Shuttle Radar Topography Mission

The Shuttle Radar Topography Mission was a 2000 NASA mission that used radar aboard Space Shuttle Endeavour to map Earth’s land-surface elevation.

Radar interferometry: A method that uses phase differences between radar signals to measure distances or surface changes. SRTM compared echoes received at two antenna positions to calculate terrain elevation.
Space Shuttle Endeavour: NASA’s fifth Space Shuttle orbiter, which flew 25 missions between 1992 and 2011. Endeavour carried SRTM into orbit and provided its operating platform.
Topographic map: A map that represents terrain shape and elevation, often with contour lines or shaded relief. SRTM measurements supply elevation information used in topographic mapping.
Global Digital Elevation Model: A gridded representation of Earth’s surface elevation covering the globe or nearly all of it. SRTM helped make broad, consistent digital terrain coverage publicly available.
Synthetic-aperture radar: A radar technique that combines successive echoes from a moving platform to create high-resolution images. The shuttle’s motion let SRTM form detailed radar images of the ground.
Space Shuttle: NASA’s reusable crewed spacecraft system, which launched and landed like an aircraft. SRTM depended on the shuttle’s cargo bay and ability to deploy a long radar mast.
Hydrology: The study of the movement, distribution, and properties of water on Earth and other planets. Researchers use SRTM elevation to model drainage networks and watersheds.
ASTER Global Digital Elevation Model: A global elevation data set derived from optical stereo images collected by the ASTER instrument. ASTER GDEM offers broader latitude coverage, while SRTM has different error and resolution characteristics.
Interferometric synthetic-aperture radar: A technique that compares the phase of radar images from different positions to infer terrain or surface displacement. SRTM used this technique to derive elevation from two radar observations.
Shuttle Radar Topography Mission mast: A 60-meter deployable structure that held SRTM’s outboard radar antenna away from the shuttle. The mast created the second antenna position needed for interferometric elevation measurements.

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OrographyBroader topic: Its elevation data enabled consistent digital mapping of terrain across much of Earth.