already reported This Seems Wrong (Aim-120C Spoofed By Small Amount of Chaff Along With Notch)

[DCS FIGHTER PILOT]

First off, yes, I am aware of what notching is and the effects it has on pulse doppler radar along with chaff. With that out of the way, I have noticed recently in multiplayer that Aim-120's seem to be getting spoofed quite easily by targets that notch and deploy chaff. For older missiles, this would seem appropriate, however for the Aim-120, it does not. Given that this is an ADVANCED medium range air to air missile, I would assume that though the missile may no longer be able to detect the target that is notching, it would still continue to fly towards the last calculated position of the target as opposed to pulling over 10g's to chase the chaff. This behavior is shown in the track provided. What is even more bizarre, is that the missile decides to go for the chaff just seconds before impact, before the chaff has much time to expand. I have been flying DCS for a while now and realize that this has always been a problem, (missiles deciding to go for countermeasures at the last second). Thoughts? 

Aim-120C Spoofed.trk

[Flappie]

 

[nighthawk2174]

1 hour ago, DCS FIGHTER PILOT said:

First off, yes, I am aware of what notching is and the effects it has on pulse doppler radar along with chaff. With that out of the way, I have noticed recently in multiplayer that Aim-120's seem to be getting spoofed quite easily by targets that notch and deploy chaff. For older missiles, this would seem appropriate, however for the Aim-120, it does not. Given that this is an ADVANCED medium range air to air missile, I would assume that though the missile may no longer be able to detect the target that is notching, it would still continue to fly towards the last calculated position of the target as opposed to pulling over 10g's to chase the chaff. This behavior is shown in the track provided. What is even more bizarre, is that the missile decides to go for the chaff just seconds before impact, before the chaff has much time to expand. I have been flying DCS for a while now and realize that this has always been a problem, (missiles deciding to go for countermeasures at the last second). Thoughts? 

Aim-120C Spoofed.trk 137.87 kB · 2 downloads

Yeah this is a big issue and has been around for a long time.  The amraam should continue to fly towards the last known intercept if notched and not just return to 1g flight (i'm also wondering if chaffed will the missile even attempt to reacquire in game right now?).  Chaff wise, irl it takes time to bloom to its full rcs (2-4 seconds depending on exact conditions) which is much longer than the time it takes to slow down to the current wind speed (often under .5 seconds).  Which should make it fall into the doppler filter.  Beyond this chaff that falls outside of the res cell of the radar should have no impact, but currently in game the missile will pull max G towards it if it gets "decoyed".  Even if all of this fails the missile could still discriminate based on range gatting irl as well.  Not to mention I wouldn't be surprised if algorithms exist to detect when a target is chaffing and to either apply some sort of filtering or target edge tracking.  Methods being developed in the late 1950's.

 

Just treat chaff like a flare but for radar missiles and the behavior we see in game makes more sense.

[TotenDead]

10 часов назад, nighthawk2174 сказал:

Yeah this is a big issue and has been around for a long time.  The amraam should continue to fly towards the last known intercept if notched and not just return to 1g flight (i'm also wondering if chaffed will the missile even attempt to reacquire in game right now?).  Chaff wise, irl it takes time to bloom to its full rcs (2-4 seconds depending on exact conditions) which is much longer than the time it takes to slow down to the current wind speed (often under .5 seconds).  Which should make it fall into the doppler filter.  Beyond this chaff that falls outside of the res cell of the radar should have no impact, but currently in game the missile will pull max G towards it if it gets "decoyed".  Even if all of this fails the missile could still discriminate based on range gatting irl as well.  Not to mention I wouldn't be surprised if algorithms exist to detect when a target is chaffing and to either apply some sort of filtering or target edge tracking.  Methods being developed in the late 1950's.

 

Just treat chaff like a flare but for radar missiles and the behavior we see in game makes more sense.

It doesnt need to "reach" its "full" RCS to make a missile blind. And if you're talkin about reality then you should also know that chaff stays in the air for a very long time and cold target might be even lost by a radar because the target might very possibly be shielded by chaff from any illumination

11 часов назад, DCS FIGHTER PILOT сказал:

 Given that this is an ADVANCED medium range air to air missile, I would assume that though the missile may no longer be able to detect the target that is notching, it would still continue to fly towards the last calculated position of the target as opposed to pulling over 10g's to chase the chaff. 

 

Oh, now that's a good point, if it's called ADVANCED it shouldn't be affected by anything. It's advanced!

[nighthawk2174]

12 hours ago, TotenDead said:

It doesnt need to "reach" its "full" RCS to make a missile blind. And if you're talkin about reality then you should also know that chaff stays in the air for a very long time and cold target might be even lost by a radar because the target might very possibly be shielded by chaff from any illumination

Oh, now that's a good point, if it's called ADVANCED it shouldn't be affected by anything. It's advanced!

From what i've read, from multiple sources, it acts more like a noise jammer it doesn't fully block the signals just degrades the power.  It's a lot like a cloud, does a thin cloud stop the sun's light (instead in our case the sun would be our radar) from coming through entirely?  Or does it just reduce the intensity of that light? So a powerful enough radar or a large enough target can still see/be seen through a chaff cloud.  On top of this the returns from the cloud can still be range gated out so long as the return from the main target beyond it is above the noise level of the radar.  And yes the AMRAAM is quite an advanced missile its resistance to things such as chaff and basic ECM techniques is indisputable excellent to superb.

 

Edit: grammer/clarification

Edited January 19, 2021 by nighthawk2174

[Blinky.ben]

There is a minimum distance between 2 objects that a radar can distinguish between the 2 radar returns. So yes the closer the missile is to the target if the contact is to use chaff at the last moments before impact the missile is more likely to find it harder to determine which is the real target or chaff but this is going to be hand in hand as to what anti clutter circuitry the radar uses. As for chaff expanding, tear up some paper and throw it in the air. Its rather instant for chaff to seperate and it doesn’t have to completely seperate to create an effect. I can’t speak for the Aim-120 just like every single person on this forums has no idea what the minimum distance would be to determine 2 targets between each other and most the data classified for the missile (unless someone here can say what the real compression ratio is and what the anti-clutter circuits are for the Aim-120), But for our radars that we use that are I would assume  to be way more advanced then what would be in a missile, is that the distance between 2 objects is more then you would expect. However the further from the contact the better chance the missile has to sort out what is what.

 

But just to point out some radar theory the larger the antenna the more accurate the radar is. so a tiny missile radar isn’t going to be as accurate as a much larger airborne or ground based tracking radar, That’s just hard rules for radars which is why I would suspect the missile radar doesn’t go active until it’s close to the contact. There is a trick that can be done to synthetically make your antenna seem larger then what it really is but I don’t know if this is something that can be discussed but I’m sure it’s on the internet how this is done. But a missile wouldn’t be able to achieve this. 

Edited January 19, 2021 by Blinky.ben

[Blinky.ben]

5 hours ago, nighthawk2174 said:

From what i've read, from multiple sources, it acts more like a noise jammer it doesn't fully block the signals just degrades the power.  It's a lot like a cloud, does a thin cloud stop the sun's light (instead in our case the sun would be our radar) from coming through entirely?  Or does it just reduce the intensity of that light? So a powerful enough radar or a large enough target can still see/be seen through a chaff cloud.  On top of this the returns from the cloud can still be range gated out so long as the return from the main target beyond it is above the noise level of the radar.  And yes the AMRAAM is quite an advanced missile its resistance to things such as chaff and basic ECM techniques is indisputable excellent to superb.

 

Edit: grammer/clarification

 

Yep it makes sense how it degrades the power of the pulse but it can also confuse the missile for that brief moment until it can process that’s it’s not the target.

 

but a “statement that the ECM techniques is indisputable excellent to  superb”. that’s a big statement from someone that unless your part of the team that build these missiles then you couldn’t have the knowledge to make such a statement.

Edited January 20, 2021 by Blinky.ben

[nighthawk2174]

 

5 hours ago, Blinky.ben said:

 As for chaff expanding, tear up some paper and throw it in the air.  Its rather instant for chaff to seperate and it doesn’t have to completely seperate to create an effect.

 

 

I mean I don't think it's really comparable here as were talking dumping this out at hundreds of mph.  Additionally there are some declass documents out there on this stuff and the average time i've seen is generally in the 2-4 second range for a chaff cloud too fully bloom.  Also no it doesn't have to completely separate but the effect will be greatly diminished from the full bloom.

5 hours ago, Blinky.ben said:

 I can’t speak for the Aim-120 just like every single person on this forums has no idea what the minimum distance would be to determine 2 targets between each other and most the data classified for the missile (unless someone here can say what the real compression ratio is and what the anti-clutter circuits are for the Aim-120), But for our radars that we use that are I would assume  to be way more advanced then what would be in a missile, is that the distance between 2 objects is more then you would expect. However the further from the contact the better chance the missile has to sort out what is what.

 

You can get a rough idea of what the res cell would be in both azimuth and depth with:

 

From my current understanding the accuracy in depth is often in the range of hundreds of feet if not much less.  With the accuracy in azimuth being larger but iirc the beamwidth on the amrram is quite small (only like 1°-2°) and considering the fact it will usually be at much shorter ranges when you a) get the lock tone and b) react it may be as little as 5 miles or less this won't be that large either.  Keep in mind this fact, at 400kts your moving at 675ft/s.  Which exceeds theses values by a lot.  And considering that chaff will drop to the current wind speed almost instantaneously (which iirc means under .5sec) its likely the chaff will only have fractions of a second to have any impact.  More if slower, less if faster.  If anything my current visualization of this is that the target will appear to for a brief moment get larger in size.  By how much is highly variable but probably not by much especially if the chaff bundle falls out of the res cell quickly.

 

Additionally monopulse systems unique way of working they will be able to tell if there is multiple targets in the resolution cell.  In general two targets will not be at the *exact* same distance and this will cause the return to shift in phase from what would be expected with one target.  With this being maximized if the two targets are moving away from each other,  in our case our chaff bundle and the targeted airplane.  This is measurable and ultimately, if I understand correctly, one can take this and 'weight' the radar towards one or the other target. 

 

On Top of all of this its possible, and I see no reason the 120 doesn't have, to have a velocity gate as well to supplement the range gate.  Meaning anything with a rapidly changing velocity or a apparent velocity not close to the targets can be filtered out as well.

 

5 hours ago, Blinky.ben said:

But just to point out some radar theory the larger the antenna the more accurate the radar is. so a tiny missile radar isn’t going to be as accurate as a much larger airborne or ground based tracking radar, That’s just hard rules for radars which is why I would suspect the missile radar doesn’t go active until it’s close to the contact. There is a trick that can be done to synthetically make your antenna seem larger than what it really is but I don’t know if this is something that can be discussed but I’m sure it’s on the internet how this is done. But a missile wouldn’t be able to achieve this. 

 

No the higher the frequency, smaller the beamwidth, and the shorter the pulse width the more accurate it is.  Just for example the AWG-9 is not as good as the APG-63 at picking out close targets.

 

4 hours ago, Blinky.ben said:

Yep it makes sense how it degrades the power of the pulse but I can also confuse the missile for that brief moment until it can process that’s it’s not the target.

 

I mean we're not talking seconds here, were talking incredible small periods of time hundreths of a second.

Edited January 20, 2021 by nighthawk2174

[Fri13]

8 minutes ago, nighthawk2174 said:

I mean I don't think it's really comparable here as were talking dumping this out at hundreds of mph.  Additionally there are some declass documents out there on this stuff and the average time i've seen is generally in the 2-4 second range for a chaff cloud too fully bloom.  Also no it doesn't have to completely separate but the effect will be greatly diminished from the full bloom.

 

Going from the memory about the Chaff distribution physics:

15 ms for chaff to create a RCS that is already larger than the aircraft.

200 ms for chaff to be about 5 meters wide in diameter.

1-2 second to be about 75-150 meters wide.

 

Depending from the weather conditions and release altitude, chaff lands in 2-48 hours.
The chaff is very effective for hours in the area where it is flying, denying the X-band radars detection and lock-in.

 

Why you are not going to release chaff for training purposes. It is extremely effective counter measurement against fighters and missiles radars if you get front or behind it, and it will scatter quickly to large areas that will block lots of radars.

 

The chaff effect is partially about "shrouding" the target, but as well generating false speeds for all directions. It is not just a "noise jammer" or "power distributor" but you get from your own radar signal the multiple speed variations, larger size than there is and every second the radar computer needs to try to solve what it is looking at, the real target moves further away.

The chaff release needs to be properly timed and at proper distance when the aircraft is beaming the radar. Most effective it is when chaff is between radar and the target. It is less effective in beaming phases but somewhat more effective behind the target. Just dumping chaff as soon the missile is launched is not going to do good as the radar can still keep a track where the target is heading and update it between the chaff releases. That is major chaff rejection that target that would be "solid light" becomes "blinking light" that has strong echoes behind. It is like a echo chamber or a room of mirrors where finding the original source for the echo is not possible.

 

And if chaff is released too early, it has less effect as the heading and all can be seen and ignored better.

Releasing chaff at proper distance, the missile needs to widen its lock gate and that means it stops guiding toward the predicted position as it needs to check does the target turn or not, and then detect the chaff and ignore it if it is detected and then continue turning to old predicted heading. And the time it takes to calculate target position on each properly timed chaff cloud, more distance does the real target get ahead of the missile turn capabilities.

 

Combine chaff release with maneuver and the computer has very difficult time to know what to track as the old track prediction becomes obsolete information and target must be reacquired, slowing down the missile kinematic capability to turn as it doesn't know where to turn or it turns to wrong direction.

This is why the amount of chaff and their timings and the maneuver that is used against different radars and missiles are classified as one trick doesn't work for all of them.

 

In DCS the chaff is like a flare, with just a few second lifetime. It literally is that every time a chaff is released, a dice is rolled for the missile every second that does it get lock on the chaff or does it maintain lock on the original target. The better CCM in newer missiles is simply that the probability for locking to chaff is far smaller as it is much higher eye counted dice. Like old missile rolls a 6 eye dice and you need to have 1-3-6 to lock on chaff. Where new missile can be a 48 eye dice and you need 1-4-12-48 to lock on the chaff. One roll per second, lifetime of chaff for 4 seconds and you get four rolls. Now you add there the missile seeker FOV and the chaff distance from that FOV and you have far greater change to have missile with 60 degree instant FOV to get lured in four seconds to chaff than missile with 12 degree FOV as the chaff can simply be outside of the seeker visibility and so on no dice is rolled.

And this is bad as it helps to create situations where example R-27ER will go after the chaff as soon as it is released even from 20 km distance. And once the lock is broken, the missile will not reacquire target.

 

 

[Blinky.ben]

Agreed we’re not talking seconds cause also remember the jet is moving at incredibly high speeds also so when talking about radar of FOV at close ranges it wouldn’t even take half a second to move outside.

 

As for the pixel resolution that’s not helping determine what is within the same pulse itself or multiple pulses close together. That comes down to pulse compression and depending how good that is will determine how close together 2 objects are to each other. You can have more then one target in a pulse which is creating a high amplitude. So pulse compression can help determine more then one contact hidden within the same pulse. I really wish I could say something but I really do t know if I’m pushing some boundary. I was going to send a link to what I’m hinting to on Wikipedia but it is so horribly wrong and written poorly I would rather not create a false fact. I will continue to find something to link tho.

 

as for chaff slowing down I again agree with you but, for the Doppler effect that isn’t decided instantly by the radar it takes time to determine this from multiple pulses. Again I agree we’re not talking seconds but with a jet moving hundreds of meters a second we don’t need to be talking seconds to have an effect. But even still a pulse hits everything no matter what, it’s the processing effect that determines the Doppler (moving). So if chaff is in the way it is going to have an effect on the pulse itself no matter how good the radar is. However will it create enough of an effect well that’s up to more variables then I think DCS could deal with (keep in mind I know nothing about coding) So we end up with a simplicity of random dice roll to decide if there is an effect or not. No radar in the world including missile radars can be completely resistant to objects in space (e.g Chaff) that’s just not possible. In the end we are talking about a pulse full of radiated energy and it bouncing back towards the radar antenna where all the actual magic begins. Yes we can manipulate a pulse for different reason but in the end if the object has any type of solid to it then it’s going to effect the pulse.

Edited January 20, 2021 by Blinky.ben

[nighthawk2174]

28 minutes ago, Fri13 said:

 

Going from the memory about the Chaff distribution physics:

15 ms for chaff to create a RCS that is already larger than the aircraft.

200 ms for chaff to be about 5 meters wide in diameter.

1-2 second to be about 75-150 meters wide.

You have a source for this?  Haven't seen these numbers before.

28 minutes ago, Fri13 said:

Depending from the weather conditions and release altitude, chaff lands in 2-48 hours.
The chaff is very effective for hours in the area where it is flying, denying the X-band radars detection and lock-in.

Well again from my current understanding its not like a wall you can still get target returns through the chaff cloud (and as it disperses i'm certain that this effect would only diminish).  Additionally not all of the chaff cloud is going to be cut to the appropriate length to have an impact on the radar.  Which will only compound the above as the chaff cloud disperses.  Just keep this in mind the amount of chaff being used to create corridors in Vietnam (for short periods) was thousands of pounds of chaff.  12lbs at the low end per/NMi.  If you wanted more coverage or where using heavier chaff materials which could be up to 20-25lbs per/NMi.

Also if it is not cut to the proper length the apparent RCS falls off rapidly.  So there's also a question is the chaff cut in a way that the frequencies being used by the amraam or TR's are covered?  Or are they out of the chaff "envelope"

 

28 minutes ago, Fri13 said:

Why you are not going to release chaff for training purposes. It is extremely effective counter measurement against fighters and missiles radars if you get front or behind it, and it will scatter quickly to large areas that will block lots of radars.

Well one reason off the top of my head is to not interfere with civilian weather and air traffic radars.

 

28 minutes ago, Fri13 said:

The chaff effect is partially about "shrouding" the target, but as well generating false speeds for all directions. It is not just a "noise jammer" or "power distributor" but you get from your own radar signal the multiple speed variations, larger size than there is and every second the radar computer needs to try to solve what it is looking at, the real target moves further away.

Yes you'll see a lot of speed variations but, as is indicated in the radar handbook the average difference can be measured in only a few m/s.  Which is going to be significantly lower than the Vgate on just about every PD radar.

28 minutes ago, Fri13 said:

And if chaff is released too early, it has less effect as the heading and all can be seen and ignored better.

Releasing chaff at proper distance, the missile needs to widen its lock gate and that means it stops guiding toward the predicted position as it needs to check does the target turn or not, and then detect the chaff and ignore it if it is detected and then continue turning to old predicted heading. And the time it takes to calculate target position on each properly timed chaff cloud, more distance does the real target get ahead of the missile turn capabilities.

But by how much?  Like I can't imagine that the effect would do enough to cause it to miss.

[Blinky.ben]

1 hour ago, nighthawk2174 said:

You have a source for this?  Haven't seen these numbers before.

Well again from my current understanding its not like a wall you can still get target returns through the chaff cloud (and as it disperses i'm certain that this effect would only diminish).  Additionally not all of the chaff cloud is going to be cut to the appropriate length to have an impact on the radar.  Which will only compound the above as the chaff cloud disperses.  Just keep this in mind the amount of chaff being used to create corridors in Vietnam (for short periods) was thousands of pounds of chaff.  12lbs at the low end per/NMi.  If you wanted more coverage or where using heavier chaff materials which could be up to 20-25lbs per/NMi.

Also if it is not cut to the proper length the apparent RCS falls off rapidly.  So there's also a question is the chaff cut in a way that the frequencies being used by the amraam or TR's are covered?  Or are they out of the chaff "envelope"

 

Well one reason off the top of my head is to not interfere with civilian weather and air traffic radars.

 

Yes you'll see a lot of speed variations but, as is indicated in the radar handbook the average difference can be measured in only a few m/s.  Which is going to be significantly lower than the Vgate on just about every PD radar.

But by how much?  Like I can't imagine that the effect would do enough to cause it to miss.

Do you know what radar they used to to test for this data? What size target is used? Is this a military radar flying through the sky. This looks to be ground based.

 

Don’t take this as any insult or attack. These are legitimate questions.

Edited January 20, 2021 by Blinky.ben

[nighthawk2174]

27 minutes ago, Blinky.ben said:

Do you know what radar they used to to test for this data? What size target is used? Is this a military radar flying through the sky. This looks to be ground based.

 

Don’t take this as any insult or attack. These are legitimate questions.

 

Well which specific data?  The first image is from a report called "Optimal Estimation of Target in Clutter (Chaff) From Radar" dated 1985.  The second is from a formally classified report Chaff Countermeasures and Air Defense Radar Design dated 1959.  The chaff laying also comes from this source, the number of lbs of chaff is for a x-band tracking radar at medium range (nike Ajax ranges) assuming a target echo of 40m^2.  Which, considering the tech probably means the number required for modern radars is MUCH higher as indicated in the final image. The final bit comes from a book called Radar Homing Guidance for Tactical Missiles dated 1986 and it was just a general statement concerning missile seekers and chaff.

Edited January 20, 2021 by nighthawk2174

[Fri13]

12 hours ago, nighthawk2174 said:

You have a source for this?  Haven't seen these numbers before.

 

I have it somewhere stored but didn't find it, why I said going from the memory.

The point is that the chaff will become effective almost immediately and it will just get stronger at time. It is not just "few seconds" lifetime as it is in the game but very long periods.

 

12 hours ago, nighthawk2174 said:

Well again from my current understanding its not like a wall you can still get target returns through the chaff cloud (and as it disperses i'm certain that this effect would only diminish). 

 

The Chaff is two-way mirror, both sides will get through - as well the echoes. But all gets various speeds (even when the chaff is stationary) and you can not solve what is the signal through it, you only get to know something is coming through (like RWR will warn from direction or a passive radar will see there is a emission in that direction where chaff is) but the chaff is scattering all the signal to all around it.

That is why it is like a wall that you can't see through it but you know it is there.

 

12 hours ago, nighthawk2174 said:

Additionally not all of the chaff cloud is going to be cut to the appropriate length to have an impact on the radar.

 

Exactly. But one thing that is not in the DCS is that there are various chaff cartridges and you load up the ones that are for the mission area threat environment. The lengths and material varies and proper ones are loaded by ground crew for the mission.

 

12 hours ago, nighthawk2174 said:

Which will only compound the above as the chaff cloud disperses.  Just keep this in mind the amount of chaff being used to create corridors in Vietnam (for short periods) was thousands of pounds of chaff.  12lbs at the low end per/NMi.  If you wanted more coverage or where using heavier chaff materials which could be up to 20-25lbs per/NMi.

Also if it is not cut to the proper length the apparent RCS falls off rapidly.  So there's also a question is the chaff cut in a way that the frequencies being used by the amraam or TR's are covered?  Or are they out of the chaff "envelope"

 

Each chaff will have some effect, but matching for the radar will be far more effective. This is as well why you do not want to release chaff from the distance as the length will be smaller than the radar wave is. At too close and the chaff is too tall. So you have a proper distance when to use the chaff at maximum effectiveness.

 

12 hours ago, nighthawk2174 said:

 

Well one reason off the top of my head is to not interfere with civilian weather and air traffic radars.

 

That is one, but same way is your long range early warning radars and just generating blind spots that you cant see through from one radar station (nee the other radar see from different angle) is just not nice thing at all if there is more traffic going around.

 

 

12 hours ago, nighthawk2174 said:

 

Yes you'll see a lot of speed variations but, as is indicated in the radar handbook the average difference can be measured in only a few m/s.  Which is going to be significantly lower than the Vgate on just about every PD radar.

 

The chaff speed doesn't matter in the air. You can't filter the chaff out just because it is just floating in the air at couple meters per second. The chaff cloud size will generate a "bouncing box" or a "mirror house". Your pulse doppler radar signal will get reflected at various distances from the could, generating various speeds and sizes constantly. Larger the cloud, more speed and size variations there is. You are basically jamming your own radar with false speed and distance information. But larger the chaff cloud grows, less signal does it block through it. Why you have the programmed pattern to maximize the chaff size for its density depending the known radar tracking you.

 

12 hours ago, nighthawk2174 said:

But by how much?  Like I can't imagine that the effect would do enough to cause it to miss.

 

That is basically the target flies past the chaff cloud and the chaff cloud is ignored by getting left behind. It is like you look that "there is huge noise coming from, but it is moving randomly and strong echo, but our target was moving to left at X speed, so lets ignore that area and concentrate to sources at left".

 

This is the chaff problem that you can't "drag it" with you. You fly at high speed away from it and radar can just ignore the "second source" and concentrate for the target that is going away from the chaff. But to brake the lock, you need just little time to lure the seeker algorithms to switch between real and false targets, to try determine that what is false and where the real should be. And every small distraction can make radar lose the target track.

 

The chaff idea in the horizontal (beaming) is that seeker that is looking at the target, will need to concentrate to the single chaff release for a moment, determine it pattern and solve question "Does this new target match the track prediction where target should be in X time? Is the new target return similar as the target was X time ago" and then return to search with the original track data. Now if the radar will spot that there is a target in predicted position and it has the original kind return, then it can ignore the new previous target as false and concentrate to trusting track. But if you drop second or third chaff at proper intervals in your path, the radar needs to go determine what is true and what is false between first, second and third clouds, and then have enough time to solve the problem that as pattern moves in prediction manner that is it more real than the previous one, and same time try to check forward in time to prediction point of original track.

 

If now the real source maneuvers out of the prediction point, the radar is left with three new sources that are in the track path, and fourth new source that is not in the track prediction but exist in the gate of possibility.

 

 

Green = Radar beam update period (sweep).

Red = Return (aircraft) on each radar sweep.

Blue Arrow = Doppler effect to determine direction and speed.

Blue Gate = Maneuver Gate, determined area where the target with measured parameters could move if maneuver.

Grey Box = Target Gate, prediction of area where the target will be on the next sweep.

 

Without doppler radar, all you get is really just the old track that target blib would be drawing behind it. So you would get a nice series of old positions after the latest. A human could make a fairly good prediction that where the next position will be, but it would still be inaccurate.

With doppler radar you get the target velocity. Now you get to know the speed on each measurement. It is not exact but more updates you get, more accurately you get the average speed. And if the target flies at constant speed (as in example) the target velocity can be know fairly accurate in few updates.

With the track history, and the target speed, one can start to predict more accurately the area in the next sweep, and sweep after it that where the target should appear. So enough updates and you know by the speed and vector that where it will be, and that is the point of intercept.

And more accurate information is known about target speed and vector, a another gate can be built, that IF LOST, where the target might have been able to go? Example a fighter flying at Mach 1.3 at 30 000 ft can not perform a 9 G turn with a 1500 ft radius. It can not stop on that position, so there is a predicted area where the target might have turned with expected speed change or vector change. So if the target is lost, the search is performed in that area. First at the smaller and then at larger before the lock is lost.

 

Each turn, speed change etc will deny the accurate prediction where the target will be. If you fly straight and steady speed then it is very easy to get very accurate pin point position where you will be in next, lets say 10 seconds.

 

But changing speed, and heading, your future position can not be known. The prediction accuracy is kept wide and large. So you can not be easily intercepted as the gate can be hundred of meters instead of just couple meters.

The radar knows where to look at so it can check that "that is where it can be".

 

Now if the ECM or just Chaff is added to that pattern, the target will lure the radar for mixed speed and headings. On each detection of the chaff the target gate widens intercept point is inaccurate. The maneuver gate changes as well because the target values has changed.

The radar system needs to determine what is real and what is false.

 

And that is fairly easy to do if the tracked target keeps flying as predicted. Like between sweeps 3 and 5, it is then easy to ignore the chaff as counter measurement and ignore the speed and heading changes as there is always something as it was predicted.

 

This is why the large bomber fleets dumping hundreds of kilos chaff doesn't work anymore as one can just target to head of the chaff cloud that is the predicted point. You can't see what is in the chaff cloud or behind it (or near it) but you can take out the "tip of the spear". And doing so you get chaffing ended and the bomber fleet would fly out of the chaff that was left behind and you get them revealed in moments and targeted.

 

But if you maneuver same time as you are releasing chaff, that is create new false vectors and speed on each release, the prediction and target gate grows and the radar needs to try to solve a major problem, what is really a real thing? It is like if you would be flipping coin in the air and suddenly your friend throws a fistful of coins up in the air at the same position. You get distracted that what is your coin. And in that moment your attention is lost and you lose a lock of your coin.

And if you don't get fooled and you just close your eyes and you time closing your fist as you have done capturing that coin last hundred times, you can believe you can capture your coin unless its timing and vector has changed.

But if it has, you have just lost your change to capture it.

 

Why the chaff release at proper distance is critical as too soon and it is easy to ignore as it is behind the prediction. And too late and the warhead can still take you off. As the warhead with RF proximity fuze will explode from sensed proximity, but the laser proximity fuze doesn't. So you can have great change to fly away from missile and releasing chaff as it will blow up itself because fuze. You can turn and put the chaff between you and radar and it doesn't know what it should look for as there are multiple targets going everywhere when radar is closer to it.

 

And I don't think that ARH missiles are modeled in DCS with actual capability to search a target after lock is broken. As they don't go dummy after lock is lost but have time period to search a target they think they should go. And this is why in DCS we should see that ARH missile can be lured to go somewhere else by the chaff, that it determines first as the target but finds it is a counter measurement and ignores it and turns back on target. Or it starts having inaccuracies in intercept on each chaff release as it needs to check is it real target or not, making maneuvering more effective method to avoid missile.

 

As the chaff is not just "a wall" that blocks things, it is multiple targets, multiple speeds, multiple vectors as well. Confusing signals from large area that match to the radar own pulses as well there are ECM pulses.

 

And more chaff in the general area, more problems radars has to see anything in there or get accurate readings for distance etc.

Considering example a dog fight where chased one will release chaff and keeps flying through the previous areas where chaff has been scattered to wide areas. And long range radars can't help as there is just one huge blob and have no idea what there happens.

There was a nice video on youtube about this how in dog fight a chaff was released and the chaser (IIRC it was F-15) gun sight went banana each time the chaff was released and it was between target and radar, until flown through and got back to measuring range, until they turned toward chaff and it went continually haywire as it was just CM all places.

 

 

 

[nighthawk2174]

7 minutes ago, Fri13 said:

The Chaff is two-way mirror, both sides will get through - as well the echoes. But all gets various speeds (even when the chaff is stationary) and you can not solve what is the signal through it, you only get to know something is coming through (like RWR will warn from direction or a passive radar will see there is a emission in that direction where chaff is) but the chaff is scattering all the signal to all around it.

That is why it is like a wall that you can't see through it but you know it is there.

 

This is not what is said in various papers on the subject, so do you have a source for this claim?

 

7 minutes ago, Fri13 said:

Each chaff will have some effect, but matching for the radar will be far more effective. This is as well why you do not want to release chaff from the distance as the length will be smaller than the radar wave is. At too close and the chaff is too tall. So you have a proper distance when to use the chaff at maximum effectiveness.

?

 

7 minutes ago, Fri13 said:

That is one, but same way is your long range early warning radars and just generating blind spots that you cant see through from one radar station (nee the other radar see from different angle) is just not nice thing at all if there is more traffic going around.

As indicated though from the above papers though the amount of chaff to generate this effect is immense and the fractions of lbs of chaff released from a self-defense loading are unlikely to affect modern PD radars too much.

 

7 minutes ago, Fri13 said:

The chaff speed doesn't matter in the air. You can't filter the chaff out just because it is just floating in the air at couple meters per second. The chaff cloud size will generate a "bouncing box" or a "mirror house". Your pulse doppler radar signal will get reflected at various distances from the could, generating various speeds and sizes constantly. Larger the cloud, more speed and size variations there is. You are basically jamming your own radar with false speed and distance information. But larger the chaff cloud grows, less signal does it block through it. Why you have the programmed pattern to maximize the chaff size for its density depending the known radar tracking you.

Yes you can, the scattered returns don't pick up a ton of doppler shift (except in the milliseconds right after release) its not enough to get past Vgates.  As indicated in the image I posted chaff will appear to have a variation of only a few m/s above and below the wind speed.

 

7 minutes ago, Fri13 said:

 

That is basically the target flies past the chaff cloud and the chaff cloud is ignored by getting left behind. It is like you look that "there is huge noise coming from, but it is moving randomly and strong echo, but our target was moving to left at X speed, so lets ignore that area and concentrate to sources at left".

Yeah and as such chaff on a fighter is not going to be effective at all against stuff like the amraam.  It will always be able to range gate and Vgate out chaff from any aspect.  If not just reject it outright once its outside the res cell, hec with monopulse even inside the res cell.

 

7 minutes ago, Fri13 said:

This is the chaff problem that you can't "drag it" with you.

Hence why towed decoys became a thing.

 

7 minutes ago, Fri13 said:

You fly at high speed away from it and radar can just ignore the "second source" and concentrate for the target that is going away from the chaff. But to brake the lock, you need just little time to lure the seeker algorithms to switch between real and false targets, to try determine that what is false and where the real should be. And every small distraction can make radar lose the target track.

I just don't see how, if it was this susceptible then it would loose lock even to rcs induced glint.  So I don't buy that chaff could cause a break lock that easy if at all.  Not to mention that it could just reacquire the target once the doppler returns of the chaff are dropped moments latter.  And its very likely the target will still be in the seeker FOV.  Not to mention the chaff would have to defeat both range gatting/Vgatting, and a whole other suite of possible countermeasures.  Including the PD filtering.

 

7 minutes ago, Fri13 said:

The chaff idea in the horizontal (beaming) is that seeker that is looking at the target, will need to concentrate to the single chaff release for a moment, determine it pattern and solve question "Does this new target match the track prediction where target should be in X time? Is the new target return similar as the target was X time ago" and then return to search with the original track data. Now if the radar will spot that there is a target in predicted position and it has the original kind return, then it can ignore the new previous target as false and concentrate to trusting track. But if you drop second or third chaff at proper intervals in your path, the radar needs to go determine what is true and what is false between first, second and third clouds, and then have enough time to solve the problem that as pattern moves in prediction manner that is it more real than the previous one, and same time try to check forward in time to prediction point of original track.

 

If now the real source maneuvers out of the prediction point, the radar is left with three new sources that are in the track path, and fourth new source that is not in the track prediction but exist in the gate of possibility.

 

 

Green = Radar beam update period (sweep).

Red = Return (aircraft) on each radar sweep.

Blue Arrow = Doppler effect to determine direction and speed.

Blue Gate = Maneuver Gate, determined area where the target with measured parameters could move if maneuver.

Grey Box = Target Gate, prediction of area where the target will be on the next sweep.

 

Without doppler radar, all you get is really just the old track that target blib would be drawing behind it. So you would get a nice series of old positions after the latest. A human could make a fairly good prediction that where the next position will be, but it would still be inaccurate.

Well this is why things such as MTI/MTD and rcs edge tracking were all developed for older pulse radars.  Plus its not going to be going in a left to right manner for tracking, even the SA2 uses a conical scan with a very tight 1° beam.  

 

 

7 minutes ago, Fri13 said:

With doppler radar you get the target velocity. Now you get to know the speed on each measurement. It is not exact but more updates you get, more accurately you get the average speed. And if the target flies at constant speed (as in example) the target velocity can be know fairly accurate in few updates.

With the track history, and the target speed, one can start to predict more accurately the area in the next sweep, and sweep after it that where the target should appear. So enough updates and you know by the speed and vector that where it will be, and that is the point of intercept.

And more accurate information is known about target speed and vector, a another gate can be built, that IF LOST, where the target might have been able to go? Example a fighter flying at Mach 1.3 at 30 000 ft can not perform a 9 G turn with a 1500 ft radius. It can not stop on that position, so there is a predicted area where the target might have turned with expected speed change or vector change. So if the target is lost, the search is performed in that area. First at the smaller and then at larger before the lock is lost.

 

Each turn, speed change etc will deny the accurate prediction where the target will be. If you fly straight and steady speed then it is very easy to get very accurate pin point position where you will be in next, lets say 10 seconds.

 

But changing speed, and heading, your future position can not be known. The prediction accuracy is kept wide and large. So you can not be easily intercepted as the gate can be hundred of meters instead of just couple meters.

The radar knows where to look at so it can check that "that is where it can be".

 

Now if the ECM or just Chaff is added to that pattern, the target will lure the radar for mixed speed and headings. On each detection of the chaff the target gate widens intercept point is inaccurate. The maneuver gate changes as well because the target values has changed.

The radar system needs to determine what is real and what is false.

 

And that is fairly easy to do if the tracked target keeps flying as predicted. Like between sweeps 3 and 5, it is then easy to ignore the chaff as counter measurement and ignore the speed and heading changes as there is always something as it was predicted.

 

This is why the large bomber fleets dumping hundreds of kilos chaff doesn't work anymore as one can just target to head of the chaff cloud that is the predicted point. You can't see what is in the chaff cloud or behind it (or near it) but you can take out the "tip of the spear". And doing so you get chaffing ended and the bomber fleet would fly out of the chaff that was left behind and you get them revealed in moments and targeted.

 

But if you maneuver same time as you are releasing chaff, that is create new false vectors and speed on each release, the prediction and target gate grows and the radar needs to try to solve a major problem, what is really a real thing? It is like if you would be flipping coin in the air and suddenly your friend throws a fistful of coins up in the air at the same position. You get distracted that what is your coin. And in that moment your attention is lost and you lose a lock of your coin.

And if you don't get fooled and you just close your eyes and you time closing your fist as you have done capturing that coin last hundred times, you can believe you can capture your coin unless its timing and vector has changed.

But if it has, you have just lost your change to capture it.

 

I think your severely underestimating the rate at which pulses are being sent out and the target data updated.  I know for a fact that, for example, on the mig-23 in its guidance mode the prf is 100khz.  Lets say you need 10 pulses to know for certain a targets position/speed/azimuth/solve for multiple targets in the res cell.  And further that the system can process data only at 5khz.  This still allows you 500 updates per second...  This is probably exceptionally low compared to something like the amraam but still that is fast.  And considering that monopulse seekers can solve for the angle between two targets in the res-cell after only two pulses...  The amount of time were talking about here makes all of the effects that chaff could induce very very very minimal.

 

7 minutes ago, Fri13 said:

Why the chaff release at proper distance is critical as too soon and it is easy to ignore as it is behind the prediction. And too late and the warhead can still take you off. As the warhead with RF proximity fuze will explode from sensed proximity, but the laser proximity fuze doesn't. So you can have great change to fly away from missile and releasing chaff as it will blow up itself because fuze. You can turn and put the chaff between you and radar and it doesn't know what it should look for as there are multiple targets going everywhere when radar is closer to it.

This is assuming that the range to the target isn't fed into the proxy fuze and isn't only turned on moments before impact or isn't its own doppler based system.  While this could be a thing actually getting the missile to fly through the chaff or close enough to actually, and only if the above assumptions are false, trigger the warhead will be rare.

7 minutes ago, Fri13 said:

As the chaff is not just "a wall" that blocks things, it is multiple targets, multiple speeds, multiple vectors as well. Confusing signals from large area that match to the radar own pulses as well there are ECM pulses.

 

And more chaff in the general area, more problems radars has to see anything in there or get accurate readings for distance etc.

Again as is stated in multiple papers though these multiple speeds are very low and can all be filtered out.  Hec its indicated in the previously classified one that this could even be a good way to filter out chaff as a target will be a pinprick in the doppler spectrum compared to chaff.  And that you will still get returns from the target with a doppler return.  Again do you have a source for this?

 

I'll leave you with this (go too 1:10)

this is a vid from a 20,000usd (per license) sim made for customers like militaries.  And here the two targets deploy chaff even while cold yet the amraam still tracks them due to range gatting and doppler.

[Fri13]

1 hour ago, nighthawk2174 said:

This is not what is said in various papers on the subject, so do you have a source for this claim?

 

Yes. As I said I do have.

 

1 hour ago, nighthawk2174 said:

?

 

Yes? Do you believe that chaff just becomes either effective or ineffective depending its type and properties?

 

1 hour ago, nighthawk2174 said:

As indicated though from the above papers though the amount of chaff to generate this effect is immense and the fractions of lbs of chaff released from a self-defense loading are unlikely to affect modern PD radars too much.

 

They are "there is a possibility" kind papers you have quoted.

 

1 hour ago, nighthawk2174 said:

Yes you can, the scattered returns don't pick up a ton of doppler shift (except in the milliseconds right after release) its not enough to get past Vgates.  As indicated in the image I posted chaff will appear to have a variation of only a few m/s above and below the wind speed.

 

Chaff speed does not matter. Chaff cloud size cause speed variation as larger it becomes, more speed variation your radar will pick up from it. That is why small amount of chaff is extremely effective when spread on large area as you get all directions and multiple speed variations. And that is the chaff weakness as when you get to that, you can start more easily disregard the chaff as chaff. You ignore that whole heading as chaff.

 

1 hour ago, nighthawk2174 said:

Yeah and as such chaff on a fighter is not going to be effective at all against stuff like the amraam.  It will always be able to range gate and Vgate out chaff from any aspect.  If not just reject it outright once its outside the res cell, hec with monopulse even inside the res cell.

 

AMRAAM is not chaff ignorant, it is chaff resistance. And only at the specific parameters. When the seeker can recognize it has chaff in its field of view, it can start to process it to be ignored and keep tracking something else. But every single chaff will lure AMRAAM further away from the real target, deny its targeting accuracy and make it hesitate in continue to intercept or to turn toward chaff for a moment. Giving valuable time for the target to escape the AMRAAM capabilities intercept it.

 

1 hour ago, nighthawk2174 said:

Hence why towed decoys became a thing.

 

Exactly, but same reason why a DRFM became so effective as it becomes similar to chaff. You lure the missile away from the real target to chase a false non-existing target.

 

1 hour ago, nighthawk2174 said:

I just don't see how, if it was this susceptible then it would loose lock even to rcs induced glint. 

 

Then you say that nothing can ever break a radar lock by any means.

 

1 hour ago, nighthawk2174 said:

So I don't buy that chaff could cause a break lock that easy if at all.

 

What do you think chaff really does? Just cause some "glitter" on the sky that shines for couple seconds like in DCS?

 

1 hour ago, nighthawk2174 said:

  Not to mention that it could just reacquire the target once the doppler returns of the chaff are dropped moments latter. 

 

Doppler is never dropped from the chaff. You need to ignore the chaff as its doppler returns doesn't make sense. It is counter measurement that is purposely causing pulse doppler radars to have all kind problems to know what there is as it speed varies constantly more the larger the cloud spreads. It is not a stationary flare like in DCS. If you have chaff cloud that is 30 meters wide, it will give larger target than that, but it will as well give a speed velocities inside that 30 meter by couple times as you are receiving multiple distances and in the general direction and going to all kind directions. Your own signal goes crazy by its return.

 

The chaff is not effective only for couple seconds when "it is moving as dropped leave and once it stops in the air it becomes invisible". You can't detect the doppler shift from the chaff as it doesn't make sense, that is why you need to ignore it after you measure it enough that it is not making sense and you lose valuable time to go after real target.

 

1 hour ago, nighthawk2174 said:

And its very likely the target will still be in the seeker FOV.  Not to mention the chaff would have to defeat both range gatting/Vgatting, and a whole other suite of possible countermeasures.  Including the PD filtering.

 

Chaff doesn't need to do anything, your own radar needs to solve a lot of false tracks and targets. It needs to figure out that all the targets and speeds the chaff continues to generate are false and that nothing can be true there, it needs to detect that did the original target get lost in there or did it go somewhere else.

And as long the chaff exist in the seeker FOV, it can causing trouble. It keeps causing trouble even from the side lobes and it is easy to calculate off when it is recognized as chaff and it can be ignored when it is not close to real target. 

 

1 hour ago, nighthawk2174 said:

Well this is why things such as MTI/MTD and rcs edge tracking were all developed for older pulse radars.  Plus its not going to be going in a left to right manner for tracking, even the SA2 uses a conical scan with a very tight 1° beam.  

 

Lets keep it simple before going for the far complex scenarios? As I said, once you start maneuvering with the chaff, your guidance is heck a lot more challenging and difficult than when it is just a straight flying steady speed target that is already challenging enough.

 

 

1 hour ago, nighthawk2174 said:

I think your severely underestimating the rate at which pulses are being sent out and the target data updated. 

 

I think you severely underestimate chaff effectiveness even on the most advanced radars today.

 

1 hour ago, nighthawk2174 said:

I know for a fact that, for example, on the mig-23 in its guidance mode the prf is 100khz.  Lets say you need 10 pulses to know for certain a targets position/speed/azimuth/solve for multiple targets in the res cell.  And further that the system can process data only at 5khz.  This still allows you 500 updates per second...  This is probably exceptionally low compared to something like the amraam but still that is fast.  And considering that monopulse seekers can solve for the angle between two targets in the res-cell after only two pulses...  The amount of time were talking about here makes all of the effects that chaff could induce very very very minimal.

 

You just said that chaff is obsolete even on the decades old radars, and it is idiotic to carry any chaff on any aircraft or use any ECM as all the radars from decades ago are perfect.

 

1 hour ago, nighthawk2174 said:

This is assuming that the range to the target isn't fed into the proxy fuze and isn't only turned on moments before impact or isn't its own doppler based system.

 

On SAM systems the proximity fuze can be set activated almost as soon the missile is launched, or only just before it is reaching the target range. It is one of the common safety mechanism and it is up to operator to decide what to do with it. And the RF proximity fuzes are commonly using doppler, that is why you can blow up the missile with chaff as it receives high doppler shift flying through/near it.

 

1 hour ago, nighthawk2174 said:

  While this could be a thing actually getting the missile to fly through the chaff or close enough to actually, and only if the above assumptions are false, trigger the warhead will be rare.

 

It would be rare as you would need to get the missile fly there. That is basically a tail chase scenario.

How you think that RF proximity fuze does detect the proximity? There has been versions for the magnetic fields but laser fuze has become the best options as it doesn't care about chaff or ECM. While RF proximity fuze can be fooled to explode early or not at all. It can be simply jammed.

 

1 hour ago, nighthawk2174 said:

Again as is stated in multiple papers though these multiple speeds are very low and can all be filtered out.

 

Filterin out doesn't mean it is not effective. That is why it needs to be specifically processed so it is ignored. And that works only on specific kind scenarios, it is not like "I turn the switch and I can't never be fooled by the chaff". 

 

1 hour ago, nighthawk2174 said:

  Hec its indicated in the previously classified one that this could even be a good way to filter out chaff as a target will be a pinprick in the doppler spectrum compared to chaff.  And that you will still get returns from the target with a doppler return.  Again do you have a source for this?

 

I do have sources. And it is nothing like you say that chaff can be perfectly filtered out by AMRAAM or any other radar as it wouldn't exist.

 

1 hour ago, nighthawk2174 said:

I'll leave you with this (go too 1:10)

this is a vid from a 20,000usd (per license) sim made for customers like militaries.  And here the two targets deploy chaff even while cold yet the amraam still tracks them due to range gatting and doppler.

 

Yes, we have at least used that. But it is not so valuable as you think.

As try to understand that chaff is not ultimate counter measurement, neither is AMRAAM ultimate missile or any radar just capable to ignore the chaff automatically.

Avoiding missiles requires proper timings, tactics and technologies. And the military tactical games can be played as much is wanted but in practice things do get differently done.

 

This is why you do not get proper chaff properties, release timings and tactics with them known as those are the classified parts. It is still reason why chaff are even today developed further, why they are carried and used even against most advanced radars, but weight is more on the ECM as with those one can render aircraft non-existing unlike with chaff.

The chaff is not as effective as it was 50-70 years ago, but it is still not obsolete or weak neither.

 

[nighthawk2174]

19 minutes ago, Fri13 said:

 

Yes. As I said I do have.

 

What are these source called?

19 minutes ago, Fri13 said:

Yes? Do you believe that chaff just becomes either effective or ineffective depending its type and properties?

Yes if the chaff isn't cut to the proper length for the radar its effect will be substantially reduced.  And different types of chaff have different properties in terms of number of dipoles per unit mass or how quickly they fall.

19 minutes ago, Fri13 said:

They are "there is a possibility" kind papers you have quoted.

And your evidence that their wrong?  Burden of proof is on you here i've based what i've said on a minimum of 8 different sources that are largely in agreement.

19 minutes ago, Fri13 said:

Chaff speed does not matter. Chaff cloud size cause speed variation as larger it becomes, more speed variation your radar will pick up from it. That is why small amount of chaff is extremely effective when spread on large area as you get all directions and multiple speed variations. And that is the chaff weakness as when you get to that, you can start more easily disregard the chaff as chaff. You ignore that whole heading as chaff.

 

If it doesn't want to get filtered out it does, if the doppler shift from the cloud is below a certain level returns from that source will be ignored.

19 minutes ago, Fri13 said:

AMRAAM is not chaff ignorant, it is chaff resistance. And only at the specific parameters. When the seeker can recognize it has chaff in its field of view, it can start to process it to be ignored and keep tracking something else. But every single chaff will lure AMRAAM further away from the real target, deny its targeting accuracy and make it hesitate in continue to intercept or to turn toward chaff for a moment. Giving valuable time for the target to escape the AMRAAM capabilities intercept it.

If its outside the main beam iirc you'll often see that returns on on the order of 40db lower than in the main lobe.  And one of the whole points of stuff like range gatting, velocity gatting, and even various filtering techniques is to minimize the error created by sidelobe clutter.  Yes as chaff is dropped there will be a brief moment that the target will appear larger and may drag the aimpoint behind the target.  I've never disagreed on this point.  Just that this would have much of an effect in the long run.  Especially if you are not dropping chaff essentially continually.  As the time the bundle would stay in the main lobe, let alone the res cell, is very small.  Again monopulse seekers like on the amraam can start to solve for unresolved targets after only a few pulses.  In the end I just don't see this being enough to either A) through off the seeker or B) how it could give enough time or produce enough error to cause a large enough miss for the proxy fuze to not hit.  As was shown in MACE the chaff was in the main lobe of the seeker inbetween the seeker and the target.  Yet it was filtered out.  The level of simulation in MACE is insane and I fully trust its results there as its in agreement with many different sources about what would happen.

19 minutes ago, Fri13 said:

 

Exactly, but same reason why a DRFM became so effective as it becomes similar to chaff. You lure the missile away from the real target to chase a false non-existing target.

 

 

Then you say that nothing can ever break a radar lock by any means.

No getting into the notch will absolutely break a lock.  I just don't see chaff breaking the lock on a PD based missile, especially monopulse based seekers.  As it falls out away from the target very quickly.  A towed decoy will stay in the main beam up until a short time before impact.  Even then based on what i've read it is still possible for seekers like the 120's monopulse to determine there is a false target, the towed decoy in our case, in the main beam and track towards the real target.  This is why more sophisticated and monopulse specific jamming techniques have had to be developed.  And even if it somehow does force a break lock it should still be fully possible for the seeker to reacquire the target.  For SARH if the main radar maintains lock, and for active if the target is still in the seekers fov/search pattern.

19 minutes ago, Fri13 said:

What do you think chaff really does? Just cause some "glitter" on the sky that shines for couple seconds like in DCS?

No, i'll reference you to my cloud metaphor above.  But the amount of chaff that would need to be used to get the effects that your visualizing is quite high.  Higher than what is loaded on aircraft in SP systems.  And even then it would have to be in the correct geometry to ensure that it fully blocked LOS.  Which would be quite rare. 

 

With SARH/Active if a continuous stream is released this is my visualization of what would happen.  It would drag the aimpoint behind the target.  Just a question of specific circumstances and target size, radar characteristics, and geometry if this is enough to matter.

 

19 minutes ago, Fri13 said:

Doppler is never dropped from the chaff. You need to ignore the chaff as its doppler returns doesn't make sense. It is counter measurement that is purposely causing pulse doppler radars to have all kind problems to know what there is as it speed varies constantly more the larger the cloud spreads. It is not a stationary flare like in DCS. If you have chaff cloud that is 30 meters wide, it will give larger target than that, but it will as well give a speed velocities inside that 30 meter by couple times as you are receiving multiple distances and in the general direction and going to all kind directions. Your own signal goes crazy by its return.

Chaff will generate a doppler shift but based on what i've read and understand is that this return will fall below the minimum doppler gate of the radar very quickly and as such will be filtered out.  

19 minutes ago, Fri13 said:

The chaff is not effective only for couple seconds when "it is moving as dropped leave and once it stops in the air it becomes invisible". You can't detect the doppler shift from the chaff as it doesn't make sense, that is why you need to ignore it after you measure it enough that it is not making sense and you lose valuable time to go after real target.

 

 

19 minutes ago, Fri13 said:

I think you severely underestimate chaff effectiveness even on the most advanced radars today.

 

And I think you are severely overestimating its effectiveness.

19 minutes ago, Fri13 said:

You just said that chaff is obsolete even on the decades old radars, and it is idiotic to carry any chaff on any aircraft or use any ECM as all the radars from decades ago are perfect.

No the whole point of that was to show how much chaff is needed to fully hide a target not that it couldn't cause increases in miss distance or break locks on the older pulse systems.  

 

19 minutes ago, Fri13 said:

On SAM systems the proximity fuze can be set activated almost as soon the missile is launched, or only just before it is reaching the target range. It is one of the common safety mechanism and it is up to operator to decide what to do with it. And the RF proximity fuzes are commonly using doppler, that is why you can blow up the missile with chaff as it receives high doppler shift flying through/near it.

 

The thing though is that the return is still going to have a minimal doppler shift is the chaff is just hovering there in the air.  So all you need is a larger doppler gate like 100kts to ensure your safe from this happening.  It would screw over just radio based ones like on the SA2/3/4 but if its a mini-doppler system then not so much.

 

19 minutes ago, Fri13 said:

I do have sources. And it is nothing like you say that chaff can be perfectly filtered out by AMRAAM or any other radar as it wouldn't exist.

Not perfectly but enough to make the chaff not very effective.  Also you claim to have sources but what are they?  They would run counter to everything I have including what i've been told by multiple pilots at this point.

19 minutes ago, Fri13 said:

This is why you do not get proper chaff properties, release timings and tactics with them known as those are the classified parts. It is still reason why chaff are even today developed further, why they are carried and used even against most advanced radars, but weight is more on the ECM as with those one can render aircraft non-existing unlike with chaff.

The chaff is not as effective as it was 50-70 years ago, but it is still not obsolete or weak neither.

 

From my current understanding the use of chaff is it being used in large bursts right as one enters the notch (in combination with ECM) to attempt to throw off immediate automatic re-acquisition attempts.  

 

Maybe not fully obsolete but in comparison to towed decoys and against monopulse or AESA seekers quite nearly; especially if just deployed alone and not used in conjunction with jammers.  

[Blinky.ben]

.

Edited January 21, 2021 by Blinky.ben

[SgtPappy]

Interesting discussion.

 

Is there public knowledge out there stating what frequencies the AMRAAM uses? If using the high end of the X-band or even Ku band, it will achieve finer res cell resolution in sacrifice for higher signal attenuation (not as much of a concern if the active range is pretty close). 

 

More advanced modern systems might even be performing FFT's to analyze the spectrum of the return and reject the wide bandwidth that chaff returns at very close ranges, thereby rejecting chaff more. Any one have good sources for these possible CCM techniques?

[nighthawk2174]

24 minutes ago, SgtPappy said:

Interesting discussion.

 

Is there public knowledge out there stating what frequencies the AMRAAM uses? If using the high end of the X-band or even Ku band, it will achieve finer res cell resolution in sacrifice for higher signal attenuation (not as much of a concern if the active range is pretty close). 

 

More advanced modern systems might even be performing FFT's to analyze the spectrum of the return and reject the wide bandwidth that chaff returns at very close ranges, thereby rejecting chaff more. Any one have good sources for these possible CCM techniques?

From what i've seen (no research yet) the amraam is ku band.  You probably could get a rough approximation based off the size of the dish and take into account its known to be a 4 element monopulse.  I have no sources on exactly how FFT is done only that its a possibility based on the 1959 paper I posted earlier which was about anti-chaff techniques that had been developed/were being developed.  But i'd be surprised if something like it couldn't and isn't being done in modern seekers like the amraam.  

Edited January 24, 2021 by nighthawk2174

[borchi_2b]

The AIM120 uses a monopulse radar, not a doppler radar for its terminal guidance, which is split into 4 segments, do to a 3d tracking. 

 

Further, a littlebit of info on the Amraam which can be found on the internet. 

 

In 1996, the AIM-120C missile was delivered to service. It was created within the framework of Phase 1 of the P3I (Pre-Planned Product Improvement, Phase 1) comprehensive upgrade program. UR differed from the reduced to 447 mm wingspan and plumage. This made it possible to place six (not four, as in the case of the AIM-120A and AIM-120B) AMRAAM missiles in the cargo bay of the F-22A Raptor, as well as reduced aerodynamic resistance (which, however, was achieved due to some deterioration of the maneuverability characteristics of the UR). The missile received an improved guidance system WGU-44/B, the mass of BC was reduced to 18 kg (while maintaining the same efficiency).

In 1998, the AGM-120C-4 BC with the advanced WDU-41B fuse was created.

In 2000, the deliveries of AIM-120C-5 (for export) and AIM-120C-6 (for use in the U.S. Armed Forces) variants, created as part of Phase 2 of the upgrade (P3I-2), began. The missiles were equipped with new software that provides better resolution as well as increased interference immunity to WGSN. Another important improvement was the introduction of more compact aerodynamic rudder drives, which made it possible to extend the fuel charge by 127 mm (and, in turn, increase the missile's range up to 105 km).

[nighthawk2174]

3 hours ago, borchi_2b said:

The AIM120 uses a monopulse radar, not a doppler radar for its terminal guidance, which is split into 4 segments, do to a 3d tracking. 

Not quite, the monopulse radar on the 120 is also a PD radar, they are not mutually exclusive.

[Beamscanner]

All the books I have indicate that Chaff becomes mostly ineffective once it decelerates below the radars velocity gate (assuming a True Pulse Doppler radar).

 

Chaff can be effective against PD when maneuvering as it can momentarily confuse tracking algorithms. And obviously it helps when flying in a doppler notch.

 

I feel like Fri13 is confusing MTI with True Pulse Doppler. MTI can only tell if something is moving, and cannot selectively filter doppler. Thus, MTI is still very susceptible to chaff. Even modern coherent MTI, such as early warning radars and anything using a Low PRF. 

 

This is why the west have explicitly distinguished MTI from Pulse Doppler. While the USSR tried to conflate the two, because they didn't want to appear too far behind the west. 

[nighthawk2174]

On 5/3/2022 at 5:26 AM, Beamscanner said:

All the books I have indicate that Chaff becomes mostly ineffective once it decelerates below the radars velocity gate (assuming a True Pulse Doppler radar).

 

Chaff can be effective against PD when maneuvering as it can momentarily confuse tracking algorithms. And obviously it helps when flying in a doppler notch.

 

I feel like Fri13 is confusing MTI with True Pulse Doppler. MTI can only tell if something is moving, and cannot selectively filter doppler. Thus, MTI is still very susceptible to chaff. Even modern coherent MTI, such as early warning radars and anything using a Low PRF. 

 

This is why the west have explicitly distinguished MTI from Pulse Doppler. While the USSR tried to conflate the two, because they didn't want to appear too far behind the west. 

According to Galinette, when I was discussing this with him iirc, when he was making the new M2K's radar model and testing against chaff just the Doppler gates alone worked 99% of the time, including going into the notch.  And its pretty clear from the one example he was able to get of it not filtering out the chaff that even the simplistic countermeasures of radar coasting or RCS edge tracking would have prevented it grabbing onto the chaff momentarily.

[Beamscanner]

6 hours ago, nighthawk2174 said:

According to Galinette, when I was discussing this with him iirc, when he was making the new M2K's radar model and testing against chaff just the Doppler gates alone worked 99% of the time, including going into the notch.  And its pretty clear from the one example he was able to get of it not filtering out the chaff that even the simplistic countermeasures of radar coasting or RCS edge tracking would have prevented it grabbing onto the chaff momentarily.

That's very interesting. Radar coasting part makes sense. Edge trackers were common with late era analog tracking radars. My gut instinct is that a digital receiver wouldn't sample at a high enough rate to perform edge tracking (I could be wrong). I'm curious if the RDI had a hybrid receiver. As I doubt the ADCs of that era had enough resolution and dynamic range to accomplish edge tracking. Obviously it would use range gating, which would follow the leading range bin, but that's not the same as edge tracking.