(06/24/1999) --- After suiting up for their practice countdown exercise, STS-93 crew members wave to onlookers as they head for the bus outside the Operations and Checkout Building for the trip to Launch Pad 39B. From rear left are Mission Specialists Michel Tognini of France, who represents the Centre National d'Etudes Spatiales (CNES), and Catherine G. Coleman (Ph.D.), Pilot Jeffrey S. Ashby, Mission Specialist Steven A. Hawley (Ph.D.), and Commander Eileen M. Collins. Collins is the first woman to serve as a Shuttle commander. The crew members have been taking part in a Terminal Countdown Demonstration Test, which familiarizes them with the mission, provides training in emergency exit from the orbiter and launch pad, and includes a launch-day dress rehearsal culminating with a simulated main engine cut-off. The primary mission of STS-93 is the release of the Chandra X-ray Observatory, which will allow scientists from around the world to obtain unprecedented X-ray images of exotic environments in space to help understand the structure and evolution of the universe. The targeted launch date for STS-93 is no earlier than July 20 at 12:36 a.m. EDT from Launch Pad 39B