The space shuttle Discovery sits on the launch pad as the rotating service structure is pulled away from the orbiter at the Kennedy Space Center in Cape Canaveral, Florida, July 12, 2005. NASA will go ahead with the first space shuttle mission since the 2003 Columbia disaster after replacing two damaged heat-resistant tiles on the shuttle Discovery, a spokesman said on Tuesday. The shuttle is scheduled to launch on July 13, 2005 for an 11-day mission to the International Space Station. REUTERS/Gary Hershorn GMH/dh