The Russian cosmonauts are said to have cameo roles in the film.moscow:
A Russian actress and director were set to return to Earth on Sunday after spending 12 days in the International Space Station (ISS) shooting scenes for the first movie in orbit.
If the project stays on track, the Russian crew will beat a Hollywood project announced last year by "Mission Impossible" star Tom Cruise together with NASA and Elon Musk's SpaceX.
Actress Yulia Peresild, 37, and film director Klim Shipenko, 38, blasted off from the Russia-leased Baikonur Cosmodrome in ex-Soviet Kazakhstan earlier this month, travelling to the ISS with veteran cosmonaut Anton Shkaplerov to film scenes for "The Challenge".
The movie's plot, which has been mostly kept under wraps along with its budget, centres around a female surgeon who is dispatched to the ISS to save a cosmonaut.
Shkaplerov, 49, and the two Russian cosmonauts who were already aboard the ISS are said to have cameo roles in the film.
The mission has not come without hitches.
As the film crew docked at the ISS earlier this month, Shkaplerov had to switch to manual control.
And when Russian flight controllers on Friday conducted a test on the Soyuz MS-18 spacecraft set to ferry the crew back to Earth, the ship's thruster fired unexpectedly and destabilised the ISS for 30 minutes, a NASA spokesman told the Russian news agency TASS.
But the spokesman said their departure is set to go ahead as scheduled.
Peresild and Shipenko will bid farewell to the ISS crew on Saturday evening, the spokesman said, and begin undocking at 0100 GMT.
They will be shepherded home by cosmonaut Oleg Novitsky, who has been on the space station for the past six months, and are set to land in Kazakhstan on Sunday at 0436 GMT.
21st-century space race
Their landing will be documented by a film crew and will also feature in the movie, Konstantin Ernst, the head of the Kremlin-friendly Channel One TV network and a co-producer of "The Challenge", told AFP.
If successful, the mission will add to a long list of firsts for Russia's space industry.
The Soviets launched the first satellite Sputnik, and sent into orbit the first animal, a dog named Laika, the first man, Yuri Gagarin and the first woman, Valentina Tereshkova.
But compared with the Soviet era, modern Russia has struggled to innovate and its space industry is fighting to secure state funding with the Kremlin prioritising military spending.
Its space agency is still reliant on Soviet-designed technology and has faced a number of setbacks, including corruption scandals and botched launches.
Russia is also falling behind in the global space race, facing tough competition from the United States and China, with Beijing showing growing ambitions in the industry.
Russia's Roscosmos space agency was also dealt a blow after SpaceX last year successfully delivered astronauts to the ISS, ending Moscow's monopoly for journeys to the orbital station.
In a bid to spruce up its image and diversify its revenue, Russia's space programme revealed this year that it will be reviving its tourism plan to ferry fee-paying adventurers to the ISS.
After a decade-long pause, Russia will send two Japanese tourists -- including billionaire Yusaku Maezawa -- to the ISS in December, capping a year that has been a milestone for amateur space travel.
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