TITLE: Station keeping close to unstable equilibrium points with a solar sail AUTHORS: Ariadna Farres and Angel Jorba Departament de Matematica Aplicada i Analisi Universitat de Barcelona Gran Via 585 08007 Barcelona, Spain E-Mails: ari@maia.ub.es, angel@maia.ub.es ABSTRACT: We have considered the movement of a Solar sail in the Sun - Earth system. Using the Circular RTBP + Solar radiation pressure as a model we have a 2D family of equilibrium points (most of them unstable) parametrised by the two angles defining the sail orientation. The knowledge of the variation of the invariant manifolds with respect to the sail orientation has permitted us design a control strategy to keep close to one of these unstable points. This strategy has been tested for two known missions, the Polar Observer and the Geostorm Warning Mission. Simulations up to 30 years have been done taking into account different fonts of errors such as errors in the position determination and on the sail orientation. In this paper we present the implementation of the control strategy and the results obtained for both missions.