The first mission to survey nearly all of the water on Earth’s surface has launched.

The international Surface Water and Ocean Topography mission, known as SWOT, lifted off aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California at 6:46 a.m. ET on Friday. The first stage of the rocket successfully landed back on Earth at 6:54 a.m. ET.

Live coverage began on NASA’s website at 6 a.m. ET.