Discovery is sitting atop NASA's 747 Shuttle Carrier Aircraft, which will fly the shuttle from Florida to Virginia. Roberto Gonzalez/Getty Images hide caption

itoggle caption Roberto Gonzalez/Getty Images

Astronauts aboard the space shuttle Discovery, seen here lifting off from Kennedy Space Center in Florida, are preparing to dock with the International Space Station Saturday. Stan Honda/AFP/Getty Images hide caption

itoggle caption Stan Honda/AFP/Getty Images