You're likely thinking of the Apollo-Soyuz Test Project (ASTP), which was a joint US-USSR space mission in 1975. It involved a docking of the American Apollo spacecraft with the Soviet Soyuz spacecraft in Earth orbit.

Here's a breakdown of the mission:

* Purpose: The primary purpose of the ASTP was to symbolize détente between the two superpowers during the Cold War. It was a significant event in international cooperation in space exploration.

* Spacecraft: The mission involved the Apollo spacecraft (launched from Cape Canaveral, Florida) and the Soyuz spacecraft (launched from Baikonur Cosmodrome, Kazakhstan).

* Crew: The American crew consisted of Thomas P. Stafford, Vance D. Brand, and Donald K. Slayton. The Soviet crew consisted of Alexei Leonov and Valeriy Kubasov.

* Docking: The two spacecraft successfully docked on July 17, 1975, after two days of independent flight. The crew members spent two days together in the docked spacecraft, conducting experiments and exchanging gifts.

* Legacy: The ASTP was a major milestone in space exploration and international relations. It marked a shift towards cooperation in space exploration between the US and USSR.

While the Apollo-Soyuz Test Project is the most prominent example of a joint US-USSR space mission, there were other instances of collaboration between the two nations, albeit on a smaller scale.

Let me know if you'd like to learn more about specific aspects of the ASTP, or any other US-USSR space missions!