Thor Agena D | KH-4 13 & RM 4

The KH-4 (Keyhole-4) was fourth version in the Corona-program to build an optical reconnaissance satellite. KH-4 13 carried the RM 4 radiometer payload (identical to RM 3) 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.

The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947.