Abstract
Abstract In this paper authors consider changing of optical characteristics of the solar sail surface during the heliocentric flight. The sail surface is a multilayer epitaxial structure, which is physically a polyamide film covered with different metals on the front and back sides. We calculate the optical characteristics of the multilayer film using the transition matrix method adapted for quantum-sized layers and taking into account the solar radiation spectrum. In order to analyse the influence of these characteristics variation on the spacecraft motion due to sail degradation we simulate the heliocentric Earth-Mercury flight.