The introduction of the Grumman WF-2 Tracer (later the E-1 Tracer) carrier-based airborne early warning aircraft in 1958 doomed the surface and submarine radar pickets as carrier escorts. Airborne radar had now evolved to the point where it could warn of an incoming attack more efficiently than a surface ship. In 1961 the DDRs and SSRs were withdrawn. All but six DDRs received anti-submarine warfare conversions under the FRAM I and FRAM II programs and were redesignated as DDs; the remaining six were somewhat modernized under FRAM II and retained in the DDR role. The SSRs were converted to other roles or scrapped. "Triton" was left without a mission. She was too large to function as an attack submarine; some alternatives were considered, including serving as an underwater national command post, but she eventually became the first US nuclear submarine to be decommissioned, in 1969.