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New NASA Satellite Will Keep Tabs on Nearly All of Earth's Water

SWOT will collect data on all of our planet's large water bodies every 21 days, offering key insights into climate, sea level rise, and freshwater.

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An animation of the SWOT satellite unfolding its 5-meter long antennae.

We live on a blue planet. More than 70% of Earth’s surface is covered by water, and a soon-to-launch satellite is set to shed light on all that liquid like never before. The Surface Water and Ocean Topography (SWOT) mission is a joint project between NASA and France’s Centre National d’Études Spatiales (CNES), plus other international collaborators, and it’s scheduled for launch on December 12.

If all goes according to plan, the three-year long venture will use an array of high-tech instruments to complete the first-ever global survey of surface water from space. Researchers expect the satellite to collect detailed data on water volume, location, and movement over time, according to a Monday press briefing.

SWOT is slated to measure 95% of Earth’s water bodies and collect a complete sample on surface waters every 21 days, filling big research gaps, according to NASA. Currently, only a few thousand lakes around the world are routinely monitored, but the new satellite will cover much more ground. All of the data will be freely available to scientists and will hopefully improve our understanding of ocean currents, sea level rise, droughts, floods, and the water cycle—which is rapidly shifting under climate change, said project researchers.


Plus, unlike existing satellites that collect water data from orbit in two dimensions, SWOT will monitor the breadth and depth of the world’s oceans, large lakes, reservoirs, and wide rivers—simultaneously offering new information on the planet’s topography as well as the status of one of our most important resources. “SWOT will provide [hydrologists] with a pair of 3D glasses,” said Lee-Leung Fu, of NASA’s Jet Propulsion Laboratory, in the news briefing.

To do so, the satellite uses a measurement system called KaRIn (KA band radar interferometer) made up of two precisely placed, stable antennae. These antennae, which must be aligned within the width of a human hair, each receive reflected radar pulses. Those dual readings allow triangulation of a single, very accurate (within ~1 centimeter) measurement of water height, explained Parag Vaze, JPL’s SWOT project manager. In order to function, the satellite also relies on an internal positioning system—to keep tabs on its relative place in space—a thermal management system, and a high-voltage power supply.


As climate change leads to increasing flooding, intensified droughts, and rising seas, the ability to predict, monitor, and respond to these shifts becomes increasingly valuable, explained Ben Hamlington, an Earth scientist at NASA’s JPL. “In the future, more communities around the world are going to be inundated with water, while in other areas some communities may just not have enough water. SWOT data is going to be used to monitor drought conditions, improve flood forecasts,” and more, he said. Information from the satellite could inform climate change adaption efforts, as well as disaster preparedness and responses, Hamlington added.

SWOT will be sent into orbit via a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California. It will take two months post-launch to turn on and unfold all of the satellite’s instruments, and after that comes calibration and checks of SWOT’s functions. Researchers expect the science mission to begin about six months after launch.