DrytreeSW 732218CH
DunkirkTDETR 076595CH Type 80
FairlightGWBTQ 862113R2 CHEL(A)
Faraid HeadRAINC 389714R10 CEW Type 80
FollySM 858195CH
ForenessWJWTR 385710R2 CHEL
GailesFULNS 327361R8 GCI Type 80
GoldsboroughJEXNZ 830138R2 CHEL(A)
Hack GreenHAKSJ 647483R6 GCI
Hartland PointHATSS 237277R8 GCI
Hayscastle CrossCHXSM 920256CH Type 80
High StreetTM 411720CH
Hill HeadNJ 947616CH
HolmptonVQJTA 367225R3 GCI(B) Type 80
Hope CoveHOPSX 716374R6 GCI
HoptonTOHTM 540990R2 CHEL(B)
InverbervieLGZNO 841734R1 CEW
Kelvedon HatchXSLTQ 561995R4 SOC Metropolitan Sector
KilchiaranECKNR 207616R11 CHEL
Killard PointIJ 605435R8 GCI Type 80
LangtoftLATTF 155129R6 GCI Type 80
Longley LaneLOASD 541365SOC Western Sector
Murlough BayURBID 213407R11 CHEL
NeatisheadBWPTG 346184R3 GCI
NetherbuttonBNTHY 464045CH
PevenseyTQ 644073CH
PolingTQ 043052CH
PortlandNIBSY 696735R1 CEW
PrestatynSYPSJ 079819R11 CHEL
RingsteadSY 751817CH
RyeTQ 968232CH
Sandwich (Ash)YTMTR 303574R3 GCI Type 80
Saxa VordAXAHP 629165R10 CEW Type 80
ScarinishFLYNM 032456R8 GCI Type 80
School HillHSLNO 908982CH
Seaton SnookDYRNZ 519280R3 GCI Type 80
SennenSW 376246CH
ShiptonKFYSE 542618R4 SOC Northern Sector
SkendlebyUPITF 438709R3 GCI
SnaefellMOISC 397869R11 CHEL
SopleyAVOSZ 163977R3 GCI Type 80
St AnnesSANSD 348303R8 GCI
St MargaretsAGCTR 370451R1 CEW
St TwynnellsTWYSR 944976R6 GCI Type 80
Staxton WoldTA 023778CH
StenigotTF 256827CH
Stoke Holy CrossTG 257028CH
SwingateTR 335429CH
TrelanveanSW 762193CH
TreleaverTELSW 766174R6 GCI(B) Type 80
TrerewRTWSW 812585CH
Trewan SandsTESSH 322754R8 GCI
TriminghamQLETG 290385R1 CEW Type 80 CHEL
Truleigh HillSNGTQ 224109R2 CHEL
VentnorOJCSZ 565784CH R1 CEW Type 80
WartlingZUNTQ 662088R3 GCI Type 80
West BeckhamTG 142389CH
West MyneZEMSS 928486R11 CHEL
West PrawleSX 771374CH
WickIKAND 326537R8 GCI

At the Radar Research Establishment in Malvern, Worcestershire a ROTOR bunker was constructed above ground to allow equipment to be tested in an operational environment. The building, locally designated as H Building, originally incorporated a replica of the sector operations centre at RAF Bawburgh. The building was demolished, June 2020.

The sites today

RAF Staxton Wold is the only Chain Home site still used as a military radar site but with no remains of the CH station on site after being rebuilt for Linesman/Mediator in 1964. Today it is the former home of an RAF TPS 77 RRH (remote radar head).[1]

RAF Boulmer is a working RAF building, which is housed in an ex-"ROTOR" R3 RAF Boulmer ('EZS') GCI R3 ROTOR Radar Station & Control and Reporting Centre in the UK Air Surveillance and Control System.

In terms of current condition, the ROTOR sites vary from demolished to intact.

For example, West Myne[2] in Somerset was the last ROTOR 3 CHEL site. It was completed in 1957 after the introduction of the Type 80 radar and after many ROTOR stations had already closed. The site was within Exmoor National Park and its creation was strenuously opposed by the National Trust who lost no time in obliterating the site immediately after closure.

Many of the buildings have been re-purposed since being active as ROTOR sites. An example is the Bawburgh R4 SOC[3] which was re-purposed as SRHQ4.1 and then RGHQ4.1 to suit the evolving needs of government. The building is intact, but it has been significantly reconfigured since its use as a ROTOR SOC, notably with the addition of an extra floor and the flooring-over of the original R4 operations well.

July 2019; Kent Underground Exploration are starting talks with TDC hoping to be given access to find and uncover the Foreness, Kent station which grid ref is TR 385710


References

Further reading

  • Watching the Skies, Jack Gough, HMSO 1993, ISBN 0117727237
  • Cold War: Building for Nuclear Confrontation 1946-89, Cocroft, Thomas and Barnwell, English Heritage 2003, ISBN 1873592817
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