A report presents a method of optimizing the orientations of three reaction wheels used to regulate the angular momentum of a spacecraft. The method yields an orientation matrix that minimizes mass, torque, and power demand of the reaction wheels while maximizing the allowable duration between successive angular-momentum dumps. Each reaction wheel is parameterized with its own unit vector, and a quadratic cost function is defined based on requirements for torque, storage of angular momentum, and power demand. Because management of angular momentum is a major issue in designing and operating an orbiting spacecraft, an angular-momentum-management strategy is parameterized and included as part of the overall optimization process. The report describes several case studies, including one of a spacecraft proposed to be placed in orbit around Europa (the fourth largest moon of Jupiter).

This work was done by David S. Bayard of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "An Optimization Approach to Orienting Three Spacecraft Reaction Wheel Actuators with Application to the Europa Orbiter," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Machinery/Automation category.

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