The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its new science satellite, SCISAT-1. Dr. Peter Bernath of the University of Waterloo is the ACE Mission Scientist, and ABB Bomem is the industrial contractor for the development of the ACE primary instrument. The principal goal of the ACE mission is to measure and to understand the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature will be made by solar occultation from a satellite in a low earth orbit. A high inclination, low earth orbit will allow coverage of tropical, mid-latitude and polar regions. The ACE primary instrument is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible and near infrared imager. The FTS, operating from 2.4 to 13.3 microns, will measure at high resolution (0.02 cm-1) the infrared absorption signals that contain information on different atmospheric layers to provide vertical profiles of atmospheric constituents. Its highly folded design results in a very high performance instrument with a compact size. The imager will monitor aerosols based on the extinction of solar radiation using two filtered detectors at 1.02 and 0.525 microns. The instrument also includes a suntracker, which provides the sun radiance to both the FTS and the imager during solar occultation of the earth's atmosphere. This paper will describe the recent developments on the ACE instrument. Results obtained with the engineering model will be given and the latest status of the flight model will be presented.