July 17, 1975: The Apollo-Soyuz Test Project link-up

Today in the history of astronomy, an astronaut and a cosmonaut shake hands in space. | Published: July 17, 2026 The culmination of years of international negotiations and training, Apollo and Soyuz linked up in space in July 1975. When the hatches opened, their respective commanders, Thomas Stafford and Aleksey Leonov, shook hands. Credit: NASA After years of planning, training, and international negotiation, the Apollo-Soyuz Test Project mission culminated in 1975 when spacecraft from the U.S. and the Soviet Union docked in space. On July 17, the Apollo and Soyuz capsules locked together, utilizing an “androgynous” system of petal-shaped plates, and their commanders, Thomas Stafford and Aleksey Leonov, shook hands. Two days of joint tech and science experiments followed. The mission set high goals for cooperation on future projects, including the ability to perform international space rescues and the future Space Shuttle-Mir docking. Elisa Neckar is senior production editor of Astronomy magazine, and the editor of the Today in the History of Astronomy feature on Astronomy.com.