CAPE CANAVERAL, Fla. -- In accordance with a Presidential Proclamation, the American Flag in the Launch Complex 39 area of NASA's Kennedy Space Center in Florida flies at half-staff to honor U.S. Rep. Gabrielle Giffords and others who were wounded or killed during a shooting spree in Tucson, Arizona. This flag and all American Flags at U.S. military and government installations across the country and abroad will remain at half-staff until sunset on Jan. 14. Giffords is the wife of NASA astronaut Mark Kelly, who is scheduled to command space shuttle Endeavour's last mission, STS-134, to the International Space Station later this year. Photo credit: NASA/Frankie Martin

CAPE CANAVERAL, Fla. -- In accordance with a Presidential Proclamation, the American Flag in the Launch Complex 39 area of NASA's Kennedy Space Center in Florida flies at half-staff to honor U.S. Rep. Gabrielle Giffords and others who were wounded or killed during a shooting spree in Tucson, Arizona. This flag and all American Flags at U.S. military and government installations across the country and abroad will remain at half-staff until sunset on Jan. 14. Giffords is the wife of NASA astronaut Mark Kelly, who is scheduled to command space shuttle Endeavour's last mission, STS-134, to the International Space Station later this year. Photo credit: NASA/Frankie Martin

CAPE CANAVERAL, Fla. -- In accordance with a Presidential Proclamation, the American Flag in the Launch Complex 39 area of NASA's Kennedy Space Center in Florida flies at half-staff to honor U.S. Rep. Gabrielle Giffords and others who were wounded or killed during a shooting spree in Tucson, Arizona. This flag and all American Flags at U.S. military and government installations across the country and abroad will remain at half-staff until sunset on Jan. 14. Giffords is the wife of NASA astronaut Mark Kelly, who is scheduled to command space shuttle Endeavour's last mission, STS-134, to the International Space Station later this year. Photo credit: NASA/Frankie Martin

KENNEDY SPACE CENTER, FLA. - Rolling back from Launch Pad 39B, Space Shuttle Discovery, atop a Mobile Launcher Platform, makes its way slowly toward the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center. The view is across the Turn Basin from an area near the NASA News Center. In the foreground is the mission countdown clock that tracks the time from before launch to landing.Once inside the VAB, Discovery will be demated from its External Tank and lifted into the transfer aisle. On or about June 7, Discovery will be lifted and attached to its new tank and Solid Rocket Boosters, which are already in the VAB. Only the 15th rollback in Space Shuttle Program history, the 4.2-mile journey allows additional modifications to be made to the External Tank prior to a safe Return to Flight. Discovery is expected to be rolled back to the launch pad in mid-June for Return to Flight mission STS-114. The launch window extends from July 13 to July 31.