NASA's plans to study the Earth's carbon dioxide were dealt a setback this week when a satellite failed to reach orbit.

The Orbiting Carbon Observatory satellite lifted off around 4:55 a.m. Tuesday, from Vandenberg Air Force Base. NASA officials said it appeared that the satellite failed to separate from its Taurus XL launch vehicle. They believe that the satellite crashed in the Pacific Ocean near Antarctica. The rocket contained hydrazine fuel, but NASA officials said they didn't believe the fuel posed any risks to humans.

NASA said it would immediately assemble a team of investigators try to determine the cause of the failure after several rounds of thorough testing indicated the satellite and booster were ready for launch.

Had the launch been successful, it would have sent one of Orbital Sciences' LEOStar-2 spacecraft about 400 miles above Earth to measure carbon dioxide around the clock with a single instrument. The observatory would have helped collect information that could have helped scientists learn more about global warming by pinpointing areas where the gas builds up.

Scientists believe that carbon dioxide is concentrated in the atmosphere at about 380 parts per million and rapidly increasing. Ground base stations and aircraft collect some information about the sources and areas of highest concentration, but NASA hoped to map concentrations around the globe every 16 days over the next two years.

The spacecraft weighed nearly 1,000 pounds and was protected by a clamshell-shaped cover that was supposed to separate but apparently did not.