Earth's surface with Space Shuttle flying above:

This is a computer-generated view of the Shuttle Radar Topography Mission (SRTM) 
scheduled to fly in September 1999.  SRTM will use the same radar instrument that 
comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar 
(SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994.  The mission 
is designed to collect three-dimensional measurements of nearly 80 percent of the 
Earth's land surface, except near the poles, with an accuracy of better than 16 meters 
(53 feet).  The regions to be mapped are home to about 95 percent of the world's 
population.  To collect the 3-D data, engineers will add an almost 60-meter-long 
(200-foot) mast, additional C-band imaging antenna and improved tracking and 
navigation devices to the SIR-C hardware to create a radar interferometer. 

The mission is a cooperative project between NASA and the National Imagery and 
Mapping Agency of the U.S. Department of Defense, to be managed by NASA's Jet 
Propulsion Laboratory for NASA's Earth Sciences Enterprise.