What was the name of the 1975 joint US-Soviet space mission?

The 1975 joint US-Soviet space mission was the Apollo-Soyuz Test Project. It was the first crewed international space mission and became one of the most visible symbols of Cold War détente.

The American Apollo spacecraft and Soviet Soyuz 19 spacecraft launched on July 15, 1975, and docked two days later. American astronauts Thomas Stafford, Vance Brand, and Deke Slayton joined Soviet cosmonauts Alexei Leonov and Valery Kubasov for joint experiments, crew exchanges, and ceremonial events. Stafford and Leonov's handshake through the open hatch became the mission's iconic image.

The flight required the two countries to solve major technical and political problems, including incompatible spacecraft systems, different atmospheric pressures, and the design of a universal docking mechanism. The resulting Androgynous Peripheral Attach System allowed either spacecraft to serve as the active or passive docking partner.

The mission is also known as Apollo-Soyuz or ASTP. The Soviets referred to it as Soyuz-Apollo, and the spacecraft itself was designated Soyuz 19. It was the final flight of an Apollo spacecraft and preceded later US-Russian cooperation such as Shuttle-Mir and the International Space Station.