"The MIMOSA-5 project aspires to a better understanding, modelling and characterization of stratospheric aerosols and of their effect on atmospheric properties using the most recent observations and scientific results. The project also seeks to study and quantify the impact of major volcanic eruptions on the physico-chemistry and dynamics of the stratosphere, the influence of stratospheric aerosols formation on climate change, and the atmospheric consequences of the interaction between these effects.The most important segment of the project is devoted to the development and extension of the three-dimensional microphysical/transport Model for STRatospheric Aerosols (MOSTRA). A significant improvement to implement is the development of a pre-processing tool deriving the most reliable aerosol field at full grid from single/multiple data sets, including extinction or size information. The scope of such a development goes beyond the stratospheric aerosol aspects and has many applications in data retrieval and in atmospheric and climate modelling. Furthermore, the microphysical module will be extended to include processes such as condensation/evaporation, nucleation but also photo- or gravito-phoresis and the addition of nonvolcanic aerosols (soot, meteoritic dusts). The simulation of volcanic eruptions will also be undertaken.The second part of the project consists in improving the quantification of aerosol radiative properties using satellite measurements. The main task will be the development of a climatology of stratospheric aerosol extinction and optical depth from the GOMOS instrument and the implementation of stratospheric corrections for tropospheric measurements. The results of these accomplishments will serve both the modelling activities and the ESA project Aerosol_CCI, a pan-European effort which aims at an enhanced characterization of aerosols both in the troposphere and in the stratosphere by the synergetic use of multiple spaceborne experiments."