Little is known of Demidov's life or experience. Judging by the patches on his suit, however, it is shown that he was a member of an unnamed Soyuz TMA mission and ISS Expedition 42.
Demidov is never seen nor mentioned in Gravity. However, it is likely he was on board the ISS and evacuated it after a debris field was triggered by a Russian missile strike. His spacesuit was later worn by Ryan Stone after she arrived at the abandoned ISS.