LOW-THRUST ECCENTRICITY-CONSTRAINED ORBIT RAISING

The problem of zero-eccentricity-constrained orbit raising in circular orbit in the presence of shadowing is analyzed using both numerical a nd analytical methods. Given the shadow arclength, piecewise constant pitch angles are selected analytically, and the location along the orb it where the pitch angle switches is optimized to effect the largest c hange in semimajor axis per revolution. Two strategies yielding near-o ptimal performance are presented, differing in whether or not a pitch reorientation maneuver is carried out inside the shadow are. These ana lytic results are also compared with the exact eccentricity-constraine d numerical solutions, which use optimally varying continuous pitch pr ofiles to maximize the change in semimajor axis after each revolution. The suboptimal analytic strategies are almost as effective as the opt imal strategy especially in higher orbit. These strategies remove the need for continuously reorienting the spacecraft attitude in pitch, pr oviding robust real-time on-board guidance capability for electric orb it transfer vehicle orbit raising applications.