NASA’s Swot satellite will monitor millions of rivers and lakes

Swot will cover the world between 78 degrees north and south every 21 days

The American space agency Nasa has launched a satellite that should transform our view of water on Earth.

The Swot mission will map the precise height of rivers, reservoirs and lakes, and track ocean surface features at unprecedented scales.

It should improve predictions of floods and droughts and help researchers better understand how the climate is changing.

NASA has asked British scientists to help set up the spacecraft using the Bristol Channel as a reference.

British researchers are placing a fleet of sensors in the estuary to “ground verify” observations made by the satellite as it flies overhead at an altitude of 890 km (550 miles).

The Surface Water and Ocean Topography mission took off from California. A Falcon rocket took her into the sky at 03:46 local time (11:46 GMT).


Plankton blooms trace swirling eddies in the South Atlantic around the Falkland Islands

It will take a few months before it is fully operational; its French-made Ka-band radar interferometer (KaRIn) has long arms that need to be unpacked first.

Once in position, however, the instrument’s antennae will begin pulsating the Earth’s surface, counting how long the reflections take to return to the spacecraft.

It is these echoes that allow Swot to determine the height very precisely.

Essentially, the satellite will photograph water masses, assess their rise and fall in detail and over a very wide band.

Swot should be able to resolve all rivers at least 100m wide and see all lakes larger than 6 hectares (15 acres).

“The amount of SWOT data on rivers and lakes will be an order of magnitude greater than what currently exists,” said Nasa project scientist Dr. Lee-Lueng Fu.

“For example, only tens of thousands of lakes have been well studied. We are going to study millions of lakes.”


Ground monitoring of water levels in some countries is rare or non-existent. Swot might help

For the ocean, Swot will see the bulges and depressions on the surface of the water associated with currents and eddies as small as 20 km (12 miles) in diameter. It is the swirling of water in eddies that extracts heat and carbon dioxide from the atmosphere, thereby mitigating the impact of global warming.

“The unprecedented information can also be used to improve our understanding of ocean circulation, and this then has the potential to provide important information for a wide range of industries like shipping, fishing and even recreation,” said explained Ben Hamlington, a NASA sailor. scientific level.

“We also know that fine-scale features are responsible for transporting pollutants around the ocean and then to our shores. Examples of this would be oil spills or ocean debris following tsunamis.”

Britain invested £12 million ($15 million) in the mission, most of which was spent on British industry.

Dr Beth Greenaway, head of Earth observation at the UK Space Agency, attended the launch in California. She told BBC News: “I’m very proud to represent the UK building elements – the part that delivers the radar pulses through the instrument at frequencies never seen before. UKSA’s partnership with the agency French space agency, Cnes, allowed engineers at Honeywell UK to build this complex duplexer.”

But the UK’s involvement also extends to the upcoming “calibration and validation” campaign in the spring, which will verify that Swot is returning correct information.

This will involve placing sensors in the Bristol Channel to make comparable observations as the spacecraft passes overhead. The estuary was chosen because it undergoes strong variations in water level. It has one of the largest tidal ranges in the world.

“Swot is going to give heights of around 10cm, so we need to know the absolute elevation at ground level to much higher accuracy,” said Professor Paul Bates from the University of Bristol, who will lead the campaign.

“We went to the tide gauges, put GPS stations there, and then we thought about things like temperature, pressure, salinity – all those sorts of potential variables. And we’ll end up with a network of elevations of very precise water around the estuary.”

Professor Bates thinks Swot should have the ability to see the famous bore that periodically ascends the channel in the lower reaches of the River Severn.

He plans to use satellite data to pursue his interest in flood modeling. It builds predictive tools that agencies can use to assess flood risk.

Swot is a cooperation between the American, French, Canadian and British space agencies.

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