Monument record ORF 177 - Cobra mist

Also known as Project 44I- L, Cobra Mist was the codename for an experimental over-the-horizon long-range surveillance radar operated by the U.S. It was designed to extend the range of conventional radar detection techniques by bouncing signals off the ionosphere. The original location chosen was in Turkey however Turkey refused to provide a base. Orfordness was chosen as almost all of Eastern Europe and the western parts of the Soviet Union would be visible. The area chosen had been heavily disturbed by bombing and required clearing before construction work could begin. Work began in 1967 and the site was completed in 1971. The buildings had to be carefully shielded to avoid being contaminated from signals being reflected locally. However testing was plagued by an unexpected mount of background noise that severely limited the detection performance. A lengthy investigation was conducted but the noise was never identified and in 1973 the system was shut down.

The AN/FPS-95 antenna consisted of 18 individual strings radiating outward from a single point near the eastern shore of Orford Ness. Each string was 2,040 feet (620 m) long, supported on masts from 42 feet (13 m) to 195 feet (59 m) high, with multiple active elements hung from the strings. The strings were arranged 8 degrees 40 minutes apart, covering an arc from 19.5 to 110.5 degrees clockwise from true north. Beneath the antenna was a large wire mesh screen acting as a reflector. The mesh extended past the hub to the east.

The site was then used by the UK Foreign Office and the BBC World Service as a radio transmitting station until it passed into private ownership in 2015 (S1)(S2).