Aquarius/SAC-D, an international spacecraft that will measure ocean surface salinity, arrived March 31 at Vandenberg Air Force Base in California in preparation for a June 9 launch aboard a United Launch Alliance Delta 2 rocket.

The spacecraft, which left São José dos Campos, Brazil, March 28, is a collaboration between NASA and Argentina’s Conae space agency. Other participants include Brazil, Canada, France and Italy.

Aquarius, the NASA-built primary instrument on Argentina’s SAC-D satellite, will map global changes in the concentration of dissolved salt at the ocean surface. The measurements will help scientists understand how changes in rainfall, evaporation and the melting or freezing of ice influence ocean circulation.

The Aquarius instrument, built by NASA’s Jet Propulsion Laboratory and Goddard Space Flight Center under the agency’s Earth System Science Pathfinder program, will measure ocean surface salinity by sensing thermal microwave emissions from the water’s surface with a radiometer.

The Aquarius/SAC-D craft will fly in a 656-kilometer high polar orbit where it will map the global ocean once every seven days.