NASA administrator Charles Bolden addresses Kennedy Space Center employees and contractors as Kennedy Space Center director Robert Cabana, right, looks on as space shuttle Atlantis (STS-135) sits in the background near the Orbiter Processing Facility (OPF) at a wheels stop event, Thursday, July 21, 2011, in Cape Canaveral, Fla. Atlantis returned to Kennedy early Thursday following a 13-day mission to the International Space Station (ISS) and marking the end of the 30-year Space Shuttle Program. Overall, Atlantis spent 307 days in space and traveled nearly 126 million miles during its 33 flights. Atlantis, the fourth orbiter built, launched on its first mission on Oct. 3, 1985. Photo Credit: (NASA/Paul E. Alers)