Editing Aquarius (SAC-D instrument)

{{short description|NASA instrument aboard the Argentine SAC-D spacecraft}}

{{use mdy dates|date=September 2021}}

'''Aquarius''' was a [[NASA]] instrument aboard the [[Argentina|Argentine]] [[SAC-D]] spacecraft.<ref name="instruments">{{cite web|url=http://www.conae.gov.ar/eng/satelites/sac-d_instrum.html |title=Aquarius/SAC-D Instruments |publisher=CONAE |access-date=January 6, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20090326064501/http://www.conae.gov.ar/eng/satelites/sac-d_instrum.html |archive-date=March 26, 2009 }}</ref> Its mission was to measure global sea surface [[salinity]] to better predict future [[climate]] conditions.<ref name="overview">{{cite web|url=http://aquarius.nasa.gov/overview-mission.html|title=Aquarius Mission Overview|last=NASA [[Goddard Space Flight Center]]|date=June 1, 2009|publisher=NASA|access-date=June 2, 2009|archive-url=https://web.archive.org/web/20090605055518/http://aquarius.nasa.gov/overview-mission.html|archive-date=5 June 2009|url-status=dead}}</ref>

Aquarius was shipped to Argentina on June 1, 2009 to be mounted in the [[INVAP]] built SAC-D satellite.<ref name="ships">{{cite web|url=http://climate.jpl.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=70|title=Salt-seeking ocean sensor to ship south|last=NASA JPL|date=June 1, 2009|publisher=NASA|access-date=June 2, 2009| archive-url= https://web.archive.org/web/20090604073257/http://climate.jpl.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=70| archive-date= 4 June 2009 | url-status= live}}</ref> It came back to [[Vandenberg Air Force Base]] on March 31, 2011.<ref name="return">{{cite web|url=http://aquarius.nasa.gov/news-status.html|title=Aquarius Space Craft Return to US|date=March 31, 2011|publisher=NASA|access-date=May 11, 2011|url-status=dead|archive-url=https://web.archive.org/web/20110518102604/http://aquarius.nasa.gov/news-status.html|archive-date=May 18, 2011}}</ref>

For the joint mission, Argentina provided the SAC-D spacecraft and additional science instruments, while NASA provided the Aquarius salinity sensor and the rocket launch platform. The National Aeronautics and Space Administration (NASA)'s [[Jet Propulsion Laboratory]] in Pasadena, California, managed the Aquarius Mission development for NASA's Earth Science Enterprise based in Washington, D.C., and NASA's Goddard Spaceflight Center in Greenbelt, Maryland, is managing the mission after launch.<ref>{{cite web |url=http://www.esr.org/aquarius_sat/aquarius_main.html |title=Aquarius / SAC-D Satellite Mission |publisher=Earth & Space Research (ESR) |access-date=October 5, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20090426014307/http://www.esr.org/aquarius_sat/aquarius_main.html |archive-date=April 26, 2009 }}</ref>

The observatory was successfully launched from Vandenberg Air Force Base on June 10, 2011. After its launch aboard a [[Delta II]] from Vandenberg Air Force Base in [[California]], SAC-D was carried into a 657&nbsp;km (408&nbsp;mi) [[Sun-synchronous orbit]] to begin its 3-year mission.<ref name="overview"/>

On June 7, 2015, the [[SAC-D]] satellite carrying Aquarius suffered a power supply failure, ending the mission.<ref>{{cite web|url=http://aquarius.umaine.edu/cgi/status_more.htm?id=116|title=Aquarius end of mission announcement|publisher=Gary Lagerloef and Sandra Torrusio|access-date=August 24, 2015|archive-date=March 13, 2017|archive-url=https://wayback.archive-it.org/all/20170313180530/http://aquarius.umaine.edu/cgi/status_more.htm?id=116|url-status=dead}}</ref>

==Background and instrumentation==

The spacecraft's mission is a joint program between the National Aeronautics and Space Administration (NASA) and Argentina's space agency, Comisión Nacional de Actividades Espaciales (CONAE). The Aquarius sensors are flown on the (now inoperative) Satélite de Applicaciones Científicas (SAC)-D spacecraft 657 kilometers (408 miles) above earth in a sun-synchronous, polar orbit that repeats itself once a week. Its instrument resolution was 150 kilometers (93 miles).

Aquarius objective was to provide insight into the effect of salt on the Earth's weather and climate systems by making the first space based observations of variations in salinity and creating global ocean salinity distribution maps. Data from the instrument will be able to show changes in the ocean's salinity on monthly, yearly and seasonal time scales.

Oceanographers use the [[Practical Salinity Scale]] (PSS) to measure salinity based on measurements of temperature, pressure and seawater conductivity and create a ratio. The PSS compares the conductivity ratio of a sample of seawater to a standard KCl solution. The oceanic average sea surface salinity is about 35 PSS (or 3.5% salt) and varies globally from 32 to 37 PSS. The Aquarius mission goal is to measure changes in salinity of 0.2 PSS.<ref name="aquarius.umaine.edu">{{cite web |url=http://aquarius.umaine.edu/docs/Aquarius_Mission_Brochure_508_Compliant.pdf |title=Aquarius / SAC-D Sea Surface Salinity from Space |access-date=November 22, 2013}}</ref>

Aquarius measured sea surface salinity by using [[Microwave radiometer|radiometers]] to detect changes in the oceans microwave thermal emissions frequencies due to salinity. Aquarius' three radiometers have antenna reflectors 2.5 meters (8.2 feet) in diameter that are able to scan a 390 kilometer (242 mile) wide swath of the ocean's surface collectively. The radiometers on Aquarius are the most accurate ever and were able to sense at a frequency of 1.4&nbsp;GHz.<ref name="aquarius.umaine.edu"/>

Raw data records from the Aquarius instrument was transmitted from CONAE to the ground station at NASA's [[Goddard Space Flight Center]] (GSFC) in Greenbelt, MD. The CONAE ground station is located in Córdoba, Argentina, where mission operations are conducted, data is processed and instrument operations are held. The processed data will create salinity related data products that will be archived for use by NASA's Physical Oceanography Distributed Active Archive Center (PO.DAAC) in Pasadena, CA's Jet Propulsion Laboratory (JPL).

==Observations and future research==

[[File:AquariusFirstImage.jpg|300px|thumb|right|Ocean Salinity Map developed with Aquarius' first light data]]

[[File:Aquarius flat 2048x1024.ogv|300px|thumb|The NASA Aquarius instrument aboard Argentina's SAC-D satellite is designed to measure global sea surface salinity. This movie shows salinity patterns as measured by Aquarius from December 2011 through December 2012. Red colors represent areas of high salinity, while blue shades represent areas of low salinity. It is important to understand salinity, the amount of dissolved salts in water, because it will lead us to better understanding of the water cycle and can lead to improved climate models. High concentrations (over 37 practical salinity units) are usually in the center of the ocean basins away from the mouths of rivers, which input fresh water. High concentrations are also in sub-tropical regions due to high rates of evaporation (clear skies, little rain, and prevailing winds) and in landlocked seas in arid regions. At high latitudes, salinity is low. This can be attributed to lower evaporation rates and the melting of ice that dilutes seawater. To sum up, salinity is low where precipitation is greater than evaporation, mainly in coastal or equatorial regions. Credit: NASA/GSFC/JPL-Caltech]]

ocean's surface produced by NASA.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/aquarius/news/aquarius20110922.html |title=Aquarius Yields NASA's First Global Map of Ocean Salinity |date=September 22, 2011 |publisher=NASA |access-date=October 5, 2011}}</ref> The first salinity maps from space were provided by the European Space Agency satellite [[Soil Moisture and Ocean Salinity satellite|SMOS]] (Soil Moisture and Ocean Salinity) that was launched in November 2009.<ref>{{cite web|title=ESA - Living Planet Programme - SMOS - ESA's water mission SMOS|url=http://www.esa.int/esaLP/ESAMBA2VMOC_LPsmos_0.html|access-date=6 December 2011}}</ref> Previous satellites enabled measurement of ocean currents, [[sea surface temperature]] and winds, and ocean color. Aquarius adds the ability to measure another ocean variable &ndash; the salt content. Measuring sea surface salinity (SSS) will supplement other satellite observations of the global [[water cycle]]: precipitation, evaporation, soil moisture, atmospheric water vapor, and sea ice extent.<ref>{{cite web |url=http://aquarius.nasa.gov/overview-benefits.html |title=Overview: Benefits |work=Aquarius |date=September 23, 2011 |publisher=NASA |access-date=October 5, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111017035216/http://aquarius.nasa.gov/overview-benefits.html |archive-date=October 17, 2011 }}</ref>

In the past, salinity measurements have been taken using instruments in buoys and on ships, however the measurements are inconsistent and don't provide accurate data over large temporal and spatial regions. Aquarius' ability to consistently map the oceans enables scientists to create more advanced computer models to study sea surface salinity and potentially forecast future climate conditions.

{{Include-NASA}}

*[https://web.archive.org/web/20071117132432/http://aquarius.nasa.gov/ Aquarius Mission Web Site]

*[https://science.nasa.gov/missions/aquarius/ NASA science missions &ndash; Aquarius]

[[Category:Earth observation satellite sensors]]

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