Abstract: Three different types of unbalance are detected and corrected while a gyroscopic inertial flywheel is continuously spinning. The gyroscope is mounted in an integrated test and correction apparatus comprising an angularly positionable mount supported on a shaker table. The mount supports a test chamber in which the spinning gyroscope is located in a low viscosity, low density atmosphere. Windows are formed in the chamber on opposite sides permitting lasers fixed on the mount to be aimed at the flywheel to burn off selected portions of its mass. A safety system is arranged within the chamber to detect whether the spot at which a given laser beam is aimed has already received a laser burn. Mass unbalance is determined, with the spin axis polar, by rotating the gyroscopic reference axes 90.degree. and recording the drift at two orientations. Radial unbalance is determined by imparting a reciprocating motion along the spin axis by means of the shaker table at the same rate as the rotation of the flywheel.