Thor-Agena

Thor-Agena was a series of American orbital launch vehicles that paired the Douglas-built Thor first stage with the Lockheed-built Agena as the second stage. The first launch attempt was in January 1959 and the first successful flight, on 28 February 1959, carried Discoverer 1, the first satellite placed in orbit by a two-stage launch vehicle. The CORONA reconnaissance satellite programme of the Central Intelligence Agency flew on Thor-Agena from June 1959 until January 1968, in 145 launch attempts, and the vehicle also launched OSCAR 1, the first non-governmental satellite, and Alouette 1, Canada's first satellite. The article distinguishes the Thor-Agena A, B and D versions, and describes the thrust-augmented variant whose 1963 failure over the southwestern United States produced a widely reported mystery cloud. It is described as a cousin of the Thor-Delta that founded the Delta family.