DENVER — A plane outfitted to measure greenhouse gases has taken off from Colorado on the first leg of a 24-day mission that will take it back and forth across the Pacific Ocean from the Arctic to the Antarctic.

The mission is part of a three-year project designed to determine when and where the gases enter and leave the atmosphere. That in turn could help policymakers who are weighing steps to minimize climate change.
The Gulfstream V flew from a Boulder-area airport to Anchorage, Alaska, on Wednesday.
From Anchorage, it will fly over the northern polar region, then to Hawaii, Fiji, New Zealand and the southern polar region before retracing its path to Alaska and returning to Colorado in mid-April.
The National Center for Atmospheric Research in Boulder is managing the project. The current mission is the third out of five.
The instruments measure chemicals, water vapor, aerosols, atmospheric pressure, temperature and wind speed. Samples are taken from sea level up to 47,000 feet, providing a record of concentrations at all altitudes.
“Previous experiments only can do like one fixed station, and with the aircraft you can actually fly and do vertical profiles of the gases you are measuring,” said Vidal Salazar, project manager. “It’s the best and the latest.”
The missions are scheduled for different seasons to cover a range of conditions. Previous missions were in January 2009 and October.
The plane, a Gulfstream V owned by the National Science Foundation, cost about $80 million including modifications and instrumentation.
The plane is called the High-performance Instrumented Airborne Platform for Environmental Research, or HIAPER. The greenhouse gas experiment is called HIPPO, for HIAPER Pole-to-Pole Observations.
The plane carries a 10-person research team along with cameras and instruments attached to the underside of each wing.