The suited STS-121 crew members stride out of the Operations and Checkout Building for a simulated countdown.

The suited STS-121 crew members stride out of the Operations and Checkout Building on their way to Launch Pad 39B for a simulated countdown. Leading the way are Pilot Mark Kelly (left) and Commander Steven Lindsey. Behind Kelly are Mission Specialists Lisa Nowak, Stephanie Wilson and Thomas Reiter of Germany, who represents the European Space Agency. Behind Lindsey are Mission Specialists Michael Fossum and Piers Sellers. The crew is taking part in Terminal Countdown Demonstration Test activities, including the dress rehearsal for launch. Mission STS-121 is scheduled to be launched July 1. Photo credit: NASA/Kim Shiflett