First results of near real time retrievals from MIPAS / ENVISAT measurements

MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is operating on board of the ENVISAT satellite and is acquiring for the first time middle infrared limb emission spectra of the Earth atmosphere from space. This combination of measurement features makes it possible to determine the vertical profile of several atmospheric trace constituents every 75 sec., both during day and night with an almost full coverage of the globe. This leads to a three dimensional measurement of the atmospheric composition with a high repetition rate, but also implies a very large amount of data to be processed. In order to handle the large data flow, an optimised code for the Level 2 near real time analysis of MIPAS data, called ORM (Optimised Retrieval Model), was developed by an international consortium of scientists under an ESA contract and has been implemented in the ENVISAT Ground Segment. This code is designed to provide in an automated and continuous mode atmospheric vertical profiles of temperature and concentrations of O3, H2O, CH4, HNO3, N2O, NO2, in the range of 12-60 km. The first few months of MIPAS measurements are dedicated to the "commissioning phase", in which verification and validation of the instrument and of the analysis code is performed. In particular, the impact on the retrieved profiles of some assumptions adopted in the code optimisation and the effect of possible unexpected atmospheric and instrumental features have to be considered and characterised. The activity performed by the ORM Team during the "commissioning phase" will be reported and preliminary results concerning pressure and temperature retrievals obtained with this code will be shown.