Revolutionizing Our View of Earth's Water
Imagine having the power to track the pulse of every major river, lake, and ocean on Earth with unprecedented precision. The Surface Water and Ocean Topography (SWOT) mission turns this vision into reality. Launched in December 2022, this revolutionary satellite represents an international collaboration between NASA, the French space agency CNES, with contributions from the Canadian Space Agency and UK Space Agency 1 2 5 .
Of Earth's surface water surveyed from space for the first time 2
For the first time in history, scientists can survey 90% of Earth's surface water from space, capturing detailed measurements of how our planet's oceans and freshwater bodies change over time 2 . This technological marvel provides a holistic view of the water cycle, offering vital insights for managing water resources, understanding climate change, and predicting natural disasters.
Previous satellite missions could only measure water levels along narrow one-dimensional tracks directly beneath them, much like looking at Earth through a keyhole 5 . SWOT has shattered these limitations with its innovative technology that enables two-dimensional mapping of water surfaces across wide swaths 1 .
The secret to SWOT's capabilities lies in its primary instrument: the Ka-band Radar Interferometer (KaRIn) 5 6 . This breakthrough technology features two radar antennas mounted on a 10-meter (33-foot) boom that create two 50-kilometer-wide swaths on either side of the satellite 2 6 . By comparing the slight phase differences between the signals received by these two antennas, KaRIn generates detailed elevation measurements of water surfaces with centimeter-scale accuracy 2 .
| Launch Date | December 16, 2022 3 5 |
| Orbit Altitude | 890 kilometers (553 miles) 2 6 |
| Orbit Inclination | 77.6° 5 |
| Coverage | 78° North to 78° South latitude 2 5 |
| Repeat Cycle | 21 days 2 4 |
| Mission Duration | Planned: 3 years 5 |
| Spatial Resolution | 15 km for oceans, able to detect rivers >100m wide and lakes >250m × 250m 1 5 |
SWOT's advanced technology enables scientists to observe phenomena previously invisible from space. For oceanography, SWOT can resolve ocean features 10 times better than previous technologies, detecting currents and eddies as small as 15-25 kilometers across 1 5 . For hydrology, SWOT provides the first global inventory of terrestrial water bodies, measuring storage changes in lakes, reservoirs, and wetlands, while estimating river discharge worldwide 1 .
This mission fundamentally transforms our ability to monitor essential aspects of our planet's water systems, from tracking regional sea level changes in coastal areas to measuring volume changes in millions of lakes and reservoirs 1 2 . The data SWOT provides is critical for understanding the Earth's water cycle amid changing climate conditions.
Recent research has demonstrated SWOT's extraordinary ability to capture fine-scale ocean processes in this region known for complex ocean dynamics .
Scientists employed SWOT's two-dimensional sea surface height measurements to validate the accuracy of different data merging methods .
The research tested SWOT's capacity to accurately capture mesoscale and submesoscale eddies—swirling ocean currents crucial for heat and nutrient transport .
The research utilized data from SWOT's science phase (September-November 2023), when the satellite followed its 21-day repeat orbit . The team employed a regional averaging method to process the original 2 km resolution SWOT data, maintaining sufficient detail to analyze fine-scale structures while ensuring compatibility with existing ocean models.
| Tool/Solution | Function in Research |
|---|---|
| SWOT CALVAL Phase Data | Provided daily rapid-sampling observations for analyzing temporal evolution of eddies |
| SWOT Science Phase Data | Primary dataset for examining spatial dynamic structures and statistical analysis |
| 2DVAR Method | Advanced merging technique with 1/12° grid resolution for reconstructing oceanic signals |
| AVISO Products | Conventional merged maps using optimal interpolation method with 1/4° grid resolution |
| Regional Averaging | Method to reduce SWOT resolution from 2 km to 1/12° for consistent analysis |
The analysis revealed that SWOT successfully detected previously unobservable fine-scale ocean signals, reducing instrument noise by two orders of magnitude compared to conventional satellites . The 2DVAR method showed significantly greater consistency with SWOT observations than the conventional AVISO products, particularly at smaller scales.
Most notably, SWOT demonstrated an unprecedented 15 km spatial resolution for detecting ocean topography features—a massive improvement over previous technologies . This capability allows scientists to observe intricate ocean dynamics that were previously beyond the resolution of satellite altimeters, opening new frontiers in oceanographic research.
SWOT provides transformative data for global freshwater management. The satellite can monitor water volume changes in lakes and reservoirs worldwide, offering critical information for regions facing water scarcity 5 . For transboundary river basins, where water sharing often causes international friction, SWOT offers objective measurements of river discharge and reservoir storage that all parties can trust 5 .
During flood events, SWOT tracks the three-dimensional shape of flood waves and measures floodwater extent and elevation across entire floodplains 5 . This data significantly improves flood modeling and prediction, potentially saving lives and reducing economic losses from these devastating natural disasters.
SWOT's high-resolution observations are transforming our understanding of ocean circulation. By detecting previously invisible small-scale currents and eddies, SWOT helps scientists better understand the ocean's role in climate regulation 2 . These fine-scale features are crucial for ocean-atmosphere exchanges of heat and carbon—major components in global climate change 1 .
For coastal communities, SWOT provides detailed information about coastal currents, storm surges, and regional sea level variations 1 . This knowledge is essential for coastal planning, navigation, and predicting the impacts of severe weather events.
| Environment | Measurement Capability | Accuracy |
|---|---|---|
| Open Ocean | Sea surface height at 2 km x 2 km posting | 1.35 cm when averaged 5 |
| Lakes & Reservoirs | Water level elevation for bodies >1 km² | 10 cm 5 |
| Rivers | Slope over 10 km flow distance | 1.7 cm/km 5 |
| Coastal Regions | Surface topography including estuaries & deltas | High-resolution monitoring within 1 km from land 1 |
The mission's data helps inform decisions about water allocation, flood preparedness, and climate adaptation worldwide 2 .
SWOT's data is freely available to scientists, resource managers, and policymakers globally, fostering collaboration and innovation.
The Surface Water and Ocean Topography mission represents a quantum leap in our ability to monitor Earth's vital water resources. By providing the first comprehensive, global survey of surface water, SWOT fills critical gaps in our understanding of the world's oceans and freshwater systems 1 2 .
"It's like putting a pair of spectacles on the previous satellites: suddenly, what was blurry is now clear; what we could only guess at from hints in the older measurements, we now see with clarity from SWOT."
The mission's freely available data empowers scientists, resource managers, and policymakers worldwide to make more informed decisions about water resource allocation, flood preparedness, and climate adaptation 2 . As SWOT continues its three-year mission, it will provide an unprecedented dataset that will transform our relationship with Earth's most precious resource—water—and help humanity navigate the water-related challenges of the 21st century.
Concept development and international partnership formation between NASA, CNES, CSA, and UKSA.
Successful launch of the SWOT satellite, beginning a new era of water observation.
Commissioning phase and initial data collection, including the South China Sea study .
Full operational phase with global data collection and distribution to the scientific community.
Potential mission extension and development of next-generation water observation technologies.