Early in the morning on December 16, 2022, NASA launched a new satellite that will map and subsequently measure changes in virtually all of the Earth’s rivers, lakes and oceans. High-resolution imaging will even be able to measure changes in ocean currents and temperatures. Scientists will use the imaging capabilities to better understand flooding, droughts and coastal erosion. One said it will “revolutionize hydrology.”
About the Satellite and Orbit
The satellite will orbit more than 550 miles high. Nicknamed SWOT (Surface Water and Ocean Topography), the mission will cover the globe between the Arctic and Antarctica at least once every three weeks.
About the size of a SUV, the satellite will measure the height of water on more than 90% of Earth’s surface. It will enable scientists to track water flow and identify potential high-risk areas.
The heart of the improvements is an innovative instrument called the Ka-band radar interferometer (KaRIn) – a major technological advance. KaRIn bounces radar pulses off the water’s surface and receives the return signal using two antennas on either side of the spacecraft.
According to NASA, for the first six months after launch, SWOT will be in a “fast-sampling” phase with a 1-day repeat orbit. Objectives in this phase include calibration and validation while studying rapidly changing phenomena.
The next phase – Operations & Sustainment – should last about three years It will have a 21-day repeat orbit to balance global coverage and sampling. NASA chose this “non-sun-synchronous orbit to minimize tidal aliasing and ensure coverage of major water bodies on land.” SWOT’s 75-mi-wide swath will result in overlapping measurements over most of the globe with an average revisit time of 11 days.
For a discussion of “tidal aliasing,” see this article in Geophysical Journal International. It’s about overcoming errors in current models that have to do with undersampling, uncertainty, imperfections and low-resolution.
Scientists Describe Anticipated Benefits
Scientists working on the mission described anticipated benefits:
- Larry Smith: “Through acquisition of high-resolution, spatially continuous measurements of inland water surface elevations, SWOT stands poised to revolutionize terrestrial hydrology in much the same way that Seasat transformed physical oceanography in 1978.”
- Mike Durand: SWOT will help us “better understand how precipitation is partitioned (runoff, evapotranspiration, storage).”
- Colin Gleason: “SWOT’s downstream estimates of river discharge will form perhaps the world’s most complete accounting of human alteration of river flow.”
- Marc Simard: It will tell us “where surface water flows and where it is stored, everywhere on Earth.”
- Doug Vandemark: “New data will aid existing weather prediction models in terms of how they resolve and predict heat and energy exchange between the atmosphere and oceans in both fair and foul weather situations.”
- Demitris Menemenlis: SWOT will give us “increased predictive skill for weather forecasting.”
- David Sandwell: It will “improve our mapping of the marine [environment] by perhaps a factor of 5.”
For More Information
To learn more, check out the following:
SWOT is a joint effort of NASA and the French space agency CNES, with contributions from the Canadian and United Kingdom space agencies.
Posted by Bob Rehak on 12/18/22
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