Precision Spacecraft Pointing Using Single-Gimbal Control Moment Gyroscopes with Disturbance

Whereas previous work has shown that gain stabilization methods in the attitude control of spacecraft can mitigate external disturbances of a e xed frequency, recent work in cases where the frequency of the disturbance is time variant is summarized here.Specie cally, theapplication ofgain stabilization in the form of a variableperiodic disturbancerejection e lter is shown to bea viablemethod ofmitigating these disturbances. To usethis e lter forthe time-variant case, the character of the source of the disturbance needs to be known a priori with some accuracy. An implementation for a spacecraft steered by single-gimbal control moment gyroscopes where the disturbance is related to the gimbal rate is demonstrated. In addition, performance of the subject e lter is demonstrated in the presence of estimation error and phase shift.