Space Shuttle Discovery on top of the mobile launcher platform and crawler-transporter makes its way to Launch Pad 39B.

Viewed from across the turn basin, Space Shuttle Discovery, on top of the mobile launcher platform and crawler-transporter, makes its way to Launch Pad 39B. First motion in 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/Ken Thornsley