Gille applies his training as a physicist to the development and use of satellite instruments to measure and track pollutants, greenhouse gases, and other chemicals in the lower and middle atmosphere. He is the U.S. principal investigator for MOPITT, an instrument flying aboard NASA's Terra spacecraft that measures the global distributions of carbon monoxide. By understanding the sources and behavior of carbon monoxide, scientists can also gain insights into a number of other pollutants. In addition, Gille is the U.S. principal investigator for HIRDLS, an instrument on NASA's Aura satellite that scientists use to study such topics as the recovery of the ozone layer and the impact of greenhouse gases on climate. Gille is a researcher in NCAR's Atmospheric Chemistry Division.