Development and testing of a GyroWheel based control system for the SCISAT-1 scientific satellite

GyroWheel is an innovative spacecraft attitude control device that provides actuating torques about three axes while measuring spacecraft angular rates about two axes. A demonstration unit will be flown on SCISAT-1, a Canadian scientific satellite, in 2003.; During normal operation of SCISAT-1, actuation is provided by a classical fixed-axis momentum wheel and magnetic torque rods. An alternative control system was developed, however, whereby GyroWheel provides actuation about all three axes, with the torque rods being required only for momentum dumping. The system is operated without angular momentum bias to suppress nutation.; Computer simulations of the system indicate that fine pointing control of SCISAT-1 using GyroWheel can be easily achieved, with a 3-σ pointing error of 0.02° and a maximum pointing error of 0.06°. This compares favourably with results for the momentum wheel and torque rod system, in which the pointing error can reach 0.2° during a typical orbit.