SAC-D (, meaning ''Satellite for Scientific Applications-D''), also known as Aquarius after its primary instrument, is an

Argentine Argentines, Argentinians or Argentineans are people from Argentina. This connection may be residential, legal, historical, or cultural. For most Argentines, several (or all) of these connections exist and are collectively the source of their ...

Earth science

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

built by

INVAP INVAP S.E. is an Argentine company that provides design, integration, construction and delivery of equipment, plants and devices. The company operates in North America, Europe, Asia Pacific, Latin America, the Middle East and Africa, and delivers ...

and operated by

CONAE The National Space Activities Commission (Spanish language , Spanish: ''Comisión Nacional de Actividades Espaciales'', CONAE) is the civilian agency of the government of Argentina in charge of the national space programme. History Sociedad ...

. SAC-D was launched from Vandenberg Air Force Base on 10 June 2011, with a planned mission life of five years. Due to a power system failure, the mission was ended on 8 June 2015.

Description

SAC-D was an international collaboration between the space agencies of Argentina and the United States,

and

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

, with participation from Brazil ( INPE), Canada ( CSA), France (

CNES CNES () is the French national space agency. Headquartered in central Paris, the agency is overseen by the ministries of the Armed Forces, Economy and Finance and Higher Education, Research and Innovation. It operates from the Toulouse Spac ...

) and Italy ( ASI). It carried five Earth observation instruments (NASA, CONAE, CSA, ASI), two space science instruments (CNES), a data collection instrument (CONAE), and a technology demonstration system (CONAE). The spacecraft's main instrument, Aquarius, was built by NASA's Jet Propulsion Laboratory and Goddard Space Flight Center. It collected data from 25 August 2011 to 7 June 2015, exceeding its intended three year primary mission. Aquarius' mission was to demonstrate that accurate measurements of salinity could be made from space, and was the first spaceborne instrument to use both passive radiometers and active radar in the L band. By measuring ocean salinity, scientists are better able to understand the Earth's

water cycle The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth across different reservoirs. The mass of water on Earth remains fai ...

and ocean circulation. Project scientists later derived a method of pulling soil moisture data from Aquarius' radiometer.

Launch

NASA launched SAC-D from

Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg S ...

's Space Launch Complex 2W aboard a

Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...

7320-10C on 10 June 2011 at 14:20:13 UTC. The launch was delayed from May 2010 because development of the spacecraft was taking longer than expected.

Accomplishments

The Aquarius instrument's surface salinity measurements contributed to a better understanding of ocean dynamics and advancing climate and ocean models, both from season to season and year to year. The models still are improving El Niño prediction. Aquarius global salinity maps show how freshwater plumes coming from the mouth of large rivers and the precipitation and evaporation over the oceans affect the salinity structure of the ocean. “The Aquarius sensor collected three years and nine months of valuable data. It was truly a pioneering effort to determine how accurately we could measure ocean salinity from space and for the first time study large and small-scale interactions of the global water cycle.” Aquarius principal investigator Gary Lagerloef of Earth & Space Research, Seattle. Aquarius provided information into the natural exchange of freshwater between the ocean, atmosphere and sea ice, which influences ocean circulation, weather and climate. Data from Aquarius showed how extreme floods affect the seas and how low-salinity river plumes affect hurricane intensity. Aquarius data was important to the Salinity Processes in the Upper Ocean Regional Study (SPURS), a year-long international field study of the oceanographic processes that sustain the maximum surface salinities in the central subtropical North Atlantic, and influence global ocean circulation. The Aquarius instrument successfully achieved its science objectives and completed its primary three-year mission in November 2014.

Failure of spacecraft

On 7 June 2015 at 12:53:17 UTC, telemetry indicated a failure of the spacecraft's Remote Terminal Unit (RTU), causing loss of onboard power regulation and attitude stabilization. While efforts were made to recover the spacecraft, the mission was declared over on 8 June.

Instruments

References

External links

SAC-D website
by CONAE

by INVAP
Aquarius website
by NASA
Aquarius website
by the University of Maine {{Orbital launches in 2011 Spacecraft launched in 2011 Satellites of Argentina Earth observation satellites