Abstract: A motor active nutation damping system employing a rotor mounted accelerometer, a platform/rotor relative rate sensor, a despin motor and a controller. In the presence of nutation, the accelerometer senses a sinusoidal acceleration whose amplitude is proportional to nutation angle and whose frequency is rotor nutation frequency, i.e., the rate at which the transverse angular momentum vector appears to rotate in rotor fixed coordinates. The controller multiplies the filtered accelerometer signal by a square wave at relative rate generated by the relative rate sensor to obtain a signal consisting of sinusoids at platform nutation frequency and higher order frequencies.