CAPE CANAVERAL, FL - JULY 8: Space Shuttle Atlantis Astronauts, Mission Specialists Rex Walheim, Sandra Magnus, Pilot Doug Hurley, and Commander Chris Ferguson walkout from the Operations and Checkout Building into the Astrovan in preparation for the countdown in Cape Canaveral, Florida. After Atlantis mission STS-135 the Space Shuttle program will come to an end. (Photo by Roberto Gonzalez/Getty Images)