"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." "This is an absolutely critical question," added David Crisp, the lead scientist for the Orbital Carbon Observatory, or OCO. "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?" Measuring carbon dioxide is not an easy task. OCO will attempt the work by using three high-resolution spectrometers to study sunlight reflected off Earth at the precise wavelengths that reveal the presence of carbon dioxide and molecular oxygen. The observatory is sensitive enough to identify columns of carbon within an area as small as about three square kilometers. The goal is to find the areas where the concentration of carbon dioxide is less than 1 part per million different than overall background levels of carbon dioxide, which are about 383 parts per million. "Our goal is to identify, on regional scales, where this atmospheric CO2 is actually going," said deputy project manager Ralph Basilio. "These measurements have never been made from space before with this accuracy," Miller added. "We are a pathfinder, we are the first to try to demonstrate how this could be done." OCO will fly over the planet in 16-day cycles from a 483-mile-high orbit in sync with the sun so that it is always the same time of day on the ground below -- 1:26 p.m. On cloudy days, the measurements will not be able to reach all the way to the ground, but over time, scientists expect to collect enough data to identify particular sources of carbon dioxide and absorption spots, known as sinks. Information will be stored on the spacecraft and radioed once a day to a collecting station in Alaska, then relayed to NASA's Goddard Space Flight Center in Greenbelt, Md., for processing. Analysis will take place at JPL and other science centers involved in the project. Once in position, OCO will operate in formation with five other Earth-monitoring spacecraft that comprise what is called the "A-Train," or afternoon constellation, which cross the equator shortly after noon every day. "We'll be able to create new and even more interesting data products," Miller said. NASA is paying about $270 million for the observatory, its launch on an Orbital Sciences' Taurus booster and two years of operation. Launch is targeted for Jan. 30 from Vandenberg Air Force Base in California.
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