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

In this paper the problem of maneuver planning is analyzed in presence of multiple constraints, with the aim to point a body–fixed axis of the spacecraft from one direction to another, for example to allow the transition between pairs of targets in the case of celestial observation. The constraints on the maneuver are due to (i) the underactuated nature of the system, that is the impossibility to provide three independent control torques, and (ii) the need of avoiding a prohibited direction during the maneuver, (e.g. a bright object that may damage the sensor). It is shown how the suggested kinematic solution requires, in general, two successive rotations in order to accomplish the desired pointing maneuver. The shortest overall angular path is computed and a test case is proposed in order to prove the effectiveness of the approach.