NASA’s Space Observatory to provide global measurements of CO2

An artist’s concept of the Orbiting Carbon Observatory Photo: NASA/JPL.

An artist’s concept of the Orbiting Carbon Observatory Photo: NASA/JPL..

February 5, 2009 NASA’s NASA’s Orbiting Carbon Observatory spacecraft and its Taurus XL launch vehicle are undergoing preparations for liftoff on February 23. The Orbiting Carbon Observatory’s mission is to collect precise global measurements of carbon dioxide (CO2) in the Earth's atmosphere to improve our understanding of the natural processes and human activities that regulate the abundance and distribution of this important greenhouse gas - important because its the leading human-produced greenhouse gas driving changes in Earth's climate. This improved understanding will enable more reliable forecasts of future changes in the abundance and distribution of CO2 in the atmosphere and the effect that these changes may have on the Earth's climate.

The Orbiting Carbon Observatory will provide the first complete picture of human and natural carbon dioxide sources as well as their "sinks," the places where carbon dioxide is pulled out of the atmosphere and stored. It will map the global geographic distribution of these sources and sinks and study their changes over time. The measurements will be combined with data from ground stations, aircraft and other satellites to help answer questions about the processes that regulate atmospheric carbon dioxide and its role in Earth's climate and carbon cycle. This will help scientists reduce uncertainties in predicting future carbon dioxide increases and make more accurate climate change predictions.

Of all the carbon humans have added to Earth's atmosphere since the start of the Industrial Revolution, only about 40 percent has remained in Earth's atmosphere. About half of the remaining 60 percent can be accounted for in Earth's ocean. The rest must have been absorbed somewhere on land, but scientists cannot yet determine specifically where this is taking place or what controls the efficiency of these land sinks. Scientists refer to this as the "missing" carbon sink and it is hoped the Orbiting Carbon Observatory can help shed some light on the conundrum.

The new observatory will collect about 8 million measurements every 16 days for at least two years with the precision, resolution and coverage needed to characterize carbon dioxide's global distribution. Scientists need these precise measurements because carbon dioxide varies by just 10 parts per million throughout the year on regional to continental scales. The Observatory's three high-resolution spectrometers spread reflected sunlight into its various colors like a prism. Each spectrometer focuses on a different, narrow color range, detecting light with the specific colors absorbed by carbon dioxide and molecular oxygen. The less carbon dioxide present in the atmosphere, the more light the spectrometers detect so by analyzing the amount of light, scientists can determine relative concentrations of these chemicals. The data will then be input into computer models of the global atmosphere to quantify carbon dioxide sources and sinks.

The Orbiting Carbon Observatory will be launched on a Taurus XL rocket into a 438-mile near-polar orbit on February 23 and will lead five other NASA satellites that cross the equator each day shortly after noon, making a wide range of nearly simultaneous Earth observations.

Darren Quick

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