Co-spin with symmetry axis stabilization, and de-spin for asteroid capture

Consideration is given to attitude control associated with capturing a free-flying asteroid using an axisymmetric spacecraft. Asymptotically stable controllers are designed to align the spacecraft axis of symmetry with a line of descent that is fixed in the asteroid, and to eliminate all relative angular velocity before capture takes place. For the special case of an axisymmetric asteroid, an analytical expression is presented for the torque required to maintain alignment of the axes of symmetry of the spacecraft and the asteroid. After the asteroid is securely captured, the angular velocity of the rigid composite body relative to an inertial frame is arrested; we present a controller that is asymptotically stable and stays within specified thrust limits.