Atomic Weapons Detection Recognition and Estimation of Yield
Last updated A photograph of an AWDREY display unit taken in situ at the York Cold War Bunker
Atomic Weapons Detection Recognition and Estimation of Yield known by the acronym AWDREY was a desk-mounted automatic detection instrument, located at 12 of the 25 Royal Observer Corps (ROC) controls, across the United Kingdom, during the Cold War. The instruments would have detected any nuclear explosions and indicated the estimated size in megatons.
The Royal Observer Corps (ROC) was a civil defence organisation intended for the visual detection, identification, tracking and reporting of aircraft over Great Britain. It operated in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down.. Composed mainly of civilian spare-time volunteers, ROC personnel wore a Royal Air Force (RAF) style uniform and latterly came under the administrative control of RAF Strike Command and the operational control of the Home Office. Civilian volunteers were trained and administered by a small cadre of professional full-time officers under the command of the Commandant Royal Observer Corps; latterly a serving RAF Air Commodore.
The United Kingdom, officially the United Kingdom of Great Britain and Northern Ireland but more commonly known as the UK or Britain, is a sovereign country lying off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea lies between Great Britain and Ireland. With an area of 242,500 square kilometres (93,600 sq mi), the United Kingdom is the 78th-largest sovereign state in the world. It is also the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017.
The Cold War was a period of geopolitical tension between the Soviet Union with its satellite states, and the United States with its allies after World War II. A common historiography of the conflict begins with 1946, the year U.S. diplomat George F. Kennan's "Long Telegram" from Moscow cemented a U.S. foreign policy of containment of Soviet expansionism threatening strategically vital regions, and ending between the Revolutions of 1989 and the 1991 collapse of the USSR, which ended communism in Eastern Europe. The term "cold" is used because there was no large-scale fighting directly between the two sides, but they each supported major regional conflicts known as proxy wars.
With the display unit mounted in a 3-foot-high (0.91m) steel cabinet, the system used two sets of five photo-sensitive cells within the detection head to record the intense flash of light produced by the detonation of the weapon followed, within a second, by a second intense flash. This double flash is characteristic of a nuclear explosion and measurement of the short gap between the two flashes enabled the weapon's power to be estimated, and the bearing to be indicated. It had a range of 150 miles (240km) in good visibility.[1][2] From 1974 AWDREY units were used together with a device known as DIADEM (Direction Indicator of Atomic Detonation by Electronic Means) which measured the electromagnetic pulse (EMP) generated by an explosion.[3] The instruments were in constant operation (state of readiness) between 1968 and 1992 and tested daily by full-time ROC officers.
A nuclear electromagnetic pulse is a burst of electromagnetic radiation created by a nuclear explosion. The resulting rapidly varying electric and magnetic fields may couple with electrical and electronic systems to produce damaging current and voltage surges. The specific characteristics of a particular nuclear EMP event vary according to a number of factors, the most important of which is the altitude of the detonation.
Operations
AWDREY was designed, built and maintained by the Atomic Weapons Establishment at Aldermaston. The design was tested for performance and accuracy using real nuclear explosions at the 1957 Kiritimati (or Christmas Island) nuclear weapon trials, after being mounted on board a ship. Although a single AWDREY unit could not differentiate between a nuclear explosion and a lightning strike, the units were installed sufficiently far apart that a lightning strike would not simultaneously register on two adjacent AWDREYs.
The Atomic Weapons Establishment (AWE) is responsible for the design, manufacture and support of warheads for the United Kingdom's nuclear weapons. It is the successor to the Atomic Weapons Research Establishment (AWRE) with its main site on the former RAF Aldermaston and has major facilities at Burghfield, Blacknest and RNAD Coulport.
Aldermaston is a mostly rural, dispersed settlement, civil parish and electoral ward in Berkshire, England. In the United Kingdom Census 2011, the parish had a population of 1015. The village is in the south the mid-Kennet alluvial plain and bounds to the south Hampshire. It is roughly equidistant from Newbury, Basingstoke and Reading, centred 46 miles (74 km) west-by-south-west of London.
Kiritimati, or Christmas Island, is a Pacific Ocean raised coral atoll in the northern Line Islands. It is part of the Republic of Kiribati.
The United Kingdom Warning and Monitoring Organisation (UKWMO) was a British civilian organisation operating to provide UK military and civilian authorities with data on nuclear explosions and forecasts of fallout across the country in the event of nuclear war.
Providing confirmation of nuclear strike on the UK
The four-minute warning was a public alert system conceived by the British Government during the Cold War and operated between 1953 and 1992. The name derived from the approximate length of time from the point at which a Soviet nuclear missile attack against the United Kingdom could be confirmed and the impact of those missiles on their targets. The population was to be notified by means of air raid sirens, television and radio, and urged to seek cover immediately. In practice, the warning would have been more likely three minutes or less.
AWDREY was the principal method by which the UKWMO would achieve its second responsibility. Simultaneous responses on two or more AWDREY units would identify the explosion as a nuclear strike.
ROC post bomb detection instruments (see Bomb Power Indicator) operated by recording the peak overpressure of the blast wave from any nearby nuclear explosion. Any ultra-high-altitude nuclear explosion, designed to knock out the UK's communications and electronic equipment would not produce a detectable blast wave, and the AWDREY system was therefore the only method of identifying these bursts.
Bomb Power Indicator known by the acronym BPI was a detection instrument, located at the twenty five British Royal Observer Corps controls and nearly 1,500 ROC underground monitoring posts, across the United Kingdom, during the Cold War that would have detected any nuclear explosions and measured the peak-overpressure of the blast waves.
Installation
The AWDREY installation consisted of three separate elements: the sensor, the detection unit and the display cabinet (timer). The sensor was mounted on the roof of the building. The detection unit was installed in a special room that was enclosed inside a Faraday cage; in the case of the Royal Observer Corps controls, this was the "Radio Room" that already protected the sensitive radio equipment from the effects of EMP.
Awdrey Timing and Logic on display in York
The display unit (timer) (shown in the photograph above) could be mounted anywhere in the building – at ROC controls this was usually on the balcony adjacent to the Triangulation Team. The three elements of the installation were connected by EMP-shielded and heavy duty cabling.
During the early phase of operations, a spare observer was required to stand next to the display unit and monitor it constantly to identify initial responses. Once a nuclear strike on the UK had been confirmed by the Director UKWMO (or his deputy), readings from AWDREY were ignored during subsequent nuclear bursts within the attack, and the readings from ROC posts became the main method of detecting and identifying any subsequent near ground bursts.
The 12 ROC AWDREY units were located at the group controls in Exeter, Oxford, Horsham, Bristol, Colchester, Carmarthen, Coventry, Carlisle, York, Dundee, Inverness and Belfast.[4] This siting pattern provided sufficient detectors that the entire UK was covered, but the units were far enough apart that a lightning storm would be unlikely to trigger simultaneous AWDREY responses at two sites.
Codeword
Royal Observer Corps reports following a reading on AWDREY were prefixed with the codeword "TOCSIN BANG". The message would also include the three-letter group identifier, followed by the time and yield reading from the AWDREY printout. E.g. "TOCSIN BANG – CAR – 11.06 (hours) – 3 megatons" (with CAR relating to Carlisle control).
The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the troposphere can be approximately divided into four basic categories:
Operation Fishbowl was a series of high-altitude nuclear tests in 1962 that were carried out by the United States as a part of the larger Operation Dominic nuclear test program. Flight-test vehicles were designed and manufactured by Avco Corporation.
The Kelvedon Hatch Secret Nuclear Bunker at Kelvedon Hatch, in the Borough of Brentwood in the English county of Essex, is a large underground bunker maintained during the Cold War as a potential regional government headquarters. Since being decommissioned in 1992, the bunker has been open to the public as a tourist attraction, with a museum focusing on its Cold War history.
Tocsin may refer to:
The Ground Zero Indicator, known by the acronym GZI was a specially designed shadowgraph instrument used by the British Royal Observer Corps during the Cold War to locate the Ground Zero of any nuclear explosion.
The Fixed Survey Meter was a specialist detection instrument used by the Royal Observer Corps during the Cold War between 1958 and 1982 to detect ionising radiation from nuclear fallout generated by a ground burst.
The Royal Observer Corps (ROC) was a civil defence organisation operating in the United Kingdom between October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down.. Composed mainly of civilian spare-time volunteers, ROC personnel wore a Royal Air Force (RAF) style uniform and latterly came under the administrative control of RAF Strike Command and the operational control of the Home Office. Civilian volunteers were trained and administered by a small cadre of professional full-time officers under the command of the Commandant Royal Observer Corps; a serving RAF Air Commodore.
Royal Observer Corps Monitoring Posts are underground structures all over the United Kingdom, constructed as a result of the Corps' nuclear reporting role and operated by volunteers during the Cold War between 1955 and 1991.
The Royal Observer Corps Orlit Post is an observation post used by the Royal Observer Corps during the Cold War to recognise enemy aircraft. Many Orlit Posts can be found near ROC Monitoring Posts.
References
↑ COCROFT, Wayne D and THOMAS, Roger J C Cold War: Building for Nuclear Confrontation 1946-1989 English Heritage, Swindon, 2003 revised 2004 (p.191 & 193)
↑ COCROFT, Wayne D and THOMAS, Roger J C Cold War: Building for Nuclear Confrontation 1946-1989 English Heritage, Swindon, 2003 revised 2004 (p.191-2)
↑ COCROFT, Wayne D and THOMAS, Roger J C Cold War: Building for Nuclear Confrontation 1946-1989 English Heritage, Swindon, 2003 revised 2004 (p.187)
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