On February 11, 2000, the The Shuttle Radar Topography Mission ( SRTM ) payload onboard Space Shuttle Endeavour launched into space. With its radars sweeping most of the Earth's surfaces, SRTM acquired enough data during its eleven days of operation to obtain the most complete near-global high-resolution database of the Earth's topography. SRTM, spearheaded by the National Geospatial-Intelligence Agency and NASA, collected data over most of the land surfaces that lay between 60° north latitude and 56° south latitude, approximately 80% of all the land on Earth.

SRTM used a key technology called radar interferometry, which compares two radar images taken at slightly different locations to obtain elevation or surface-change information. Unlike earlier missions, SRTM was the first mission to use single-pass interferometry, which means that the two images were acquired at the same time, one image taken from the radar antenna in the shuttle payload bay and the second from the second radar antenna attached to the end of a 60-meter (200-foot) mast that extended from the payload bay once the Shuttle was in space. Combining the two images produces a single 3-D image.

Shuttle Endeavour Liftoff

Radar Mast Extended

Radar Beams Sweep Earth

For more information on the Shuttle Radar Topography Mission (SRTM), please view the following Fact Sheets in .PDF format:
        -  Mapping the World in Three Dimensions by NASA-JPL.pdf
        -  Seeing Earth's Surface in 3-D by JPL.pdf
        -  X-SAR / SRTM Brochure by DLR.pdf