Perigee Attitude Maneuvers of Geostationary Satellites During Electric Orbit Raising

When full-electric orbit-raising trajectories begin in a classic geostationary transfer orbit with low initial perigee altitude, the need for deployed solar arrays to power the propulsion system significantly increases the aerodynamic and gravity gradient torques. In fact, the torque magnitudes in the first few perigee passages may become a challenging requirement for the attitude control system. Apart from oversizing actuators, other solutions may include the need for a backup thruster system or raising the perigee altitude, implying mass penalties and cost. This paper presents the design of an optimal attitude maneuver at the perigee that can be undertaken using nominal reaction wheels. Attitude paths avoiding saturation of the wheels while dumping accumulated momentum are obtained performing a physically consistent modeling of aerodynamic torques and using pseudospectral methods to solve the trajectory optimization problem. The optimization of solar array positions is also explored to further constrain the problem or improve the maneuver performance. Resulting mass and cost savings can be significant, which could be used for additional payload or to significantly extend the operational life of the satellite.