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| SCISAT: Fourier Transform Spectrometer (FTS) |
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Background
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 SCISAT. |
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The ACE-FTS was built in co-operation with the Canadian Space Agency by ABB Bomem of Québec 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.
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