IR imaging incorporate automatic target recognition,allow it "see" thru clutter,but it does not provide full 100% accuracy, older gen. of IR use multi element seeker, case was during kosovo air war, when F-15C try shoot down a serb super galeb fighter/trainer,galeb fly low to evade the interception,the F-15C pilot o fire her AIM-9L,to the pilot amazement the missile hit her target, according to the pilot under this event,even the AIM-9L IR seeker due to ground clutter and thermal signature,it could degrade IR ability to track her target.specially locking to low flying target.he own admission he just got lucky.