ROBUST OPTIMIZATION OF DESCENT TRAJECTORIES ON IRREGULAR-SHAPED BODIES IN THE PRESENCE OF UNCERTAINTY

High levels of uncertainty are associated to the characterization of the environment around small bodies in the Solar System. In an effort to develop efficient methods to consider uncertainty in the analysis of missions to irregular-shaped bodies, the problem of robust and efficient optimization of descent trajectories in the presence of uncertainty is addressed in this paper. The gravitational field around the body is modeled using an optimized mascons approach, for computational efficiency and reduced approximation error. Random processes in the system are discretized and approximated using stochastic quadrature rules, which allow for efficient computation of relevant statistical quantities in the system. A single optimal control history is then solved for and applied to all discrete cases of the uncertain system. A general formulation for the problem of optimal descent on irregular-shaped bodies is developed, and the described methodology is applied to the problem of minimum impact velocity with uncertainty in the total mass of the body.