Soyuz 13 was launched December 18, 1973
for a week long mission. It was designed to test the new Soyuz 7K-T
spacecraft but also featured a large Orion 2 astrophysical camera
in place of the docking
On board were Pyotr Klimuk and Valentin Lebedev. Their callsign for the mission was Kavkas (Caucasus).
The original mission was to have been the first docking with the Salyut 2 space station. This failed in orbit and so the spacecraft was modified to have a large UV camera. This took up most of the orbital module.
Additional experiments included spectrozonal photography of specific areas of the earth's surface, and continued testing of space craft's on-board systems. They also conducted experiments that would have been done of the Salyut space station.
The mission also marked the first time that crews from US and the USSR had been in space at the same time, with Skylab 3 still occupying Skylab.
The capsule landed 200 km to the southwest of Karaganda, Kazakhstan, though the recovery was hampered because of a snowstorm.
The crew that flew the mission were not the original crew. When the assignments for Soyuz 13 were first published in July 1973 it was Vorobyov/Yazdovsky (Prime); Klimuk/Sevastyanov (Backup). A month later this became Vorobyov/Yazdovsky(Prime); Klimuk/Ponomaryov (Backup). Then in September 1973 they became Vorobyov/Yazdovsky (Prime); Klimuk/Lebedev (Backup). They were again changed at the launch site to Klimuk/Lebedev as the prime crew.