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16 December 2022 3 min read

Panoramic view looking east towards the Bass Strait altimeter validation site from the new GNSS reference station on Three Hummock Island. Christopher Watson, University of Tasmania.

When studying water across the Earth’s surface, researchers have relied on instruments that measure at specific locations, such as gauges in rivers or the ocean, or that are space-based to gather data.

The first-of-its-kind SWOT satellite, led by NASA and the French space agency Centre National d’Etudes Spatiales (CNES) will help scientists to study ocean features and freshwater bodies with 10 times the resolution of current technologies, improving how we address climate change and help communities prepare for a warming world.

Launching today, SWOT will orbit over the Integrated Marine Observing System (IMOS University of Tasmania-CSIRO) Satellite altimetry calibration facility in the Bass Strait as part of its initial validation phase.

In this first phase, SWOT will orbit the earth 14 times a day repeating the same few ground tracks every day for three months, with two of those paths crossing the Bass Strait and Albany in Western Australia.

The satellite will continue into the second phase where it will orbit 292 times every 21 days to deliver global coverage of the earth.

Of the three satellite altimetry calibration facilities around the globe (Bass Strait, Australia, California, USA and Corsica, France) only the Australian facility will be covered in the validation phase of the satellite from mid-March to mid-June 2023, solidifying Australia’s place in the growing satellite verification space.

The new GNSS reference station on Three Hummock Island. Data from this site will be used to improve the positioning of buoys and other sensors in Bass Strait, providing an Australian contribution to SWOT calibration and validation. Christopher Watson, University of Tasmania.

Navigating the waters

If the mission is successful, SWOT will be able to provide a global inventory of water resources to help scientists better understand where the water is, where it’s coming from, and where it’s going.

The data and observations collected can help improve flood mapping and our models to monitor droughts and sea level rise.

Co-leader of the IMOS satellite altimetry calibration facility and the Australian Antarctic Program Partnership (AAPP) – Oceanography project CSIRO’s Benoit Legresy says the new technology will have huge benefits for Australia.

“While classic satellite altimeters can map the ocean topography quite well, the quality of measurement tends to degrade from around 50km to the coast,” he says.

“SWOT changes the lens on how we observe and use the ocean topography.

“It boasts a new radar interferometric system that will bring the essential ‘pixel size’ of ocean topography maps from 25km today down to 2km over the next 12 months.

“That’s very close up to the coast, the closest we’ve ever been through satellite imagery.

“It also has a Land Surface Water Level mode to capture the level of large rivers and lakes and flood plains – this has huge potential to serve Australia during its drought and flood seasons.”

What’s next for SWOT down under?

Partnering with international scientists, the AAPP and CSIRO will conduct a voyage in the Antarctic Circumpolar Current south of Tasmania to investigate newly accessible ocean processes in more detail in conjunction with the new SWOT satellite mapping.

Legresy says the voyage will explore where strong currents, cyclonic and anticyclonic activities, and strong interactions with the atmosphere in hotspot regions of energy transfer in the climate system where CO2 is absorbed, and heat is transferred into the ocean depth and across towards the pole.

“The Antarctic Circumpolar Current is the strongest ocean current on the planet and generally isolates the mid-latitudes from the polar climate,” says Legresy.

“Because it is strong it also generates a lot of turbulent behaviour, but around Antarctica, there are five hotspots of turbulent behaviour which let most of the heat from the mid-latitude towards the pole.

“One of these hotspots is in the south of Tasmania. Not only is it more accessible for our scientists and national vessel Investigator, but it is right under one of the initial paths of the satellites.

“This provides a solid base of analysis before the Southern Ocean Investigator voyage embarks.

Overall, Legresy says SWOT will offer much better vision of the fine whirls and other ocean processes enabling more integrated studies and monitoring.

“This promises lots of new ocean applications as the world ocean decades develop,” says Legresy.

“There will surely be impressive results to come in the coming year to illustrate this new lens view on our blue planet.”

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