The mighty Yukon River and nearby lakes appear in red in this image produced using data recorded on June 18, 2023, by the international Surface Water and Ocean Topography (SWOT) satellite as it passed over Alaska. The satellite measures the height of nearly all the water on Earth's surface, providing one of the most detailed, comprehensive views yet of the planet's ocean and fresh water.

The mission is a collaboration between NASA and the French space agency, CNES (Centre National d'Études Spatiales). SWOT will address some of the most pressing climate change questions of our time, offering insights into areas including how a warming world is accelerating Earth's water cycle, leading to more volatile precipitation patterns. SWOT will also help researchers better understand how climate change affects water storage in lakes, rivers, and reservoirs, and how communities can better manage water resources and prepare for floods and other disasters.

SWOT passed over the Yukon River and recorded this data during a period called calibration and validation, when the mission confirms the accuracy of its data. Calibration involved ensuring SWOT's software and hardware – including its main scientific instrument, the Ka-band Radar Interferometer (KaRIn) and its antenna – operate as designed. During validation activities, dozens of research teams headed into the field to measure water levels and the slope of rivers, including the Yukon. Mission scientists then compared field measurements to the data taken by the satellite to ensure SWOT's accuracy.

In mid-June, the team of freshwater researchers tasked with gathering data on the Yukon drifted down the waterway around midnight – the same time as SWOT passed overhead, collecting its own data on the river.

Launched on Dec. 16, 2022, from Vandenberg Space Force Base in central California, SWOT is now in its operations phase, collecting data that will be used for research and other purposes.

SWOT was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. NASA's Jet Propulsion Laboratory, which is managed for the agency by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA provided the KaRIn instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES provided the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations. CSA provided the KaRIn high-power transmitter assembly. NASA provided the launch vehicle and the agency's Launch Services Program, based at Kennedy Space Center, managed the associated launch services.