European Space Agency astronaut Roberto Vittori of Italy works on the mid-deck of the space shuttle Endeavour as the crews prepare for undocking from the International Space Station in this image from NASA TV May 29, 2011. [Photo/Agencies]

Members of the Space Shuttle Endeavour and International Space Station crew shake hands during hatch closing ceremonies as the shuttle prepares to undock from the station in this still image taken from NASA TV May 29, 2011. [Photo/Agencies]