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NASA's Aquarius Launched To Help Map the Oceans' Salt
oxide7 writes "NASA launched a satellite featuring an brand-new instrument which will be able to measure the saltiness of Earth's oceans. Data from the Aquarius/SAC-D spacecraft will help scientists understand better the processes that drive ocean circulation and the movement of freshwater around the planet."
But, the ocean is in the other direction!
rewriting history since 2109
This is Slashdot. It's ok to use words like "salinity" in the summary.
That would be one hell of a fast boat.
Learning HOW to think is more important than learning WHAT to think.
or, perhaps, really big.
rewriting history since 2109
Salinity and temperature are the only things that alter the energies emitted and reflected by the ocean at certain centimetre wavelengths (frequency, 1.43 GHz). The atmosphere is almost transparent - no pesky gas, cloud or mostly rain. After that, you've got to model the galactic radiation which is also reflected and causes a lot of problems- luckily it's well known as it doesn't alter quickly very often.
BTW, the NASA Aquarius web site talks sheer nonsense that this is first salinity satellite. SMOS, launched by ESA, has been mapping the seas for a year or more.
http://oceancolor.gsfc.nasa.gov/WIKI/AQ(2f)GS(2f)AquariusInstrumentDescription.html
The instrument is a kind of radar called a scatterometer. It measures the amount of L-band (1400 MHz-ish) power reflected back by the ocean's surface. If you compare the amount scattered back in Horizontal and Vertical polarization, you can tell the dielectric properties of the water (mostly conductivity changes). In general, the reflection in vertical polarization (perpendicular to the surface) is more strongly affected by epsilon (dielectric constant) than horizontal pol, and both change with angle of incidence. (why polarized sunglasses help looking into water, block the Hpol and you get rid of most of the reflection)
The challenge is in measuring the very small changes, so the instrument has a variety of schemes to calibrate out changes in transmitter power, atmospheric losses, receiver gain, etc. (not to mention that the sea surface roughness has an effect.. a frosted window reflects a different amount of light than a shiny smooth one).
For EE geeks, think of an instrument like this as flying a VNA with a measurement uncertainty 0.1dB.
$287 million. It was paid for by NASA and CONAE, the Argentine space agency. The satellite was built by Argentina and tracking and control are CONAE's responsibility, not NASA's.
But don't worry, next year Argentina will be testing their own rocket (Tronador II), so you won't have to worry about spending money for NASA next time Argentina wants to put a sat in orbit.
The following is a link to a blog set up by NASA scientists. It describes what the satellite will see and why it is important. http://www.realclimate.org/index.php/archives/2011/06/the-age-of-aquarius/
This project was funded and executed largely by Argentinia. The U.S is in a sad place when Americans are chanting "he'll no we can't!" and Argentina (of all places) is picking up the slack.
I am. Born and raised in New England.
And I am mad as hell at what they've done to my country.
--
BMO
The Aquarius/SAC-D salinity-sensing instrument is not exactly brand-new. It is an L-band microwave radiometer based on the same principle as the one on the SMOS satellite launched in October 2009. Still, it helps to have more satellites monitoring the oceans.
Whenever I think of a spacecraft named "Aquarius," I think of the LM that the Apollo 13 astronauts used as a lifeboat to survive the trip back to Earth after their Service Module was damaged after launch. After delivering those astronauts safely back to LEO and being heroically jettisoned into the atmosphere to meet her demise, that spacecraft deserved to have its name retired.
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