The Space Shuttle Endeavour sits atop NASA's Shuttle Carrier Aircraft (SCA) at the NASA Dryden Flight Research Center at Edwards Air Force Base, Calif., Thursday, Sept. 20, 2012. Endeav

 

              The Space Shuttle Endeavour sits atop NASA
The Space Shuttle Endeavour sits atop NASA's Shuttle Carrier Aircraft (SCA) at the NASA Dryden Flight Research Center at Edwards Air Force Base, Calif., Thursday, Sept. 20, 2012. Endeavour returned to its California roots after a wistful cross-country journey that paid homage to NASA workers and former Arizona Rep. Gabrielle Giffords and her astronaut husband. (AP Photo/Jae C. Hong)