(05/06/1998) --- STS-91 Mission Specialist Wendy B. Lawrence is learning how to operate an M-113 armored personnel carrier during Terminal Countdown Demonstration Test (TCDT) training activities. The TCDT is held at KSC prior to each Space Shuttle flight to provide crews with an opportunity to participate in simulated countdown activities. 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. The STS-91 flight crew also includes Commander Charles Precourt; Pilot Dominic Gorie; and Mission Specialists Franklin Chang-Diaz, Ph.D.; Janet Kavandi, Ph.D.; and Valery Ryumin, with the Russian Space Agency. Andrew Thomas, Ph.D., will be returning to Earth with the crew after living more than four months aboard Mir