Herbert Nett

MIPAS ground processor and data products

As an ESA-provided payload instrument on board ENVISAT the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) will routinely acquire atmospheric limb emission spectra in the middle infrared region. Due to its high radiometric sensitivity and spectral resolution capabilities a large number of middle atmospheric constituents can be detected that are of primary interest in the various disciplines of atmospheric research. The ENVISAT ground segment concept foresees generation and near real time dissemination of MIPAS data products up to the level of pressure (p), temperature (T) and volume-mixing-ratio (VMR) profiles for the high priority target species O/sub 3/, H/sub 2/O, CH/sub 4/, N/sub 2/O, HNO/sub 3/. The basic algorithms have been defined and are currently being verified in various ESA supported studies. End-to-end tests based on simulated instrument raw data have been carried out, using prototype versions of the Level 1B (processing from raw data up to calibrated radiance spectra) and Level 2 algorithm components (retrieval of vertical p, T and VMR profiles). Runtime checks have been performed for the critical profile retrieval modules. For a reference scenario (p, T plus five trace gas retrievals for a single, 16 heights elevation sequence; one iteration per retrieval), a total runtime of /spl sim/150 s has been achieved on an IBM RS/6000 model 397.

The ADM-Aeolus wind retrieval algorithms

The ADM-Aeolus is primarily a research and demonstration mission flying the first Doppler wind lidar in space. Flexible data processing tools are being developed for use in the operational ground segment and by the meteorological community. We present the algorithms developed to retrieve accurate and representative wind profiles, suitable for assimilation in numerical weather prediction. The algorithms provide a flexible framework for classification and weighting of measurement-scale (1–10 km) data into aggregated, observation-scale (50 km) wind profiles for assimilation. The algorithms account for temperature and pressure effects in the molecular backscatter signal, and so the main remaining scientific challenge is to produce representative winds in inhomogeneous atmospheric conditions, such as strong wind shear, broken clouds, and aerosol layers. The Aeolus instrument provides separate measurements in Rayleigh and Mie channels, representing molecular (clear air) and particulate (aerosol and clouds) backscatter, respectively. The combining of information from the two channels offers possibilities to detect and flag difficult, inhomogeneous conditions. The functionality of a baseline version of the developed software has been demonstrated based on simulation of idealized cases.

ENVISAT-MIPAS: instrument commissioning & early results

The Michelson Interferometer for Passive Atmospheric Sounding forms part of the atmospheric payload on board ESAs polar orbiting Envisat, launched on 1 March 2002. It is going to sense the Earths limb emission in a broad spectral range in the thermal infrared, allowing to detect a large number of atmospheric trace gases in a height range from the upper tropopause up to the lower mesosphere. Primary activities during the initial four weeks of in-orbit operation include the verification of the instruments health status and its communication with the ground segment. The subsequent CalVal phase comprises various special calibration measurements, with a focus on radiometric and spectral characterisation, as well as the line-of-sight pointing accuracy. Moreover, dedicated analyses will be carried out in order to validate critical components of the on-ground Level 1B and Level 2 processing stages and to optimise primary algorithm settings.