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Instrument: ACE-FTS : Fourier Transform Spectrometer
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The Fourier Transform Spectrometer (ACE-FTS)


The Fourier Transform Spectrometer (ACE-FTS) is the primary
instrument selected for the Atmospheric Chemistry Experiment
(ACE) mission onboard the SCISAT satellite. A second instrument,
Measurements of Aerosol Extinction in the Stratosphere and
Troposphere Retrieved by Occultation (MAESTRO), is also onboard

The ACE-FTS was built in co-operation with the Canadian Space
Agency by ABB Bomem of Qu?bec City. Funding for the ACE mission,
including both Canadian instruments, was provided by the
Canadian Space Agency?s Space Science Program.

How ACE-FTS functions

The ACE-FTS instrument is designed to simultaneously measure the
temperature, trace gases, thin clouds, and aerosols found in the
atmosphere using a solar occultation technique. For this
technique to work, the orbiting satellite must first point to
the Earth's horizon during sunrise or sunset. As the sun "moves"
through the thin band of atmosphere at the horizon, its rays are
partly absorbed by the various gases in the atmosphere at
different altitudes. It is these gases and their distribution
that the high-resolution, infrared ACE-FTS will measure. Thus,
as the instrument observes the rising or setting sun, it can
perform its measurements throughout the whole thickness of the
atmosphere. Aerosols such as those caused by gases ejected by
volcanoes will also be measured.

SCISAT?s low orbit of 650 km above the Earth will give the
ACE-FTS instrument extensive coverage with an emphasis on
mid-latitude areas, such as Canada and the United States, as
well as the polar region. The area to be scanned will be from
about 4 km above the cloud tops (or the boundary layer for clear
scenes) up to about 100 km. SCISAT will orbit the Earth 15 times
a day, providing 30 daily opportunities (sunrises and sunsets)
to take its precise measurements.

Complements other experiments

ACE-FTS will measure the density of a large number of chemicals
in order to make an accurate estimate of both chemical loss and
the movement of ozone in the polar winter and springtime. Its
results will be complemented by those gathered by MAESTRO. The
overall ACE mission will work in conjunction with other
instruments and missions planned by NASA, the European Space
Agency, and other international partners over the next decade to
gain a better understanding of the chemistry and dynamics of the
stratosphere with an emphasis on ozone.

View the SCISAT homepage at:

[Summary provided by the Canadian Space Agency]