Zigzagging around the globe on a jet may not sound like the most environmentally-friendly activity, but environmental science professor Steven C. Wofsy and his team are doing just that in an effort to measure the carbon dioxide concentration in the atmosphere.

A modified plane, outfitted with equipment, technicians, and scientists, will make five flights by 2011 as part of a $4 million, three-year mission to collect samples of air from different parts of the world. The first round of flights began Friday and is scheduled to be finished by the end of January.

“What we will get out of this is a chemical picture of the atmosphere like you were slicing an orange and get[ting] a cross section of the orange,” said Wofsy, speaking from a Federal Aviation Association hanger in Anchorage, Alaska. “If you take a slice of the middle, you see all kinds of wonderful structures that tell you how it is put together and how it functions.”

During the first leg of the mission, the crew will go from Colorado to Montana to Alaska to New Zealand to the American Samoa to the South Pole to Tahiti to Easter Island to Costa Rica and then back to Colorado.

The first two parts of the mission, Montana and Alaska, have been successfully completed, Wofsy said, adding that the researchers found “a very marked difference between the air you find in the United States and the arctic.”

Unlike satellite imagery, the previous source of data on carbon dioxide concentrations, the plane will be able to collect actual samples of the air and from a much closer range.

“We are interested in the sources of the gases from the ocean, China, and North America,” Wofsy said. “We know which countries are emitting—we are trying to see how much. We are not trying to point fingers.”

The plane collects data through four different “classes,” Wofsy said.

The first class of instruments “sit[s] on the wing and measure[s] right there in real time.” Such instruments “measure little particles and the water in the atmosphere.” The second class collects data every second through an inlet in the cabin of the plane. A third class takes in air every minute or two. And the fourth class collects actual samples of air and seals them in canisters for later study.

The first and second classes of instruments “provide a continuous view of what you get as you pass though the air,” Wofsy said. The third and fourth classes “can help you put the point data in context, so you have a tremendous amount of cross data between the various measurements.”

The data the plane collects will be “fed into computer models” in order to help “put together the picture of where the carbon dioxide is coming from,” said Bob Henson, a science writer at the National Center for Atmospheric Research.

The outputs of such models could potentially contribute to global discussions about the environment, he said.

The mission, which has been in the works since 2004, will cost “$2 million for the science and another $2 million for the operations—the fuel, pilots, maintenance of the aircraft,” and is being funded and supported by the center for atmospheric research and the National Science Foundation, which owns the plane.

“This plane is not sold for commercial use—it is sold for very high-end executives, and we of course don’t have it configured anything like they would,” Wofsy said.

—Staff writer Elyssa A. L. Spitzer can be reached spitzer@fas.harvard.edu.