Part of the Surface Water and Ocean Topography (SWOT) satellite's science instrument payload sits in a clean room at NASA's Jet Propulsion Laboratory during assembly.

Once fully assembled and launched into orbit, the SUV-size spacecraft will make global surveys of Earth's surface water. By measuring the height of the water in the planet's ocean, lakes, and rivers, researchers can track the volume and location of the finite resource around the world. The data will help with monitoring changes in floodplains and wetlands, measure how much fresh water flows into and out of lakes and rivers and back to the ocean, and track regional shifts in sea level.

SWOT is being jointly developed by NASA and Centre National d'Etudes Spatiales (CNES), with contributions from the Canadian Space Agency (CSA) and United Kingdom Space Agency (UKSA). JPL, which is managed for NASA by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA is providing the Ka-band Radar Interferometer (KaRIn) instrument, a GPS science receiver, a laser retroreflector, and a two-beam microwave radiometer. CNES is providing the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, nadir altimeter, and the KaRIn RF subsystem (with support from the UKSA). CSA is providing the KaRIn high-power transmitter assembly. NASA is providing associated launch services.