  This paper considers the coupled orbit and attitude dynamics of a dumbbell
spacecraft around an asteroid. Geometric methods are used to derive the coupled
equations of motion, defined on the configuration space of the special
Euclidean group, and then a nonlinear controller is designed to enable
trajectory tracking of desired landing trajectories. Rather than relying on
sliding mode control or optimization based methods, the proposed approach
avoids the increased control utilization and computational complexity inherent
in other techniques. The nonlinear controller is used to track a desired
landing trajectory to the asteroid surface. A monocular imaging sensor is used
to provide position and attitude estimates using visual odometry to enable
relative state estimates. We demonstrate this control scheme with a landing
simulation about asteroid Itokawa.
