The Apollo Soyuz Test Project (ASTP) was the first manned international space mission conducted jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as an American Apollo spacecraft docked with a Soviet Soyuz capsule on July 17, 1975.
The three American astronauts Thomas P. Stafford, Vance D. Brand and Deke Slayton, as well as the two Soviet cosmonauts Alexei Leonov and Valery Kubasov conducted both joint and separate scientific experiments, including a solar eclipse arranged by the Apollo module to enable instruments on the Soyuz photographing the solar corona.
The project and its handshake in space were a symbol of détente between the two superpowers during the Cold War.
The pre-flight work also provided useful technical experience for later joint U.S.-Russian space flights, such as the Shuttle-Mir program and the International Space Station.