December 7, 2008
NASA Plans Launch Of Space Probe To Measure CO2 Levels
The often contentious debate about global warming has been absent a critical component: an accurate measurement of precisely how much carbon dioxide (CO2) is in the air, and how it is being recycled by the planet.
To address the matter, NASA will embark on a new mission early next year called the Orbital Carbon Observatory (OCO).
"We will uncover all kinds of patterns and cycles in carbon dioxide that people never thought existed. It'll be just like when the first ozone measurements were made," said project scientist Chip Miller with the Jet Propulsion Laboratory (JPL) in Pasadena, CA, during an interview with the Discovery News.
"We get at the question of the sources of carbon dioxide and see how much is pulled out (of the atmosphere) by land and how much by seas."
Levels of CO2 are considered by many scientists to be the central indicator of global warming. CO2 traps reflected sunlight, and there is little that can remove the gas once it is emitted into the atmosphere. Plants, soils and the oceans can reabsorb CO2, but the process takes time.
According to Miller, the average lifetime for carbon dioxide is about 300 years, with roughly 20 percent of atmospheric carbon dioxide lasting 10,000 years or longer.
About 97 percent, or roughly 300 billion metric tons per year, of CO2 comes from natural sources such as decaying plants, breathing animals, forest fires, volcanic eruptions and other naturally occurring events. The remaining three percent, about 8 billion metric tons per year, is derived from human activities such as burning coal, driving cars, farming, industrial production and other practices.
While three percent may not sound significant, there is widespread consensus that CO2 emissions from human practices are responsible for raising the Earth's temperature.
"It's such a small portion, but it does seem to be tilting the balance," said Miller.
The missing piece of the puzzle, however, is precise measurements of the amount of carbon being emitted into the atmosphere and the amount coming out.
It's a difficult measurement to obtain, and so far the data has been derived from roughly 100 ground sites throughout the world and from rough extrapolations from sales of oil, coal and natural gas. The presumption is that these fuels would ultimately be burned, releasing CO2 into the atmosphere. However, not all countries provide such sales information.
Despite the challenges in gathering precise figures, scientists believe the economic data is accurate to within 10 percent.
"When we add together what we know about the system, we can't account for about 2 billion metric tons from the atmosphere," Miller told Discovery News.
"Balancing the carbon budget is one of the key things that scientists are trying to do now," he added.
"This is an absolutely critical question," said David Crisp, the OCO's lead scientist.
"Where is the other half of the carbon dioxide that we emit into the air going over time and will the Earth continue to absorb (it) as we go into the future?" he said during an interview with Discovery News.
Measuring carbon dioxide is a complicated task. The OCO will utilize three high-resolution spectrometers to study sunlight reflected off the
Earth at the precise wavelengths that indicate the presence of carbon dioxide and molecular oxygen.
The observatory is sensitive enough to distinguish CO2 columns within an area as small as three square kilometers. The program's goal is to locate areas with CO2 concentrations less than 1 part per million different than background levels, which are typically about 383 parts per million.
"Our goal is to identify, on regional scales, where this atmospheric CO2 is actually going," said Ralph Basilio, OSO deputy project manager.
"These measurements have never been made from space before with this accuracy," said Miller.
"We are a pathfinder, we are the first to try to demonstrate how this could be done."
OCO will fly over the planet in a 483-mile-high orbit in 16-day cycles. It will be synchronized with the sun such that it is always 1:26 p.m. on the ground below. Measurements will not be able to reach all the way to the ground on cloudy days. However, over time, scientists expect to gather enough data to identify sources of CO2 and absorption spots, called sinks.
The spacecraft will store the data and transmit the information once each day to a collecting station in Alaska. From there it will be sent to NASA's Goddard Space Flight Center in Maryland for processing, with analysis taking place at JPL and other locations.
Once in its proper position, OCO will operate in formation with five other Earth-monitoring spacecraft, known as the "A-Train," or afternoon constellation. The "A-Train" crosses the equator shortly after noon each day.
"We'll be able to create new and even more interesting data products," said Miller.
NASA is targeting a January 30 launch of the OCO from California's Vandenberg Air Force Base. The observatory, along with its launch on an Orbital Sciences' Taurus booster and two years of operation, are expected to cost NASA about $270 million.
Image Courtesy Of NASA
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