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Cobra Mist

Ok, not WW2, but the story of 'Cobra Mist' is surely worthy of a post? At the height of the Cold War, the Pentagon was in the process of developing a number of intelligence gathering systems, one of them being 'Cobra Mist'.  This was part of the 'Cobra' programme, a series of systems to monitor Russian and potentially Chinese missile tests.  'Cobra Mist' was an over-the-horizon  'backscatter'  radar designed to bounce a strong signal off the ionosphere to cover a range of between 575 miles to 2300 miles to the east. Its purpose was to monitor aircraft, detect missile and satellite launchings behind the 'Iron Curtain'. If successful, it was hoped an early warning of a nuclear attack could be increased from 5 minutes to 15 minutes. It was essentially a private project between the US and UK Governments,  largely excluding NATO. It was almost entirely funded by the US Government to the sum of anything between £35M - £55M. The construction site was on Orfordness, Suffolk, the contract being awarded to Balfour  Beatty & Co as a concession to the British. 


Above: Planned coverage of 'Cobra Mist'.

Such a construction project would not go unnoticed, and the purpose of this project was 'explained' as purely an ionospheric research station, the same explanation given for the development of RDF at Orfordness in 1935!!

The construction programme began in in 1968, and at its height employed nearly 500 people. 



Above: Construction of 'Cobra Mist'


The system comprised a vast 18 string fan shaped antenna, consisting of 189 aerials arranged in a semicircular fan covering half a square mile facing directly at the Soviet Plesetsk missile testing site in north-western Russia. The transmission equipment was buried in a building known as the Ballum Pit and the receivers etc housed in a large building (known as the Integrated Technical Services Building)  built on piles to protect against flooding.  




Above: Top two images show the fan-shaped array. Bottom image shows the ground net associated with the array made up of high quality aluminium wire and designed to cut out 'noise'. 

The 'Cobra Mist' project was run by the Signals and Intelligence specialists from the 81st Radio Research Squadron . 


Badge of 81st Radio Research Squadron

The project was scheduled for operation by July 1972, but due to 'noise' problems this was rescheduled to 1973. The 'noise' problems were never resolved and due to economic considerations the project was terminated in June 1973. The 'noise' was described as a sharp repetitive tapping noise, at first thought to originate from Russian trawlers attempting to jam the signal. Apparently it was later confirmed as coming from a Russian over the horizon radar system, known as Duga-3 (actually known to NATO at the time and code named as the 'Steel Yard')


Above: Duga-3

The secrecy of 'Cobra Mist' has led to  stories linking it to UFO's.  The signals were so strong that ships were warned if they carried potentially explosive materials which could be exploded by sparks caused from static, an aircraft exclusion was set up, reports received of interference to TV signals and even a local bus company complaining that the 'death rays' were causing its buses to brake down!  The building was taken over by BBC World Service (they have recently vacated it). 








Above: 'Cobra Mist' ITS building today, recently vacated by BBC World Service. 




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