Discoverer I was the first of a series of satellites part of the CORONA reconnaissance program. This satellite didn't take a camera or film system as it was intended as a test. There were issues communicating with the satellite during flight with only intermittent signals being read.
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.