Live coverage: Soyuz blasts off on third mission for O3b

Bidding their crewmates farewell, a Russian cosmonaut and two NASA astronauts boarded their Soyuz ferry craft, undocked from the International Space Station and fell back to Earth Tuesday, landing safely on the snowy steppe of Kazakhstan to close out a 168-day mission.

Astronaut Scott Kelly and cosmonaut Mikhail Kornienko are making final preparations for return to Earth Tuesday evening, closing out a record 340-day stay aboard the International Space Station where they served as medical test subjects to learn more about the long-term effects of weightlessness, space radiation and isolation.

A Russian Soyuz ferry ship carrying a Russian commander and two NASA astronauts caught up with the International Space Station Friday and executed a flawless docking to close out a two-day rendezvous that began with launch Wednesday from the Baikonur Cosmodrome in Kazakhstan.