page_title: Surface Water and Ocean Topography
section_title: Satellite characteristics
hierarchical_section_title: Surface Water and Ocean Topography / Satellite characteristics
caption_attribution_description: English: diagram illustrating the swaths of data that SWOT will collect. The interferometer will produce two parallel tracks, with a Nadir track from a traditional altimeter in the gap between the swaths. The overall width of the swaths will be approximately 120 km. Français&#160;: diagramme illustrant les fauchées sur lesquelles SWOT collectera des données. L'interféromètre produira deux traces parallèles, avec une trace au nadir d'un altimètre traditionnel dans l'espace entre les fauchées. La largeur totale des fauchées sera d'environ 120 km.
context_page_description: The Surface Water and Ocean Topography mission is a future satellite jointly developed by NASA and CNES, the French space agency, in partnership with the Canadian Space Agency and UK Space Agency. The objectives of the mission are to make the first global survey of the Earth's surface water, to observe the fine details of the ocean surface topography, and to measure how terrestrial surface water bodies change over time. While past satellite missions like the Jason series altimeters have provided variation in river and lake water surface elevations at select locations, SWOT will provide the first truly global observations of changing water levels, slopes, and inundation extents in rivers, lakes, and floodplains. In the world's oceans, SWOT will observe ocean circulation at unprecedented scales of 15-25 km, approximately an order of magnitude finer than current satellites. Because it uses wide-swath altimetry technology, SWOT will almost completely observe the world's oceans and freshwater bodies with repeated high-resolution elevation measurements, allowing observations of variations.
context_section_description: The primary instrument on SWOT is the Ka-band Radar Interferometer (KaRIn), which uses radar interferometry and synthetic aperture (SAR) technology. Because SWOT operates at relatively short wavelengths (compared to the Ku band Jason series) and at near-nadir incidence angles (<5°), it is designed to be uniquely appropriate for measuring water surface elevations and inundation extents. The satellite will fly two radar antennae at either end of a 10-meter mast, allowing it to measure the elevation of the surface across a 120 km wide swath. The new radar system is smaller but similar to the one that flew on NASA's Shuttle Radar Topography Mission, which made high-resolution measurements of Earth's land surface in 2000. A conventional nadir altimeter will also be flown, and measure just beneath the satellite, as was done on the Topex/Poseidon, Jason series and SARAL missions. Launch on a SpaceX Falcon 9 rocket is planned for April 2022. SWOT will have a mission lifetime of three years.
caption: Diagram of SWOT data collection
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