Cosmonauts Day 1975 Cover Autographed by Pyotr Klimuk and Valentin Lebedev of Soyuz 12
Stamp shows the portrait of both cosmonauts
Soyuz 13 (Russian: Союз 13, Union 13) was a 1973 Soviet crewed space flight, the second test flight of the redesigned Soyuz 7K-T spacecraft that first flew as Soyuz 12. The spacecraft was specially modified to carry the Orion 2 Space Observatory. The flight, crewed by Pyotr Klimuk and Valentin Lebedev, was the Soviet Union's first dedicated science mission, and was the first mission controlled by the new Kaliningrad Mission Control Center.