STS-125 Pilot Gregory C. Johnson serves as a guinea pig to demonstrate emergency escape apparatus in Florida.

STS-125 Pilot Gregory C. Johnson serves as a “guinea pig” to demonstrate emergency escape apparatus from the 195-foot level of the fixed service structure on Launch Pad 39A at NASA's Kennedy Space Center in Florida. Looking on are Mission Specialists Andrew Feustel, Megan McArthur and Mike Massimino. The crew is at Kennedy to take part in terminal countdown demonstration test, or TCDT, activities before launching on space shuttle Atlantis’ mission to service NASA’s Hubble Space Telescope. TCDT provides astronauts and ground crews with an opportunity to participate in various simulated countdown activities, including equipment familiarization, emergency training and a simulated launch countdown. Atlantis is targeted to launch Oct. 10. Photo credit: NASA/Kim Shiflett