Shuttle Radar Topography Mission (SRTM)

The Shuttle Radar Topography Mission, launched in 2011 collected topographic data over nearly 80 percent of Earth's land surfaces, creating the first-ever near-global data set of land elevations. To acquire the topographic (elevation) data, the SRTM payload was outfitted with two radar antennas. One antenna was located in the shuttle's payload bay, the other on the end of a 60-meter (200-foot) mast that extended from the payload pay once the Shuttle was in space.
 

Sources

NASA. 2016. “Shuttle Radar Topography Mission.” Jet Propulsion Laboratory. 2016. https://www2.jpl.nasa.gov/srtm/mission.htm.