(03/30/1998) --- The crew of STS-90 participate in Terminal Countdown Demonstration Test (TCDT) activities 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 crew include, left to right, Commander Richard Searfoss, Payload Specialist James Pawelczyk, Ph.D., Mission Specialist Dafydd (Dave) Williams, M.D., with the Canadian Space Agency, Mission Specialist Richard Linnehan, D.V.M., Pilot Scott Altman, Mission Specialist Kathryn (Kay) Hire, and Payload Specialist Jay Buckey, M.D. 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