A gyroscope is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axle is free to assume any orientation. Gyroscopes can be used to keep a platform or reference frame in a specified orientation relative to the earth, several spacecraft have been equipped with gyroscopes to maintain their orientation in space. The applications of gyroscopes include aircraft, drones, and satellites to help them balance and stay upright. Gyroscopes are also used in toys, compasses, and other mechanical and electronic instruments to measure or maintain orientation.