Tony Antonelli tries on his helmet to complete the suit before heading to Launch Pad 39A for a simulated launch countdown.

At NASA's Kennedy Space Center in Florida, STS-119 Pilot Tony Antonelli tries on his helmet to complete the launch-and-entry suit before heading to Launch Pad 39A for a simulated launch countdown. The astronauts are at Kennedy to prepare for launch through Terminal Countdown Demonstration Test activities. The TCDT includes equipment familiarization and emergency egress training. The crew is targeted to launch on the STS-119 mission Feb. 12 on space shuttle Discovery. During the 14-day mission, the crew will install the S6 truss segment and solar arrays to the starboard side of the International Space Station, completing the station's truss, or backbone. Photo credit: NASA/Kim Shiflett