5 Things to Know About How the SWOT Looks for Water in the World – NASA’s Sea Level Change Portal


The International Surface Water and Ocean Topography Mission will provide high-resolution data on salt and fresh water on Earth’s surface.

SWOT media reel

SWOT press kit

On Dec. 12, NASA will launch the Surface Waters and Ocean Topography (SWOT) satellite into Earth orbit from Vandenberg Space Force Base in California atop a Falcon 9 rocket. The mission is a collaborative effort between NASA and the French space agency CNES (Centre Nationale d’Etudes du Spaces) – with Contributions from the Canadian Space Agency (CSA) and the British Space Agency – that would survey the water in more than 90% of the planet’s surface.

The satellite will measure the rise of water in bodies of fresh water on Earth and the oceans, providing insights into how the ocean is affecting climate change; how a warming world affects lakes, rivers, and reservoirs; and how communities can better prepare for disasters, such as floods.

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The Black Sea from space

The SWOT satellite, scheduled for launch in December, will help researchers study ocean features such as currents and eddies in places like the Black Sea closer to the coast than previous ocean-monitoring satellites. Credit: NASA Earth Observatory

Here are five ways SWOT will change what we know about water on Earth:

1. SWOT will survey almost all of the water on Earth’s surface for the first time.

Water is essential to life on this planet. But they also play an important role in storing and transporting much of the extra heat and carbon trapped in Earth’s atmosphere due to greenhouse gas emissions. They also affect our weather and climate. SWOT will help researchers track the Earth’s water budget – where the water is today, where it is coming from, and where it will be tomorrow. This is key to understanding how water resources change, the impact of these changes on local environments, and how the ocean interacts with and affects climate change.

2. You’ll see the Earth’s water SWOT at higher resolution than ever before.

The spacecraft’s scientific instruments will display the planet’s freshwater bodies and oceans with unprecedented clarity. SWOT will be able to collect data on ocean features less than 60 miles (100 kilometers) wide, helping to improve researchers’ understanding of the ocean’s role in climate change. Earth’s seas have absorbed more than 90% of the excess heat trapped in the atmosphere by human-caused greenhouse gas emissions. Researchers believe that short-lived ocean features, such as fronts and eddies, absorb much of that heat — and the extra carbon that produced it.

By providing a high-resolution view of freshwater bodies, SWOT will help create a more complete picture of the Earth’s water budget. Many large rivers remain a mystery to researchers, who cannot provide them with monitoring tools for various reasons, including inaccessibility. The spacecraft’s instruments will monitor the full length of nearly all rivers over 330 feet (100 meters) wide, displaying them in three dimensions for the first time. Similarly, where Earth and satellite technologies currently provide data on only a few thousand of the world’s largest lakes, SWOT will expand that number to more than 1 million lakes larger than 15 acres (62,500 square metres).

NASA and CNES (the French space agency) are collaborating to conduct the first global survey of fresh water on Earth’s surface and study subtle ocean currents through a new mission called SWOT, or Surface Water and Ocean Topography. SWOT will collect data on the Earth’s salt elevation and fresh water – including oceans, lakes and rivers – to enable researchers to track the location of the water over time, which will help measure the effects of climate change. Image credit: NASA/JPL-Caltech/CNES/Thales Alenia Space

3. The satellite will tackle some of the most pressing climate change issues of our time.

An important part of predicting our future climate is determining the point at which the ocean slows the absorption of excess heat trapped in the atmosphere and begins releasing it back into the air, where it can accelerate global warming. The SWOT will provide important information about the global heat exchange between the ocean and the atmosphere, allowing researchers to test and improve climate predictions. In addition, the satellite will help fill in gaps in researchers’ picture of how sea level is changing along coastlines, providing insights that can then be used to improve computer models for projecting sea level rise and predicting coastal flooding.

4. SWOT data will be used to inform decisions about our daily lives.

Climate change is also accelerating the Earth’s water cycle, leading to more erratic precipitation patterns, including torrential rains and severe droughts. Thus, some communities across the world will experience floods while others will experience drought. The SWOT data will be used to monitor drying conditions for lakes and improve flood forecasts for rivers, providing essential information for water management agencies, disaster preparedness agencies, universities, civil engineers and others who need to track water in their local areas.

5. This mission paves the way for future NASA Earth missions while also building on a long-standing international partnership.

With its innovative technology and commitment to engaging a diverse community of people who plan to use mission data, SWOT is setting a course for future Earth observation missions. The measurements from SWOT—and the tools needed to support researchers in analyzing the information—will be free and accessible. This will help enhance search activities and applications by a wide range of users, including those who might not normally have access to this knowledge.

Such an ambitious mission is possible because of the decades-old collaboration between NASA and the National Center for Space Studies that began in the 1980s to observe Earth’s circumference. This partnership pioneered the use of a space instrument called an altimeter to study sea level with the launch of the TOPEX/Poseidon satellite in 1992. The NASA-CNES partnership has gone on uninterrupted for three decades and has expanded to include work with other agencies, including the CSA and the British Space Agency for SWOT, as well as ESA (European Space Agency), European Organization for the Exploitation of Meteorological Satellites, and European Commission’s Sentinel-6 Michael Freilich satellite, launched in November 2020.

Data from the SWOT satellite will help people monitor freshwater resources and help communities prepare for the consequences of climate change. Image credit: NASA/JPL-Caltech/CNES/Thales Alenia Space

More about the mission

SWOT is being developed jointly by NASA and the French National Center for Space Studies, with contributions from the Canadian Space Agency and the British Space Agency. The Jet Propulsion Laboratory, operated by NASA’s California Institute of Technology in Pasadena, California, leads the American component of the project. For the flight system payload, NASA provides a Ka-Band Radar Interferometer (KaRIn) instrument, a GPS science receiver, a laser retroreflector, a dual-beam microwave radiometer, and NASA Instrument Operations. The National Center for Space Studies provides the Doppler Orbiter and Radiometric Integrated Location-by-Satellite System (DORIS), the dual-frequency Poseidon altimeter (developed by Thales Alenia Space), and the KaRIn radio frequency subsystem (together with Thales Alenia Space and with support from the space agency British), the satellite platform and the ground control part. CSA provides the KaRIn high power transmitter assembly. NASA provides the launch vehicle and associated launch services.

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