SWOT: Expert reveals how radar tech will track Earth's water pulse like never before

Ultimately, SWOT is designed to provide scientists with an unprecedented perspective of the life-giving fluid covering 70 percent of the planet, offering fresh insights into the causes and effects of climate change.

Interesting Engineering (IE) spoke with Tamlin Pavelsky – hydrology science lead for SWOT, based at the University of North Carolina. We asked him to delve deeper into what we can expect from the mission. 

An unprecedented view of Earth's surface water using radar tech

"SWOT is a new satellite jointly developed by NASA and CNES (the French space agency), with contributions from Canada and the UK," Pavelsky told IE. In fact, the project took almost 20 years to develop, from conception to launch. 

He highlighted that the satellite uses a sophisticated microwave radar system – two antennas operating at the spectrum's Ka-band frequency (KaRIn) – to collect height-surface data of seas, lakes, reservoirs, and rivers over 90 percent of the planet in high-definition detail.

This radar tech will allow scans to be taken through cloud cover and darkness over significant portions of the Earth. 

As a result, scientists will be able to precisely map their data in two dimensions regardless of the weather or time of day. Better yet, they can do so far more quickly than before. The water-tracking satellite revealed its first stunning views a few weeks ago, showing ocean currents like the Gulf Stream in unprecedented detail.

For comparison, earlier studies of water bodies generally depended on data collected at specific locations, such as river or ocean gauges, or from satellites that could only track measurements along a one-dimensional line, necessitating extrapolation to fill in data gaps.

"It will allow us to have a much better understanding of the surface water components of the water cycle and how they vary in space and time," Pavelsky said.

"This is really important because it will provide a baseline understanding against which we can compare future changes," Pavelsky said. "From short-term variations like floods and droughts (which SWOT will observe) to long-term patterns like human-caused climate change."

SWOT will help measure how much carbon dioxide is absorbed by the oceans

"SWOT matters because water matters – it is both our most important resource and our greatest hazard," Pavelsky highlighted.

One of the major objectives of the mission is to investigate how oceans naturally reduce global temperatures and climate change by absorbing carbon dioxide and heat from the atmosphere. 

Around ninety percent of the surplus heat retained in the Earth's atmosphere as a result of greenhouse gas emissions created by humans is thought to have been absorbed by the oceans.

By scanning the oceans from orbit, SWOT is designed to assess minute variations in surface elevations around smaller currents and eddies, which are thought to be the primary locations for the oceans' absorption of heat and carbon. According to a press release by NASA's JPL (Jet Propulsion Laboratory), the satellite can accomplish this with a resolution that is ten times higher than previous technology.

SWOT's program scientist, Nadya Vinogradova Shiffer, pointed out in an article in The Guardian that studying this carbon-absorbing mechanism could help climate scientists answer a critical question: What is the tipping point where oceans begin to release massive amounts of heat back into the atmosphere rather than absorbing it? Or, in other words, when do they start speeding up global warming rather than mitigating it? 

By offering fresh data on tides, sea levels, and ocean currents, the satellite will help improve oceanographic models. Scientists may then be able to better predict ocean behavior and extreme weather occurrences like hurricanes and storm surges.

New data will also identify areas of the ocean that are particularly rich in biodiversity or that are threatened by human activities like overfishing or pollution. This information can be used to support marine conservation efforts and protect vulnerable marine ecosystems.

Keeping tabs on increasing water levels along coastlines 

And that's not all. The impact of rising water levels on coastlines will also be investigated using SWOT's capacity to distinguish tiny surface features. The extent of saltwater intrusion into estuaries, wetlands, and subsurface aquifers could be predicted with more accuracy from data collected along tidal zones.

SWOT's mission will last at least three years and will provide researchers with multiple assessments of Earth's water resources, allowing them to better track changes in the planet's rivers and lakes due to seasonal shifts and significant weather events. This way, it could pinpoint areas vulnerable to human activity and climate change. 

Recently, SWOT's Ka-band Radar Interferometer instrument (KaRIn) examined the elevation of water features on Long Island – an island in New York State, U.S. – depicted as brilliant pink splotches in one of the mission's first-ever images. Different heights of the land are represented by the hues of purple, yellow, green, and blue.

"[It's like] taking the pulse of the world's water system, so we'll be able to see when it's racing, and we'll be able to see when it's slow," Pavelsky recently said to The Guardian. 

Overall, "SWOT will help us better understand the patterns of sea level rise along our coasts, how the amount of water stored in reservoirs around the world changes (and, to some degree, how those reservoirs are operated), and how the flow of water through rivers changes over time," Pavelsky told IE. 

SWOT will first operate off the coast of California

"The first water bodies we look at with SWOT have been carefully picked to help us understand how well SWOT data performs," he said. 

"We will have teams in the field collecting on-the-ground data in rivers and lakes around the world during the first six months of SWOT's operations."

Pavelsky reveals that oceanographers will also collect data at critical points in the ocean (such as off the coast of California, in the Gulf Stream off the Eastern U.S., and the Mediterranean). "We'll use the data they collect to understand SWOT's performance," he noted. 

In addition to ground-based observations, measurements will be compared to other satellite missions. In this way, scientists will be able to create global maps in unprecedented detail.

Once fully operational, the aim is for SWOT to analyze 1.3 million miles (2.1 million kilometers) of rivers, as well as millions of lakes that are difficult to sample up close and along coasts.

In order to encourage communities to use the data for planning and monitoring local water levels, NASA also wants to make the information accessible to the general public along with user-friendly tools.

SWOT to pave the way for future NASA Earth missions

Overall, the SWOT mission could potentially revolutionize our knowledge of Earth's water systems and their global effects.

Its preliminary photos, as revealed in this article, provide a tantalizing glimpse of how SWOT can measure specifics of smaller lakes, ponds, and rivers in ways that satellites previously could not. No doubt, the lessons learned from the satellite will lead to new questions, blazing a trail for future Earth-observing missions.

For the benefit of academics, decision-makers, and water resource managers, the data obtained will be used to create a remarkable accounting of all the water bodies on the surface of the Earth that make life as we know it, possible.