The response of the Space Infrared Telescope Facility's attitude control system to a nod command is studied under a wide variety of conditions. Several engineering issues are explored: the effects of variations in the structural model, relocation of sensors and actuators, the influence of the fine guidance sensor sampling period, resolution and noise on the system response, torque and rate integrating gyro noise and disturbances. Simulation results using control moment gyros and reaction wheels as actuators are presented. Rajan, N. Ames Research Center...