NEW DYNAMIC VARIABLES FOR MOMENTUM-BIAS SPACECRAFT

This paper introduces two new seven-parameter representations for spac ecraft attitude dynamics modeling. The seven parameters are the three components of the total system angular momentum in the spacecraft body frame, the three components of the angular momentum in the inertial r eference frame, and an angle variable. These obey a single constraint as do parameterizations that include a quaternion; in this case, the c onstraint is the equality of the sum of the squares of the angular mom entum components in the two frames. The two representations are nonsin gular if the system angular momentum is nonzero and obeys certain orie ntation constraints. The new parameterizations of the attitude matrix, the equations of motion, and the relation of the solution of these eq uations to Euler angles for torque-free motion are developed and analy zed.