Space Shuttle Discovery Commander Steve Lindsey is helped by members of the white room crew as he prepares to board the orbiter for the final spaceflight in this still image taken from video, February 24, 2011. [Photo/Agencies] 

Space shuttle Discovery lifts off from the Kennedy Space Center in Cape Canaveral, Florida, February 24, 2011. Space shuttle Discovery blasted off from the Kennedy Space Center in Florida on Thursday on its final mission carrying supplies and spare parts to the International Space Station. [Photo/Agencies] 

Space shuttle Discovery lifts off from the Kennedy Space Center in Cape Canaveral, Florida, February 24, 2011. Space shuttle Discovery blasted off on Thursday on its final mission carrying supplies and spare parts to the International Space Station. NASA plans to retire its shuttle program this year after two other spaceships in the shuttle fleet, Endeavour and Atlantis, make their last flights in the coming months. [Photo/Agencies]