The second stage of the Saturn 1B booster was mated with the Saturn 1B first stage in the Kennedy Space Center's Vehicle Assembly Building.

The second stage of the Saturn 1B booster for the United States mission on the Apollo Soyuz Test Project was mated with the Saturn 1B first stage in the Kennedy Space Center's Vehicle Assembly Building today. Mating was completed at 9:50 a.m. The U. S. ASTP launch with mission commander Thomas Stafford, command module pilot Vance Brand and docking module pilot Donald Slayton is scheduled at 3:50 p.m. EDT July 15.

The first international crewed spaceflight was a joint U.S.-U.S.S.R. rendezvous and docking mission. The Apollo-Soyuz Test Project, or ASTP, took its name from the spacecraft employed: the American Apollo and the Soviet Soyuz. The three-man Apollo crew lifted off from Kennedy Space Center aboard a Saturn IB rocket on July 15, 1975, to link up with the Soyuz that had launched a few hours earlier. A cylindrical docking module served as an airlock between the two spacecraft for transfer of the crew members.
Photo credit: NASA