Multiple scattering of light and its impact on observations of extensive air showers

Atmospheric scattering of light emitted by an air shower not only attenuates direct fluorescence light from the shower, but also contributes to the observed shower light. So far only direct and singly-scattered Cherenkov photons have been taken into account in routine analyses of the observed optical image of air showers. A Monte Carlo method for evaluating the contribution of multiply scattered light to the optical air shower image is presented, as well as results of simulations at various atmospheric conditions. Presented are parameterizations of scattered light contributions to measured shower signals, which can be implemented into UHE shower reconstruction in the fluorescence technique.