(01/14/2000) -- At Launch Pad 39A, STS-99 Mission Specialists Gerhard Thiele (Ph.D.), of the European Space Agency (in front), and Janet Kavandi (Ph.D.) prepare to practice emergency egress procedures with a slidewire basket. Seven slidewires, with flatbottom baskets suspended from each wire, extend from the Fixed Service Structure at the orbiter access arm level. These baskets could provide an escape route for the astronauts until the final 30 seconds of the countdown in case of an emergency. The crew is taking part in Terminal Countdown Demonstration Test (TCDT) activities that provide the crew with simulated countdown exercises, emergency egress training, and opportunities to inspect the mission payloads in the orbiter's payload bay. STS-99 is the Shuttle Radar Topography Mission, which will chart a new course, using two antennae and a 200-foot-long section of space station-derived mast protruding from the payload bay to produce unrivaled 3-D images of the Earth's surface. The result of the Shuttle Radar Topography Mission could be close to 1 trillion measurements of the Earth's topography. Besides contributing to the production of better maps, these measurements could lead to improved water drainage modeling, more realistic flight simulators, better locations for cell phone towers, and enhanced navigation safety. Launch of Endeavour on the 11-day mission is scheduled for Jan. 31 at 12:47 p.m. EST.