Aquarius/SAC-D Observatory Will Study Ocean Circulations
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
salinity.
NASA Artists' Image
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.
SAC-D Satellite Being Prepared For Shipping
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, and 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 above the Earth. Its measurements
will produce monthly estimates of ocean surface salinity with a
spatial resolution of 93 miles. 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.