Atlas SLV-3A/Agena D paired the uprated, long-tank Atlas SLV-3A first stage with Lockheed's restartable Agena D upper stage. The SLV-3A was 117 inches longer than SLV-3, carried roughly 48,000 pounds more usable propellant, and used uprated MA-5 engines. This configuration flew Research Test Series/MIDAS payloads, OGO 5, and early CANYON signals-intelligence missions from 1966 through 1969.