

This image of the International Space Station (ISS), with Earth as a backdrop, was taken from Space Shuttle Discovery on Sept. 8, 2009, as the two spacecraft began their relative separation. NASA/AP
Family of the newly arrived International Station Expedition 33/34 crew members (l. to r.) – Russian cosmonaut Oleg Novitskiy, NASA astronaut Kevin Ford, and Russian cosmonaut Evgeny Tarelkin – talk via phone to the crew from the Russian Mission Control Center in Korolev, Russia, shortly after the three joined (back l. to r.) flight engineer Aki Hoshide of the Japan Aerospace Exploration Agency, Expedition 33 Comdr. Sunita Williams of NASA, and Yuri Malenchenko of the Russian Federal Space Agency, on Oct. 25, 2012. Bill Ingalls/NASA/AP
The moon, at center with the limb of Earth near the bottom, transitions into the orange-colored troposphere, the lowest and most dense portion of Earth's atmosphere, in this image made available by NASA and photographed by the Expedition 28 crew aboard the International Space Station. NASA/AP
Astronaut Michael Good, STS-132 mission specialist, as seen from the space shuttle Atlantis's forward cargo bay, works during the mission's final space walk at the International Space Station, May 21, 2010. NASA/AP
NASA astronaut Kevin Ford, Expedition 34 commander, watches a water bubble float freely between him and the camera, showing his image refracted, in the Unity node of the International Space Station. NASA released the photo Jan. 30, 2013. NASA/Reuters
Naoko Yamazaki, an astronaut with the Japan Aerospace Exploration Agency, works at a robotic workstation in the Destiny laboratory of the International Space Station, April 15, 2010. NASA/Reuters
NASA astronaut John 'Danny' Olivas works outside the ISS during mission STS-128's third and final spacewalk supporting construction and maintenance of the orbital outpost on Sept. 5, 2009. NASA/Handout/Reuters
Space shuttle Atlantis crew members Robert Satcher (l.), Mike Forman, and Randy Bresnik (r.) arrive aboard the ISS after opening the hatch between the two spacecraft in this image from NASA TV Nov. 18, 2009. NASA TV/Reuters
Astronaut Koichi Wakata of the Japan Aerospace Exploration Agency, Expedition 18/19 flight engineer, works inside the Kibo laboratory airlock of the ISS. NASA
Astronaut Garrett Reisman, Expedition 16 flight engineer, uses a digital camera to expose a photo of his helmet visor during the mission's first scheduled session of extravehicular activity, as construction and maintenance continue on the ISS in March 2008. Also visible in the reflections in the visor are components of the station, the docked space shuttle Endeavour, and a blue and white portion of Earth. NASA/AP
Expedition 20 crew members pose for an in-flight photo in the Harmony node of the ISS on Oct. 1, 2009. Pictured clockwise from bottom center are Russian commander Gennady Padalka, cosmonaut Roman Romanenko, NASA astronaut Nicole Stott, Canadian Space Agency astronaut Robert Thirsk, European Space Agency astronaut Frank De Winne, and NASA astronaut Michael Barratt. NASA/Reuters