The Shuttle Radar Topography Mission, which flew aboard NASA's Space Shuttle Endeavour during an 11-day mission in 2000, made the first near-global topographical map of Earth, collecting data on nearly 80 percent of Earth's land surfaces.
The instrument's design was essentially a modified version of the earlier Shuttle Imaging Radar instruments with a second antenna added to allow for topographic mapping using a technique similar to stereo photography.
The SRTM radar contained two types of antenna panels, C-band and X-band. The near-global topographic maps of Earth called Digital Elevation Models (DEMs) are made from the C-band radar data. These data were processed at the Jet Propulsion Laboratory and are being distributed through the United States Geological Survey's EROS Data Center (http://eros.usgs.gov/). Data from the X-band radar are used to create slightly higher resolution DEMs but without the global coverage of the C-band radar. The SRTM X-band radar data are being processed and distributed by the German Aerospace Center, DLR (http://www.dlr.de/eoc/en/desktopdefault.aspx/tabid-5515/9214_read-17716/).
Several new web sites have posted SRTM data in different formats than available at the USGS site or the Seamless Server. Users may want to check the Global Land Cover Facility (http://glcf.umiacs.umd.edu/data/srtm/index.shtml) or the CGIAR Consortium for Spatial Information (http://srtm.csi.cgiar.org/) for SRTM data.