In one embodiment, an actuator for positioning of mirrors in an optical system is provided and includes an actuator base and a reaction mass assembly. The reaction mass assembly includes a reaction mass support member having biasing features formed as a part thereof and a reaction mass that is coupled to the biasing features such that the reaction mass is suspended on biasing elements in six degrees of freedom (DOF). The support member is fixedly connected to the actuator base; however, the reaction mass is not directly attached to the actuator base but rather is supported in the reaction mass support member in a manner that allows it to have six DOF.