More to the point, detecting a stealth aircraft is very different from shooting at a stealth aircraft.
This radar would likely not have the location accuracy of where exactly the B-2 was to accurately engage it with a missile. Your accuracy would be limited by the rate of RF pings the B-2 is putting off, and then the margin-of-error of these RF waves and receiver.
This is one difference between the B-2 and stealth fighters like the F-22 & F-35: The latter are not necessarily designed to be invisible, only impossible to reliably hit. Their shapes and radar-absorbent paint deflect, diffuse, or absorb the high-frequency bands used in the terminal guidance of missiles. So they are hard to target. But they can be picked up at range by long-distance, long-wavelength VHF and UHF radars. These frequencies, used in early-warning radars, have too low-optical resolution* however to be any good at aiming guns or missiles. The B-2's "flying wing" shape is able to not-interfere with these wavelengths though, and hence hides from them. In that sense, this is somewhat interesting, if neutered for the reasons you mention.
*You can only localize the detection to a few sq hundred meters, even kms.
Not to sound skeptical, but I've seen some stuff Ratheon was putting out at least 10-15 years ago and I think it had some pretty impressive optical sensors. Are we including the various infrared frequencies?
Optical and infrared sensors have improved a lot and can be a useful supplement but due to limited field of view and interference from weather you generally can't count on them for primary search. Unless the target is really time sensitive, B-2 mission planners try to fly at night in bad weather when those sensors are seriously degraded.
I doubt it. If people are able to photograph dark birds at night, I see no reason why a missile with much bigger optics and more efficient (wider band and monochrome) sensors wouldn't be able to find a plane.
A lot of Russian planes have Electro Optical systems for targeting. Usually they are IR based locking onto hot engines and such like a typical Fox 2 (Heat seeking missile) Range of IR tracking is pretty small for head on planes and more importantly your missile needs to know where to look in the first place to acquire the target. Also stealth aircraft have reduced heat signatures making it harder to pick them out against the background. Also you have problems with determining contrast against the background due to diffraction.
Essentially the passive array in this article is in the class of "Early Warning Radar" which is used to alert Combat Air Patrol aircraft and SAM sites where to start looking for the contact.
If you wanted to use this with a networked radar guided missile you would have problems with terminal guidance. If the missile could acquire the target as it came into radar range for the radar cross section of a stealth aircraft, there is very little chance it would have the energy to track the target. It would essentially need to make a right turn midair to track on the target. All the while the missile's radar will be making the plane's RWR light up like a Christmas tree.
Recently in DC they detected a plane that did not respond to warnings. The optical system then also detected the plane and panic ensued. Problem was the radar system was showing a phantom and the optical system saw a nearby plane and thought it was confirming the phantom.
Hopefully the US has learned something in the past 32 years since that incident. It seems that even our allegedly sophisticated adversaries haven’t in the present time.
At least the Russian team was merely operating a Buk in a clandestine op in the middle of a field in Ukraine (and the US ship was technically in Iranian territorial waters in 1988 during an actual war), I’m curious what Iran’s excuse was shooting it down in their own property?... maybe we’ll learn more about it eventually. Bellingcat was able to provide the actual team member names and wiretaps of the Russian soldiers.
All the stealth craft also included some IR avoidance as a matter of course, IR seeking missiles existed at the time these were designed. It's unclear if a more modern missile would still be sensitive enough to lock on and avoid chasing flares.
The techniques they used to decrease the IR visibility are pretty neat. The engine nozzles are over the wings and there are a lot of airflow tricks used to cool it down faster so from below there might not be enough plume to track from a surface launched missile coming, from below at least.
Conventional IR countermeasures (spatial, spectral etc.) really are becoming a thing of the past.
When you’re talking about terminal IR guidance on any modern missile, generally the IRCCM will be so good that the probability of defeat with a flare cocktail is below an acceptable risk threshold. DIRCM is the current answer to this problem and—to tie this in with the parent comment—renders terminal IR guidance much less effective than MMW or other RF guidance.
And also, searching the top speed of a B-2 at 628mph, if detected at 150 miles out only gives them 14 minutes. Which is both a lot, or a little. Depending on how prepared for action someone is.
Well since there are so few B2 and they are essentially irreplaceable, I imagine standard wartime doctrine for the adversary would be to ignore target protection as a concern and go straight for the plane even at the risk of losing several of yours by flying over territory you don't control.
In reality, what would make a difference is coordinating communications and decision making.
This radar would likely not have the location accuracy of where exactly the B-2 was to accurately engage it with a missile. Your accuracy would be limited by the rate of RF pings the B-2 is putting off, and then the margin-of-error of these RF waves and receiver.
This is one difference between the B-2 and stealth fighters like the F-22 & F-35: The latter are not necessarily designed to be invisible, only impossible to reliably hit. Their shapes and radar-absorbent paint deflect, diffuse, or absorb the high-frequency bands used in the terminal guidance of missiles. So they are hard to target. But they can be picked up at range by long-distance, long-wavelength VHF and UHF radars. These frequencies, used in early-warning radars, have too low-optical resolution* however to be any good at aiming guns or missiles. The B-2's "flying wing" shape is able to not-interfere with these wavelengths though, and hence hides from them. In that sense, this is somewhat interesting, if neutered for the reasons you mention.
*You can only localize the detection to a few sq hundred meters, even kms.