But having "memory" doesn't mean you are actually seeing the target, it merely will show where it would be expected to be if he maintained its heading (which doesn't normally happen). Also same difficulty is with Su-27 radar, when really close and you don't know exactly where he is, you only know approximation, because he's so close it's pretty much impossible to reacquire him... and if you keep looking at radar instead of trying to get visual, and he sees you, you are pretty much dead.