Topic summary
SACLOS

Extracted from the Wikipedia article Semi-automatic command to line of sight.
Wire and radio-guided SACLOS
With wire- and radio-guided SACLOS, the sighting device can calculate the angular difference in direction from the missile position to the target location. It can then give electronic instructions to the missile that correct its flight path so it is flying along a straight line from the sighting device to the target. Most anti-tank SACLOS systems, such as Milan and TOW, use a strobe or flare (visible, infrared (IR) or ultraviolet (UV) light) in the tail of the missile with an appropriate sensor on the firing post, to track the missile's flight path. The launching station incorporates a tracking camera with two lenses. A wide field of view lens that locates and "gathers" the missile near the center of the gunners line of sight immediately after launch, and a narrow view lens with automatic zoom that accomplishes the fine tracking adjustments. In most configurations, the narrow field camera utilizes electronics that translate the brightest spot in the view – the flare or strobe of the missile – into an electrical impulse. This impulse changes as the missile leaves the center of the field of view, and the electronics automatically apply a correction instruction in the opposite direction of the change to re-center the missile.