(03/31/1998) --- Members of the STS-90 crew participate in mock emergency egress activities during the Terminal Countdown Demonstration Test (TCDT) at KSC's Launch Pad 39B. The TCDT is held at KSC prior to each Space Shuttle flight to provide crews with the opportunity to participate in simulated countdown activities. The STS-90 crew members shown here are, front to back, Payload Specialists James Pawelczyk, Ph.D., and Jay Buckey, M.D., and Mission Specialist Richard Linnehan, D.V.M. Columbia is targeted for launch of STS-90 on April 16 at 2:19 p.m. EDT and will be the second mission of 1998. The mission is scheduled to last nearly 17 days