At Chkalovsky Airbase outside Star City, Russia, Expedition 23 Commander Oleg Kotov is greeted at the foot of the stairs of the plane that brought him home from Kazakhstan June 2, 2010 after he and Flight Engineers T.J. Creamer and Soichi Noguchi landed in the Soyuz TMA-17 spacecraft earlier in the day to wrap up 163 days in space. Kotov is assisted by Alexei Krasnov (R), the head of Piloted Programs for the Russian Federal Space Agency. Credit: NASA/Stephanie Stoll

At Chkalovsky Airbase outside Star City, Russia, Expedition 23 Commander Oleg Kotov is assisted down the stairs of the plane that brought him home from Kazakhstan June 2, 2010 after he and Flight Engineers T.J. Creamer and Soichi Noguchi landed in the Soyuz TMA-17 spacecraft earlier in the day to wrap up 163 days in space. Kotov is flanked by Chief Cosmonaut Yuri Gidzenko (L) and Alexei Krasnov (R), the head of Piloted Programs for the Russian Federal Space Agency. Credit: NASA/Stephanie Stoll

Astronauts Tracy Caldwell Dyson, flight engineer on Expeditions 23 and 24, left, and Doug Wheelock, Expedition 24 flight engineer and commander of Expedition 25, discuss their mission to the International Space Station during a visit to NASA Headquarters in Washington, Wednesday, March 16, 2011. (NASA/Paul E. Alers)

Astronauts Tracy Caldwell Dyson, flight engineer on Expeditions 23 and 24, left, and Doug Wheelock, Expedition 24 flight engineer and commander of Expedition 25, discuss their mission to the International Space Station during a visit to NASA Headquarters in Washington, Wednesday, March 16, 2011. (NASA/Paul E. Alers)

Astronauts Tracy Caldwell Dyson, flight engineer on Expeditions 23 and 24, left, and Doug Wheelock, Expedition 24 flight engineer and commander of Expedition 25, discuss their mission to the International Space Station during a visit to NASA Headquarters in Washington, Wednesday, March 16, 2011.