1975-05-13 USA ASTP Control Centers Joint Simulation

An Apollo–Soyuz Test Project joint simulation cover, postmarked at Houston, Texas with a machine cancel on May 13, 1975.

On May 13, 1975, NASA's Johnson Space Center in Houston and the Soviet Mission Control Center near Moscow began a 25½-hour joint simulation of the upcoming Apollo–Soyuz mission. The exercise began about one hour before the planned Soyuz launch and involved the mission-control teams and crew simulators in both countries.

The simulated spacecraft were "launched" and then put through a variety of flight maneuvers. Importantly, this wasn't simply an exercise performed independently by NASA and the Soviet Union. The two control centers were actually linked together, with communications exchanged by, voice, teletype, data fax and television. This allowed the teams to practice the complicated coordination that would be required during the real mission.