A Stability Criterion for an Artificial Earth Satellite

The equation of rotation of the spacecraft about a set of control axes are developed to reveal the required functions of a momentum exchange control system when subjected to external disturbances. A linear control system is designed and the three-axis characteristic equation is developed. This ninth order equation has coefficients which vary with the particular attitude references in use, and with the particular desired attitude. The number of and location of the references are variables. Reference information and commanded attitude data are lumped into two constants and lines of constant minimum system damping are plotted parametricly. Thus before slewing to a new attitude, the degree of damping or instability may be readily determined.