Atomic Weapons Detection Recognition and Estimation of Yield

[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.

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.

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.

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.

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.