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The Atmospheric Chemistry Experiment (ACE): Status and Latest Results

Peter Bernath(1)

(1) University of York, Heslington, York, YO10 5DD, United Kingdom


ACE (also known as SCISAT) is making a comprehensive set of simultaneous measurements of numerous trace gases, thin clouds, aerosols and temperature by solar occultation from a satellite in low earth orbit. A high inclination (74 degrees) low earth orbit (650 km) gives ACE coverage of tropical, mid-latitudes and polar regions. A high-resolution (0.02 cm-1) infrared Fourier Transform Spectrometer (FTS) operating from 2 to 13 microns (750-4400 cm-1) is measuring the vertical distribution of trace gases, and the meteorological variables of temperature and pressure. Aerosols and clouds are being monitored using the extinction of solar radiation at 0.525 and 1.02 microns as measured by two filtered imagers as well as by their infrared spectra.

A dual spectrograph called MAESTRO extends the wavelength coverage to the 400-1000 nm spectral region. The principal investigator for MAESTRO is T. McElroy of the Environment Canada. The FTS and imagers have been built by ABB-Bomem in Quebec City, while the satellite bus has been made by Bristol Aerospace in Winnipeg. ACE is part of the Canadian Space Agency's small satellite program, and was launched by NASA on 12 August 2003 for a nominal 2-year mission. ACE is also a third party ESA mission.

The first results of ACE have been presented in a special issue of Geophysics Research Letters ( in 2005 and recently a special issue on ACE validation has been prepared for Atmospheric Chemistry and Physics ( by K. Walker and K. Strong; more information can be found at A mission overview and status report will be presented. Science results for a few selected topics including the detection of organic molecules such as formaldehyde and formic acid in the troposphere as well as carbon dioxide profiles will be discussed.


Workshop presentation