The Atmospheric Chemistry Experiment (ACE): Aerosol and gas analysis from orbit*

The ACE (Atmospheric Chemistry Experiment) satellite has been in orbit since August 2003. The primary ACE instrument is a high-resolution infrared Fourier transform spectrometer (ACE-FTS) that uses the Sun as a light source to measure atmospheric composition during sunrise and sunset (solar occultation). The long ACE time series allows changes in atmospheric composition to be measured. For example, ACE-FTS monitors changes in the abundance of halogenated gases associated with the Montreal Protocol on Substances that Deplete the Ozone Layer. More recently, infrared transmittance spectra of clouds and aerosols (e.g., polar stratospheric clouds and sulfate aerosols) have been measured. These particles can be characterized by fitting their infrared extinction to determine size and composition.