Ballistic Missile Early Warning System
First deployed in the 1960s, the Ballistic Missile Early Warning System (BMEWS) provides early warning and tracking of ballistic missile launches over the Arctic toward North America. Three installations, at Thule, Greenland, Flyingdales, United Kingdom, and Clear, Alaska each scan 120 degrees of the sky. They are operated by the U.S. Air Force.
At each base, the key components are a detection (i.e., early warning) and a tracking radar, and associated signal processing, power generation, etc. The sensor data is sent to the North American Aerospace Defense Command, whose main headquarters is in California. Originally, the warning radar was an AN/FPS-50 with a AN/FPS-49 tracking radar. These have been upgraded to electronically scanned phased array technology.
The original purpose was strategic warning for retaliation, but it is now part of broader ballistic missile defense. In the present system, its role would be providing information on the midcourse segment of the missile flight, with initial detection coming from infrared surveillance satellites that would detect the heat of the launch, and, in later versions, of the rocket motor plume. Other radars, such as the AN/FPS-85, would detect submarine-launched ballistic missiles approaching the Atlantic coast.