sentences:  Operating as an arm of the United States Air Force Civil Defense service, the second GOC supplemented the Lashup Radar Network and the Permanent System radar stations.Observations were telephoned directly to filter centers and the information was in turn relayed to Air Defense Command ground control interception centers.By 1952 the GOC program was expanded into Operation Skywatch, consisting of 750,000 volunteers aged 7 to 86 years old working in shifts at over 16,000 posts and 73 filter centers.