Entrance bungalow to former ROTOR station at Kelvedon Hatch
ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Sovietbombers. 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. Data from these stations was sent to a network of control stations, mostly built underground, using an extensive telephone and telex network.
Work also began on a new microwave frequency radar to replace Chain Home c.1957. The experimental system 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 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. Many of the operations rooms, recently completed, were sold.
ROTOR called for the continual upgrading of the network over time, both the radars and the command and control systems. The introduction of the carcinotronradar 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 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". This role was eventually abandoned, leaving only the task of locating aircraft carrying jammers to keep the BMEWS radars free from interference and prevent a successful sneak attack by missiles. 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.
As the threat of German air attack became ever more remote, UK radar operations were wound down late in the war, and by the time the war ended were already largely unused. When the war ended, there was a general feeling that another war was at least ten years in the future. Given the rapid ongoing improvements in radar systems through this period, the Air Ministry felt there was no point introducing new radars that would likely become obsolete in a few years. They planned to allow radar to continue developing through this period and use the existing WWII-era systems in the meantime.[1]
To consider the issue in more depth, the Cherry Report was commissioned in 1945. This report noted that the increasing speeds of new bombers, and especially future designs that were jet-powered, would travel across the plotting boards of the existing Dowding system so rapidly that they would fly off the maps before the interception could be arranged. The report suggested that a radar with 250 miles (400km) range would be needed to replace the existing AMES Type 7/GCI systems, which were limited to about 90 miles (140km) against bomber-sized targets. Estimating that such a radar would be available around 1957, the report suggested that existing GCI stations should receive upgraded antennas with more accuracy, new electronics for better performance, upgrades to their display systems, four Type 13's for height measuring, and two Type 14 units for anti-jamming use.[2] Additionally, their information would be sent to six new command centres, who would produce much larger maps of the airspace, up to 1,000 miles (1,600km) across. Additionally, all of the sites would be upgraded with hardened bunkers to allow them to survive a near miss.[3]
New urgency
The Berlin Blockade of July 1948 led to concerns about the next war's estimated time-frame. A White Paper on the state of the network was completed in March 1949. This found that the stations were in a terrible state, with many of them suffering weather damage and a number of them having been broken into and vandalized. A complete defense would also require 1152 fighters and 265 AA regiments, of which only 352 fighters and 75 regiments were actually available.[4] All of this was given extreme urgency with the 29 August 1949 test of the first Soviet atomic bomb. That month, a new directive stated RAF Fighter Command's mission was the defense of Great Britain.[5]
It was known that the Soviets had made exact copies of the B-29 Superfortress as the Tupolev Tu-4, and these aircraft had the performance needed to reach the UK with a nuclear payload. These were fast, but not fast enough to escape the existing radars if they were upgraded as the Cherry Report suggested. 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. This was, in part, a stop-gap measure anticipating the availability of the dramatically improved radar, which was now known as the Microwave Early Warning, which was expected in the 1957 time-frame. Interception guidance would still be handled by existing systems in either case.[2]
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, where 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 (3.0m) concrete walls with all equipment, operations generators and air conditioning located inside.[3]
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.
As work on the Microwave Early Warning system began, researchers at the Royal Radar Establishment were experimenting with new cavity magnetrons and crystal detectors that, combined with a ad hoc antenna, increased the range of their existing microwave radars on the order of four times. While the resulting "Green Garlic" did not meet all of the requirements for the original MEW, it was close enough and would be available years earlier.
The decision was made to make the MEW a long-term development with additional features such as moving target indication while the Green Garlic would be mated to an enormous antenna that would give it range over 200 nautical miles (370km; 230mi). Installations, under the name AMES Type 80, began in 1954 with the first systems declared operational the next year. As installations continued, it was found that the accuracy was such that it could also be used to direct the interceptors, with no need to forward the information to the ROTOR control centres. By concentrating all of the plotting 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. During the same period, the introduction of the first surface-to-air missiles rendered the anti-aircraft guns obsolete, and the Army handed the air defence mission entirely to the RAF. All of the AAOR sites were closed.
A few of the ROTOR and AAOR stations were re-used for Regional Seats of Government or local authority wartime headquarters. 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.
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.[citation needed]
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).[6]
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[7] 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[8] 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
Related Research Articles
Royal Air Force Boulmer or more simply RAF Boulmer is a Royal Air Force station near Alnwick in Northumberland, England, and is home to Aerospace Surveillance and Control System (ASACS) Force Command, Control and Reporting Centre (CRC) Boulmer.
Royal Air Force Buchan or more simply RAF Buchan is a former Royal Air Force station near Peterhead in Aberdeenshire, Scotland.
Remote Radar Head Saxa Vord or RRH Saxa Vord, is a Royal Air Force radar station located on the island of Unst, the most northern of the Shetland Islands in Scotland. As of July 2019 it is once more a fully operational radar station, after closure in 2006. The station's motto Praemoneo de Periculis reflects its role. RAF Saxa Vord is further north than Saint Petersburg in Russia, and on the same latitude as Anchorage, Alaska. The station was named after Saxa Vord, which is the highest hill on Unst at 935 ft (285 m). It holds the unofficial British record for wind speed, which in 1992 was recorded at 197 mph (317 km/h) — just before the measuring equipment blew away.
RemoteRadarHeadStaxton Wold or RRH Staxton Wold is an air defence radar station operated by the Royal Air Force, located near Scarborough in North Yorkshire, England. As it has been a radar site continuously since 1939, it has a claim to be the oldest working radar station in the world.
Ground-controlled interception (GCI) is an air defence tactic whereby one or more radar stations or other observational stations are linked to a command communications centre which guides interceptor aircraft to an airborne target. This tactic was pioneered during World War I by the London Air Defence Area organization, which became the Royal Air Force's Dowding system in World War II, the first national-scale system. The Luftwaffe introduced similar systems during the war, but most other combatants did not suffer the same threat of air attack and did not develop complex systems like these until the Cold War era.
Linesman/Mediator was a dual-purpose civil and military radar network in the United Kingdom between the 1960s and 1984. The military side (Linesman) was replaced by the Improved United Kingdom Air Defence Ground Environment (IUKADGE), while the civilian side (Mediator) became the modern public-private National Air Traffic Services (NATS).
The Hack Green Secret Nuclear Bunker is a former government-owned nuclear bunker located at Hack Green, Cheshire, England.
Royal Air Force Ventnor or more simply RAF Ventnor is a former Royal Air Force radar station located 0.7 miles (1.1 km) north east of Ventnor on the Isle of Wight, England. It was initially constructed in 1937 as part of a World War II coastal defence programme codenamed Chain Home. The site played an important role during the Second World War, providing early warnings of incoming bomber attacks carried out by the Luftwaffe.
Remote Radar Head Trimingham or RRH Trimingham is a former TPS-77 radar station situated on the coast in the English county of Norfolk. The site is located on the coast road between Cromer and Mundesley, 1 kilometre east of the village of Trimingham but the activity has now moved to RRH Neatishead due to the threat from coastal erosion. The radar station was a satellite station of RAF Neatishead. This radar station was controlled and maintained by a section of Radar Technicians and Operators and supported by a team of Ground Engineers. Trimingham provided extensive coverage of the East coast of the United Kingdom and helped contribute to the recognised air picture and defence of the United Kingdom. The type 93 became operational on the site in April 1997.
Royal Air Force Holmpton or more simply RAF Holmpton is a former Royal Air Force Cold War era nuclear bunker that was built in the 1950s as an early warning radar station as part of the ROTOR Radar Defence Programme. Located just south of the village of Holmpton, in the East Riding of Yorkshire, England, RAF Holmpton remained a part of the Defence Estate right up to 8 December 2014 when it was sold into private ownership after 62 years of military service.
RAF Wartling was a Royal Air Force station located near the village of Wartling in East Sussex. It was a Second World War and later Cold War Ground Controlled Interception (GCI) station built to complement the nearby Chain Home station at RAF Pevensey.
RAF Patrington, was a Ground-controlled interception (GCI) station of the Royal Air Force in the East Riding of Yorkshire, England. The base was operational during the Second World War, but was replaced by RAF Holmpton during the Cold War, although Patrington's domestic site remained open until the mid-1970s to house personnel for Holmpton. Some of the buildings of the old technical site survive abandoned near to Patrington Haven, but the domestic site has had a holiday park built upon it.
RX12874, also known as the Passive Detection System (PDS) and by its nickname "Winkle", was a radar detector system used as part of the Royal Air Force's Linesman/Mediator radar network until the early 1980s. Winkle passed out of service along with the rest of the Linesman system as the IUKADGE network replaced it.
The AMES Type 80, sometimes known by its development rainbow code Green Garlic, was a powerful early warning (EW) and ground-controlled interception (GCI) radar developed by the Telecommunications Research Establishment (TRE) and built by Decca for the Royal Air Force (RAF). It could reliably detect a large fighter or small bomber at ranges over 210 nautical miles, and large, high-flying aircraft were seen out to the radar horizon. It was the primary military ground-based radar in the UK from the mid-1950s into the late 1960s, providing coverage over the entire British Isles.
The AMES Type 85, also known by its rainbow code Blue Yeoman, was an extremely powerful early warning (EW) and fighter direction (GCI) radar used by the Royal Air Force (RAF) as part of the Linesman/Mediator radar network. First proposed in early 1958, it was eleven years before they became operational in late 1968, by which time they were already considered obsolete. The Type 85 remained the RAF's primary air defense radar until it was replaced by Marconi Martello sets in the late-1980s as part of the new IUKADGE network.
The AMES Type 7, also known as the Final GCI, was a ground-based radar system introduced during World War II by the Royal Air Force (RAF). The Type 7 was the first truly modern radar used by the Allies, providing a 360 degree view of the airspace around the station out to a distance of about 90 miles (140 km). It allowed fighter interceptions to be plotted directly from the radar display, a concept known as ground controlled intercept, or GCI.
The AMES Type 84, also known as the Microwave Early Warning or MEW, was a 23 cm wavelength early warning radar used by the Royal Air Force (RAF) as part of the Linesman/Mediator radar network. Operating in the L-band gave it improved performance in rain and hail, where the primary AMES Type 85 radar's performance dropped off. It operated beside the Type 85 and RX12874 in Linesman, and moved to the UKADGE system in the 1980s before being replaced during UKADGE upgrades in the early 1990s.
Exercise Ardent was a massive military exercise carried out by the Royal Air Force (RAF) over the United Kingdom in 1952. It pitted Bomber Command against a combined defensive force from Fighter Command, Fleet Air Arm, several squadrons of the Royal Canadian Air Force (RCAF) and additional units from the USAF and various European NATO allies. Additionally, various British Army and Territorial Army anti-aircraft forces were included, along with the Royal Observer Corps and their RAF liaisons. Over 200,000 members of the various armed forces were involved in total, with around 1,300 aircraft flying over 7,500 sorties. It was the largest air exercise held since World War II, besting even the multinational Operation Sky Shield of the early 1960s.
The Improved United Kingdom Air Defence Ground Environment, normally shortened to either UKADGE or IUKADGE, was the Royal Air Force's (RAF) ground-controlled interception system covering the British Isles during the 1990s. It consisted of a number of ground-based radar sites, links to airborne early warning aircraft and Royal Navy ships, a telecommunications system to send digital data and voice communications on a protected network, and processing systems based on VAX-11/780 computers. The network ultimately contained a dozen long-range radars including four Marconi Martello, two General Electric TPS-592, and six Plessey AR-320.
Morris, Alec (1996). "UK Control & Reporting System from the End of WWII to ROTOR and Beyond". In Hunter, Sandy (ed.). Defending Northern Skies. Royal Air Force Historical Society.
Further reading
Cold War: Building for Nuclear Confrontation 1946-89, Cocroft, Thomas and Barnwell, English Heritage 2003, ISBN1873592817
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
