A constraint monitor algorithm for the Cassini spacecraft

The spacecraft is commanded to turn from one point in space another by commanding attitude, rate, and acceleration profiles, which the Attitude Controller is required to execute faithfully. Constraint Monitor algorithm performs appropriate checks to ensure the legality and the realizability of the instantaneous attitude, rate, and acceleration commands. When the command is found to be unrealizable because of hardware limitations or because it may enter a constraint space, Constraint Monitor modifies it appropriately such that the legality of the command is maintained. In doing so it ensures that the rate and acceleration are not outside the capabilities of the attitude control hardware and that certain sensitive spacecraft boresights are protected from exposure to bright objects. 1. tion and Science Objectives The spacecraft, scheduled for launch in October 1997, will arrive at Saturn in 2004. On its way to Saturn, it will fly by Venus, Earth, and Jupiter to pick up the needed gravit...