STS-120 Mission Specialist Scott Parazynski is putting on his launch and entry suit for a simulated launch countdown or TCDT.

STS-120 Mission Specialist Scott Parazynski is putting on his launch and entry suit for a simulated launch countdown, part of the prelaunch terminal countdown demonstration test, or TCDT. His name patch reflects the nicknames the crew gave each other for the event. The TCDT provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization, emergency training and the simulated countdown. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Launch of Discovery on mission STS-120 is targeted for Oct. 23 at 11:38 a.m. EDT on a 14-day mission. Photo credit: NASA/Kim Shiflett