Optimal low thrust orbit correction in curvilinear coordinates

The minimum-time, constant-thrust transfer between two close, coplanar, quasi-circular orbits is studied using a novel non-linear formulation of relative motion in curvilinear coordinates. The Optimal Control Problem in the thrust orientation angle is treated from a quantitative and qualitative point of view, using the direct and indirect methods respectively. The former yields numerical solutions for a wide range of thrust parameters, while a better understanding of the physics is achieved seeking for an approximate solution of the latter. Fundamental changes in the structure of the solution with the thrust parameter are identified.