Single-Axis Pointing of Underactuated Spacecraft with Residual Angular Momentum'

The problem of aiming a body-fixed axis along an inertially fixed direction is dealt with, when only two reaction wheels can exchange angular momentum with the spacecraft platform. The feasibility of the pointing maneuver for an arbitrary body-fixed axis is assessed in the presence of a non-zero angular momentum for the system. Two control laws are then developed, which allow for completing the desired pointing maneuver from arbitrary initial conditions. Performance two controllers are compared by means of numerical simulation for a configuration representative of a small-size satellite.