PROJECT SUMMARY (max 3000 characters) The principal goals of the project are the observational and theoretical investigation of complex cosmic objects where the processes of dust scattering, absorption and emission play significant roles. Special attention will be paid to both linear and circular polarization as an important source of information on the nature of dust grains. The main areas of the project are: * Observational analysis of dusty objects (evolved stars, young stellar objects, comets, stars with protoplanetary discs and planets) in polarized light, physical modelling and interpretation of the observations. * Mathematical modelling, development of sophisticated radiative transfer methods and software based on the Monte Carlo method. * Development of light scattering theory and computer codes to calculate the optical properties of non-spherical inhomogeneous particles and laboratory measurements of light scattering characteristics of irregularly shaped particles. * Creation of an electronic database containing information and tools required for efficient consideration of light scattering in astronomy. The research activities will include: * Photometric, polarimetric, spectral, imaging observations of selected late-type stars, young stellar objects, comets, stars with circumstellar discs and planets and their interpretation. * Development of the Monte Carlo technique including new criteria for the estimation of variance finiteness, optimization of weight modeling of trajectories in optically thin and optically thick media, etc. and creation of new computer codes for the calculation of polarized radiation transfer in dusty cosmic objects contained aligned non-spherical scatterers. * Applications of special versions of the separation of variables method and new approaches to the T-matrix method for computation of the optical properties of layered non-spherical particles and direct measurements of the characteristics of light scattered by submicron particles. * Updating and extension of the existing Jena-Petersburg database of optical constants for astronomy (JPDOC) and the database of optical properties of non-spherical scatterers (DOP), their supplementation with data from laboratory experiments, radiative transfer codes, atlas of models, etc. The following results are expected: * Detailed models of several dusty objects including estimates of characteristics of cosmic dust grains and their spatial distribution, conclusions on the properties of magnetic fields and the relationship between various dust populations, new knowledge on the evolutionary state of different objects. * Various Monte Carlo codes which will give the possibility to calculate the wavelength dependencies of extinction and polarization, spectral energy distributions, the profiles of dusty features, images and polarization maps of dusty circumstellar environments from ultraviolet to sub-millimetre wavelengths. * A series of efficient numerical codes based on exact and approximate methods in light scattering by small particles, a set of experimentally obtained data on the characteristics of light scattered by particles of different kinds. * An unique WWW database which will cover all aspects of light scattering applications in astronomy - from the laboratory measurement of optical constants and the optical properties of various cosmic dust analogs, to sophisticated radiative transfer codes and an atlas of models for different dust configurations, distributions of sources, grain properties.