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Some radar questions


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Hi, I have some questions regarding a2a radars which we use in DCS. I am aware that there are different types but I guess my questions are rather generic.

 

Lets assume we want to lock a target to fire a SARH missile.

 

Our radar switches from search mode to STT and then into some kind of tracking mode. All those 3 modes are detected differently on the enemy RWR.

 

Question1: What is the difference between STT and the mode in which the radar guides the missile? Is it the same but with more energy (or shorter pulses) being used? If so, why is the latter mode not being used for STT? I assume energy saving is no high priority?

 

Question2: How long does the radar stay in this tracking mode? How does it know that the missible is dead and it can return to another mode? Is there a data link for each missile and when this link is down the plane assumes the missile is dead?

 

Question3: Is it possible to manually enable tracking mode without shooting a missile? Could be used to spoof launches (in bad weather conditions) and to force the enemy defensive without "wasting" a missile.

 

Thanks for reading!

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Hi, I have some questions regarding a2a radars which we use in DCS. I am aware that there are different types but I guess my questions are rather generic.

 

Lets assume we want to lock a target to fire a SARH missile.

 

Our radar switches from search mode to STT and then into some kind of tracking mode. All those 3 modes are detected differently on the enemy RWR.

 

Question1: What is the difference between STT and the mode in which the radar guides the missile? Is it the same but with more energy (or shorter pulses) being used? If so, why is the latter mode not being used for STT? I assume energy saving is no high priority?

There is no difference. The only thing different is the radar generating a datalink channel for the missile.

 

Question2: How long does the radar stay in this tracking mode? How does it know that the missible is dead and it can return to another mode? Is there a data link for each missile and when this link is down the plane assumes the missile is dead?

As long as the target can be tracked. In general, the radar is just one of the sensors. The computers aboard the aircraft are the "brain". For the rest of your question, that is correct, more or less.

 

Question3: Is it possible to manually enable tracking mode without shooting a missile? Could be used to spoof launches (in bad weather conditions) and to force the enemy defensive without "wasting" a missile.

 

Thanks for reading!

Yes it is, but not in DCS :smilewink:

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STT is Single Target Track. ARH missiles like AMRAAM have a 2-way link that tells the firer when the ARH head has locked, I guess for SARH the radar just waits until the target explodes and disappears off scope.

 

http://www.tscm.com/rdr-mode.pdf

Usually, there is only a 1-way datalink, only the most modern (and most expensive) missiles have 2-way datalinks. In the former case the aircraft only computes the time when the ARH seeker goes active. In the latter case, the missile can send the information it has acquired a target.
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There is no difference. The only thing different is the radar generating a datalink channel for the missile.

But not every (most?) SARH missile has a data link capabilitie or do they? :huh:

What SARH missiles have data link? A data link is not really needed for a SARH missile as it just homes in on the reflected radar energy of the target, or not?

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But not every (most?) SARH missile has a data link capabilitie or do they? huh.gif

What SARH missiles have data link? A data link is not really needed for a SARH missile as it just homes in on the reflected radar energy of the target, or not?

That's right, the datalink is not a requirement (as a matter of fact, for any missile) but it allows the missile to be launched at longer ranges and also increases the hit probability because the seeker has to be on in terminal phase only. The prime example is the R-27ER (AA-10C).

 

If no datalink is used/available, the missile still homes in on the reflected radar signal - then there is no difference in radar operation. On the other hand, if you get locked in STT by enemy radar, you always have to assume the missile launch is imminent or in progress.


Edited by Bimbac
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Thanks guys, always great to see how much knowledge this forum provides :)

 

There is no difference. The only thing different is the radar generating a datalink channel for the missile.

So the RWR detects the communication plane<->missile via datalink and assumes a missile is active?

That means if the missile does not have DL there is no way for a RWR to differ between STT and an active missile?

 

Are there many aircrafts capable of spoofing launches? I assume that would be a powerful tactic. If not, why is that?

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RWR condition for warning of launch is up to operator. Sometimes it is as simple as lock signal strength very high (close, within possible range). Even if RWR may attempt to discover actual launch by signal operator may choose to assume launch based on lock strength.

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Thanks guys, always great to see how much knowledge this forum provides smile.gif

 

 

So the RWR detects the communication plane<->missile via datalink and assumes a missile is active?

That means if the missile does not have DL there is no way for a RWR to differ between STT and an active missile?

DL can't be detected by the RWR.

 

I've got the feeling that multiple things get mixed up here. I'm also interested in the OP's question, so I will try to rephrase it:

 

When I get locked by an enemy aircraft my RWR will warn me of that lock. Now, what is when the enemy aircraft, that has locked me up, will shoot a non-DL-capable SARH missile at me? Will I get a missile warning on my RWR? If so, how does the RWR know about the missile?


Edited by QuiGon

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DL can't be detected by the RWR.

 

I've got the feeling that multiple things get mixed up here. I'm also interested in the OP's question, so I will try to rephrase it:

 

When I get locked by an enemy aircraft my RWR will warn me of that lock. Now, what is when the enemy aircraft, that has locked me up, will shoot a non-DL-capable SARH missile at me? Will I get a missile warning on my RWR? If so, how does the RWR know about the missile?

Surely it's the MAWS/MLD that detects that.

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So the RWR detects the communication plane<->missile via datalink and assumes a missile is active?

That means if the missile does not have DL there is no way for a RWR to differ between STT and an active missile?

 

Are there many aircrafts capable of spoofing launches? I assume that would be a powerful tactic. If not, why is that?

It's not that simple. Only the most modern and advanced EW systems can detect the M-links. As I have written before, there is no way to tell for the RWR the missile is underway, so everytime you get locked in STT, you could be fired upon. That's the reason why the STT lock is considered a hostile act/intent in general ROE. I cannot answer the rest of your question.

RWR condition for warning of launch is up to operator. Sometimes it is as simple as lock signal strength very high (close, within possible range). Even if RWR may attempt to discover actual launch by signal operator may choose to assume launch based on lock strength.
It's not about the strength, signal modulation, and PRF would be more relevant.

DL can't be detected by the RWR.

 

I've got the feeling that multiple things get mixed up here. I'm also interested in the OP's question, so I will try to rephrase it:

 

When I get locked by an enemy aircraft my RWR will warn me of that lock. Now, what is when the enemy aircraft, that has locked me up, will shoot a non-DL-capable SARH missile at me? Will I get a missile warning on my RWR? If so, how does the RWR know about the missile?

It can.

 

The rest has been answered above.

Surely it's the MAWS/MLD that detects that.
No, MAWS works differently. It's based on the detection of the IR/UV rocket motor characteristics, unique to the missile - it cannot recognize the difference between enemy and friendly missiles, so in intense close combat, there would be many false alarms - comms discipline with the appropriate Fox calls could reduce the problem at the expense of the increased pilot's workout.
Edited by Bimbac
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DL can't be detected by the RWR.

Yeah I was not clear, I was referring to the whole system, not only the RWR. But you matched my question, so thanks for rephrasing :)

 

@Bimbac: Thank you very much for the explaination.

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While we're on the topic of warning equipment, why is it that there is no altitude indication (i.e. the transmitter is above or below you) for RWR's?

 

We have the ability to compare radar signal strength in between port and starboard, front and back but why is there no RWR pair for the top and bottom of the aircraft?

 

I have had no luck finding any mathematical derivation for the RWR sorting algorithm or any kind of article for this question online.

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While we're on the topic of warning equipment, why is it that there is no altitude indication (i.e. the transmitter is above or below you) for RWR's?

 

We have the ability to compare radar signal strength in between port and starboard, front and back but why is there no RWR pair for the top and bottom of the aircraft?

 

I have had no luck finding any mathematical derivation for the RWR sorting algorithm or any kind of article for this question online.

The reason is quite simple. The airframe is relatively small, and RWR is not the only system which needs antennae to function :) Besides, the interferometers need to scan quite a broad spectrum at the expense of accuracy. You should see the RWR as an aid to point your radar or other sensors in the right direction so you could acquire the target and as an Early warning device. There are ways to use the Electronic Warfare suite in more advanced forms, but since it's classified, I can't say anything more. Sorry.
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Depending on the missile seeker it may need a specific waveform to guide (for instance the seeker may rely on CW illumination of its target). Upon detection of this waveform the RWR will issue a launch warning. I was explained that's how the launch warning work in the F-16 for instance.

If the missile home without requiring a specific waveform then you should'nt have a launch warning, you'll only know that you are locked. However if the RWR detects a missile emiter then it will display this emitter (likely as the most urgent threat to deal with).

More elaborate logic might be used than this simple one but that's a good start to begin to understand RWR.

An other way to detect a missile launch is through a dedicated device that monitor the IR signature of rocket engine. (the mirage in dcs has this feature). However I read somewhere that those where prone to high false alarm rate and therefor not as useful as they might be.

 

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Depends on the equipment. For example one of the eagle's wing antennae is split so it can make some form of altitude determination. Not all aircraft have this.

 

 

 

While we're on the topic of warning equipment, why is it that there is no altitude indication (i.e. the transmitter is above or below you) for RWR's?

 

We have the ability to compare radar signal strength in between port and starboard, front and back but why is there no RWR pair for the top and bottom of the aircraft?

 

I have had no luck finding any mathematical derivation for the RWR sorting algorithm or any kind of article for this question online.

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No, MAWS works differently. It's based on the detection of the IR/UV rocket motor characteristics, unique to the missile - it cannot recognize the difference between enemy and friendly missiles, so in intense close combat, there would be many false alarms - comms discipline with the appropriate Fox calls could reduce the problem at the expense of the increased pilot's workout.

Not all MAWS is IR/UV based. E.g. the Typhoon uses a radar-based MAWS. The direction of travel indicates whether it is a threat or not.

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The reason is quite simple. The airframe is relatively small, and RWR is not the only system which needs antennae to function :) Besides, the interferometers need to scan quite a broad spectrum at the expense of accuracy. You should see the RWR as an aid to point your radar or other sensors in the right direction so you could acquire the target and as an Early warning device. There are ways to use the Electronic Warfare suite in more advanced forms, but since it's classified, I can't say anything more. Sorry.

 

Thank you for the answer! Do you mean to say that more antennae would decrease accuracy? As I understand, you would have identical antennae and they would all be capable of receiving signals from the same bandwidth so you would not be increasing detectable bandwidth anyway from adding more of the same antenna. Did I misunderstand?

 

Depends on the equipment. For example one of the eagle's wing antennae is split so it can make some form of altitude determination. Not all aircraft have this.

 

So I gather it's more of a practical thing rather than being physically impossible. I also thought to myself yesterday that the 4 antennae are the minimum number you need as you can easily bank 90 degrees and determine attitude from there.

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Thank you for the answer! Do you mean to say that more antennae would decrease accuracy? As I understand, you would have identical antennae and they would all be capable of receiving signals from the same bandwidth so you would not be increasing detectable bandwidth anyway from adding more of the same antenna. Did I misunderstand?

 

So I gather it's more of a practical thing rather than being physically impossible. I also thought to myself yesterday that the 4 antennae are the minimum number you need as you can easily bank 90 degrees and determine attitude from there.

No, what I meant was that there is limited space on the airframe and some distance between the various systems' antennae is desirable to ensure correct functioning, not mentioning the space for the multiple systems under the surface or the excess weight. The required wavelength dictates the size of the antenna - it can't be random, or "made to fit," and the position is critical too - to allow the proper function. Your conclusions are correct, more or less.
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I have had no luck finding any mathematical derivation for the RWR sorting algorithm or any kind of article for this question online.

 

There are a lot, you just need to look at the right place

:P This sound like shameless self-advertising, but if you are interested in radar and RWR, I am sure this will entertain you

https://basicsaboutaerodynamicsandavionics.wordpress.com/


Edited by garrya
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While we're on the topic of warning equipment, why is it that there is no altitude indication (i.e. the transmitter is above or below you) for RWR's?

 

You have that data (above/ below) on SPO-15 Russian RWR, fitted to Flanker and MiG-29 in DCS.

 

Also earlier people questioned the ability of RWR to detect missile link.

But what the RWR can recognize isn't just a matter of antennas, it's a matter of intelligence.

You have to teach the RWR what signal to identify and the corresponding alert to display in the cockpit.

Off course RWR can record for post action analysis.

But recording a fighter to missile link is certainly not an easy task...

 

Also different radars can be ambiguous for RWR (like between MiG-29 and Su-27 for instance, even if these are not the same radar).


Edited by jojo

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But recording a fighter to missile link is certainly not an easy task...

 

 

Why not? It's transmitted on the radar sidelobes by the radar itself, on the same frequencies. RWRs were capable of dealing with them back when the command signals were completely separate as well.

 

 

 

Also different radars can be ambiguous for RWR (like between MiG-29 and Su-27 for instance, even if these are not the same radar).

 

 

 

I don't believe they should be, for a bunch of reasons. But I could easily be wrong. :)

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