Magnetic Attitude Control System for Spinning Small Spacecraft

A magnetic Attitude Control Subsystem (ACS) designed for minimum power weight, and cost is presented. The ACS subsystem was designed and built by ITHACO for the Small Communications Satellite Cluster (SCSC), integrated by Defense Systems Incorporated for the Defense Advanced Research Projects Agency. The basic spacecraft configuration is a flat cylinder, having a mass of 22.7 Kg with a diameter of 47.2 cm and 17.0 cm height. Hardware for the ACS design includes a two-axis magnetometer, two TORQRODs, a Horizon Crossing Indicator and the host microprocessor. During acquisition mode, the ACS spins up and stabilizes the spacecraft with a spin rate of 3 RPM (within 10%) and the spin-axis to within 5° of the orbit normal. Simulation results show that the above objectives can be achieved with the 1 Am2 TORQRODs within 4 orbits with total ACS orbital average power consumption of 190 mW and total ACS mass of 0.428 Kg.