A high-precision whiskbroom scanner control system, which is used on earth observation satellites, is discussed. This
control system is required to keep high angular precision with ultra-smooth rotation. We designed a feedback control
system consisting of a rate loop for rotation-speed control and a position loop for angular control. Adding a feedforward
control system using cyclic memory, 1st order rotational synchronizing disturbance caused by eccentric load has been
compressed over 50 dB. As a result, high pointing accuracy with a standard deviation of 0.003 degree or less has been
achieved in rotating with a constant speed of 79.4 rpm.