Shuttle Radar Topography Mission
Space shuttle mission that mapped Earth's topography in high resolution.
The Shuttle Radar Topography Mission (SRTM) was an international research effort that produced the most complete high-resolution digital topographic database of Earth available until the ASTER GDEM was released in 2009. It flew on the 11-day STS-99 mission of the Space Shuttle Endeavour in February 2000. The project was spearheaded by the U.S. National Geospatial-Intelligence Agency (NGA) and NASA. The technique used was interferometric synthetic aperture radar, based on the older Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) system flown on the Shuttle in 1994. A critical change was the addition of a second antenna mounted on a 60-meter mast that extended from the payload bay, enabling single-pass interferometry. The radar operated in both X-band and C-band; C-band provided wider coverage, while X-band offered higher resolution but had many coverage gaps because the mission orbit was optimized for the American C-band mission. The payload was transferred to the Smithsonian National Air and Space Museum in 2003 and is displayed at the Steven F. Udvar-Hazy Center. The American data releases are based on C-band data, processed at a 1-arcsecond resolution level. The C-band datasets contain no-data areas in mountains and deserts, affecting all summits over 8,000 meters and most over 7,000 meters, though these voids amount to less than 0.2% of the surveyed area. The elevation models are arranged in tiles covering one degree of latitude and longitude, named by their southwestern corners. Raw data resolution is one arcsecond (about 30 meters along the equator) for Africa, Europe, North America, South America, Asia, and Australia; three-arcsecond data (about 90 meters) is available for the rest of the world. Elevations were calculated relative to the WGS84 ellipsoid, with EGM96 geoid separation values added for released products. Intermap Technologies was the prime contractor for processing the data. The resulting digital elevation models are freely downloadable and widely used in geographic information systems.
- field
- Topographic mapping / Remote sensing
- nationality
- International (led by U.S. NGA and NASA)
- known_for
- First near-global high-resolution digital elevation model
- coverage
- 56°S to 60°N
- resolution
- 1 arcsecond (30 m) for most land; 3 arcsecond (90 m) globally
Lore & Background
The Shuttle Radar Topography Mission (SRTM) was an international research effort that produced digital elevation models covering a near-global scale between 56°S and 60°N. It flew on the 11-day STS-99 mission of the Space Shuttle Endeavour in February 2000. The mission was spearheaded by the U.S. National Geospatial-Intelligence Agency (NGA) and NASA. The instrument was an interferometric synthetic aperture radar system, a development of the earlier SIR-C/X-SAR design used on the Shuttle in 1994. A critical change was the addition of a second antenna, enabling single-pass interferometry. One antenna remained in the payload bay, while the other was mounted on a 60-meter mast that extended once in orbit. The radar operated in both X-band and C-band. C-band provided a wider aperture and thus broader coverage beneath the Shuttle’s track, whereas X-band had a narrower aperture but higher resolution; the mission orbit was optimized for C-band coverage, resulting in many gaps in the X-band data. The payload was later transferred to the Smithsonian National Air and Space Museum and is displayed at the Steven F. Udvar-Hazy Center in Chantilly, Virginia.
Reader's Guide
The Shuttle Radar Topography Mission (SRTM) was an international research effort that produced near-global digital elevation models covering latitudes from 56°S to 60°N, creating the most complete high-resolution topographic database of Earth available before the 2009 release of the ASTER GDEM. The mission flew aboard the Space Shuttle Endeavour during the 11-day STS-99 mission in February 2000. It employed interferometric synthetic aperture radar, a technique using two antennas to generate topographic data in a single pass. One antenna was located in the Shuttle’s payload bay, while the other was mounted on a 60-meter mast that extended once in orbit. The radar operated in both C-band and X-band; C-band provided wider coverage beneath the Shuttle’s track, while X-band offered higher resolution but narrower coverage, resulting in many gaps in the X-band data because the mission orbit was optimized for the American C-band mission rather than the German-Italian X-band effort. The project was spearheaded by the U.S. National Geospatial-Intelligence Agency and NASA. Intermap Technologies served as the prime contractor for processing the interferometric data. The resulting elevation models are widely used in geographic information systems and are freely downloadable in the .hgt format. The C-band data, processed at 1-arcsecond resolution, covers Africa, Europe, North America, South America, Asia, and Australia; the rest of the world is available at 3-arcsecond resolution. The SRTM payload, including its canister, mast, and antenna, was transferred to the Smithsonian National Air and Space Museum in 2003 and is displayed at the Steven F. Udvar-Hazy Center in Chantilly, Virginia.
Did You Know?
- The SRTM used a 60-meter mast extending from the shuttle's payload bay to enable single-pass interferometry.
- The SRTM payload is on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia.
- The X-band dataset has many gaps because the mission orbit was designed for C-band coverage.
Frequently Asked Questions
What are the Shuttle Radar Topography Mission's powers/role?
SRTM's core ability is generating high-resolution digital elevation models of Earth's land surface, achieving roughly 30-meter resolution over most terrain and 90-meter resolution across the full globe. It accomplished this through an 11-day radar mapping campaign that produced the most complete high-resolution topographic dataset of its era.
Why is the Shuttle Radar Topography Mission important?
Before SRTM, no single effort had produced a near-global, high-resolution digital topographic map of Earth's landmasses. It filled that gap by delivering the first comprehensive elevation database spanning 56°S to 60°N, fundamentally changing how researchers and engineers model terrain.
What territory does the Shuttle Radar Topography Mission cover?
SRTM mapped land surfaces between roughly 56 degrees south latitude and 60 degrees north latitude, encompassing nearly all inhabited and ecologically significant regions on the planet. The 30-meter resolution applies to most land areas, while the 90-meter resolution extends across the full global coverage.
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