Single-Axis Pointing of Underactuated Spacecraft in the Presence of Path Constraints

A strategy for attitude path planning that performs single-axis pointing in the presence of obstacles along the angular path and constraints on admissible rotation axes is presented. The proposed kinematic solution is based on the identification of the crossing condition for a baseline single-step maneuver with an undesired set of pointing, seen as a conical obstacle along the attitude path. If crossing with the forbidden region occurs, an alternative two-step maneuver is selected, where both rotation axes are admissible and the cones spanned by the sensor boresight are tangent to the prohibited cone. Given the small number of admissible two-step maneuvers (eight at most), it is possible to select the shortest overall angular path with limited computational effort. The test case discussed demonstrates the effectiveness of the approach and provides further insight into the geometry of the cones.