ATTITUDE-CONTROL OF AN ORBITING TETHERED GYROSTAT

Certain classes of space-borne experiments can only be performed in a disturbance free environment. The unique dynamic characteristics of te thered satellites make these constellations ideal candidates to serve as isolation platforms. An effective method of implementing three-axis attitude control for tethered satellites is to simultaneously move th e attachment point of the tether with respect to the satellite mass ce nter (for pitch and roll) and to torque against a reaction wheel (for yaw). Nonlinear dynamical equations are derived for the model of an el astic tether connecting an orbiting parent spacecraft and a gyrostat p ayload. Simple proportional-derivative (PD) feedback control laws are developed and the performance of the controller is verified with numer ical simulation. Results show that the derived three-axis controller i s extremely effective in achieving desired payload performance.