F-102's and TF-102's (two-seat trainer version)were deployed to Tan Son Nhut initially because ground radar sites frequently painted small aircraft penetrating South Vietnamese airspace from the north.
The F-102, a supersonic, high altitude fighter interceptor designed to intercept Soviet bombers was given the mission of intercepting,identifying and, if necessary, destroying small aircraft, flying from tree top level to 2000 ft at speeds less than the final approach landing speed of the F-102.