The Atmospheric Chemistry Experiment (ACE) is the mission on-board Canadian Space Agency's science satellite,
SCISAT-1. ACE consists of a suite of instruments in which the primary element is an infrared Fourier Transform
Spectrometer (FTS) coupled with an auxiliary 2-channel visible (525 nm) and near infrared imager (1020 nm). A
secondary instrument, MAESTRO, provides spectrographic data from the near ultra-violet to the near infrared, including
the visible spectral range. In combination, the instrument payload covers the spectral range from 0.25 to 13.3 micron. A
comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature are being made
by solar occultation from this satellite in low earth orbit. The ACE mission measures and analyses the chemical and
dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination
(740), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions. The ACE/SciSat-1 spacecraft
was launched by NASA on August 12th, 2003.
This paper presents the status of the ACE-FTS instrument, after four years on-orbit. On-orbit performance is presented.
The health and safety status of the instrument payload is discussed. Optimization of on-orbit performance is presented as
well as operational aspects. Aspects related to reliability of FTS are discussed as well as potential future follow-on