Soyuz 31 was the sixth mission to visit the Salyut 6 space station and carried the the EP-4 crew, which visited the long-duration Soyuz 29 resident crew. The mission began on August 26, 1978, 14:51:30 UTC, launching Commander Valery Bukovsky and Research Cosmonaut/Flight Engineer Sigmund JÃ¤hn, the first German cosmonaut, into orbit. They docked with the station the next day. During their stay on the station, crew conducted various scientific experiments. Soyuz 31 crew swapped vehicles with the Soyuz 29 (EO-2 expedition) crew, which allowed for a longer stay in orbit for EO-2.
The mission concluded with a safe landing back on Earth on September 3, 1978, 11:40:34 UTC.