Semi-analytical adaptive guidance computation for autonomous planetary landing

A novel algorithm for autonomous landing guidance computation is presented. The trajectory is expressed in polynomial form of minimum order to satisfy a set of 17 boundary constraints, depending on 2 parameters: time-of-flight and initial thrust magnitude. The consequent control acceleration is expressed in terms of differential algebraic (DA) variables, expanded around the point of the domain along the nominal trajectory followed at the retargeting epoch. The DA representation of the objective and constraints gives additional information about their sensitivity to variations of the optimization variables, which is exploited to find the desired fuel minimum solution (if existing) robustly and with a very light computational effort.