The KH-4 (Keyhole-4) was fourth version in the Corona-program to build an optical reconnaissance satellite. KH-4 24 also carried the RM 5 radiometer payload for background measurements for the MIDAS program.
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.