MIPAS is a high-resolution Fourier Transform Infrared spectrometer which is designed to measure concentration profiles of various atmospheric constituents on a global scale. It will observe the atmospheric emissions from the Earth horizon (limb) in the mid infrared region (4.15 µm - 14.6 µm) providing global observations of photochemically interrelated trace gases in the middle atmosphere, in the tropopause and in the upper troposphere.
These data will contribute to the development of a better understanding in the following research areas:
The instrument is designed to allow the simultaneous measurement
of more than 20 relevant trace gases, including the complete NOy
family and several CFCs. The atmospheric temperature as well as the
distribution of aerosol particles, tropospheric cirrus clouds and
stratospheric ice clouds (including Polar Stratospheric Clouds) are
further important parameters which can be
The data are obtained with complete global coverage, for all seasons and independent on illumination conditions, allowing measurement of the diurnal variation of trace species.
The atmospheric emissions will be measured at the horizon of the Earth (limb) over a height range of 5 to 150 km. This observation geometry allows the maximum measurement sensitivity and a good profiling capability to be achieved.
The MIPAS data products are calibrated high-resolution spectra
which are derived on ground from the transmitted interferograms.
From these spectra, geophysical parameters such as trace gas
concentrations, temperature profiles, mixing ratios, are retrieved
permitted to establish global maps of atmospheric
MIPAS will perform measurements in either of two pointing
regimes: rearwards within a 35° wide viewing range in the
anti-flight direction and sideways within a
The sideways range is important for observations of special
events, like volcano eruptions, trace gas concentrations above
major traffic routes or concentration gradients across the
dawn/dusk border. In nominal measurement mode, MIPAS will perform
series of measurements at different tangent heights by performing
elevation scan sequences with a duration of 75s in the rearward
viewing range. Such an elevation scan sequence comprises typically
For special event observations, viewing elevation scans sequences in the sideways range can be commanded. Radiometric calibration will be performed using two measurements:
Another calibration mode will be required for the inflight determination of the line of-sight pointing direction, which is based on the observation of stars crossing the instrument field of view and subsequent correlation of the actual with the predicted time of star crossing.
The MIPAS blockdiagram depicts the functional elements and their relationship. The radiation emitted from the observed scene will enter MIPAS through the Front-End Optics comprising an azimuth scan mirror, an elevation scan mirror and a telescope. The radiation propagates through a dual slide, dual port Michelson-type interferometer, which is designed to provide an unapodized spectral resolution of better than 0.035 cm-1 throughout the observed spectral range.
The input signals are divided at the beamsplitter inside the
interferometer and directed to cube corners moving at a constant
velocity of 25 mm/s along a path of 100 mm. Hence one spectrum is
typically recorded within 4 s. From the cube corners the IR beam is
reflected to the beam recombiner and then directed to
Depending on the optical path difference in the two interferometer arms, the recombined signal is an intensity modulated interferogram. The optical path difference signal for the interferogram sampling is derived from a reference laser the interferogram. The output signal enters the Focal Plane Subsystem where beam size matching, beam splitting and optical filtering is performed.
After optical filtering the input spectrum is separated into eight narrow spectral bands for detection by eight Hg:Cd:Te-detectors operating at about 70 K.
After pre-amplification, the eight signals are amplified, lowpass filtered and digitized by the analogue processing part of the Signal Processing Electronics. Its digital part separates the spectral range of interest by complex filtering, undersamples the input sequences individually and equalizes channels to be combined.
Word length truncation is then performed to reduce the data rate
MIPAS is developed under leadership of Dornier Satellitensysteme GmbH.