Aquarius/Satélite de Aplicaciones Científicas (SAC)-D observatory

NASA's Aquarius instrument was a suite of three radiometers that used microwave readings to measure thermal emissions from the ocean surface, which could be correlated with ocean salinity. It was the primary instrument aboard the Satélite de Aplicaciones Científicas (SAC)-D observatory, a collaborative effort with CONAE, Argentina's space agency.

Aquarius studied variations in ocean salinity and how they were connected to changes in the global water cycle. It made NASA's first space-based global observations of ocean salinity at the surface, flying 657 kilometers (408 miles) above Earth in a polar orbit. It repeated the orbit every seven days, mapping monthly, seasonal and yearly changes in salinity with a resolution of 150 kilometers (93 miles).

Aquarius helped generate operational maps of ocean salinity distribution.