Aquarius to Study the Power of Sea Salt   
   June 7, 2011: A new observatory is about to leave Earth to map a powerful   
   compound of global importance: Common everyday sea salt.   
       
   An artist's concept of Aquarius/ SAC-D in orbit. [more] Researchers suspect   
   that the salinity of Earth's oceans has far-reaching effects on climate, much   
   as the salt levels within our bodies influence our own delicate internal   
   balance. An international team of scientists from NASA and the Space Agency of   
   Argentina, or CONAE, will investigate this possibility with the aid of a   
   satellite named "Aquarius/SAC-D," scheduled to launch on June 9th.   
       
   "Based on decades of historical data gathered from ocean areas by ships and   
   buoys, we know the salinity has changed over the last 40 years," says Aquarius   
   principal investigator Gary Lagerloef. "This tells us there's something   
   fundamental going on in the water cycle."   
       
   Salinity is increasing in some ocean regions, like the subtropical Atlantic,   
   which means more fresh water is being lost through evaporation at the sea   
   surface. But no one knows why this is happening; nor can anyone pinpoint why   
   other areas are experiencing more rainfall and lower salinity. To solve these   
   mysteries, scientists need a comprehensive look at global salinity.   
       
   Within a few months, Aquarius will collect as many sea surface salinity   
   measurements as the entire 125-year historical record from ships and buoys.   
   [...]   
   A NASA video explains the role of ocean salinity in Earth's water cycle.   
       
   "Salinity, along with temperature, governs the density of seawater," says   
   Lagerloef. "The saltier the water, the denser it is, and density drives the   
   currents that determine how the ocean moves heat around the planet. For   
   example, the Gulf Stream carries heat to higher latitudes and moderates the   
   climate. When these currents are diverted by density variations, weather   
   patterns such as rainfall and temperature change."   
       
   Scientists have gathered an ensemble of measurements over the ocean--e.g.,   
   wind speed and direction, sea surface heights and temperatures, and rainfall.   
   But these data do not provide a complete picture.   
       
   "We've been missing a key element - salinity," says Lagerloef. "A better   
   understanding of ocean salinity will give us a clearer picture of how the sea   
   is tied to the water cycle and help us improve the accuracy of models   
   predicting future climate."   
   [...]   
   A pre-launch view of the Aquarius radiometer. [more] Aquarius is one of the   
   most sensitive microwave radiometers ever built, and the first NASA sensor to   
   track ocean salinity from space.   
       
   "It can detect as little as 0.2 parts salt to 1,000 parts water -- about the   
   same as a dash of salt in a gallon of water. A human couldn't taste such a low   
   concentration of salt, yet Aquarius manages to detect it while orbiting 408   
   miles above the Earth."   
       
   The Aquarius radiometer gets some help from other instruments onboard the   
   satellite. One of them helps sort out the distortions of the choppy sea.   
   CONAE's Sandra Torrusio, principal investigator for the Argentine and other   
   international instruments onboard, explains:   
       
   "One of our Argentine instruments is another microwave radiometer in a   
   different frequency band that will measure sea surface winds, rainfall, sea   
   ice, and any other 'noise' that could distort the Aquarius salinity   
   measurement. We'll subtract all of that out and retrieve the target signal."   
       
   Torrusio is excited about the mission.   
       
   "I've met so many new people, not only from Argentina, but from the US and   
   NASA! It's been a great experience to work with them and exchange ideas. We   
   may come from different places, but we all talk the same language. And it   
   isn't English - it's science."   
       
   Working together, these international "people of science" will tell us more   
   about the ocean's role in our planet's balance - and in our own - no matter   
   where we live.   
       
   For whatever we lose (like a you or a me),   
   It's always our self we find in the sea.   
   (e.e. cummings)"   
       
   Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Aquarius/SAC-D: This multipurpose observatory continues the long-standing   
   partnership between NASA and the Argentine Comisi¢n Nacional de Actividades   
   Espaciales, or CONAE. NASA provided launch vehicles and science instruments,   
   while CONAE contributes the spacecraft, mission operations, and science   
   instruments for their national space program. The NASA Aquarius instrument to   
   measure ocean salinity is the prime instrument on the Aquarius/SAC-D mission.   
   JPL will manage the NASA Aquarius implementation through its commissioning   
   phase and archive mission data. Goddard will manage Aquarius instrument   
   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.   
       
   SAC stands for Sat‚lite de Aplicaciones Cient¡ficas. This is "D" in this   
   series of four science application satellites Argentina has built in   
   collaboration with NASA.   
       
   A radiometer is essentially a sensitive radio receiver, which, in this case,   
   detects natural microwave emissions given off by the ocean's surface. The   
   Aquarius radiometer scans the sea surface to measure the emitted power in a   
   certain frequency band (1400-1430 MHz) that is proportional to the water's   
   salt content.   
       
   There are an average of 35 parts per thousand of salt in the ocean (this ratio   
   varies from 32-37 in open ocean areas). That is, the ocean is 3 1/2 percent   
   salt, and in 1 kilogram seawater there's about 35 grams of salt. Since   
   salinity levels in the open ocean vary by only about five parts per thousand,   
   the instrument must be very sensitive.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.62   
    * Origin: NCS BBS (1:3828/7)