TRADEX, the Tracking and Discrimination Experiment, is the original major sensor in a program to develop a ballistic missile radar signature data base. The radar became operational at the Regan Test Site (Kwajalein Atoll) in 1963 as a UHF tracker and and L-band illuminator. The radar was modified to add a VHF capability; this remained its configuration until 1970, when the system was modified and the antenna rebuilt to support coherent operation at L-band and S-band. The system remains an L-band tracker and S-band illuminator.

TRADEX is a high-sensitivity, wide bandwidth coherent instrumentation and tracking radar. TRADEX supports many operating modes, including full range and angle tracking and signature collection at L-band and range-only track with signature collection at S-band. Target resolution at L-band is 15 meters; at S-band, target resolution is nominally 5.5 meters.