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NASA Mission Will Observe Earth's Salty Seas For Climate Clues

May 17, 2011

Steve Cole 
Headquarters, Washington      

Alan Buis 
Jet Propulsion Laboratory, Pasadena, Calif. 

RELEASE: 11-150


WASHINGTON -- Final preparations are under way for the June 9 launch 
of the international Aquarius/SAC-D observatory. The mission's 
primary instrument, Aquarius, will study interactions between ocean 
circulation, the water cycle and climate by measuring ocean surface 

Engineers at Vandenberg Air Force Base in California are performing 
final tests before mating Aquarius/SAC-D to its Delta II rocket. The 
mission is a collaboration between NASA and Argentina's space agency, 
Comision Nacional de Actividades Espaciales (CONAE), with 
participation from Brazil, Canada, France and Italy. SAC stands for 
Satelite de Applicaciones Cientificas. 

In addition to Aquarius, the observatory carries seven other 
instruments that will collect environmental data for a wide range of 
applications, including studies of natural hazards, air quality, land 
processes and epidemiology. 

The mission will make NASA's first space observations of the 
concentration of dissolved salt at the ocean surface. Aquarius' 
observations will reveal how salinity variations influence ocean 
circulation, trace the path of freshwater around our planet, and help 
drive Earth's climate. The ocean surface constantly exchanges water 
and heat with Earth's atmosphere. Approximately 80 percent of the 
global water cycle that moves freshwater from the ocean to the 
atmosphere to the land and back to the ocean happens over the ocean. 

Salinity plays a key role in these exchanges. By tracking changes in 
ocean surface salinity, Aquarius will monitor variations in the water 
cycle caused by evaporation and precipitation over the ocean, river 
runoff, the freezing and melting of sea ice. Salinity also makes 
seawater denser, causing it to sink, where it becomes part of deep, 
interconnected ocean currents. This deep ocean "conveyor belt" moves 
water masses and heat from the tropics to the polar regions, helping 
to regulate Earth's climate. 

"Salinity is the glue that bonds two major components of Earth's 
complex climate system: ocean circulation and the global water 
cycle," said Aquarius Principal Investigator Gary Lagerloef of Earth 
& Space Research in Seattle. "Aquarius will map global variations in 
salinity in unprecedented detail, leading to new discoveries that 
will improve our ability to predict future climate." 

Aquarius will measure salinity by sensing microwave emissions from the 
water's surface with a radiometer instrument. These emissions can be 
used to indicate the saltiness of the surface water, after accounting 
for other environmental factors. Salinity levels in the open ocean 
vary by only about five parts per thousand, and small changes are 
important. Aquarius uses advanced technologies to detect changes in 
salinity as small as about two parts per 10,000, equivalent to a 
pinch (about one-eighth of a teaspoon) of salt in a gallon of water. 

Aquarius will map the entire open ocean every seven days for at least 
three years from 408 miles (657 kilometers) above Earth. Its 
measurements will produce monthly estimates of ocean surface salinity 
with a spatial resolution of 93 miles (150 kilometers). The data will 
reveal how salinity changes over time and from one part of the ocean 
to another. 

The Aquarius/SAC-D mission continues NASA and CONAE's 17-year 
partnership. NASA provided launch vehicles and operations for three 
SAC satellite missions and science instruments for two. Aquarius was 
built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., and 
the agency's Goddard Space Flight Center in Greenbelt, Md. JPL will 
manage Aquarius through its commissioning phase and archive mission 
data. Goddard will manage Aquarius mission operations and process 
science data. NASA's Launch Services Program at the agency's Kennedy 
Space Center in Florida is managing the launch. 

CONAE is providing the SAC-D spacecraft, an optical camera, a thermal 
camera in collaboration with Canada, a microwave radiometer; sensors 
from various Argentine institutions and the mission operations center 
there. France and Italy are contributing instruments. 

For more information about Aquarius/SAC-D, visit: 




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