Canadian satellite
SCISAT-1
is a Canadian
satellite
designed to make observations of the
Earth's atmosphere
. Its main instruments are an optical Fourier transform infrared
spectrometer
, the ACE-FTS Instrument, and an ultraviolet
spectrophotometer
, MAESTRO. These devices record spectra of the Sun, as sunlight passes through the Earth's atmosphere, making analyses of the chemical elements of the atmosphere possible.
Design and construction
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SCISAT is a relatively small satellite weighing 150 kg (330 lb). It is partly drum shaped and measures about 1.5 metres by 1.5 metres. The
Canadian Space Agency (CSA)
coordinated its design, launch and use. The main contractors were
Bristol Aerospace
of
Winnipeg, Manitoba
, who were prime contractor for the bus, and ABB Bomem Inc. of
Quebec City, Quebec
who developed the ACE-FTS instrument. The total development cost of SCISAT, as estimated
[4]
by the CSA in 2003, was about CDN$60M. As of
20 years after launch, the satellite and its instruments are still operating.
ACE-FTS
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The
ACE-FTS
instrument is the main payload of the SCISAT-1 spacecraft. The primary scientific goal of the Atmospheric Chemistry Experiment (ACE) is to measure and understand the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. The principle of ACE measurement is the solar occultation technique. A high inclination (74 degrees), low Earth orbit 650 km (400 mi) will provide ACE coverage of tropical, mid-latitudes and polar regions.
The spectrometer is an adapted version of the classical Michelson interferometer using an optimized optical layout. Its highly folded double-pass optical design results in a very high performance instrument with a compact size. A signal-to-noise ratio (SNR) better than 100 is achieved, with a field-of-view (FOV) of 1.25 mrad and an aperture diameter of 100 mm (4"). A
semiconductor
laser
is used as the metrology source of the interferometer sub-system.
The auxiliary Visible/Near-infrared Imager (VNI) monitors aerosols based on the extinction of solar radiation using two filtered detectors at 0.525 and 1.02 micrometres. The instrument also includes a Suntracker mechanism providing fine pointing toward the radiometric center of the Sun with stability better than 3 μrad. The ACE-FTS instrument was launched on August 12, 2003.
ABB
was the prime contractor for the design and manufacturing of the ACE-FTS instrument.
MAESTRO
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The Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instrument aboard SCISAT-1 measures the vertical distribution of
ozone
,
nitrogen dioxide
, water vapour, and
aerosols
in the
Earth's atmosphere
.
[5]
MAESTRO consists of a UV-VIS-NIR
spectrophotometer
that measures the 285-1030 nm spectral region.
[6]
Orbit
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SCISAT passes through the Earth's shadow 15 times per day, profiting from the
occultation
of the Sun to make a spectrographic analysis of the structure and chemistry of those parts of the upper atmosphere that are too high to be reached by balloons and airplanes and too low to be visited by orbiting satellites. This kind of analysis can help understand the depletion of the
ozone layer
and other upper atmosphere phenomena.
SCISAT was placed in
low Earth orbit
, or LEO, by a
Pegasus rocket
launched from a
NASA
Lockheed L-1011
carrier aircraft on August 12, 2003 from
Vandenberg Air Force Base
. Expected to operate for two to five years, it was still operational in 2018. Current information may be obtained from the ACE Mission Information for Public Data Release report.
[7]
The
University of Waterloo
,
York University
, the
University of Toronto
, and several other Canadian universities collaborated in the design of the experiments, and in several aspects of the testing of the satellite.
References
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External links
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Launches are separated by dots ( ? ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ).
Crewed flights
are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
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