The incoming crew of three will spend nearly five months on board the International Space Station before returning to Earth.
ALMATY, Kazakhstan — A Soyuz capsule packed with three astronauts successfully docked Friday with the International Space Station, taking the size of the full crew on the orbiting laboratory to six.
American Tom Marshburn, Russian Roman Romanenko and Canadian Chris Hadfield traveled two days in the capsule before linking up with the space station's Russian Rassvet research module.
The docking took place about 255 miles above the capital of Kazakhstan.
Almost three hours passed before pressure was equalized between the capsule and the space station, allowing for safe entrance.
As the hatches were unlocked, the arriving trio was welcomed by NASA astronaut Kevin Ford and Russian colleagues Oleg Novitsky and Yevgeny Tarelkin.
The six colleagues exchanged hugs and posed for photos as they floated in the weightless atmosphere of the station.
Minutes after entry, Hadfield could be heard saying in English: "I love what you've done with the place."
Hadfield flew to the space station in 2001, when he spent 11 days at the facility and performed two spacewalks. He will take over as the space station's first-ever Canadian commander in its 14-year history when the crew now on board prepares to leave in March.
Family members spoke with the astronauts for the first time since the launch in a linkup from the Korolyov space center outside Moscow.
"It was just a heck of a ride of for three of us. It's like being on a crazy dragster, just a fun, crazy zip up to space," Hadfield said, speaking to his son.
The incoming crew will return to Earth May 14.
Their mission began with a launch from the Russian-leased Baikonur space port in southern Kazakhstan.
The International Space Station is the biggest orbiting outpost ever built and can sometimes be seen from the Earth with the naked eye. It consists of more than a dozen modules built by the United States, Russia, Canada, Japan and the European Space Agency.
The station crew will have some time off to celebrate several winter holidays in orbit — Christmas, the New Year and then Orthodox Christmas — before tackling a list of about 150 science experiments and station maintenance, including two spacewalks.
Among the studies will be medical research into how the human cardiovascular system changes in microgravity.
"When you live in an environment like that, the heart actually shrinks. Your blood vessel response changes. It actually sets us up to cardiovascular problems," Hadfield said. "We have a sequence of experiments that's taking blood samples and monitoring our body while we're exercising and doing different things to try and understand what's going on with our cardiovascular system," he said.
The research is expected to help doctors unravel the aging process on Earth, which is similar in many respects to what happens to the human body in weightlessness.
In addition to medical research, the space station serves as a laboratory for fluid physics and other microgravity sciences, a platform for several astronomical observatories and a test bed for robotics and other technologies.
(Reuters contributed to this report.)