A Soyuz spacecraft with two Russian cosmonauts and one NASA astronaut docked with the International Space Station (ISS) on Saturday after a six-hour flight begun on Friday, a spokesman for the Russian Federal Space Agency (Roscosmos) said.
The Soyuz TMA-16M automatically docked with the MIM-1 smaller research mode, the spokesman said.
The hatches between the spacecraft and the ISS were due to be opened about two hours after docking, when necessary safety checks had been done.
The Soyuz brings the Expedition 43 crew to the station - Russians Gennady Padalka and Mikhail Korniyenko and American Scott Kelly.
Korniyenko and Scott Kelly will perform their first one-year stay at the ISS rather than of a normal six-month mission. Scientists expect that such a lengthy stay in orbit will produce new data on changes in the human organism caused by weightlessness that would be used in designing training methods for long-haul flights such as a flight to Mars.
Padalka will stay six months at the ISS but he may set a personal record for the total amount of time spent in space. He would have clocked up 878 days. Today's record of 803 days belongs to Sergei Krikalev, a former head of the Cosmonaut Training Center.
One-year missions have not been practiced since the de-orbiting of Russia's Mir space station, which was scrapped nearly 20 years ago.
The organizers had a job finding candidates for the one-year mission, according to Valery Bogomolov, deputy director of Russia's Institute of Medical and Biological Problems.
"It wasn't too easy to find candidates for the one-year flight. There are a lot of good cosmonauts who want to go into space any time but not for a year - either their families are objecting or the cosmonauts themselves don't want to lose a year," Bogomolov said when asked how Korniyenko was selected.
In the United States, it also took a long time to find candidates. One reason was that NASA looked for twin brothers one of whom would go into space and the other stay on Earth. The brothers' health conditions would then be compared to find out effects of space factors such as zero gravity and high-level radiation.
Scott Kelly has a twin brother, Mark, who is very much like him, Bogomolov said.
Asked whether there would be more one-year missions at the ISS, Bogomolov said there were disagreements about that.
"At our Cosmonaut Training Center, not everyone is too happy with one-year expeditions. Because such flights would affect the training cycle and cause changes to schedules. In a word, there's a lot of subjective and objective factors involved," he said.
Asked whether two-year flights were a possibility, Bogomolov said: "It's difficult to fly for two years. There will probably be two-year missions when you can bring your wife and children with you. And why not either?"
The Expedition 43 crew will carry out about 50 experiments. "I'm going to perform seven experiments under an American program. They are joint, interesting and technologically advanced experiments. They will enable others to fly after us," Korniyenko told a pre-liftoff news conference.
Korniyenko said he and Kelly would have a much more intensive sports exercise program than the rest of the crew in order to minimize adverse affects of weightlessness.
"Whereas during my six-month flight I spent one hour per day on sports, during my one-year flight I will spend two hours each day. I'll be training on an exercycle, treadmill," he said.
Padalka said there would be a spacewalk as well. "It's planned for the end of June. The purpose is to install additional equipment on the surface of the station," he said.
Korniyenko, when asked whether he and Padalka will bring a red flag with them to mark the 70th anniversary of the Soviet victory in the Great Patriotic War, said: "We sure will."
Meanwhile, they have a Russian tricolor ready.
"We have a flag of the Russian Federation - quite small because our personal outfit capacity would prevent us from bringing anything larger with us. This flag will be stamped by Russian Post on May 9 and delivered to the Earth," he said.
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