The Tech Behind Aquarius: NASA's Most Advanced Climate Satellite

Posted 10/11/2011 at 2:43pm | by Gord Goble

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In NASA's salt-seeking probe, new and old come together to show us the future

The Fifth Dimension advised us in its massive chart-topper of 1969 that "This is the dawning of the age of Aquarius." A time when "Peace will guide the planets and love will steer the stars," an era that brings about "the mind's true liberation." And, looking back, we can say with some confidence that many minds certainly experienced at least momentary liberation in the wild and experimental days of the late 1960s.

Today, however, there is an all-new age of Aquarius, one that began on June 10, 2011. It was on that day that NASA, in conjunction with Argentina's Comisión Nacional de Actividades Espaciales (CONAE), launched a Delta II rocket from Southern California's Vandenberg Air Force base.

Atop that rocket sat a spacecraft known as "SAC-D" (Satellite for Scientific Applications-D), a vehicle designed to orbit the earth for many years hence. A vehicle veritably festooned with scientific devices—known as "instruments" in the outer space fraternity—each developed to monitor various activities on or above the earth. A vehicle and payload that will ultimately help scientists better understand our world and what we're doing to it, and that many consider a critical step in the gauging of our future.

That's all well and good, you say, but where's the Aquarius connection? Well, nestled amongst all those instruments - and the high-tech awesomeness they represent - is perhaps the slickest and most important instrument of all: a device that will observe the surface salinity of our oceans and hopefully pave the way to a firmer grasp of climate change.

Dubbed "Aquarius" in honor of the water-bearer constellation, it quickly became the focal point of the mission for many. Inevitably, it was only a matter of time before Aquarius the instrument had also become the erroneous yet popular name of the spacecraft itself.

And that, boys and girls, is how SAC-D became known as Aquarius. Until we put a Millennium Falcon up there, it's one of the spiffiest pseudonyms to ever orbit the earth.

Convoluted naming conventions aside, the SAC-D spacecraft and its cargo are doing a lot of interesting stuff right now, 408 miles above our heads. We recently had a chance to speak with several men intimately familiar with the Aquarius instrument in particular—Principal Investigator Gary Lagerloef, Aquarius Instrument Manager Simon Collins, and Technical Lead for Flight Software Alex Murray—to get a better understanding of the tech behind the headlines. We can confidently say that if you've ever wondered what makes a mission like this tick, you've come to the right place.

We Have Liftoff

Though launched just a few months ago as part of the SAC-D mission, NASA's Aquarius instrument is no newcomer. Not by a long shot. Indeed, says Lagerloef, "We started in the mid-1990s thinking about this stuff. Aquarius was eventually one of two missions (from an original roster of 18 candidates) that were selected in a 2002 call for proposals."

From the very start, the mission has been linked with the Argentine space agency. For SAC-D, CONAE would provide the satellite—and several additional instruments—while NASA would deliver the primary instrument (Aquarius) and the rocket launch. Like many rocket flights, SAC-D was delayed more than once as scientists and designers put together the final pieces. But in 2009, when NASA shipped the Aquarius to Argentina in June for mounting on the assembled satellite, the proverbial ball really began to roll. The finished product was then shipped back in March of 2011, and in June it was space-bound.

As we alluded earlier, Aquarius is but one of several instruments aboard what is very much an international satellite. Other prominent instruments include ROSA (Radio Occultation Sounded for Atmosphere) from the Italian space agency ASI (Agenzia Spaziale Italiana). Essentially a highly sophisticated GPS receiver dedicated to the analysis of climate change, ROSA detects modifications to its signal as it passes through the earth's atmosphere and with that creates atmospheric profiles.

From France's CNES (Centre National d'Études Spatiales) comes two instruments—ICARE and SODAD. The former studies the effect of cosmic radiation on electronics, and the latter observes orbital debris and micrometeorites. Five CONAE instruments complete the picture, including radiometry, imaging, and infrared data collection devices.

Imagine all of these devices working harmoniously together for years in the blackness of space, controlled remotely and without hands-on input, while the craft they inhabit orbits at constant elevation of 408 miles and completes an orbit every 98 minutes (!), and you begin to see the inherent fragility of such a mission.

Dig a little deeper though and the whole thing seems only more incredible.

For one, Alex Murray tells us the core SAC-D spacecraft is…well, not particularly large, at approximately eight feet tall and eight feet wide. Apart from the size—or lack thereof—and all the goodies tagging along for the ride, Murray also points to the cabling as one of the biggest headaches, likening it to the interior of a desktop computer but far, far more complex.

Alex, we PC nerds feel your pain.

Just consider what it takes down here on Earth simply to watch over the spacecraft and its primary instrument. Mission operations in Cordoba, Argentina, handles observatory operations and control, service platform processing and storage, telemetry and stored data processing, orbit maneuvering, and much more. Tracking stations—a total of six—in such far flung locales as Poker Flats, Alaska; McMurdo, Antarctica; Svalbard, Norway; Wallops, Virginia; Matera, Italy; and Malindi, Kenya ensure SAC-D never disappears from view. Ground stations help keep everything together. NASA's Goddard Space Flight Center processes the data it receives from CONAE, and NASA's Physical Oceanography Distributed Active Archive Center disseminates that data.

We could go on, but we think you get the picture.

Yet despite all the earth lifelines, most of what goes on in the SAC-D and in the Aquarius instrument itself is designed to be autonomous. More than that though, it's designed to be long-lasting. Really long lasting. You see, although the mission is pegged as a three-year stint, Gary Lagerloef tells us that as long as something doesn't break down (even spacecraft are privy to unforeseen mechanical foibles as the rigors of time take their toll), the mission will last a whole lot more. "It's a minimum of three years. We'll have achieved our key objectives in three years, but as has been proven in the past, earth sciences satellites can continue doing their job for ten years or more."

Lagerloef points to QuickScat, a satellite launched aboard a U.S. Air Force Titan II launch vehicle in June of 1999 to monitor winds over the world's oceans and in turn help forecast critical stuff like save heights, aviation weather, and last but certainly not least, the development of major storms. QuickScat was thought to have a useful life of two to three years, yet it continued to fully function and relay key data more than a decade later.

Even when its antennae essentially stopped spinning in November of 2009, thus rendering its primary objective defunct, all was not lost. Indeed, QuickScat continues even today to play the role of orbiting Energizer Bunny, albeit in a reduced capacity, cross-calibrating data for other earth sciences spacecraft.