(06/22/1999) --- STS-93 Mission Specialist Catherine G. Coleman (Ph.D.) smiles for the photographer before climbing into an M-113 armored personnel carrier at the launch pad to take part in emergency egress training. In preparation for their mission, the STS-93 crew are participating in Terminal Countdown Demonstration Test activities that also include a launch-day dress rehearsal culminating with a simulated main engine cut-off. Others in the crew are Commander Eileen M. Collins, Pilot Jeffrey S. Ashby, and Mission Specialists Steven A. Hawley (Ph.D.) and Michel Tognini of France, who represents the Centre National d'Etudes Spatiales (CNES). Collins is the first woman to serve as a mission commander. 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. Chandra is expected to provide unique and crucial information on the nature of objects ranging from comets in our solar system to quasars at the edge of the observable universe. Since X-rays are absorbed by the Earth's atmosphere, space-based observatories are necessary to study these phenomena and allow scientists to analyze some of the greatest mysteries 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