On 15 Juy 1975, the US and the USSR launched an Apollo spacecraft (Apollo-ASTP) and a Soyuz spacecraft (Soyuz 19), respectively, as a joint effort called the Apollo-Soyuz Test Project (ASTP), a post-Moon-race 'goodwill' flight to test a common docking system for space rescue. Soyuz 19, with its two man crew, had a flawless launch, and achieved an initial orbital of 220.8 by 185.07 km at the desired inclination of 51.80 degrees, with the period of the first orbit being 88.6 minutes. The Apollo was launched 7.5 hours later, with a three man crew who maneuvered their spacecraft into a proper configuration for docking with the Soyuz. The docking occurred on the third flight day, 17 July 1975. After docking, crew transfers took place, with the Apollo crew first visiting the Soyuz. Leonov was on the American side for 5 hours, 43 minutes, while Kubasov spent 4:57 in the command and docking modules. The combined Apollo-Soyuz crews conducted various mainly ceremonial activities, performed joint experiments, and presented radio and TV reports. After the joint experiments were completed, the spacecraft disengaged, and each continued its separate mission.

After being docked for nearly 44 hours, Apollo and Soyuz parted for the first time and were station-keeping at a range of 50 meters. The Apollo crew placed its craft between Soyuz and the Sun so that the diameter of the service module formed a disk which blocked out the Sun, creating an artificial solar eclipse so the Soyuz crew could take photographs of the solar corona. After this experiment Soyuz moved toward Apollo as the active ship for the second docking.

Three hours later Apollo and Soyuz undocked for the second and final time. The spacecraft were moved to a 40 meter station-keeping distance to perform an ultraviolet absorption experiment. With all the joint flight activities completed, the ships then went on their separate ways. Soyuz 19 landed safely in Kazakhstan on 21 July 1975.

See also Apollo-Soyuz Test Project Soyuz crew on Wikipedia

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1975-065A