CAPE CANAVERAL - A NASA satellite being prepared for launch early on Tuesday is expected to reveal details about where carbon dioxide, a greenhouse gas tied to climate change, is being released into Earth's atmosphere on a global scale.
The two-year, $465 million project, known as the Orbiting Carbon Observatory, or OCO, also will be able to pinpoint where the planet's forests and ocean are reabsorbing atmospheric carbon, a cycle that is key to Earth's temperature.
More than 50 years of measurements show that about half the amount of carbon dioxide put into the atmosphere - by natural processes and human activities - end up being reabsorbed. The proportion has remained fairly constant even as the total amount of atmospheric carbon has climbed from concentrations of 315 parts per million in the 1950s to 400 parts per million today, studies by the U.S. National Oceanic and Atmospheric Administration and the Scripps Institution of Oceanography show. (The studies can be found at http://www.esrl.noaa.gov/gmd/obop/mlo/ and at http://keelingcurve.ucsd.edu/ .)
"What's quite remarkable is that over time half of what we've released has been absorbed by the plants or the ocean, but it's very variable from year to year," OCO project manager Ralph Basilio, with NASA's Jet Propulsion Laboratory in Pasadena, California, told reporters during a prelaunch news conference.
"Understanding what controls that variability is really crucial. If we can do that today, it might inform us about what might happen in the future," he said.
The observatory will be positioned 438 miles (705 km) above the planet and inclined so that it passes over the same point on Earth at the same time every 16 days, giving scientists insight into how levels of carbon dioxide change over weeks, months and years.
"The data we will provide will help our decision-makers at both the local and federal levels be better-equipped to understand carbon dioxide's role in climate change because (the observatory) will be measuring this greenhouse globally," Betsy Edwards, program executive at NASA Headquarters in Washington, told reporters.
Because the observatory's target areas will be small - about 1 square mile (3 square km) - scientists expect to be able to pinpoint top carbon emitters, though monitoring is not among the mission's goals.
"In principle we fully expect to be able to see points where there are large emissions, compared to points nearby, but this is really not a mapping mission. This is more of a sampling mission," Basilio said.
NASA hoped to have OCO flying in 2009, but a launch accident claimed the satellite. Congress agreed to fund a replacement, OCO-2, which is scheduled for launch from Vandenberg Air Force Base in California at 5:56 a.m. EDT (0956 GMT) on Tuesday aboard a United Launch Alliance Delta 2 rocket.