Spacecraft Attitude-Formation Tracking Using Line-of-Sight Measurements

Based on line-of-sight measurements between an arbitrary number of spacecraft in formation or to distant stars, attitude-formation-control systems are developed. The proposed control systems are unique in the sense that they do not require constructing the full attitudes of spacecraft and comparing them between spacecraft to obtain the relative attitudes indirectly. Instead, the control inputs are directly expressed in terms of line-of-sight measurements to control attitude formation precisely and efficiently. The proposed geometric nonlinear controllers are developed on the special orthogonal group to avoid singularities associated with local coordinates, and they guarantee asymptotic stability in the presence of fixed disturbances. Numerical examples are presented to illustrate the desirable properties of the proposed system.