 The first specification for what became AN/SPS-48 (and the complementary AN/SPS-49) was written in 1956.The AN/SPS-48 replaced AN/SPS-39 on the , "Coontz" and classes between 1967 and 1975 under the Guided Missile Frigate Anti-Air Warfare Modernization Program.The AN/SPS-48E included a digital receiver and signal processor that could automatically detect and track very small targets, even when jammed.