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5.5. Attitude Control Subsystem. The IUE stabilization and attitude control subsystem consists of all equipment used to maintain or change the direction at which the spacecraft is pointing. In order for spacecraft attitude to be controlled, there must be some sort of attitude sensors, some equipment capable of producing a change in the orientation of the spacecraft (actuators) and an interface between the two. The IUE is capable of controlling attitude using a number of combinations of sensors, actuators, and interface. This subsystem is without question the most complex subsystem aboard the IUE spacecraft. It was designed to be simple, light weight, low powered and reliable on one hand, and on the other hand, it was required that the control subsystem satisfy precise pointing and slew accuracy specifications. The principal requirements that have largely influenced the control subsystem design philosophy are the following: