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KENNEDY SPACE CENTER, FLA. -- STS-120 crew members practice emergency egress from Launch Pad 39A after completing a simulated launch countdown, culmination of the prelaunch terminal countdown demonstration test, or TCDT. Leading the way to the slidewire baskets is Mission Specialist Scott Parazynski, with Mission Specialist Daniel Tani and others behind him. The TCDT at NASA's Kennedy Space Center provides astronauts and ground crews an opportunity to participate in various launch preparation activities, including equipment familiarization and emergency training. The STS-120 mission will deliver the U.S. Node 2 module, named Harmony, aboard space shuttle Discovery to the International Space Station. Discovery is targeted to launch on its 14-day mission at 11:38 a.m. EDT on Oct. 23. Photo credit: NASA/Kim Shiflett