Radio masts negating stealth

Lo all - been reading ATS for ages but never posted... :-p

Ok - So basically i've heard allot about the use of commercial radio mast signals being used to track and target (US) stealth aircraft - Namely the F117 night hawk shot down in bosnia... (Think it was bosnia, could have been chechnya though, my historys crap).

I understand the basics of how stealth works but i really can't get my head round how this could work - I mean if you can't use reflected EM radiation (the very point of stealth) all your left with is the shadow in the radio "umbrella" the aircraft casts. Thats all very well and good but at any workable distance the shadow created would be huge and totally unusable for targeting.
The only way i could even specualte on this working would be using at least 3 different signal types and triangulating each one seperately but you'd need detectors EVERYWHERE, know all the individual wave types and an intergrated targeting system that would make the star wars programme blush. (Not something your average bosnian has)
So - is this true or just rumour and wishfull thinking?

[edit on 2-9-2006 by Polskoo24]

Welcome!

I'm no expert in the field, but I'm pretty sure I read something about this in a Popular Mechanics or similar magazine several years ago.

I found one link that discussed it back in 2004. I think you are talking about #3, right?

www.electronicaviation.com...

1) One technique uses conventional radar to search for discintive patterns of air turbulence, because it's very hard to supress air turbulence.

2) Another technique looks for enegry-drops or shadows in radar illumination reflections. This is done by merging information from several ground-based radars, none of which is capable of detecting the aircraft on its own. So basically it's piecing infromation from different radars to form a big picture of where the plane should be.

3) A passive radar system listens to low-frequency radio waves and utilizes high-speed computers to distinguish signals that are bouncing off moving objects in the air. Serbians may have used low band radars to track and shoot down the F-117 in 1999.

4) Stealth cannot be created in every frequency.

Yeah - Number 2 was kinda what i had in my head, Although that they can just switch to higher EM band and target it like a normal aircraft is a little scary.
I mean when you think about it - Have the US ever offensively used B2's, F117 (or the new f22's) in a country with realtively developed telecommunications network...?
Maybey thats why the middle east is such a popular holiday destination for US munitions :-D

It's been suggested that cell towers could be used to track stealth aircraft.

Stealth technology doesn't absorb radar signals, it scatters them in different directions. If your radar transmitter and reciever are in the same place, and the signals aren't reflected back in the direction they came from, the radar will never "see" the aircraft.

Cell tower work because your transmitter and reciever aren't in the same place. The EM radiation from the cell tower strikes the jet, is scattered in different directions, and is picked up by several other cell towers in other locations. Apply enough computer power and you can track any aircraft, stealth or not, as they scatter EM accross the cell network.

What's impressive is how much information you can gather with such a system. Radars, including the cell tower system when used as such, can pick up resonence - if or how much the target is vibrating. This relates to engine RPM, which can tell you what kind of engine(s) the aircraft is using. This in turn tells you if its civil or militay, and can get even more specific than that in some cases.

Pretty impressive stuff. But as Polskoo pointed out, it only works if you've got sufficiently dense cell towers.

The russian long wave radar can actually track stealth BUT teh wave length is too long to direct weapons - BUT they can track it

There's a few things you can do against stealth aircraft, none of them are great, but better than nothing. Using a bistatic (2 radars) array will give you better accuracy but increase the calculations by a power of two. Now, the number of calculations you'll have to do goes up at a rate of N^2 where N is the number of radars you have. This is because you've got an NxN matrix of data at any given time. This will get you something, but remember they try to scatter the radar in all directions. You actually do get signal back off a stealth aircraft, it's just filtered as noise by the radar. Another thing is to put stupid amounts of power through your radar and have very sensitive receiving equipment. Or if you want to use a telescope you can get a Schlieren of the aircraft in flight.

There's another thing called a flash dance, it uses things like cell towers or scattered radar arrays to bounce many signals off in very short bursts. It keeps the plane's radar of balance so you can't drop bombs on them because you can't get a lock.

The F-117 in wherever it got shot down was for a very specific reason. It flew the same route into the country every day. Eventually they put a SAM site right under the flight path. At 5 miles, you can almost always detect a stealth aircraft. They did and shot it down. It may not have been exactly like this, but it's the basic idea.

I wonder if the system you are talking about is similar to the concept of PCL, or Passive Coherent Location. Essentially as described, it uses existing sources of emmisions such as mobile phone towers, VHF/UHF radio transmitters and the like to track aircraft. Due to the sheer number of transmitters, it is almost impossible to jam everything, and if you incorporate multiple receivers, then it becomes a very powerful system indeed. Longer wavelengths, as mentioned previously, do have have an impact in increasing the RCS of a platform (most stealth platforms are optomised within certain bands, usually fire control and AI radar frequencies). PCL is something that China has shown a lot of interest in. However, while the concept is good, the reality is that there are still a lot of challenges remaining to get the system to a level where it is operationally effective (multiple targets, interference and noise problems, incorporation into a common operating picture, and the simple fact that you might know something is there, but what can you do about it if you can't fire weapons?).

A search on PCL and Stealth will bring up a surprising number of detailed publications and briefs on the concept. Hope this helps.

So - what kind of range are we talking here with passive radar noise / Mutiple radar detection systems...? I mean, I realise that if your talking Air to Air at 70 miles+ with an F22 doing Mach 2, It's pretty doubtfull your going to be able to track/target it.

But what about Ground to air defence systems against ground attack aircraft...?

I mean this raises some serious questions about the F35 (Like it doesn't already have enough problems: Melting its own carrier on take off and landing...) - If this thing is going to be the US's main bomber (not its biggest, but surely most used) and the UK's only combat aircraft that'll be deployable outside of europe: Whats the point in spending ALL that money on a stealth system that won't offer that much protection...?

Im sure this technologys in it's infancy but if its something that comes down to computer number crunching it'll ownly be a matter of time.

Simple, all that will tell you is that something is there. Now you still have to vector something to it, and these things won't be able to provide a lock, just knowledge that it's there. The aircraft radar is far less effective, this and the fact that you've got nonstealthy aircraft attacking things like this before while the stealthy platforms are still flying.

Now, you can use anti-SR-71 tactics to try to shoot down the stealthy platforms. You launch a missile into the path of the stealthy aircraft and hopefully it will be in range by the time the seeker head goes active. If not, you just wasted a missile. Within about 10 miles (usually activation distance of most seekers) you can usually detect a stealth aircraft. Now, from the rumors circulating about the F-22, maybe none of this will help.

Yeah, the problem (as LoBs states above) is tying the tracking radar into a fire-control solution.

The long wavelength radar does not provide sufficient resolution for a missile shot. Its concievable that the various other methods discussed here will, then the challenge is to present that data to a SAM site in sufficient time to allow them to launch missiles. They may even be able to use the off-board radar as a means of guidance, meaning the SAM battery need not reveal its position by using its own radar system.


Now, if the radar emitters could be de-coupled from the civilian power grid and there are a sufficient number, that would represent a major challenge to any penetrating airforce, HARMs would become effectively useless against SAMs, and depending on radar illumination times, they might not have time to get a lock on a radar emitter.

If you can get enough information on an aircraft to gauge roughly where it is and where its going, hitting it with a missile shouldn't be too hard.

Modern heat seeking missiles are sensitive enough to track aircraft from any angle; the heat from air friction on the leading edges is enough to get a lock on even stealth aircraft from a good distance away. So add in a GPS/INS "autopilot" mode to an IR homing missile, give it LOAL (Lock on after launch) capability, and you've got all you need.

Most IR missiles are good for several km of range, while I'm guessing the tracking innacuracy via. radar is hundreds of meters at most. Fly the missile into the flightpath of the target aircraft via. remote guidance, and the IR seeker can take over once it gets close enough to track the target on its own.