Workers at Vandenberg Air Force Base prepare to offload the Aquarius/SAC-D spacecraft from a U.S. Air Force plane.

Workers at Vandenberg Air Force Base in California prepare to offload the Aquarius/SAC-D spacecraft from a U.S. Air Force C-17 transport plane. The aircraft traveled from Campos, Brazil. Following final tests, the spacecraft will be integrated to a United Launch Alliance Delta II rocket in preparation for the targeted June launch to low Earth orbit.

Aquarius, the NASA-built primary instrument on the SAC-D spacecraft, will map global changes in salinity at the ocean's surface. Salinity is a key measurement for understanding how changes in rainfall, evaporation and the melting of freezing of ice influence ocean circulation and are linked to variations in Earth's climate. The three-year mission will provide new insights into how variations in ocean surface salinity relate to these fundamental climate processes. Photo credit: VAFB/30th Space Wing