Satellite to pinpoint sources and sinks of CO₂

20:59 23 February 2009 by Catherine Brahic, New Scientist
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Update 10.53 GMT According to NASA's website, the mission was not successful. The rocket lifted off from Vandenberg Air Force Base, California, at 0155 PST (0955 GMT) but data received at a later stage of the flight suggested that the fairing -- a part of the rocket intended to reduce drag -- failed to separate. "OCO did not achieve orbit successfully," says George Diller of NASA. "Controllers are checking the status of the spacecraft, to confirm location and orbit. Right now we do know we have not had a successful launch and will not be able to have a successful mission."

At 0151 PST (0951 GMT) on Tuesday, we will be one step closer to understanding how some carbon dioxide ends up building a dangerous greenhouse above our heads, while the rest of it gets sucked into the bowels of the Earth.

That is the planned launch time for NASA's new climate-monitoring instrument, the Orbiting Carbon Observatory, which will blast off from California's Vandenberg Air Force Base. (You can watch the launch on NASA TV.)

What is the Orbiting Carbon Observatory?

The OCO is NASA's latest climate-spying satellite. Despite the amount of attention that climate science receives, it is the first satellite to monitor precisely where and when carbon dioxide is being emitted and where and when it is being absorbed.

Hopefully, it should be able to pinpoint Earth's mysterious "missing" carbon. Humans currently emit 8.5 billion tonnes of carbon each year, mostly as carbon dioxide. Not all of that ends up in the atmosphere.

In fact, of all the carbon emitted since the dawn of the Industrial Revolution, just 40% has accumulated above our heads and built up the greenhouse effect. The remaining 60% has been absorbed by carbon 'sinks' -- natural reservoirs on land and at sea where carbon is stored away as organic material, like trees and plankton. When scientists measured how much carbon has ended up in the world's oceans, they found just half of that 60%. The other 30% is still missing, presumably stored away in a land-sink.

How will the OCO improve on existing observations?

Most data on the sources and sinks of carbon dioxide is collected from instruments mounted on aeroplanes and land-based towers at some 100 locations around the globe. The problem is these measurements are neither systematic nor comprehensive -- they do not cover the entire planet. For instance, it's impossible to know just how much carbon dioxide is absorbed in the middle of the Pacific Ocean or the Amazon rainforest and how that changes from year to year or between seasons.

That's a problem because oceans and large tropical forests are the biggest carbon sinks on Earth. Not knowing exactly how they suck up carbon, and in what quantities, means we don't know the true impacts of deforestation, among other things.

How will the OCO make its measurements?

It will use spectrometers to measure the intensity of sunlight that is reflected off the Earth. Different gas molecules in the atmosphere, such as CO₂, absorb radiation at specific wavelengths. So scientists will use the OCO to look for the "molecular fingerprints" of this absorption in sunlight that has bounced off the Earth's surface. It will focus on layers of the atmosphere at altitudes lower than 5 kilometres -- which is to say, right above the carbon sources and sinks.

How will the satellite fit into other climate-monitoring programmes?

A Japanese instrument called the Greenhouse gases Observing Satellite, or GOSAT, launched on 23 January. Together, GOSAT and OCO will give scientists an unprecedented map of CO₂'s fate.

OCO will also be part of a lineup of NASA satellites called the "A train." The satellites follow each other, measuring different aspects of the climate, such as humidity and temperature, building up an increasingly complete picture of what makes Earth tick.

Link to article: http://www.newscientist.com/article/dn16650-satellite-to-pinpoint-sources-and-sinks-of-co2.html