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Instrument: MIPAS : Michelson Interferometer for Passive Atmospheric Sounding
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Description
The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a
core European Space Agency (ESA) instrument on the ENVISAT spacecraft
(launched March 1, 2002). MIPAS is a high-resolution Fourier-transform
spectrometer designed to measure the concentration profiles of atmospheric
constituents on a global scale. MIPAS will observe the atmospheric
emissions from the Earth horizon (limb) throughout the mid-infrared
region, which will allow the simultaneous measurement of more than 20
trace gases, including the complete family of nitrogen-oxygen compounds
and several CFCs. MIPAS will provide global data coverage, including the
polar regions. The instrument measures atmospheric radiation in the
spectral-coverage range 4.15 um to 14.6 um. This covers almost the
complete mid-infrared region, and thus the emission lines of many
atmospheric species are captured.

In order to determine the concentration profiles of the atmospheric trace
gases, MIPAS will measure a series of spectra from different tangent
heights. A basic elevation scan sequence will comprise 16 high resolution
spectra or up to 75 spectra with a reduced spectral resolution. A typical
elevation scan will start at about 50 km tangent height and descend in 3
km steps to 5 km. It will also be possible to code different elevation
scan sequences within the tangent height range in variable step sizes.

Measurements are possible in either of two pointing regimes. One pointing
regime is rearwards in the anti-flight direction within a 35 ! wide range
used for good earth coverage and the polar regions. The second pointing
regime is sideways within a 30 ! wide range on the anti-Sun side. This
viewing direction is provided for the observation of volcanic eruptions,
air-traffic corridors, or concentration gradients across the dusk/dawn
terminator.

The MIPAS instrument uses eight detectors. The spectral range is split
into five bands, where each band is covered by one or two specific
detector pairs (A, B1, B2, C and D). In a typical data collection orbit,
16 scene measurements will be recorded in sequence for different
atmospheric elevations, followed by two deep space measurements. This
takes approximately 80 seconds and repeats for the duration of measurement
in the orbit. This gives 75 scans per orbit. One spectrum consists of
35000 samples and takes four seconds. One altitude scan requires 16
spectra measurements and one deep space offset measurement. The altitude
scan lasts about 75 seconds. The spectrum is converted in a single
interferogram and would be appriximately 62 Kbytes.

For more information on MIPAS see:
http://auc.dfd.dlr.de/info/AUC/MIPAS/

For more information on ENVISAT, see:
http://envisat.esa.int/