Time optimal de-orbiting of solar sails

Abstract

Increasing interest in optimal low-thrust orbital transfers was triggered in the last decade by technological progress in electric propulsion and by the ambition of efficiently leveraging on orbital perturbations to enhance the maneuverability of small satellites. This paper focuses on time optimal disposal maneuvers using solar radiation as a propulsive means. After formulating the necessary conditions for optimality, the numerical solution of the two-point boundary value problem is facilitated by averaging the Hamiltonian with respect to both satellite and Sun longitudes. Initial conditions for the osculating trajectory are finally inferred via a near-identity transformation that carefully approximate the quasi-periodic oscillations of both state and adjoint variables. Classical approaches for the assessment of this transformation are shown to be inadequate to the problem at hand because of the particular structure of the Hamiltonian.