Mission Specialists Bonnie Dunbar and Andrew Thomas check out oxygen masks in the bunker at KSC's Launch Pad 39A.

STS-89 Mission Specialists Bonnie Dunbar, Ph.D., and Andrew Thomas, Ph.D., check out oxygen masks in the bunker at KSC’s Launch Pad 39A. The seven astronauts assigned to the eighth Shuttle-Mir docking flight are completing Terminal Countdown Demonstration Test (TCDT) activities. A dress rehearsal for launch, the TCDT includes emergency egress training at the launch pad and culminates with a simulated countdown. Dr. Thomas will transfer to the Russian Space Station Mir and succeed David Wolf, M.D., who will return to Earth aboard Endeavour. The Space Shuttle Endeavour is undergoing preparations for liftoff, scheduled for Jan. 22. Dr. Thomas will live and work on Mir until June