SWOT illustration
The Surface Water and Ocean Topography (SWOT) spacecraft, launched Dec. 16, was developed by NASA and the French space agency CNES to study changing water levels in oceans and lakes. Credit: CNES

SAN FRANCISCO – Lee-Lueng Fu, project scientist for NASA’s first global survey of Earth’s surface water, is shocked by how well the mission is going.

A couple of days after the primary instrument on the joint NASA-French Space Agency CNES Surface Water and Ocean Topography (SWOT) satellite was turned on, engineers brought Fu a sea-surface-height image that looked too good to be real.

“I said, ‘You guys are trying to pull a cruel joke on me,’ because it usually is not possible to get things so clear,” Fu said Dec. 12 at the American Geophysical Union Fall meeting here.

Often, it takes months to fine-tune algorithms to improve data quality. For SWOT’s Ka-band Radar Interferometer, ocean observations were clear immediately.

“Once you see such clarity, you immediately know that something is working really right,” said Fu, a NASA Jet Propulsion Laboratory fellow and senior research scientist.

NASA researchers at the AGU meeting lauded the performance of other Earth-observation sensors as well. Tropospheric Emissions: Monitoring of Pollution “is working incredibly well,” said Barry Lefer, NASA tropospheric composition program manager. The Earth Surface Mineral Dust Source Investigation spectrometer on the International Space Station is an “exquisite instrument” that “is exceeding all our expectations,” said Robert Green, EMIT principal investigator.


Even against that backdrop, praise for SWOT stood out.

“The performance of this mission was not possible even in my wildest dreams,” Fu said, adding that SWOT is his fourth NASA mission.

Particularly on the oceanography side, SWOT “worked out of the box,” said Tamlin Pavelsky, SWOT hydrology science lead. For hydrology, “we see the promise of how great it’s going to be. But we need to write new software to process this data better.”

SWOT’s improved performance will allow researchers to monitor water levels in smaller lakes and rivers than they expected.

Prior to launch in December 2022 on a SpaceX Falcon 9 rocket, SWOT was expected to view lakes as small as 6 hectares. Instead, SWOT may observe some 6 million lakes as small as one hectare.

“I’m confident that we’ll see pretty much all of those lakes at least some of the time,” said Pavelsky, a University of North Carolina professor of Earth, marine and environmental sciences.

Debra Werner is a correspondent for SpaceNews based in San Francisco. Debra earned a bachelor’s degree in communications from the University of California, Berkeley, and a master’s degree in Journalism from Northwestern University. She...