Royal Observer Corps: Encyclopedia II - Royal Observer Corps - Cold War

Royal Observer Corps - 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.

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 communcation between themselves.

Royal Observer Corps - 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.

Adapted from the Wikipedia article "Cold War", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki