Goes on-orbit storage mode attitude dynamics and control

摘要

A unique method of spin-stabilized control for on-orbit storage of the normally 3-axis stabilized GOES I/M series spacecraft is described. Magnetic dipole coils are used to precess the spin axis angular momentum to approximately track the Sun at the one degree-per-day solar rate. Sun impingement constraints on sensitive instrument cooler radiators limit the maximum spin axis-to-Sun cone angle to 20 deg, when the spin axis attitude must be reset using thruster control. Ad hoc control methods for acquisition of the major-axis spin were developed by the GOES mission operations team using features of the thruster control logic not originally designed for such a purpose. High-fidelity simulations were required to optimize the spin-up sequence and ensure stability of the spin. Long-term attitude dynamics are particularly influenced by solar radiation pressure torque. This paper describes the method of spin acquisition and the attitude dynamics of the Z-Axis Precession (ZAP) storage mode. Techniques used to refine the control of the spin dynamics are also presented together with mehtods developed for spin-axis attitude and spin rate determination without a full sensor complement. The feasibility of the mehtod has been proven in flight for two different GOES spacecraft. the GOES-9 spacecraft was placed into the ZAP storage mode because of momentum wheel degradation and has remained within 6 deg of the Sun line for over one year with no groudn intervention required.