In this work, a novel strategy is developed to implement a trajectory tracking controller for a two-degree-of-freedom underactuated control moment gyroscope (CMG). A change of variables is first performed to obtain a convenient form that facilitates the interconnection between the actuated and underactuated gimbals. A model-based controller is proposed to ensure asymptotic tracking of the actuated gimbal to a reference signal. This reference is designed under a singular perturbation framework, and the Tikhonov solution is employed to generate a signal that guarantees asymptotic trajectory tracking of the underactuated gimbal. Theoretical stability analysis and numerical simulations are presented to validate the proposed approach.