The satellite will use three fast, high-resolution spectrometers to measure the amount of CO2 between the satellite and the ground. The satellite will travel at 7 kilometers per second, and will take snapshots of CO2 levels three times a second, so each snapshot will cover a stretch about 2.5 kilometers long. The spectroscopy systems used on other satellites are much slower: their exposures take longer, so they sample a longer stretch–about 50 kilometers, Crisp says. The faster timing will allow the satellite to better see small gaps between clouds that would otherwise block the measurements. The satellite has a near-polar orbit, circling the earth in a north-south orientation. As the OCO orbits, the earth spins beneath it, so that on each pass, the satellite sees a different swath of earth.
“It’s going to be a vast increase in the amount of data that carbon-cycle scientists have had to work with,” says Britton Stephens, who studies the emissions and absorption cycles of CO2 at the National Center for Atmospheric Science, in Boulder, CO. “It’s really going to revolutionize the way they do their work.”
Once scientists have analyzed the data, it could have direct policy implications, Stephens says. The results could suggest, for example, how much emphasis should be placed on giving countries incentives to leave forests intact. Or the results might suggest the need to act more quickly to reduce CO2 emissions.
The satellite will also give researchers a better sense of carbon emissions from sources other than burning fossil fuels. While scientists have an accurate understanding of how much CO2 is emitted by sources such as power plants and automobiles, they don’t know much about emissions from burning firewood or other biomass, or from clearing land for agriculture with “slash and burn” techniques. The satellite could therefore provide a clearer picture of how much a given country is emitting altogether, which could be important for enforcing emissions treaties. “Countries will claim reductions in their emissions in order to get credit for them. Who’s checking on those claims? How do you check them? The only way is to measure this greenhouse gas around the world. As far as society is concerned, that’s the greatest potential value of this satellite,” Prinn says.
But long-term monitoring will likely have to come from future projects, he says. The satellite is only designed to last two years, and it lacks the redundant systems needed to keep it going if some components fail, says Mike Miller, head of the earth-sciences satellite group at Orbital Sciences, based in Dulles, VA. Orbital Sciences is the company that built the satellite and will launch it. (NASA’s JPL developed the instruments onboard the satellite.)
However, if the OCO validates the spectroscopy approach to measuring CO2 levels, similar satellites could follow the OCO’s lead. The recent economic stimulus bill could help too, since it includes nearly a billion dollars for NASA and the National Oceanic and Atmospheric Administration (NOAA).