• Traditionally, seekers have been simple correlation trackers and a set of gimbals that are used to measure the angle rates of the target. 

        - Infrared seekers detect and track a hotspot on a target (hot engine compartment on a ground vehicle or the jet plume on an aircraft).

• One method would be to take a simple set of detectors: 

        - The aim is to move the detector so as to maximise the signal from the central detector compared to the outer ring - the central region can be ‘dead' for ‘bang-bang' control (size = ‘static margin').
        - By doing this, it is possible to track the way in which the target is moving relative to the line of sight of the seeker.
        - Although this is contains a relatively large amount of mechanical noise from the gimbals, the signals can be filtered to produce a smooth signal.