Vibration reduction for flexible spacecraft following momentum dumping with/without slewing

Vibrations following the firing of thrusters to dump wheel momentum degrade pointing performance of a reaction-wheel controlled spacecraft, The use of input shaping is suggested to modulate thruster pulses with a set of properly timed impulses to suppress vibrations after dumping momentum. An exact solution is obtained for thruster switching times in the idealized case of no constraints, With realistic constraints on the thruster, permissible attitude error, and elastic deflection, an optimization problem is solved. The solution is a modification of a concatenated set of pulses for the idealized case, each set designed to dump a fraction of the total momentum with vibration reduction, It is shown that momentum can be dumped during slewing maneuvers along with vibration suppression, resulting in a reduction of slew time with no additional fuel consumption. In this case input shaping is applied to both reaction wheel anti thruster commands to minimize residual vibrations, Results of large angle slewing and momentum dumping with and without reaction wheel saturation are presented for the next generation space telescope.