Sitting on the platform Space Shuttle Discovery rolls toward Launch Pad 39B via the crawler transporter.

Sitting on the mobile launcher platform, Space Shuttle Discovery rolls toward Launch Pad 39B via the crawler transporter. First motion of the shuttle from NASA's Vehicle Assembly Building was at 12:45 p.m. EDT. The rollout is an important step before launch of Discovery on mission STS-121 to the International Space Station. Discovery's launch is targeted for July 1 in a launch window that extends to July 19. During the 12-day mission, Discovery's crew will test new hardware and techniques to improve shuttle safety, as well as deliver supplies and make repairs to the station. Photo credit: NASA/Dimitri Gerondidakis