Counterstealth radars

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SpudmanWP

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Unread post19 Nov 2018, 18:31

IIRC VHF does not have the accuracy to provide targeting data.
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ricnunes

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Unread post19 Nov 2018, 22:26

SpudmanWP wrote:IIRC VHF does not have the accuracy to provide targeting data.


Absolutely.

For example one of the most advanced if not the most advanced VHF (AESA) Russian radar, the Nebo-M has a range resolution of 500 meters:

Image

You can download a better quality of the document here:
https://drive.google.com/open?id=0BwK-B ... TUwc09OOTA

If I'm not mistaken X-Band Radars have range resolutions measurable between centimeters and single meter values. For example:
https://ieeexplore.ieee.org/document/1626085

That's a HUGE diference in terms of range resolution (which affects target data accuracy) between VHF AESA radar (low accuracy) and a generic X-Band radar (high accuracy).
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stealthflanker

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Unread post21 Nov 2018, 15:05

ricnunes wrote:
You can download a better quality of the document here:
https://drive.google.com/open?id=0BwK-B ... TUwc09OOTA

If I'm not mistaken X-Band Radars have range resolutions measurable between centimeters and single meter values. For example:
https://ieeexplore.ieee.org/document/1626085

That's a HUGE diference in terms of range resolution (which affects target data accuracy) between VHF AESA radar (low accuracy) and a generic X-Band radar (high accuracy).


Does it wise to compare Air defense Radar with a SAR Radar which works in different principles despite their operating band ?

Range Resolution of a radar is mainly dependent on pulse width. Which you can simply calculate by following :
http://www.radartutorial.eu/01.basics/R ... on.en.html

large range resolution just means that your radar have very long pulsewidth and likely unable to tell that there are 2 aircrafts that flies close apart. You can still vector fighter or even SAM there providing it has an active guidance and hope both aircrafts are foes.

The resolution value displayed there is just typical of air defense radar.

The one you should really look for accuracy is the RMS value for coordinate measurement. From the brochure it looks very good to me, but i guess it's just typical too considering that the radar works in multiple bands.
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michaelemouse

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Unread post11 Jan 2019, 17:30

I agree with stealthflanker: The utility of an early warning radar isn't to go through the whole killchain on its own but to provide early warning to cue more precise but shorter-ranged sensors. If Russia can get an S-400 within the 500 meters of the Nebo-M's range resolution, the Nebo-M will have done its part of the job.

This does raise the question of how good missile sensors can be at getting a targeting quality track against stealth aircraft, even if the illuminating signal is from their own radar or from an X-band fighter that's been vectored by the early warning radar.



I see in rocnunes' document that the Nebo-M has 4 degrees of angular resolution. Even with monopulse technique?
Is it possible to use an analog of the monopulse technique but to increase range resolution?
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wrightwing

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Unread post11 Jan 2019, 21:07

michaelemouse wrote:I agree with stealthflanker: The utility of an early warning radar isn't to go through the whole killchain on its own but to provide early warning to cue more precise but shorter-ranged sensors. If Russia can get an S-400 within the 500 meters of the Nebo-M's range resolution, the Nebo-M will have done its part of the job.

This does raise the question of how good missile sensors can be at getting a targeting quality track against stealth aircraft, even if the illuminating signal is from their own radar or from an X-band fighter that's been vectored by the early warning radar.



I see in rocnunes' document that the Nebo-M has 4 degrees of angular resolution. Even with monopulse technique?
Is it possible to use an analog of the monopulse technique but to increase range resolution?


It's not quite that simple. It's not just getting a missile within 500m, and letting its onboard seeker do the rest. Secondly, against an F-22 or F-35, the detection range would be less than 50km. They could attack the site from more than twice that distance, without ever being detected.
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count_to_10

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Unread post11 Jan 2019, 23:05

The lower the frequency the radar, the easier it is to spoof or jam. In any realistic scenario, these systems will just mean that ECM will be part of the plan, and start up far enough in advance so as not to give away timing any more than the political situation will.
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michaelemouse

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Unread post12 Jan 2019, 00:54

wrightwing wrote:It's not quite that simple. It's not just getting a missile within 500m, and letting its onboard seeker do the rest.


I'm interested in learning what other steps are involved in the killchain. I thought a major advantage of fire & forget active seekers was that you could do just that. Just not with 100% effectiveness (since no technology or tactic is 100% effective in EW).


wrightwing wrote: Secondly, against an F-22 or F-35, the detection range would be less than 50km. They could attack the site from more than twice that distance, without ever being detected.


10% of the range against a 1 square meter RCS target? Is this accounting for the fact that their control surfaces result in a step change in detectability when lit up by low freq radar? I can't say it's impossible since I haven't done the math.



Lest I give the impression that I think the stealth of the F-35 and F-22 is useless because of low freq radar, not at all. I am however curious about how much of a problem low freq radar can be and how to decrease its effectiveness. It seems like jamming, ELINT and anti-radiation seekers will be even more important allies of stealth than they usually are. A lot of low freq radars have low mobility which makes them prime targets for a cruise missile.
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wrightwing

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Unread post12 Jan 2019, 02:29

michaelemouse wrote:


I'm interested in learning what other steps are involved in the killchain. I thought a major advantage of fire & forget active seekers was that you could do just that. Just not with 100% effectiveness (since no technology or tactic is 100% effective in EW).

500m resolution doesn't = 500m CEP




10% of the range against a 1 square meter RCS target? Is this accounting for the fact that their control surfaces result in a step change in detectability when lit up by low freq radar? I can't say it's impossible since I haven't done the math.


That's correct. Remember not only can the F-22/35 see the threat emitters long before they can be seen (and minimize any spikes,) but threat early warning radars aren't looking at their entire search volume, continuously. It takes time to detect, much less track.

Lest I give the impression that I think the stealth of the F-35 and F-22 is useless because of low freq radar, not at all. I am however curious about how much of a problem low freq radar can be and how to decrease its effectiveness. It seems like jamming, ELINT and anti-radiation seekers will be even more important allies of stealth than they usually are. A lot of low freq radars have low mobility which makes them prime targets for a cruise missile.

You're correct that these types of radars are typically either low mobility, or fixed sites. It's not economically feasible to have overlapping coverage, everywhere. They're certainly priority targets in any first wave attacks, and as previously mentioned, they're more easily spoofed by EW/EA.
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marsavian

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Unread post12 Jan 2019, 11:44

I can't say it's impossible since I haven't done the math.


Less than 50km against the Nebo-M implies an RCS at least of 0.0001 sq m, the infamous F-22 marble quote which the pea/pebble F-35 has supposedly bettered. Can it be done in VHF ? Well documentation of the F-117 shot down implies its low frequency RCS could have been as low as 0.002 sq m and technology has moved on since then.

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hornetfinn

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Unread post14 Jan 2019, 12:41

The resolution and coordinate measurement accuracy are very often misundersood especially considering the whole kill chain. Given these values for Nebo-M, it will measure range with 90m accuracy and azimuth and elevation will give about 350m accuracy against targets 100km away. In real life the values might be somewhat lower, but likely not that much though.

Anyway when considering the kill chain things will get significantly worse. The missile will go to location where target is calculated to be in the future and not where it was several seconds ago. Nebo-M has data output rate of 5-10 seconds except in sector search mode where it can be much better since the radar is not rotated. That mode is usually used for ballistic missile defense like the number of simultaneously tracked targets also indicates. Anyway since there are hundreds of meters of uncertainty in each measurement, the flight path and speed of target will have fairly big uncertainty and errors in estimating where it will be when the missile gets there. Especially so if target changes course or speed. I'd say that normally the search box for higher frequency radars will be much larger than 500m box.

Normally the kill chain after early warning radars like Nebo-M would likely include some surveillance and target acquisition radar working in S- or C-bands. Then there is fire control radar working in C-band or (usually) higher to give fire control quality tracks. Sometimes there might be no surveillance and target acquisition radar, especially with more powerful AD systems that have better search capabilities and longer ranged radars. But kill chain doesn't end there as there is almost always missile seeker (except with some command guided missiles) which also has to acquire the target far enough to engage it succesfully. Missile seeker has to detect and track the target far enough for the missile to successfully intercept the target. It's very unlikely that the missile will be heading directly towards the right spot in the sky when the seeker sees the target. So the missile will need time and space to search, detect and then track the target. Then it needs time and space to maneuver to correct intercept heading. Breaking the chain anywhere will make it not able to kill the target. If the missile seeker can not track the target sufficiently early, it will not have time or space to maneuver to kill it. VLO stealth will make it really difficult to maintain the kill chain reliably, especially when combined with EW/EA and countermeasures.
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