The third such system, the joint US-UK Cobra Mist, was the first such truly operational system in the world, and work began on constructing the huge shell shape site with all its aerials in the late 1960s. This time, its job was to pick up Soviet aircraft and missile activity as far away as Russia"s Far North. In 1972, when it began operating, it attracted the attention of more than its fair share of Soviet spy trawlers. Just one year later it was suddenly closed down due to noise interference.