Aquarius is making NASA's first space-based global observations of ocean surface salinity, flying 657 kilometers (408 miles) above Earth in a sun-synchronous polar orbit that repeats every seven days. This NASA Earth System Science Pathfinder mission is mapping global changes in ocean surface salinity with a resolution of 150 kilometers (93 miles), showing how salinity changes from month to month, season to season and year to year. Scientists are combining Aquarius data with in-water measurements to generate operational maps of ocean salinity distribution.