Err..
The guidance of TOW missile does not rely directly on infrared seeker like a infrared homing missile (ex: Sidewinder). Though the gunner use a IR camera to keep the reticle on the target, it can be performed by an optical day sight.
Actually, the gunner tracks the target, and a rear-mounted flare/beacon is on the missile. The command and launch unit (CLU) -which is aligned with the gunner sight- tracks the missile using the IR beacon and give orders to the missile through the despooling wire to keep it on the line-of-sight.
This is SACLOS: semi-automatic command to line-of-sight.
Try this
link
It depends on what you are interested, the system that tracks the rear beacon of the missile or rather infrared imaging applied to guidance systems. In the latter case, I suggest you to look at another ATGM like Javelin or Trigat LR/Pars 3