STS-121 Mission Specialist Thomas Reiter is helped by the Closeout Crew to prepare for entering Discovery and the launch.

In the White Room on Launch Pad 39B, STS-121 Mission Specialist Thomas Reiter is helped by the Closeout Crew to prepare for entering Discovery and the launch. Situated on the end of the orbiter access arm, the White Room provides access into the orbiter on the pad. The crew is preparing for the third launch attempt in four days; previous attempts were scrubbed due to weather concerns. During the 12-day mission, the STS-121 crew will test new equipment and procedures to improve shuttle safety, as well as deliver supplies and make repairs to the International Space Station. The launch of Space Shuttle Discovery on mission STS-121 is the 115th shuttle flight and the 18th U.S. flight to the International Space Station. Photo credit: NASA/Regina Mitchell-Ryall & Tony Gray