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Subject: HA-100 type radar vs stealth
Bluewings12    2/17/2008 5:22:06 PM
Can a HA-100 type radar detect , track and give the means to destroy a stealth air target ? The answer seems to be a big yes : h*tp://www.nxtbook.com/nxtbooks/aw/dti1007/index.php?startpage=32 It has to be noted that the refresh rate is one second , which is equivalent to a fast military rotor driven radar . As it is said , the radar and its software build a "very pure" picture of anything flying bigger than 1 meter and at up to 100km . Thales says that the HA-100 has the biggest signal processing capacity of any other Thales radar . I say that such system coupled with IR SAMs or IR missile equipped Fighters can shotdown a stealth target (Aircraft , Cruise missile , etc). Some say that it is not possible or at least not that easy . Debate ... Cheers .
 
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displacedjim       2/17/2008 9:41:41 PM

I do not claim to be an expert in radar systems, so everyone feel free to correct any mistakes you see.

 

***EVERYTHING*** I feel like talking about has utterly nothing to do with some sort of theoretical U.S. v. France engagement.  I find the idea utterly absurd and I consider anyone who would waste our time discussing it to be at the very best possible to be an amateur, and much more likely to be a total a$$-hole.  Therefore anytime I cite a specific equipment nomenclature, please bear that in mind.

 

Systems like HA-100 are radars, and the receiver still detect targets using a signal scattered off the target just like all radars do.  They still operate under the same electromagnetic physics, for example the same standard radar equation for determining maximum detection range of a given target.  One difference in operation is it needs to account for multiple emitters remote from the transmitter.  The same concerns about emitter power, system gains, radar cross section, receiver sensitivity, distance from emitter to target and from target to receiver all apply.

 

By using local FM stations it operates in about the 88 to 108 MHz range (at least that's the range of FM radio stations in America anyway).  It's commonly thought that LO targets have less reduction in RCS at such low frequencies.  By using multiple emitters the signals are scattered off of different aspects of the target and at different angles to the target.  It's commonly thought that LO targets typically have less reduction in RCS in side and rear aspect as compared to the frontal aspect.

 

Because the emitters are omni-directional and because the receive antenna is a circular array of dipoles, less energy is radiated in the specific direction(s) needed to detect any given target than is typically done by military EW radars.  Particularly note that I think this may mean that detection range for a given target at low altitude may be much better than detection range of that same target at high altitude due to the propagation pattern of dipole antennas.  I think that is one significant factor why these systems seem to be advertised in particular as being low altitude detection systems.  Thus the maximum range to detect even a flying barndoor like a commercial airliner is much less than a typical military EW radar.  Because LO materials and shaping still affords significant reduction in RCS at these frequencies, the maximum range to detect an LO target is certainly less than the range to detect an airliner.

 

Because it must use TDOA calculations to determine the location of the target, it can not directly measure the velocity of the target.  It must perform a great deal of processing to find the target position, and then calculate the velocity based on the change in position from one datum to the next.  When it can detect the target using at least either three or four (I don't know which) emitters, then it can get altitude as well as an X-Y position, and consequently then form a 3-D vector of what the target is doing.  Maintaining a target track requires continuous returns from multiple emitters as the target flies through the area.

 

This may provide the detection and tracking necessary to start the kill chain and attempt to engage an LO target, but it does not guide weapons to the target.  BW has suggested somethi

 
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dwightlooi       2/18/2008 12:12:17 AM
The problems with these type of system are as follows:-

(1) It is hard to get a positional fix on anything this way. Basically, it works like this. Say you have a TV/Radio broadcast tower "A", passive receiver "B" and aircraft "C". Using a map, or GPS locator, we can quite precisely know the distance between "A" and "B". Now, if we receive a reference signal from "A" and a reflected signal from "C", we can use DSP to compute the difference in distance between "AB" and "AC+CB". The problem is we do not know the distance "AC" or "CB", only "AC+CB". In otherwords we can only place the position of C in a volume where it is possible for "AC+BC" to be equal to the difference you calculated. This is not an edge, it is a volume. In otherwords, you do not have any kind of positional fix at all. To get one, you will need multiple radiation sources or multiple receivers or both. Now what you have is a bunch of volumes which intersect. This narrows down your volume of possible locations for "C". Even then, it is a rough guess which depending on the position of all the pertinent entities can be anyway from the size of a football field to the size of a state!

(2) It is hard to tell one contact from another. In the discussion in (1) we are talking about the aircraft "C" being the ONLY possible source of reflected energy. In reality there can be more than one any number of aerial reflectors. The problem is that you cannot tell one from another. Say there are two enemy aircrafts in the sky, they both reflect RF radiation, So, each passive receiver and RF source pair now generates two volumes. And you cannot know which volume applies to which target because you don't know -- they both reflect the same signal! This then degrades you propability volume calculations drastically. Imagine that you now have 500 different possible targets and you cannot tell which of the exponentially huge number of possibility volumes belong to which reflector. Now the system becomes unusable.

(3) On top of the two probability problems discussed above, we have a physics problem. The resolution of RF detection is directly proportional to the wavelength of the electro magnetic spectrum used. For modern radars, it is more or less it is about 10 times the wavelength. For X-band (3cm wavelength) it is about 0.3 m (good enough for an AAM to kill you). For FM (2m wavelength) it is about 20m. Looking at the sky with a 20m resolution is not good enough for navigation much less fire direction.

(4) Stealth or not, aircrafts are very poor radio reflectors. Imagine trying to listen to your radio not from the broadcast source but gets reflected from a 747 overhead. First, of the wattage broadcasted, only a few millionth actually hit the 747 the rest went in other directions. And of that only a few millionth gets reflected in the one specific direction you have your receiver set up at. It is tough picking that up from the back ground noise.

(5) FM broadcasts -- being non-directional and weak -- is exceptionally easy to jam. In war time, stealth aircrafts or not, it'll be relatively easy to simply flood the airwaves with jamming signals in the FM frequency bands that you rely on. Unlike jamming a high power, directional microwave device like a traditional radar, only very minimal power is is needed to drown out the omni directional FM stations.

 
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WarNerd       2/18/2008 3:38:36 AM
If so, the system detects stealth aircraft by detecting their shadow.  This would only be effective in a limited set of geometries for transmitter, receiver, and target locations, but with enough transmitters and networked receivers you could achieve acceptable coverage.  The number required will probably be prohibitively larged.


(1) It is hard to get a positional fix on anything this way. Basically, it works like this. Say you have a TV/Radio broadcast tower "A", passive receiver "B" and aircraft "C". Using a map, or GPS locater, we can quite precisely know the distance between "A" and "B". Now, if we receive a reference signal from "A" and a reflected signal from "C", we can use DSP to compute the difference in distance between "AB" and "AC+CB". The problem is we do not know the distance "AC" or "CB", only "AC+CB". In otherwords we can only place the position of C in a volume where it is possible for "AC+BC" to be equal to the difference you calculated. This is not an edge, it is a volume. In otherwords, you do not have any kind of positional fix at all. To get one, you will need multiple radiation sources or multiple receivers or both. Now what you have is a bunch of volumes which intersect. This narrows down your volume of possible locations for "C". Even then, it is a rough guess which depending on the position of all the pertinent entities can be anyway from the size of a football field to the size of a state!

(2) It is hard to tell one contact from another. In the discussion in (1) we are talking about the aircraft "C" being the ONLY possible source of reflected energy. In reality there can be more than one any number of aerial reflectors. The problem is that you cannot tell one from another. Say there are two enemy aircrafts in the sky, they both reflect RF radiation, So, each passive receiver and RF source pair now generates two volumes. And you cannot know which volume applies to which target because you don't know -- they both reflect the same signal! This then degrades you probability volume calculations drastically. Imagine that you now have 500 different possible targets and you cannot tell which of the exponentially huge number of possibility volumes belong to which reflector. Now the system becomes unusable.

(3) On top of the two probability problems discussed above, we have a physics problem. The resolution of RF detection is directly proportional to the wavelength of the electro magnetic spectrum used. For modern radars, it is more or less it is about 10 times the wavelength. For X-band (3cm wavelength) it is about 0.3 m (good enough for an AAM to kill you). For FM (2m wavelength) it is about 20m. Looking at the sky with a 20m resolution is not good enough for navigation much less fire direction.


(1&2)   The antenna looks like a RDF type, so the system should have an angle to work with as well as a distance.  That will narrow down the volume of solutions greatly.  Network it with a second system on a decent baseline would nail down the reflecting target.
 
(3)   Actually resolution is 1/2 the wavelength.  The 10x wavelength requirement is the result of techniques used to suppress spurious returns.
 
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Bluewings12       2/18/2008 11:46:28 AM
Thanks for the replies :-)

I don 't know very much about radar techniques but it seems to me that you are wrong .
You all more or less say that a HA-100 type radar cannot pinpoint a target , but it can . If it couldn 't , why the Germans (as an exemple) want to try the radar at the Frankfurt main airport as the main radar ? Over a civilian airport , the air controlers need to know which aircraft they' re tracking and with great accuracy and furthermore , amongst many other targets . You don 't mess around with civilian lives .
So ?

What I would like to know is the altitude range of such radar .
Regarding the engagement of a LO target with IR weapons , it is obviously possible , the HA-100 could even be used as the primary source for aquiring and passing over the data needed for a launch , being from a SAM site or from a Fighter .
I cannot see any problem there .

How to jam such radar is a different topic , but we can still talk about . From what I read , FM radio waves are indeed relatively easy to jam .

Cheers .
 
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displacedjim       2/18/2008 1:08:49 PM
I for one have never said systems like HA-100 can not provide accurate position information about a target.  One thing I suggest we bear in mind is that the terms "primary radar" and "secondary radar" have specific meanings in air traffic control terminology, and they don't mean the one you use first or only, and the one you use second or as a back-up.  In ATC, "primary radar" means (at leat until now) a radar that emits a signal and detects aircraft from the scattered return signal off the aircraft.  In ATC, "secondary radar" means tracking an aircraft using other receivers that are interrogating the aircraft and processing the return from the aircraft's transponder to deduce aircraft position, altitude, velocity, etc.  This might have some bearing on how it will be used at Frankfurt and whether any other radar data will also be used.  That said, I do not doubt that it can provide tracking of aircraft in the local area around the Frankfurt airport that is good enough for ATC.
 
 
 
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displacedjim       2/18/2008 1:18:17 PM
"The problem here" regarding the IR engagement is pretty much the same as all the past discussions of IR engagement of targets.  1.  Name the SAM like I said before.  2.  We have barely entered into the possibility of lock-on after launch of IR missiles, for the large majority of the world that is not an option and therefore they need to get their fighters right up close to an LO target so they can get a lock-on before launch, and for the rest of us it only sometimes will be an option and is likely to be a more difficult, lower-propability engagement.  It may present possibilities that otherwise are not available regarding engaging LO targets, but it certainly seems likely to me to not be anywhere close to "negating" or "ending" the advantage of LO as some people are always seeking to find.
 
 
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Bluewings12       2/18/2008 1:53:08 PM
I hear you loud and clear Jim .

""One thing I suggest we bear in mind is that the terms "primary radar" and "secondary radar" have specific meanings in air traffic control terminology, and they don't mean the one you use first or only, and the one you use second or as a back-up""

Ok .

""
That said, I do not doubt that it can provide tracking of aircraft in the local area around the Frankfurt airport that is good enough for ATC.""

And also good enough for military purposes .

""
1.  Name the SAM like I said before.""

Crotale , Roland , Mica VL ...

""
2.  We have barely entered into the possibility of lock-on after launch of IR missiles""

Well , the LOAL capability of Mica IR has been validated long ago , it is just that the Rafales and Mirages need a software update (F3) .

""
it certainly seems likely to me to not be anywhere close to "negating" or "ending" the advantage of LO as some people are always seeking to find.""

I agree with you Jim , certainly not negating or ending the advantage of LO but surely degrading it .

Cheers .
 
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Phaid       2/18/2008 2:56:25 PM
So much hype and speculation over what is fundamentally such a brittle system.

These things are well suited for civilian applications, where the emissions environment is predictable.  I notice that it was tested in a very flat area -- this is an obvious requirement due to the line of sight nature of FM.  In order to work properly it needs to be surrounded by a good number of emitters -- I believe the article said eight were used in this case.  This is easily met in an urban area, but not necessarily available anywhere else.  So, already the system faces serious restrictions on where it can be deployed.

In terms of "busting stealth", nobody really knows what the effect of the kind of LO measures aircraft like the B-2 or F-22 have on FM reflection.  Sure, the geometry features are not optimized for FM frequencies, but that doesn't mean they absolutely will not work.  Also, those aircraft do not rely solely on scattering emissions, they also absorb a great deal of RF energy.  Against a powerful, directed military radar that is not sufficient, but with FM we're talking about much weaker signals.

More importantly in terms of general military applications, as others have pointed out, this kind of system can trivially be rendered useless through jamming.  In fact, you don't even need a real jammer; a few unexpected FM broadcasts in the same area would spoil the "very pure" picture of the RF environment the radar needs to work, and the radar would fall on its face.
 
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displacedjim       2/18/2008 3:19:02 PM

I hear you loud and clear Jim .



""One thing I suggest we
bear in mind is that the terms "primary radar" and "secondary radar"
have specific meanings in air traffic control terminology, and they
don't mean the one you use first or only, and the one you use second or
as a back-up""



Ok .



""
That said, I do not doubt
that it can provide tracking of aircraft in the local area around the
Frankfurt airport that is good enough for ATC.""



And also good enough for military purposes .



""
1.  Name the SAM like I said before.""



Crotale , Roland , Mica VL ...



""
2.  We have barely entered into the possibility of lock-on after launch of IR missiles""



Well , the LOAL capability of Mica IR has been validated long ago , it
is just that the Rafales and Mirages need a software update (F3) .



""
it certainly seems likely
to me to not be anywhere close to "negating" or "ending" the advantage
of LO as some people are always seeking to find.""



I agree with you Jim , certainly not negating or ending the advantage of LO but surely degrading it .



Cheers .



 
 
No, those SAMs don't cut it.  "Name the SAM like I said before."  Here's what I said before:
"First, there's essentially no such thing at this time as an IR SAM in this context.  Name one that can lock on to and engage a target at 25,000ft+ (not to mention an F-22 at 40,000ft+)."
None of the SAMs you mentioned can do that.
 
Well, I'll agree that the French HA-100 and Rafale F3 with MICA-IR will soon degrade to some degree the LO capability of Russia to attack France with some Kh-555 or whatever they call thoise cruise missiles that they might be getting some year soon that might have some LO capability.  Congratulations.
 
 
 
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