Surface Water Ocean Topography Mission

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The Surface Water Ocean Topography (SWOT) Mission is a future satellite mission, jointly developed by NASA and CNES, the French space agency, to make the first global survey of Earth’s surface water and measure submesoscale ocean circulation. It is one of 15 missions that the 2007 National Research Council’s Decadal Survey of Earth Science and Applications recommends NASA implement in the coming decade.[1] Launch by a SpaceX Falcon 9 rocket is planned for April 2021.[2]

SWOT is being developed by an international group of hydrologists and oceanographers to provide a better understanding of the world's oceans and its terrestrial surface waters.[3] It will give scientists their first comprehensive view of Earth's freshwater bodies from space and more much detailed measurements of the ocean surface than ever before.[4]

SWOT is collaboration between NASA, CNES, the French space agency, and the Canadian Space Agency (CSA).[5] The NASA contributions are currently being designed and constructed at NASA's Jet Propulsion Laboratory (JPL). It builds on the very successful 25-year partnership between the two agencies to use radar altimetry to measure the surface of the ocean that began with the TOPEX/Poseidon mission.

The primary instrument on SWOT is based a new type of radar called the Ka-band Radar Interferometer (KaRIN), which uses radar interferometery technology[6]. The satellite will fly two radar antennae at either end of a 10-meter (33-foot) mast, allowing it to measure the elevation of the surface along a 120- kilometer (75-mile)-wide swath below. 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.[7]

The mission’s science goals are to

  • Provide sea surface heights and terrestrial water heights over a 120-kilometer wide swath with a ±10-kilometer gap at the nadir track.
  • Over the deep oceans, provide sea surface heights within each swath with a posting every two kilometers x two kilometers, and a precision not to exceed 0.5 centimeters when averaged over the area.
  • Over land, download the raw data for ground processing and produce a water mask able to resolve 100-meter-wide rivers and (250 m)2 lakes and reservoirs. Associated with this mask will be water level elevations with an accuracy of 10 centimeters and a slope accuracy of one centimeter/one kilometer.[8]
  • Cover at least 90 percent of the globe. Gaps are not to exceed 10 percent of Earth's surface.

SWOT will have a mission lifetime of three years. NASA contributions to the total mission costs are $755M[9], with additional contributions from CNES, including launch service costs slated at $112 million.[2]


  1. ^ "Earth Science and Applications from Space:National Imperatives for the Next Decade and Beyond". 
  2. ^ a b "Watery mission: SpaceX and NASA join forces on 2021 monitoring project". 
  3. ^ "Measuring Global Oceans and Terrestrial Freshwater from Space" (PDF). 
  4. ^ "Following the Water with the Ocean Surface Topography Mission". 
  5. ^ media, Government of Canada, Canadian Space Agency, Directions of communications, Information services and new. "2016-17 Report on Plans and Priorities". Canadian Space Agency website. 
  6. ^ [NULL]. "SWOT: Technology". Retrieved 2017-04-19. 
  7. ^ "NASA’s Shuttle Radar Topography Mission". 
  8. ^ Biancamaria, Sylvain; Lettenmaier, Dennis P.; Pavelsky, Tamlin M. (2016-03-01). "The SWOT Mission and Its Capabilities for Land Hydrology". Surveys in Geophysics. 37 (2): 307–337. Bibcode:2016SGeo...37..307B. ISSN 0169-3298. doi:10.1007/s10712-015-9346-y. 
  9. ^ NASA's Earth Science Mission Portfolio. NASA Office of Inspector General. 2016. p. 62. 

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