Thor Agena A

Thor DM-21 Agena A

Mission Profile

The Thor Agena A (Thor DM-21 Agena A) was an early two-stage American launch vehicle pairing the Thor IRBM first stage with Lockheed's Agena A upper stage, representing the first operational combination of the Thor booster with an Agena restartable engine. Standing 23.5 m tall with a 2.4 m diameter and a liftoff mass of 56 tonnes, it generated 758 kN of first-stage thrust. First flying in January 1959 under the Thor IRBM Program, the Thor Agena A launched the first Discoverer reconnaissance satellites, initiating America's decades-long capability for photographic intelligence collection from orbit.