Objectives

MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is a space-borne high-resolution limb emission Fourier transform infrared spectrometer, designed for measurement of atmospheric constituents. It will be part of the core payload of the Envisat Satellite of the European Space Agency (ESA). Launch is scheduled for July 2001. MIPAS will be able to measure a manifold of atmospheric trace constituents of major importance to ozone chemistry, atmospheric composition monitoring, and global change at global coverage, independently of sunlight, i.e. also during night or polar winter. Species to be measured by MIPAS are the nitrogen family (N₂O, HNO₃, NO, NO₂, ClONO₂, N₂O₅ and others), chlorine reservoirs (ClONO₂, HOCl), chlorine source species (CFC-11, CFC-12, CFC-22, CCl₄; possibly also CFC-113, HCFC-123, HCFC-141b, and HCFC-142b), chlorine radicals (ClO), dynamic tracers (H₂O, N₂O, CH₄, CF₄, SF₆) and many more, e.g., CO, OCS, NH₃, HCN, C₂H₂, or C₂H₆. Since ESA's operational data products will, due to restrictions by near real time processing, include only vertical profiles of five key species (O₃, H₂O, HNO₃, N₂O, CH₄) and pressure and temperature, extension of this list of species to be analysed is of major scientific value. The major objective of this proposal is to fill this gap in the list of data products, while ensuring quality and comparability of data products provided by different scientific groups.

Improvement of data quality, with respect to precision, accuracy, and vertical resolution. The latter is in particular important for assessment of stratospheric-tropospheric exchange processes.
Extension of altitude coverage of data products in the troposphere and upper atmosphere. While the first is of major importance for assessment of stratospheric-tropospheric exchange processes, the latter is useful for better understanding of radiative processes. This issue also includes dedicated processing of MIPAS spectra recorded at non-standard observation scenarios, e.g., finer tangent-altitude spacing, wider altitude-coverage of the tangent altitudes, or side-viewing observations.

The second major goal is to gain confidence in the strategies and involved computer codes and to give proof to the international scientific community of the reliability and appropriateness of the approaches as well as the quality of data products. This includes:

Cross-validation of radiative transfer models used by the different groups, detection of deficiencies in the codes by means of cross-comparison, and upgrading in order to remove the discrepancies.
Cross-comparison of employed retrieval strategies and algorithms, and upgrading by removal of detected deficiencies.
Standardization of results in terms of data quality and characterization with respect to vertical resolution and retrieval error estimates.
Understanding of differences in results achieved by the various involved strategies applied to real measurement data, and detection, understanding, and tentative removal of systematic residuals in the best-fit spectra. This objective includes also the understanding of unexpected MIPAS instrument behaviour (possible unpredicted instrumental errors) and understanding of unexpected signals in the atmospheric spectra (e.g., due to non-local thermodynamic equilibrium (NLTE)emissions or missing or erroneous spectroscopic reference data)
Final data product validation by cross-comparison to external measurement data (GOMOS, SCIAMACHY, and others).

The improved understanding of radiative transfer modelling and retrieval approaches will be shared with the scientific community by publication of the results in reports and tentatively in easily accessible scientific journals. New spectroscopic data and vibrational temperature data will be forwarded to interested and qualified users on request. Characterization and validation of data products will be extensively reported and made public for the scientific community by appropriate media to be agreed by the consortium. Candidate media are, among others, printed reports and internet web pages.