The universe is thought to harbor uncounted worlds that are home to water. The one we know best, of course, is our own, and as of 3:46 a.m. PT this morning, we set about working to know it better still. That was the moment, as NASA reports, that the SWOT (Surface Water and Ocean Topography) satellite blasted off aboard a SpaceX Falcon 9 rocket to begin a three year campaign to study the height and health of freshwater bodies and oceans across 90% of the Earth’s surface.

Jointly built by NASA and the Centre National d’Études Spatiales (CNES), the French space agency, SWOT will monitor the entire Earth’s surface between 78 degrees north latitude and 78 degrees south latitude—from the Arctic Circle to the Antarctic Circle—once every three weeks, …