The Atmospheric Spectroscopy group at the Université Libre de Bruxelles (ULB) is part of the “Service de Chimie Quantique et Photophysique”. It has a recognized expertise in experimental and theoretical molecular spectroscopy. The atmospheric spectroscopy group currently counts 13 researchers, including 4 PhD students. The principal activities in the group are related to the remote-sensing of composition from satellites. Building on its expertise in fundamental spectroscopy, the group has indeed acquired a leading position for the atmospheric radiative transfer modeling in the thermal infrared and also for the development of atmospheric aerosol and trace gases retrieval methods. It owns and maintains sophisticated radiative transfer models, including in particular the FORLI series for IASI mission, of particular relevance for the present project. In the frame of IASI, the group has continuous and strong interactions with the French CNRS/LATMOS/IPSL group. IASI calibrated radiances are processed by the two entities to provide concentration distributions of climate and chemistry trace gases, including CO and O3 which are among the target pollutants in this Project. Recently the ULB expertise was also expanded to the sounding of atmospheric aerosols.