Stock Photo - 01/14/2000 ___ STS_99 Mission Specialist Gerhard Thiele, who is with the European Space Agency, goes through countdown procedures aboard the Space Shuttle Endeavour during Terminal Countdown Demonstration Test TCDT activities for the mission. The TCDT includes a simulation of the final launch countdown. 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