The STS-91 crew participates in a simulated walk-out from the Operations and Checkout Building to board a van which will take them to Launch Complex 39A during Terminal Countdown Demonstration Test (TCDT) activities. The TCDT is a dress rehearsal for launch and ends with a mock launch countdown culminating in a simulated main engine cut-off. From left to right, the crew members are (front row) Pilot Dominic Gorie; Mission Commander Charles Precourt (waving); and Mission Specialist Wendy B. Lawrence; and (back row) Mission Specialists Valery Ryumin, with the Russian Space Agency; Janet Kavandi, Ph.D.; and Franklin Chang-Diaz, Ph.D. STS-91 is scheduled to be launched on June 2 with a launch window opening around 6:10 p.m. EDT. The mission will feature the ninth Shuttle docking with the Russian Space Station Mir, the first Mir docking for Discovery, the conclusion of Phase I of the joint U.S.-Russian International Space Station Program, and the first flight of the new Space Shuttle super lightweight external tank. Andrew Thomas, Ph.D., will be returning to Earth with the crew after living more than four months aboard Mir