Systems for distinguishing between friendly ground targets and those of a foe

Systems are provided for distinguishing between friendly ground targets and those of a foe and for receiving passive communications from friendly ground targets by providing friendly ground targets with reflector means adapted to modulate or otherwise change the character of laser light striking the reflector surface. The target is illuminated with a laser beam and the reflected laser energy is examined to determine whether it differs in character from that normally reflected from a target. Modulation of the laser beam can be accomplished by changing the reflectivity of the reflector means according to a selected sequence or pattern.