Washington: A Russian Soyuz spacecraft, with three crew on board, on Saturday docked with the International Space Station (ISS), a media report said.
According to a statement issued by American space agency NASA, Russian cosmonaut Mikhail Kornienko, 54, and American astronaut Scott Kelly, 52, are to spend 342 days aboard the orbiting laboratory - about twice as long as a standard mission on the station, Sky News reported.
The stay is aimed at measuring the effects of a prolonged period of weightlessness on the human body, a step toward possible missions to Mars or beyond, the statement said.
The Soyuz capsule - also carrying Russia's Gennady Padalka, 56, for a six-month stay - docked about six hours after launching from Russia's manned space facility in Kazakhstan.
The trip marks the longest amount of time that two people will live continuously at the ISS, though a handful of Russian cosmonauts spent a year to 14 months at the Russian space station Mir in the 1990s.
"This is the first time we're doing it as an international partnership, which is one of the great success stories of the ISS," Kelly said at a news conference ahead of the launch.
"If we ever go beyond Low Earth orbit again, perhaps to Mars, because of the cost and the complexity it will most likely be an international mission, so I see this as a stepping stone to that," he added.
Kelly and Kornienko, both of whom have flown multiple missions to orbit and have each previously spent about six months on the ISS, are set to stay on the space station until March 2016.
Three crew members - Russian Anton Shkaplerov, Italian Samantha Cristoforetti and American Terry Virts - are currently on board the space station, due to leave in May.
Russia last month confirmed that it will continue using the ISS in partnership with Nasa until 2024, after threatening to pull out and stop financing it in 2020.