The Strawman series of ELINT/SIGINT satellites, known for decades only as "Heavy Ferrets", are the fourth variation of Agena-based ELINT satellites. These satellites were designed to detect, map and investigate SAM and ABM radars.
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.