Despite the fact that B-52 have extensive electronic warfare capability likely complemented by specialized EW airborne assets, and despite the extreme horror and suffering that B-52 carpet bombing will lead to, they do provide a unique opportunity.
B-52 have notoriously high IR signatures. In fact they light up even on poor IR sensors as engines must supply high thrust and energy input. They have high energy in virtually the entire IR band as most turbofans do. But unlike fighters, they are slow moving machines. Whats more they are notoriously low maneuverable with extremely poor agility, having been derived from decade old airliner.
Their electronic warfare units like all others, also provide relatively easy passive detection and localization or can be forced to for this purpose (e.g. Iran using fast transient mobile radar activation and de-activation, just long enough to force EW units to respond but not long enough to get localized ). Despite conventional self protection, they are the most vulnerable airborne asset US is sending.
They are also likely the most cheapest for US to run per kg dropped that is. Disturbingly and I mean that with extreme anxiety for Iranian civilians, they are also notorious for causing extreme injuries to civilians and children as we have seen in Vietnam war. Probably one of the the most inhuman weapons of all except nuclear.
Still due to the fact that compared to all other bombers, they are the most easiest to shot down, using the most easily available seeker type, namely IR.
Iran has plenty of IR or combined IR/optical sensors. Posses well developed missile integration capability. I sincerely hope that "surprises" Iran talks about include at least low to medium altitude IR air defense missiles.
B-52s's fundamental vulnerability stems from the fact that it has so many places where it emits high energy IR signatures. For example engines are distributed over large span wings, and a lot of them, and are visible in IR sensors from a wide range of angles.
That means despite flares, this large distribution of IR emitters, creates " a group". Modern signal processing ranging from traditional Particle filters to random finite set based particle filters (all based on Bayesian approach off course) and even batch based stochastic estimations approaches such as Gauss–Newton and associated Polynomial Filters can have implementations that easily track groups of targets as one target entity for cases like this.
I remember at some conference some one told me, Raytheon tried to develop Gauss–Newton and associated Polynomial Filters framework but probably felt it was too involved and went back to Kalman filter bank approach. Likely engineers went back to what they have been doing for decades.
It is quiet straightforward though. I don't see the problem. it allows dealing the signal drift much better and with guaranteed avoidance of stochastic filter instabilities that can occur even in relatively simple Kalman filter implementations . Anyway, rest of the world has extensively implemented all such approaches.
All of these frameworks are widely known and have been extensively implemented from Pakistan to Iran, Turkey and obviously China to all major warring nations that are big enough or advanced enough. Modem implementations of such frameworks make B-52 especially vulnerable as we will see below. US due to lack of ammunition is being forced to use B-52, hopping nothing will happen.
B-52 with its large flexible wings with heavy engines ( having distinct low frequency vibrational modes ) makes it much much easier to distinguish it from flares when using IR sensors. The large widely separated engines emitting massive IR signatures have high most angle visibility and not to mention other heat emission sources that such large aircraft has making it an extremely vulnerable target. Signal processing can be easily geared with additional few 100 lines of codes to deal with this horrifying machine.
I am sure and sincerely hope that Iran anticipated these aircraft. They are the most threatening to civilians. They also have unique vulnerabilities that an intelligent adversary can exploit to at least shoot some of them down, during at least carpet bombing type raids.
Once few go down, they will be pulled back. Iran does need Prior warning in some areas and in others real time response can be enacted, achieving the same objective.
US likely want to use them against Iranian army defending its borders. But they likely have mountain and other natural or built structures likely underground even so it won't be easy and Iran can survive this.
We know that Iran's detection and tracking abilities remain intact for the most part. So that strength is still there.
Shooting down B-52 therefore likely is and should be the highest priority of Iran.
