Thor-Agena was a series of orbital launch vehicles. The rockets used Thor first stages and Agena second stages. They are thus cousins of the more famous Thor-Deltas, which founded the Delta rocket family. The first attempted launch of a Thor-Agena was in January 1959. The first successful launch was on February 28, 1959, launching Discoverer-1.
Among other uses, the clandestine Corona program used Thor-Agenas from June 1959 until January 1968 to launch US military reconnaissance satellites operated by the CIA. During this program, Thor-Agena launch vehicles were used in 145 launch attempts now known to have been part of satellite surveillance programs.
Also, Alouette 1, Canada's first satellite, was launched on a Thor-Agena-B.
The Discoverer 14 satellite used in the Corona spy satellite program was launched by a Thor-Agena-A. On 1960-08-19 usable photographic film from the satellite was recovered by a C-119 recovery aircraft. This was the first successful recovery of film from an orbiting satellite and the first mid-air recovery of an object returning from Earth orbit.
First successful launch: Nov 12, 1960 with Discoverer 17