Abstract: Apparatus for controlling the output power of a laser diode the beam of which is directed in a selected direction toward a target so as to enable a missile or the like to be directed along the beam toward the target. The apparatus includes a circuit which supplies a variable amount of power to the diode, and a circuit which is responsive to the radiation emitted by the diode, and the latter circuit generates a signal which is proportional to the magnitude of the emitted radiation. A control circuit is provided which is initiated into operation at the time of firing of the missile and generates a signal which represents the desired increase in magnitude of the radiation emitted by the diode during the time of travel of the missile toward the target.