SWOT Data Products Fully Validated

After years of pre-launch preparation and 18 months of post-launch effort, all science data products from the Surface Water and Ocean Topography (SWOT) mission are fully validated. The data have a temporal range of April 2023 to present and are openly available through NASA Earthdata Search as well as through NASA's Physical Oceanography Distributed Active Archive Center (PO.DAAC) and CNES (Centre National d'Etudes Spatiales, the French space agency). More than 6 petabytes (PB) of SWOT science data products have been generated through the end of July 2024.

"Validation of the SWOT products means that the accuracy of the measurements in the products has been quantified and known limitations have been identified and articulated to users," says Dr. Shailen Desai, NASA's Measurement System Engineer for SWOT, via email. A Data Chat with Desai provides a detailed description of the SWOT calibration and validation (cal/val) process.

Launched on December 16, 2022, SWOT is conducting the first global survey of Earth surface water; acquiring precise measurements of water surface height over the oceans, river, lakes, and reservoirs; and monitoring how those water bodies change over time. The mission is a partnership between NASA and CNES, with contributions from CSA (Canadian Space Agency) and the United Kingdom Space Agency.

The data validation effort included teams from the SWOT project at NASA's Jet Propulsion Laboratory in Southern California and at CNES. The SWOT project also collaborated with teams at various universities that were tasked with collecting airborne and field campaign data to support the mission.

Desai notes that validation was especially challenging due to the use of a first-of-its-kind instrument aboard the satellite to measure the height and extent of water over the ocean and in inland water bodies. The instrument, the Ka-band Radar Interferometer (KaRIn), acquires data with better accuracy and higher spatial resolution than any prior space-based instrument. With no comparable data available with which to compare the KaRIn observations, the SWOT team had to develop novel approaches to validate these global measurements.

Validation efforts will continue through the life of the SWOT mission to further improve the quality of SWOT science data products and resolve known deficiencies. A new version of the products is planned for release in 2025 by reprocessing all available data with additional improvements to the processing methodology.

The release of validated science data products is a significant milestone for the SWOT project and the user community. "With SWOT science data products now validated, users can apply the provided measurements to their scientific research or applications with confidence," says Desai.

Learn More

• Webinar: Accessing Data for the World's Water with SWOT (March 2024)
• PO.DAAC Cookbook: SWOT Data Tutorials
• PO.DAAC Tutorial: How to download PO.DAAC SWOT data using the High-level Tool for Interactive Data Extraction (HiTIDE)
• Workshop: PO.DAAC SWOT Data Access (February 2024)