A Chinese 200Nms control momentum gyroscope (CMG) on display at the trade exhibition accompanying the 2013 International Astronautical Congress (IAC), which was held in Beijing, China. A CMG is an attitude control actuator used to maintain or adjust the orientation of large spacecraft or space stations in orbit: a heavy spinning wheel is made to tilt or 'gimbal' and this causes a gyroscopic torque (measured in Nms) that rotates the spacecraft about a given axis.