(03/19/2002) -- STS-110 Mission Specialists Ellen Ochoa and Rex J. Walheim are in the slidewire basket, part of emergency egress equipment on the launch pad. The crew is taking part in Terminal Countdown Demonstration Test activities, which also include a simulated launch countdown, held at KSC prior to each Space Shuttle flight. Scheduled for launch April 4, the 11-day mission will feature Shuttle Atlantis docking with the International Space Station (ISS) and delivering the S0 truss, the centerpiece-segment of the primary truss structure that will eventually extend over 300 feet.