Clear Air Station is a Ballistic Missile Early Warning System (BMEWS) radar site which is one of three in the world. Built in 1959 it was used to detect enemy missile attack. It is now used to track satellites and space debris and covers 120 degrees in azimuth and approximately 3,000 nautical miles in range. It is located 40 miles north of Mount McKinley and 80 miles south of Fairbanks. Air Force personnel stationed there receive overseas pay and their families are not permitted on the base due to its top secret security status.