Royal Observer Corps

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ROC Crest. An Elizabethan coast watcher – from the time of the Spanish Armada – holding aloft a torch, the whole encircled by a wreath of laurel and surmounted by the royal crown, the motto being Forewarned is Forearmed.

The Royal Observer Corps (ROC) was a defence warning organisation operating in the United Kingdom between 1925 and 1995. It was created to provide a system for detecting, tracking and reporting aircraft over Britain. In 1955 the detection and reporting of nuclear blasts and fall-out was introduced. By 1965 the aircraft role was no longer needed and the corps formed the field force for the United Kingdom Warning and Monitoring Organisation (UKWMO).

1 World War I
- 1.1 Afterwards
2 World War II
3 Cold War
- 3.1 'Post'-Cold War
- 3.2 Instrumentation
4 Main Source
5 External links
6 See also

[edit] World War I

The ROC had its beginnings during World War I. At the beginning of the war the need for an air raid warning system was not envisioned, but raids by Zeppelin airships starting in 1915 indicated that a warning system was needed. A system of observers was soon organised with a series of some 200 posts established in strategic areas, initially these were manned by troops, but these were soon replaced by police, coordinated by area with telephone contact to anti-aircraft (AA) defences. This system proved to be reasonably successful in combating the Zeppelin.

In 1917 Germany started using fixed wing bombers and the number of airship raids diminished rapidly. To answer this new threat Major General E B Ashmore, who could fly and had been in command of an artillery division in Belgium, was appointed to devise improved systems of detection, communication and control. A system to be called the Metropolitan Observation Service was created, this covered the London area, known as the London Air Defence Area, and was soon extended towards the coasts of Kent and Essex. The system met with some success and although it was not fully working until late summer 1918 (the last air raid took place on 19 May) the lessons learnt were to provide valuable grounding for later developments.

	Air Raids
	Aeroplanes	Airships	Deaths
1914	3	0	0
1915	4	42	186
1916	28	126	302
1917	341	30	650
1918	59	10	178
Total	435	208	1316

[edit] Afterwards

After the Armistice it was intended that the knowledge and skills learnt during the war should be kept alive. These plans came to nothing and by the end of 1920 all networks and associated anti-aircraft hardware had disappeared.

In 1922, responsibility for air defence was transferred from the War Office, which was responsible for the Army, to the Air Ministry. Major General Ashmore, who had been responsible for matters during World War I, now reported to a new Air Raid Precautions (ARP) committee set up in January 1924. Experiments were now carried out around Romney Marsh and the Weald. These were intended to optimise the arrangement of observation posts and control centres. In 1925 these experiments were extended to cover parts of Essex and Hampshire and by October a sound methodology had been worked out. On 29 October 1925 the Observer Corps came into official existence. Within a year four Groups existed in SE England, covering much of Kent, Sussex, Hampshire and Essex. The plan was that the country would be covered by 18 of these groups. The involvement and cooperation were needed between the Royal Air Force (RAF), the Army, the British police forces and the General Post Office (GPO), then responsible for the national telephone system.

In January 1926 observers were being recruited as special constables by county constabularies. Each post was to be manned by a sergeant and six constables, recruits were to be part-time volunteers with no pay, no uniform and no allowances; lapel badges would be issued, but would have to be paid for. In 1929 the control of the Observer Corps passed to the Air Ministry, although chief constables retained responsibility for personnel and recruitment matters.

During the 1930s the number of groups increased until, by 1936, England was covered south east of a line drawn from Flamborough Head to Poole Harbour. By 1939 practically the whole of Great Britain was covered, the western extremities of the West Country, Wales and Scotland were included in 1940, in 1941 the last group Portree was formed in the Western Isles

[edit] World War II

[edit] Preparation

At the end of September 1938 the crisis which resulted in the Munich Agreement lead to the Corps being called out for a week. This exercise proved to be invaluable as it drew attention to organisational and technical problems and gave time for solutions to be sought. Exercises held throughout 1939 enabled necessary modifications to methods and structure. The Observer Corps would evolve over the coming years, a process aided by the keenness with which Corps members from every walk of life addressed the process.

[edit] War

On 24 August 1939 Chief Constables issued mobilisation notices to all members of the Observer Corps. War was eventually declared on 3 September, posts and centres would be manned continuously until 12 May 1945, four days after VE Day on 8 May 1945.

The first months of World War II were known as the Phoney War. There was little significant enemy aircraft activity over Britain. The Battle of Dunkirk started at the end of May 1940, Allied troops were cut off by the German army in north-east France. This resulted in the evacuation of British troops in Operation Dynamo which ended on 4 June. During this time the RAF lost 944 aircraft, half of these being fighters. Observer Corps posts in Kent and around the Thames estuary were able to play some part by plotting aircraft while they were over England. It was however an extremely useful period for training and practice which proved to be extremely valuable within a few months.

After the Fall of France the German aim was air superiority over Britain to be achieved by destroying RAF fighters in the air and on the ground, and by bombing aircraft factories. Winning the Battle of Britain, as it was soon called, was Germany's prerequisite in preparation for the invasion of Britain, Operation Sealion.

The British Chain Home radar system was able to provide warning of enemy aircraft approaching the British coast, but once they had crossed the coastline the Observer Corps provided the only means of tracking them. During the period from July to October 1940 the Corps was fully stretched 24 hours a day plotting aircraft and passing this essential information to RAF groups and sectors. The Battle of Britain saw the start of the Blitz, the shift of German bombing from airfields to cities, the Observer Corps provided the information which enabled air raid warnings to be issued. The Blitz itself continued until early in the summer of 1941 and bombing on a reduced scale continued until March 1945.

After the successes of 1940 and early 1941 the corps was retitled the Royal Observer Corps (the ROC); it was to continue as a civilian organisation and be administered by the Royal Air Force, and for the first time women members would be recruited. Members of both sexes were employed in two forms: Class A who were required to work for 56 hours a week, and Class B members who undertook up to 24 hours duty per week.

For the rest of the war the ROC provided an essential part of Britain's air defences. In 1944, during preparations for the invasion of France called Operation Overlord, a request for volunteers produced over 1,000, 800 of whom performed valuable aircraft recognition duties as seaborne volunteers. Shortly after D-Day the first V1 flying bombs started arriving provided the corps with another way of proving its worth. On 12 May 1945, when it was certain that all Luftwaffe aircraft were grounded, the ROC stood down.

[edit] Methodology

The Colchester (No 18) Group - Post organisation in 1944

The headquarters of each Group operated from a Centre and controlled about 30 to 40 Posts each of which would be some 10 km to 20 km from its neighbour. By 1945 there were 40 centres covering England, Wales and Scotland, controlling in total more than 1,000 posts, The ROC did not operate in Northern Ireland until 1954.

If you know the height of an aircraft it is possible, from its horizontal bearing and vertical angle, to calculate a position. Posts were equipped with a mechanical sighting instrument mounted over a gridded map. After setting the instrument with an estimate of the aeroplane's height, the observer would align a sighting bar with the aircraft. This bar was mechanically connected to a vertical pointer which would indicate the position of the aircraft on the post map.

Observers in posts reported the map coordinates, height and number of aircraft for each sighting to their Centre. At each Centre plotters sat around a large table map, they had head sets continuously connected to a Cluster of posts, usually three in number.

The plotting table consisted of a large map with grid squares and posts marked. Counters were placed on the map at the reported positions, each of which indicated the height and the number of aircraft represented, a colour coding system indicated the time of observation in 5 minute segments. The table was surrounded by plotters, each communicating with a cluster of posts. Over time the tracks of aircraft could be traced, the colour coding enabled the extrapolation of tracks and the removal of stale ones. From 1942 long range boards were introduced to centre operations rooms, tellers in contact with neighbouring groups could handover incoming and outgoing tracks which were plotted on this map.

Duties in the operations room included: plotters working on the plotting table and on the long range board; tellers communicating with neighbouring ROC groups, with fighter operations rooms, with anti-aircraft and searchlight units; alarm controllers in contact with the police, with the national alert system, with the Ministry of Home Security and with local factories; an interrogator liaising with the ground controlled interception (GCI) radar units; and the Duty Controller, his assistant and a post controller who supervised the plotters and posts.

Obviously it was essential that observers could correctly identify an aeroplane. In 1939 aircraft recognition was not yet the highly prized skill it was to become in the Observer Corps. The other services felt that accurate identification was impossible. Observers realised that this was a deficiency and the raised profile of aircraft recognition was driven from below. Identification literature with aircraft silhouettes and data, started almost entirely as a private initiative instigated by observers.

[edit] Cold War

In September 1947, over a year after VE Day, the ROC held its first small scale exercise in southern England, which included for the first time substantial numbers of jet aircraft. Another year later the first large scale exercise took place; in the last two of its four days of this radar only was used. By the mid-1950s the greater speed of aircraft and the improved performance of radar lead to a reduced need by the RAF for the ROC's services in tracking aircraft; another rôle in defence against nuclear weapons was announced in June 1955. The first significant exercise involving the ROC in handling nuclear data was in 1956. In 1957 the British government's policy became clear and reliance would be placed on the nuclear weapons, within ten years any pretence that there was an aircraft recognition and reporting role for the ROC had all but gone.

In 1957 the United Kingdom Warning and Monitoring Organisation (UKWMO) was set up under Home Office control. It was intended that UKWMO would provide civil and military authorities in Britain with information during a nuclear attack. The ROC would provide the first data on the positions and extent of the attack. This data would be used by UKWMO, in conjunction with weather information from the Meteorological Office, to produce a forecast of radioactive fallout. As this fallout occurred its strength and position would be mapped using data from posts, enabling further fallout forecasts to be given.

To enable the ROC's centre and post structure would need to undergo physical and organisational change. The Groups were reorganised the number being reduced from 40 to 31, the Corps now covered Northern Ireland for the first time. It would now be necessary for Centres and posts to be occupied for at least seven days after any nuclear event: centres were expanded with increased accommodation, emergency power generation and air handling and filtration, and underground posts were constructed with concrete under a 200 mm slab, they were 4.75 metres long and 2.25 metres in length and height. Power would be supplied from a 12 volt car battery. Conditions in these posts cramped, cold and damp, it was fortunate for observers that long occupation was never necessary.

Initially communications were by telephone, replaced in 1964 by Tele-talk units, these used landlines with transistorisation to boost power. The vulnerability of land lines lead to VHF radio being installed with one post in each cluster; clusters had local arrangements for communication between themselves.

[edit] 'Post'-Cold War

Following the stand-down of the main field force of the ROC in September 1991, and the disestablishment of the UKWMO following what was described by HM Queen Elizabeth II at the ROC Royal Review as "the end of the Cold War", the remnant elements of the Corps entered a new and highly-uncertain phase. Reduced to less than 300 members in total over the whole UK, the original retained Nuclear Reporting Cells (NRCs) found themselves tasked with the challenge of providing a comprehensive Nuclear, Biological and Chemical (NBC) warfare analysis and warning service for the Military Home Commands, on a reserve-manned basis as NBCCs.

The removal of any Home Office involvement in the ROC from 1991 onwards resulted in the "Remnant Elements" becoming effectively a single reserve Directly Administered Unit within RAF Strike Command (RAFSTC), commanded by Group Captain (GND). All still-serving members were required to remove their original ROC Group designations from their air force uniforms, and to accept moves towards a change in conditions of service during any Transition-To-War (TTW) that would make them effectively members of the Royal Auxiliary Air Force (RAuxAF), with protected rights, and closer links were made with the war-appointable flights of the Royal Air Force Volunteer Reserve (RAFVR).

Despite having successfully built upon the extensive NBC reporting trials carried out earlier with the RAF Regiment, meeting full NATO standards and evalutions (STANAGs and OPEVALs), and the total support of the RAF for keeping the ROC in the orbat, the conclusion reached by the UK MoD was that retention of the Corps in its NBC Cell role was "desirable but not essential in the existing format". As a consequence, the remaining part-time members of the ROC were stood-down in a Corps Banner laying-up ceremony at RAF College Cranwell on 8 Dec 1995. The ROC Banner hangs in the Rotunda at RAFC Cranwell alongside other stood-down Air Force units and squadrons that are subject to liability for reactivation in the future.

[edit] Instrumentation

The Ground Zero Indicator, the GZI or shadograph, consisted of four horizontally mounted pinhole cameras within a metal drum, each camera contained a sheet of photosensitive paper on which were printed horizontal and vertical calibration lines. The flash from a nuclear explosion would produce a mark on one or two of the papers within the drum. The position of the mark enabled the bearing and height of the burst to be estimated. With triangulation between neighbouring posts these readings would give an accurate height and position. The altitude of the explosion was important because a ground or near ground burst would produce more radioactive fallout.

The Bomb Power Indicator consisted of a pressure gauge whose dial could register the peak pressure reached when the pressure wave from a nuclear explosion passed the post. When related to the distance of the explosion from the post this pressure would indicate the power of the explosion.

For the measurement of ionising radiation

The RSM2 or Radiac Survey Meter No 2 a meter which counted the particles produced by radioactive decay. This meter suffered from a number of disadvantages: it required three different types of batteries, it contained valves which were liable to failure and it had to be operated from outside the protection of the post. This was superseded in by the FSM.

The FSM or Fixed Survey Meter introduced in 1958, it could be operated from within the post with a cable leading to the detector on the post roof. In 1985 this instrument was replaced by the PDRM 82.

The PDRM82 or Portable Dose Rate Meter which was manufactured by Plessey, it gave more accurate readings and had batteries which lasted many times longer.