Thirty billion tons of carbon dioxide waft into the air from the burning of fossil fuels each year. About half stays in the air. The other half disappears. Where it all goes, nobody quite knows.

With the Orbiting Carbon Observatory, a NASA satellite scheduled to be launched on Tuesday from Vandenberg Air Force Base in California, scientists hope to understand better the comings and goings of carbon dioxide, the main heat-trapping gas behind the warming of the planet.

The new data could help improve climate models and the understanding of the “carbon sinks,” like oceans and forests, that absorb much of the carbon dioxide.

Annual variations  in some years, all of the excess carbon dioxide disappears; in some years, all of it stays in the air  indicate that some of the sinks may fill up and spill some of the absorbed carbon dioxide back into the air.