Counterstealth radars

Unread postPosted: 16 Nov 2018, 18:00
by steve2267
Not sure where to put this thread. I plunked it here because it has more to do with the VLO design and construction of the F-35, and also to the F-22 for that matter, than vs XYZ (other aircraft) or tactics.

Question: To what extent can massive computational number crunching be applied to VHF / UHF radars to develop weapons quality tracks of the F-35 or other VLO aircraft?

Submitted for consideration: comments & reporting regarding the Lockheed Martin APY-9 radar on the NG E-4D Advanced Hawkeye.

While I tend to take anything Majumbles says with a huge grain of salt, this story and others I have found suggests that sophisticated filters and time-motion analysis of UHF radar returns may enable the E-4D's APY-9 radar to detect and track Chinese and Russian VLO tactical aircraft, and by extension, possibly F-35 and F-22 as well. Of course, even if true, this simply means that all other 4th gen and earlier aircraft will be all that more naked in the electromagnetic spectrum as well.

The U.S. Navy’s Secret Counter-Stealth Weapon Could Be Hiding in Plain Sight

By: Dave Majumdar June 9, 2014

The Northrop Grumman E-2D Advanced Hawkeye maybe the U.S. Navy’s secret weapon against the emerging threat of enemy fifth-generation stealth fighters and cruise missiles.

The key to that capability is the aircraft’s powerful UHF-band hybrid mechanical/electronically-scanned AN/APY-9 radar built by Lockheed Martin. Both friend and foe alike have touted UHF radars as an effective countermeasure to stealth technology.

One example of that is a paper prepared by Arend Westra that appeared in the National Defense University’s Joint Forces Quarterly academic journal in the 4th quarter issue of 2009.

“It is the physics of longer wavelength and resonance that enables VHF and UHF radar to detect stealth aircraft,” Westra wrote in his article titled Radar vs. Stealth.

UHF-band radars operate at frequencies between 300MHz and 1GHz, which results in wavelengths that are between 10 centimeters and one meter long.

Typically, due to the physical characteristics of fighter-sized stealth aircraft, they must be optimized to defeat higher frequencies in the Ka, Ku, X, C and parts of the S-bands.

There is a resonance effect that occurs when a feature on an aircraft—such as a tail-fin tip— is less than eight times the size of a particular frequency wavelength. That omni-directional resonance effect produces a “step change” in an aircraft’s radar cross-section.

Effectively what that means is that small stealth aircraft that do not have the size or weight allowances for two feet or more of radar absorbent material coatings on every surface are forced to make trades as to which frequency bands they are optimized for.

That would include aircraft like the Chengdu J-20, Shenyang J-31, Sukhoi PAK-FA and indeed the United States’ own Lockheed Martin F-22 Raptor and tri-service F-35 Joint Strike Fighter.

Only very large stealth aircraft without protruding empennage surfaces — like the Northrop Grumman B-2 Spirit or the forthcoming Long Range Strike-Bomber — can meet the requirement for geometrical optics regime scattering.

“You can’t be everywhere at once on a fighter-sized aircraft,” one source told USNI News earlier in the year.

However, as Westra and many other sources point out, UHF and VHF-band radars have historically had some major drawbacks. “Poor resolution in angle and range, however, has historically prevented these radars from providing accurate targeting and fire control,” Westra wrote.

Northrop Grumman and Lockheed Martin appear to have overcome the traditional limitations of UHF-band radars in the APY-9 by applying a combination of advanced electronic scanning capability together with enormous digital computing power in the form of space/time adaptive processing.
The Navy would not directly address the issue, but service officials did say the APY-9 provides a massive increase in performance over the E-2C Hawkeye 2000’s radar.

“The E-2D APY-9 radar provides a significantly enhanced airborne early warning and situational awareness capability against all air targets including threat aircraft and cruise missiles,” said Naval Air Systems Command spokesman Rob Koon in an emailed statement to USNI News.

“The modern technology of the APY-9 radar provides a substantial improvement in performance over the E-2C’s APS-145 radar whose heritage dates back to the 1970s.”

[ blah blah blah ]

https://news.usni.org/2014/06/09/u-s-navys-secret-counter-stealth-weapon-hiding-plain-sight


The article by Westra is attached to this post as a PDF.

I know we have discussed the fact that VHF can detect stealth aircraft, but the consensus has been they cannot develop a weapons quality target track. This "space/time adaptive processing" mentioned suggests that Lockheed Martin (unclear of Northrop Grumman's role) has developed algorithms that, when applied to the data from the AESA radar, can develop these tracks.

Does this make sense?

What is to prevent the Russians from applying the same techniques to S300, S400, Sx00 IADS? I am assuming here that these IADS already use VHF or UHF radars. (Or has this all been discussed elsewhere and I've simply missed it? Although my searches for "APY-9" and "counterstealth" came back empty. Some discussion of Advanced Hawkeye, but from a netcentric point of view.)

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 18:34
by lbk000
Perhaps nothing prevents it, but by further moving the battlespace into the software realm, it opens up more opportunities to outmaneuver and defeat the opponent. Speculating with another guy half a year ago, I suggested that true 6th generation would not be so much about Manned Unmanned Teaming as the Europeans seem to think (as that is still in the 'networking' mindset, I see that as simply an elaboration upon 5th generation), but rather as the full migration of aerial attack into the cyber battlespace (5th generation gets everyone to adopt the network, so now let's talk about exploiting and abusing it). The 6th generation platform would be a high mobile, highly survivable hacking cubicle where the aerial nature of the platform allows [relative] physical access and the hardware and software toolkit to tickle adversary electronics into hindering their efforts.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 18:37
by quicksilver
Why would anyone who actually knows something about this kind of thing, talk about it in the public domain?

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 19:33
by marsavian
RAM still works to some extent against longer wave radar but not as effectively. Also the long term travel of Stealth aircraft is towards tailless aircraft which are less detectable by VHF. Finally even in the best case the best VHF radar get a target track they are still not going to see the F-22/F-35 frontal RCS any larger than about 0.01 sq m X-band equivalent which is still good enough for a standoff weapon from the F-22/F-35 like an SDB to take out the VHF radar from about 50nm in relative safety. If it is detected if can then jam to reduce the detection/tracking range.

Radar Vs Stealth features is a constant changing battle of improvements on both sides but the F-22/F-35 are good for at least the first half of this century and then PCA and later designs can take over. Stealth aircraft are not suddenly going to become non-stealthy and this is more of a threat to J-20 and Su-57 with their best case frontal RCS of 0.05 and 0.1 sq m in the X-band which will be more like 0.5 and 1 sq m X-band equivalent in VHF. They will be very vulnerable to the E-4 sending tracks to fighters nearby.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 19:38
by SpudmanWP
Many fail to take tactics into account (cough - APA, Winslow, etc - cough). If a system threatens the actions that the attacker wants to do, they will adapt to either go around it or use a multi-prong force (CMs, VLO munitions, SDB, JDAM, MALD-J, etc) to take it out before it can significantly interfere with the operation.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 19:44
by blindpilot
steve2267 wrote:....

Does this make sense?

What is to prevent the Russians from applying the same techniques to S300, S400, Sx00 IADS? I am assuming here that these IADS already use VHF or UHF radars. (Or has this all been discussed elsewhere and I've simply missed it? Although my searches for "APY-9" and "counterstealth" came back empty. Some discussion of Advanced Hawkeye, but from a netcentric point of view.)


This falls into the realm of "Those that say don't know, and those who know won't say," but ...

There are many other facets to the question than simply "hard to target" resolution.

One example is the size of the E2D radar. VHF/UHF radars are large because of the physics. Power and range of detection of these systems are also a consideration, etc etc. The target's RWR systems can more easily detect them as opposed to LPI X-Band, even with modern frequency agile radars. This is why we hear such things as targeting EW-ARF support aircraft instead of the fighter bombers themselves. Ground Systems are equally large/clumsy "targets of opportunity." The US Navy has to have numerous integrated systems of systems to protect the E2.

You will not soon see an APY-9 hanging off of an F-18 Superhornet (or SU-35 et al), so an SU-57 (or F-35) is not likely to have such power/computers/radars packed in their fighter sized nose. Ground based setups have a similar issue. That "mobile truck" is not very mobile and makes a very juicy DEAD target. So "even if" the even if doesn't last much past the first hour, without considerable support assets, all of which become weak link targets in a kill chain.

That's just one element of the overall kill chain. In the end. We will not know in the unclassified world, and EW in general is a black art of much complexity. But the VLO stealth of F-22/35 aircraft will continue to have range/detection/jamming margins even in more hostile circumstances.

MHO,
BP

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 19:50
by steve2267
The part that caught my eye was the application of space/time adaptive computing algorithms to UHF returns to fish out where the targets are. If it works as advertised for the APY-9, then it is only a matter of time before the other side figures it out. I do not think it negates VLO designs, rather it is simply a response in the neverending game of weapon -- counterweapon, tactic -- countertactic.

The countertactic to a counterstealth radar counter to VLO aircraft design may very well be rooted in the ISR / SA aspect of the F-35 design that BlindPilot touched on in a different thread today... and that would be the development of hypersonic weapons deployable from the F-35 (or maybe the B-21?). If you find it, then you can fix it, then you can kill it. The F-35 finds and fixes the target with its sensors, then either kills it with a hypersonic AGM (yet to be developed), or hands it off to another vehicle in a hunter-killer pack (B-21?) which deploys the hypersonic AGM. Why hypersonic? Because from 50-100nm, it has the potential to reduce the reaction time of the enema from minutes to tens of seconds. This would further force the enema to continue to expend dollars (or rubles or yuan) on defensive systems, which stealth has done.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 20:04
by steve2267
So if the question is re-phrased, "Why can't the S300, S400, Sx00 systems apply similar algorithms to UHF and/or VHF radars to find VLO objects?"

The answer appears to be, "They can, but..."

blindpilot wrote:
This falls into the realm of "Those that say don't know, and those who know won't say," but ...

There are many other facets to the question than simply "hard to target" resolution.

One example is the size of the E2D radar. VHF/UHF radars are large because of the physics. Power and range of detection of these systems are also a consideration, etc etc. The target's RWR systems can more easily detect them as opposed to LPI X-Band, even with modern frequency agile radars. This is why we hear such things as targeting EW-ARF support aircraft instead of the fighter bombers themselves. Ground Systems are equally large/clumsy "targets of opportunity." The US Navy has to have numerous integrated systems of systems to protect the E2.


And translating... a UHF / VHF radar has to be physically large, and makes for a rather large, immobile target which is itself easily identified by its emissions. If you can find it, then you can fix it, then kill it...

blindpilot wrote:You will not soon see an APY-9 hanging off of an F-18 Superhornet (or SU-35 et al), so an SU-57 (or F-35) is not likely to have such power/computers/radars packed in their fighter sized nose. Ground based setups have a similar issue. That "mobile truck" is not very mobile and makes a very juicy DEAD target. So "even if" the even if doesn't last much past the first hour, without considerable support assets, all of which become weak link targets in a kill chain.


Here is a followup question: Is it theoretically possible to construct a larger UHF / VHF radar from disparately / separate, much smaller emitters and receivers? For example, astrophysicists do something very similar by constructing radio telescope arrays from individual radio telescopes (https://en.wikipedia.org/wiki/Very_Large_Array). Could not such a large UHF or VHF radar be constructed from separate fighter-sized radars, using a network topology similar to MADL to share necessary data between compute nodes? I am guessing we have the compute power available on the ground now, and may have in the F-35 with the Block 4 processor upgrades, but it is possible the data sharing which could be done via fiber optic on the ground, may exceed MADL's capabilities. That is to say... the amount of data that has to be shared to compute a solution may physically not be possible based on the physics required to share such data via radio-waves.

If so... a fourship of Stubbies, or maybe an eightship etc... might have the ability to detect VLO vehicles by working cooperatively.

This could be a mathematician's delight (and an engineer's nightmare)...

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 20:09
by steve2267
To add to my previous post:

Or does the physics of VHF / UHF wavelengths preclude a transceiver physically fitting into a vehicle as small as a tactical fighter?

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 20:14
by SpudmanWP
steve2267 wrote:does the physics of VHF / UHF wavelengths preclude


Short answer, yes.

In order for a phased radar array to work, the elements have to be spaced at a certain distance in order for the beam to be focused & steered. Longer wavelengths (UHF) require the elements to be spaced further apart and conversely short wavelengths (x-band) require tighter packing.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 16 Nov 2018, 21:25
by citanon
I think another factor going against VHF UHF is the bandwidth of the signal. Fundamentally, the more complex (information dense) a signal is (or can be), the more difficult the signal will be to detect, decode, and jam (and that's just a straightforward fact based on physics).

The information carrying capacity of a radio frequency band is inversely proportional to the wavelength. While UHF VHF bands might be less vulnerable to stealth shaping, their signals are fundamentally simpler, and therefore easier to detect and jam. This means there are probably good ways of defeating them with active techniques whereas the passive techniques can defeat xband.

There's no free lunch here. VHF and UHF do not do so well in the face of Moore's Law and are not magic bullets. Stealth vs stealth fights are going to be network on network, multi band Multi spectral, all assets contributing, distributed sensor type fights. If thats not your game plan or you don't have at least some stealth platforms on your side you will probably just lose.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 17 Nov 2018, 02:51
by fidgetspinner
https://www.nature.com/articles/s41598-017-14306-y#Fig5

"In modern digital radar receivers, real-time signal processing at 500 MSa/s sampling rate is not a problem, thus real-time target detection can be realized by the proposed radar. When detecting a long range target, to ensure the de-chirped signal has a frequency within the real-time processing bandwidth of the receiver, chirp rate of the transmitted LFM signal can be reduced by adjusting the bandwidth and repetition rate of input IF-LFMCW signal, as demonstrated in Fig. 3. However, this may result in bandwidth reduction and thus degrade the range resolution. To address this problem, a photonic delay line, such as a span of optical fiber, can be inserted before the PM to introduce a known time delay to the reference optical signal. This time delay (denoted as Δτ’) is used to cancel out part of the time delay (Δτ) corresponding to the wireless transmission of the LFM signal, and hence a low-frequency de-chirped signal is achieved with Δf = 4k(Δτ − Δτ’). When calculating the actual target distance, an extra distance of cΔτ’/2 should be added. With this method, real-time processing is still realizable for long range target detection, as long as the transmitted signal power is large enough. Besides, by applying this photonic delay line technique to reduce the de-chirped frequency, the requirement for real-time target detection can be relaxed.

The range resolution of a radar is related to the operation bandwidth. Conventional K-band radars usually have a bandwidth of several hundreds of megahertz, and the range resolution is ~15 cm21,22. A terahertz radar can achieve a range resolution of ~1.5 cm23, but the performance is limited by the complex electric circuits and the short detection range. Photonics-based radar has the potential for a very broad operation bandwidth, which, however, has not been fully developed in previous demonstrations. For example, the photonics-based radar in11 has a maximum bandwidth of 200 MHz, corresponding to a range resolution of 7.5 m. In our experimental demonstration, the 8-GHz bandwidth is restricted by the bandwidth of the antenna pair. As for the proposed photonic signal generation and de-chirp processing, the operation bandwidth is only limited by the electro-optical modulators and photodetectors. Thus the proposed radar has the potential to be operated with a bandwidth of tens or even hundreds of gigahertz, making it possible to achieve an ultra-high-range-resolution below 1 cm.
Conclusion

We have proposed and demonstrated a photonics-based real-time high-resolution radar applying optical signal generation and de-chirp processing within a compact configuration. The LFM signal generated by optical frequency quadrupling has a very large bandwidth that is required in a high-resolution radar. Besides, photonic de-chirping of the reflected echoes avoids the use of electrical frequency conversion and high-speed ADCs, making it possible for real time processing of a broadband signal in radar receivers. Performance of the proposed method is investigated through an established radar operating at K-band with an 8-GHz bandwidth. The experimental results confirm the feasibility and good performance of the proposed radar scheme, which is a promising solution for real-time ultra-high-range-resolution target detection."

Russian articles from time to time wont shut up about applying this to mig-41, su-57, su-35 including drones and ships. So can someone dumb this source down for me? an quote like, "Performance of the proposed method is investigated through an established radar operating at K-band with an 8-GHz bandwidth." makes me assume that they are getting k-band quality radar resolution in lower frequencies like X-band.

http://weaponews.com/news/11884-kret-ha ... he-6t.html

“Concern radio-electronic technologies (kret) has created an experimental model radiovolnah radar for the fighter 6th generation, which will replace the pak fa (t-50), reports tass deputy general director of the enterprise Vladimir mikheev. According to mikheev, "Progress in developing avionics for the aircraft of the sixth generation is, and in particular in respect to radio-optical photonic antenna array it on a radar locator". In r & d (research work) on the basis of the experimental sample is constructed and the emitter and the receiver. All of this work, is the location – emitted microwave signal, it is reflected back, we acquired and processed, the resulting radar image of the object. Look at what you need to do to it was optimal, he said in an interview. The deputy director noted that "Now the research is a full-fledged model of this radio-optical photonic antenna array, which will work out the characteristics of a production model". We understand what it (the radar) must be in any geometric size, on what bands and what power should work, he added. Kret also fulfills the technology specific elements of the new radar its emitter, photonic crystal, foster tract resonators. Serial sample locator do when we move to the stage of experimental design work (okr), for example, by order of the war department, said mikheyev. He explained that "Conventional radar station (radar) radiation is generated by vacuum-tube or semiconductor devices, the efficiency is relatively low – 30-40%". The remaining 60-70% of the energy is converted into heat. The new radar a radar signal is obtained by converting photonic crystal laser coherent energy in a microwave radiation.This transmitter efficiency will be not less than 60-70%.

That is a big part of laser energy will be converted into a radar, with the result that we can create a radar of high power, said the deputy director. The locator will not be a separate module in the nose of the aircraft, it will be a distributed system. Something similar can be seen today on the fifth generation fighter t-50 radar which operates in different bands and in different directions. In fact it is a single locator, but he exploded on the plane. It turns out about three or four different radars, which are comfortably placed around the fuselage and can simultaneously observe all the space around the aircraft, said mikheyev. Radiophony radar will be able to see, according to our estimates, far beyond the existing radar."

They other perk to this kind of radar that I see is that 60-70% minimum transmitter efficiency can be achieved while they describe modern radars having this amount of percentage transmitted to heat. And of course overheating is a problem for every aircraft radar.

If anyone can dumb down the explanation of the 1st source let me know since this topic pretty much relates to the subject of this thread.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 19 Nov 2018, 07:58
by garrya
Space/time processing (also known as STAP) is a technique where the signal is analysed both in the frequency domain and in the time domain.
stap.PNG

stap2.PNG

stap3.PNG


Find out more here: http://www.dtic.mil/dtic/tr/fulltext/u2/a293032.pdf

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 19 Nov 2018, 08:18
by garrya
fidgetspinner wrote:Russian articles from time to time wont shut up about applying this to mig-41, su-57, su-35 including drones and ships. So can someone dumb this source down for me? an quote like, "Performance of the proposed method is investigated through an established radar operating at K-band with an 8-GHz bandwidth." makes me assume that they are getting k-band quality radar resolution in lower frequencies like X-band.
If anyone can dumb down the explanation of the 1st source let me know since this topic pretty much relates to the subject of this thread.

I think it is important for you to first understand their terminology. Range resolution is the ability of a radar to separate two targets that are close together in range and are at approximately the same azimuth. Together with the beam width, you got the resolution cell (which is how you determine the accuracy of a radar), but that the topic for another time. The range resolution capability is determined by pulse width. A radar pulse in free space occupies a physical distance equal to the pulse width multiplied by the speed of light, which is about 984 feet per microsecond. If two targets are closer together than one-half of this physical distance, the radar cannot resolve the returns in range, and only one target will be displayed.
Image


It is the minimum separation required between two targets in order for the radar to display them separately on the radar scope so smaller value for range resolution is desirable.
Image


As explained earlier, the longer the pulse, the worse the resolution would be. Range resolution is proportional to pulse width and inverse proportional to bandwidth.
Image


Shorter pulse will improve range resolution but will also reduce the power of the transmitted radar wave, thus reduce radar detection range.
Image


To improve radar detection range and range resolution at the same time, a technique called pulse compression was invented. The basic principles of pulse compression are simple. Instead of transmitting a square pulse with the same characteristic from start to finish, radar instead transmits very long pulses that can be divided into several sub-pulses after matched filtering.Thus, radar range resolution would then depend on the length of the sub pulses rather than total pulse length. Pulse compression can be either phase or frequency coded.
Image


One of the first form of pulse compression is chirp compression (also known as linear frequency modulated pulse) where the frequency of pulse either increase or decrease with time.
Image

So for your article you only need to pay attention to:
. On one hand, in radar transmitters direct generation of linear frequency modulation (LFM) signals by means of direct digital synthesizers (DDS) is limited to a few gigahertz3. Although this bandwidth can be expanded by multiple stages of frequency up-conversion, the signal quality would be inevitably deteriorated which eventually affects the detection performance. On the other hand, the precision of analog-to-digital converters (ADCs) in the receiver drops rapidly as the input bandwidth and sampling rate increase, which severely restricts the resolution as well as the processing speed. Recently, microwave photonic technologies have been proposed as a promising solution for the generation, detection, and processing of high-frequency RF signals taking advantage of the high-frequency and broadband operation capability provided by optical components.
.....
In the transmitter, a broadband LFM signal is generated by frequency quadrupling of a low-speed electrical signal applying a single integrated electro-optical modulator. In the receiver, the reflected LFM signal is de-chirped to a low-frequency signal based on photonic frequency mixing. The implementation of photonic de-chirping can directly process high-frequency and large bandwidth signals without any electrical frequency conversion. After photonic de-chirping, ADC with a moderate sampling rate can be used in the receiver and real-time signal processing is realizable. In the proposed system, the bandwidth limitations due to electrical signal generation and processing is eliminated.


does it make sense now?

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 19 Nov 2018, 17:49
by laos
The method that I would apply would be to build AESA VHF radar. Radar would be scanning mechanically in azimuth using stacked multi beam. When possible target is detected radar would switch to use multi beam mono-pulse method to provide targeting data.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 19 Nov 2018, 18:31
by SpudmanWP
IIRC VHF does not have the accuracy to provide targeting data.

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 19 Nov 2018, 22:26
by ricnunes
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).

Re: F-35 (and F-22) vs Counterstealth radars

Unread postPosted: 21 Nov 2018, 15:05
by stealthflanker
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.

Re: Counterstealth radars

Unread postPosted: 11 Jan 2019, 17:30
by michaelemouse
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?

Re: Counterstealth radars

Unread postPosted: 11 Jan 2019, 21:07
by wrightwing
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.

Re: Counterstealth radars

Unread postPosted: 11 Jan 2019, 23:05
by count_to_10
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.

Re: Counterstealth radars

Unread postPosted: 12 Jan 2019, 00:54
by michaelemouse
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.

Re: Counterstealth radars

Unread postPosted: 12 Jan 2019, 02:29
by wrightwing
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.

Re: Counterstealth radars

Unread postPosted: 12 Jan 2019, 11:44
by marsavian
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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Re: Counterstealth radars

Unread postPosted: 14 Jan 2019, 12:41
by hornetfinn
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.

Re: Counterstealth radars

Unread postPosted: 04 Jun 2019, 03:02
by blain
How effective are radars like the Nebo-M and the Chinese JY-27 at providing targeting data? Fighters like the F-22 and F-35 are optimized to counter shorter wave length radars, but I assume they have some ability to counter longer wave length radars in the VHF/UHF bands. A lot depends on time and distance. Providing range and azimuth of a fighter at 50 miles to SAM battery or fighters is lot different than providing it at 100 or 200 miles.

How valuable are these types of radars at providing early warning?

Re: Counterstealth radars

Unread postPosted: 04 Jun 2019, 05:18
by Corsair1963
blain wrote:How effective are radars like the Nebo-M and the Chinese JY-27 at providing targeting data? Fighters like the F-22 and F-35 are optimized to counter shorter wave length radars, but I assume they have some ability to counter longer wave length radars in the VHF/UHF bands. A lot depends on time and distance. Providing range and azimuth of a fighter at 50 miles to SAM battery or fighters is lot different than providing it at 100 or 200 miles.

How valuable are these types of radars at providing early warning?



Is anyone redesigning or stopping development of Stealth Fighters???

Re: Counterstealth radars

Unread postPosted: 04 Jun 2019, 09:07
by blain
Corsair1963 wrote:
blain wrote:How effective are radars like the Nebo-M and the Chinese JY-27 at providing targeting data? Fighters like the F-22 and F-35 are optimized to counter shorter wave length radars, but I assume they have some ability to counter longer wave length radars in the VHF/UHF bands. A lot depends on time and distance. Providing range and azimuth of a fighter at 50 miles to SAM battery or fighters is lot different than providing it at 100 or 200 miles.

How valuable are these types of radars at providing early warning?



Is anyone redesigning or stopping development of Stealth Fighters???


My question isn't about the survivability of stealth fighters or its value. The technology is disruptive to an adversary's kill chain. Long range search radars can be countered with jamming, decoys, and a hard kill. Supposedly the IAF destroyed a JY-27 a few months ago in Syria. My question has to do with to what extent can a F-22/35 be detected by these radars. Detection will depend on the aircraft's profile and aspect but at what point does it show up on radar. I woulds assume that even though stealth fighters are optimized to defeat shorter wave length radars, it still has some ability to counter modern search radars.

Re: Counterstealth radars

Unread postPosted: 04 Jun 2019, 11:41
by hornetfinn
Sure long wave radars have better ability to detect stealth aircraft. In the F-117 shootdown in 1999 the VHF P-18 managed to detect the F-117s at 30 km away or closer. P-18 can detect regular small fighter at about 120-160 km away at the altitude the F-117 was flying. So the stealth properties definitely affected that VHF radar significantly.

So yes such low frequency radars can be useful for early warning because high frequency radars are more affected by shaping and RAM. Problem is that such low frequency radars are large and rather expensive and prone to jamming and hard kill measures due to their size and high power transmissions.

Re: Counterstealth radars

Unread postPosted: 05 Jun 2019, 19:57
by wrightwing
blain wrote:

My question isn't about the survivability of stealth fighters or its value. The technology is disruptive to an adversary's kill chain. Long range search radars can be countered with jamming, decoys, and a hard kill. Supposedly the IAF destroyed a JY-27 a few months ago in Syria. My question has to do with to what extent can a F-22/35 be detected by these radars. Detection will depend on the aircraft's profile and aspect but at what point does it show up on radar. I woulds assume that even though stealth fighters are optimized to defeat shorter wave length radars, it still has some ability to counter modern search radars.


The extent that they can be detected, depends on the range. The ESM systems on the F-22/35 can detect the JY-27, etc... long before they're detected, which still allows them to fly around threats (or engage them beyond their detection ranges.) "Counter-stealth" radar doesn't mean that stealthy aircraft can be detected at conventional ranges. It just means that they do a better job at detection, than radars operating in different frequency bands.

Re: Counterstealth radars

Unread postPosted: 05 Jun 2019, 23:43
by michaelemouse
hornetfinn wrote:Sure long wave radars have better ability to detect stealth aircraft. In the F-117 shootdown in 1999 the VHF P-18 managed to detect the F-117s at 30 km away or closer. P-18 can detect regular small fighter at about 120-160 km away at the altitude the F-117 was flying. So the stealth properties definitely affected that VHF radar significantly.

So yes such low frequency radars can be useful for early warning because high frequency radars are more affected by shaping and RAM. Problem is that such low frequency radars are large and rather expensive and prone to jamming and hard kill measures due to their size and high power transmissions.



Low-freq radars also have the disadvantage that even if you can see the enemy, you know what type of unit it is, you have a pretty good idea of its range, speed etc. That doesn't mean your missile is going to hit. You need frequently updated precise targeting data if you want to hit something from 50km away while that something is trying to avoid dying and then kill you. I'm not sure a targeting quality track could be had with VHF or UHF radar. The impression I get is that it would be like trying to shoot someone with a rifle at 300 meters by hip-firing. It's romantic in its enthusiasm.

I understand why low-freq radars would have higher SWAP requirements than high-freq ones and be more vulnerable to hard-kills but why is it more prone to jamming? I would have thought their large size and high power transmissions would give them an edge so there's something I'm not getting.

Re: Counterstealth radars

Unread postPosted: 06 Jun 2019, 06:55
by hornetfinn
michaelemouse wrote:I understand why low-freq radars would have higher SWAP requirements than high-freq ones and be more vulnerable to hard-kills but why is it more prone to jamming? I would have thought their large size and high power transmissions would give them an edge so there's something I'm not getting.


That's mostly because the frequency range is significantly smaller and jamming power does not need to be spread over large frequency range. For example VHF frequency range is only 270 MHz (30 to 300 MHz) whereas X-band frequency range is 4000 MHz (8 to 12 GHz). So 10 kW jamming power would mean only 2.5 Watts for each MHz in X-band case and 37 Watts in VHF case meaning about 15 times higher effective jamming power. So comparatively low frequency radar will be more affected by jamming if similar power levels are used.

Another thing is that there will be a lot lower number of VHF radars than say X-band radars in the battlefield. So jammers can concentrate on smaller number of threat radars which will further increase the jamming effects.

Larger size and high power does give some advantages in jamming resistance which will counteract those above things somewhat. But still low frequency radars will likely be more affected by jammers.

Re: Counterstealth radars

Unread postPosted: 06 Jun 2019, 20:20
by michaelemouse
hornetfinn wrote:
michaelemouse wrote:I understand why low-freq radars would have higher SWAP requirements than high-freq ones and be more vulnerable to hard-kills but why is it more prone to jamming? I would have thought their large size and high power transmissions would give them an edge so there's something I'm not getting.


That's mostly because the frequency range is significantly smaller and jamming power does not need to be spread over large frequency range. For example VHF frequency range is only 270 MHz (30 to 300 MHz) whereas X-band frequency range is 4000 MHz (8 to 12 GHz). So 10 kW jamming power would mean only 2.5 Watts for each MHz in X-band case and 37 Watts in VHF case meaning about 15 times higher effective jamming power. So comparatively low frequency radar will be more affected by jamming if similar power levels are used.

Another thing is that there will be a lot lower number of VHF radars than say X-band radars in the battlefield. So jammers can concentrate on smaller number of threat radars which will further increase the jamming effects.

Larger size and high power does give some advantages in jamming resistance which will counteract those above things somewhat. But still low frequency radars will likely be more affected by jammers.



That's a good explanation, thanks. I hadn't thought about it in terms of Jamming power divided by the number of MHz in the relevant frequency bands. Frequency hopping can only take you so far when you have a limited number of hopping options.