The
Shuttle Radar Topography Mission (
SRTM) is an international research effort that obtained
digital elevation models on a near-global scale from 56° S to 60° N, to generate the most complete high-resolution digital topographic database of Earth prior to the release of the
ASTER GDEM in 2009. SRTM consisted of a specially modified
radar system that flew on board the
Space Shuttle Endeavour during the 11-day
STS-99 mission in February 2000, based on the older
Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR), previously used on the Shuttle in 1994. To acquire
topographic (elevation) data, the SRTM payload was outfitted with two radar antennas. One antenna was located in the Shuttle's payload bay, the other – a critical change from the SIR-C/X-SAR, allowing single-pass interferometry – on the end of a 60-meter (200-foot) mast that extended from the payload bay once the Shuttle was in space. The technique employed is known as
interferometric synthetic aperture radar.