Would VHF radar+two stage IR SAM against stealth fighter?

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falcon.16

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Unread post14 Sep 2019, 23:45

hornetfinn wrote:
falcon.16 wrote:I have a doubt, if for example, we can use a VHF radar and we have for example a adquisition box of 3-4 kms on accuracy, is it impossible to guide a missile enough near for in terminal phase the internal seeker radar of the missile to track and engage the stealth target?

S-300 have very big missiles which maybe have enough big radar seeker for helping to VHF radar in terminal phase to track himself the stealth fighter...

Of course, we do not know exactly which data russian missile seekers have...but maybe 4-5 kms detection range against VLO is possible.


If we assume that VHF radar can track the stealth target continuosly can guide the missile against such an acquisition box, there are still serious problems for the missile. It still needs to search for the target itself and then lock on to it and guide itself against the target. If the detection range is only 4-5 km, then the missile would be very close to the search box and has to scan very wide angles. If we say that the detection range is 5 km and acquisition box is 3 km wide, then the missile would have to scan something like +-15 degrees in both azimuth and elevation. This takes rather long time with current seeker technology and the missile would very likely be too close to maneuver effectively even if it manages to find and track the target. Even finding the target would have fairly low probability of success. AESA seeker would have better probability of success. IR seekers would have similar problems as current mechanically scanned radar seekers. It would either have short range with wide field of view optics or long search time with narrow field of view optics.

I think either the acquisition box needs to be shrunk significantly or seeker technology improved tremendously before such tactics would work well. VLO stealth makes things pretty difficult for missile engagement in any case.


I understand it, thanks for the post. And if VLO target use electronic countermeasures, really i see near of impossible for a SAM system to do a kill chain.
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falcon.16

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Unread post14 Sep 2019, 23:49

southerncross wrote:Modern VHF systems work cooperatively with UHF and shorter band radars, like seen in Nebo-M. The longer wavelength radar makes the coarse target detection and the high-power, high frequency ones get an improved quality data based on that.

Nevertheless, VHF radars with modern processing technology have accuracy like 200 m range, 20 arcmin azimuth and 1.5º in elevation, better even in the case of higher arrays like 55Zh6 Nebo-U. From APA:

Image
There is some inconsistency in cited error bounds for target tracking. This chart shows worst case performance (range error = 200 m; azimuth error = 0.5° and elevation error = 1.5°), with the best case range error at 100 metres and best case azimuthal error at 0.3°. This performance is of the same order as the S-band 64N6E family of PESAs used as SAM battery acquisition radars


Nebo-M is claimed to have an instrumental range of 1800 km and very long distance detection of small targets:
The goal with an EPR of 0.1 m2 (the combat unit of an RCBM or a ULTR) can be detected at a range of 600-650 km, and 0.01 m2 - 300-350 km.


Regarding the seekers, AESA models are starting to come online, see performance below for a small (100 mm diameter) one for MRAAMs. Scanning fast is not a problem for them of course. And then, switching on the seeker late is good to reduce the reaction time of the attacked plane, so a very early detection by the active seeker would also not be desirable.

As to how easy it is to hunt down a proficiently managed AD unit, the story of Zoltan Dani's 3rd missile detachment of the 250th Yugoslav Air Defense Battalion under overwhelming NATO air superiority and constant SEAD raids is a well known but still recommended read.



Good information about seeker of the new R77 missiles, thanks.
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hornetfinn

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Unread post16 Sep 2019, 10:43

southerncross wrote:Modern VHF systems work cooperatively with UHF and shorter band radars, like seen in Nebo-M. The longer wavelength radar makes the coarse target detection and the high-power, high frequency ones get an improved quality data based on that.

Nevertheless, VHF radars with modern processing technology have accuracy like 200 m range, 20 arcmin azimuth and 1.5º in elevation, better even in the case of higher arrays like 55Zh6 Nebo-U. From APA:

Image
There is some inconsistency in cited error bounds for target tracking. This chart shows worst case performance (range error = 200 m; azimuth error = 0.5° and elevation error = 1.5°), with the best case range error at 100 metres and best case azimuthal error at 0.3°. This performance is of the same order as the S-band 64N6E family of PESAs used as SAM battery acquisition radars


Nebo-M is claimed to have an instrumental range of 1800 km and very long distance detection of small targets:
The goal with an EPR of 0.1 m2 (the combat unit of an RCBM or a ULTR) can be detected at a range of 600-650 km, and 0.01 m2 - 300-350 km.



Those are acquisition box accuracies, but that's not the same as the target search/acquisition box for the missile. That acquisition box is just measurement accucary in each detection but target search box for the missile is significantly larger. There are several reasons for this:

1. Data update interval is 5-20 seconds with those VHF and UHF radars. So the target data is always somewhat old when targets are not flying totally straight and level with constant speed.

2. Target speed and flight direction is calculated from several consecutive detections and has rather large errors with accelerating, decelerating or maneuvering targets when using low frequency radars. If we assume one aircraft is flying straight and level with constant speed. Then each detection can have error of about +- 900 m at 100 NMI range with UHF radar. So each detection 5-20 seconds from each other has that same uncertainty. That means the speed and direction will have very big errors/uncertainties especially when target maneuvers at all. Uncertainty is pretty large when the target moves about 1500m to 6000m between each consecutive detection.

Using both high and low frequency radars helps if all those radars can detect and track the target. However if those high frequency radars are incapable of detecting and tracking the stealth target, then it doesn't really help much. Of course there is higher chance of detecting and tracking something when using multiple different sensors.

southerncross wrote:Regarding the seekers, AESA models are starting to come online, see performance below for a small (100 mm diameter) one for MRAAMs. Scanning fast is not a problem for them of course. And then, switching on the seeker late is good to reduce the reaction time of the attacked plane, so a very early detection by the active seeker would also not be desirable.


Sure, AESA seekers will have big advantages when they become operational. Switching seeker on late is good when the target track data is of very high quality meaning the search box is small. If the search box is large, then the missile can easily get in situation where it can possibly detect and track the target but is too close to maneuver against it.

southerncross wrote:As to how easy it is to hunt down a proficiently managed AD unit, the story of Zoltan Dani's 3rd missile detachment of the 250th Yugoslav Air Defense Battalion under overwhelming NATO air superiority and constant SEAD raids is a well known but still recommended read.


That was good example how AD unit can avoid destruction and be somewhat effective in the process. Of course that was 20 years ago and SEAD technology and other air to ground systems and weapons have improved tremendously since then.
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garrya

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Unread post16 Sep 2019, 17:15

southerncross wrote:Nebo-M is claimed to have an instrumental range of 1800 km

Instrumented range of a radar system, is the maximum that the system will process and display.
Low frequency radars have long pulse width and very low PRF so their instrumentral range are always long
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Unread post16 Sep 2019, 18:12

hornetfinn wrote:Those are acquisition box accuracies, but that's not the same as the target search/acquisition box for the missile. That acquisition box is just measurement accucary in each detection but target search box for the missile is significantly larger. There are several reasons for this:

1. Data update interval is 5-20 seconds with those VHF and UHF radars. So the target data is always somewhat old when targets are not flying totally straight and level with constant speed.

That is a good point, thanks.

I was trying to find more details about the data update interval time, do you know why they are so long? I can understand this as a result of the antenna turning at 12 rpm (5 s min update time results), but when the radar is switched to sector scanning mode the beam could be kept on the acquired target for a shorter update interval couldn't it?
Using both high and low frequency radars helps if all those radars can detect and track the target. However if those high frequency radars are incapable of detecting and tracking the stealth target, then it doesn't really help much. Of course there is higher chance of detecting and tracking something when using multiple different sensors.

That seems at least the approach they are using and I guess anybody would do the same. Apart from the much improved detection conditions once the lower frequencies radars are cueing the higher frequencies ones, the idea apparently is also to play with the distribution of the different radars regarding the attack vectors, so that aspects suboptimal from RCS management point of view are exposed, allowing reduced detection distances. Inside an IADS this is possible even with relatively remote radars, so it is indeed many times more powerful than considering isolated batteries. Apart from that, increasing power of the arrays (500 kW peak for L-band Protivnik-GE) and improving their processing is a relatively accessible strategy to ensure better detection ranges.
Sure, AESA seekers will have big advantages when they become operational. Switching seeker on late is good when the target track data is of very high quality meaning the search box is small. If the search box is large, then the missile can easily get in situation where it can possibly detect and track the target but is too close to maneuver against it.

Sure, and low RCS gives a very small window to achieve a hit, that may be a good reason for mating low and high freq. radars, so that the missile is already in as good a path as possible when it activates the seeker.

Another AESA seeker that appeared some time ago, also with mechanical steering for increased FoV
27_175654_398256486d17af8.jpg

That was good example how AD unit can avoid destruction and be somewhat effective in the process. Of course that was 20 years ago and SEAD technology and other air to ground systems and weapons have improved tremendously since then.

Sure things have changed quite a bit. The idea was only to illustrate that even when plans are carefully prepared and means more than enough for the mission, competent enemies can still make a big difference and that surprises happen, so IMHO better to keep triumphalism and 200% certainties far away from anything related to military planning, I really don't think that is the way true professionals work.
garrya wrote:Instrumented range of a radar system, is the maximum that the system will process and display.
Low frequency radars have long pulse width and very low PRF so their instrumentral range are always long

Yes, I was not making any detection range claim vs. a given RCS target, but just show the rough power / performance level of the radar. In general instrumentation limit has to make ultimately sense for the kind of performance of the equipment. Detection range of 650 km against 0.1 sqm RCS fits IMHO well with 1800 km instrumental range.

BTW, as update to the data I posted:

Nebo-SVU from Rossoboronexport
Target positioning accuracy:
range, m - 100
azimuth, ang.min. - 20
elevation (for angles exceeding 5 deg), deg - 1,5
(limitation in altitude accuracy forced by the reduced number of vertical elements, this parameter is much improved in other VHF radars but they are less mobile)

APA also produced some estimates for RLM-M VHF component of Nebo-M
Image
https://www.ausairpower.net/APA-Nebo-SVU-Analysis.html
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Unread post21 Sep 2019, 13:51

Further info on VHF radars which was maybe not commented: this Chinese system is claimed to be capable of guiding missiles due to its use of an array of scattered receptors that substantially increases its accuracy:

http://www.globaltimes.cn/content/1151216.shtml
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Unread post30 Sep 2019, 08:15

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nebo-m.png
Sector scan can give 1-10 second data updates
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hornetfinn

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Unread post30 Sep 2019, 11:18

southerncross wrote:Further info on VHF radars which was maybe not commented: this Chinese system is claimed to be capable of guiding missiles due to its use of an array of scattered receptors that substantially increases its accuracy:

http://www.globaltimes.cn/content/1151216.shtml


It's not that difficult to make a low frequency radar system which can do that. All it takes is really huge antenna and put modern signal processing system in. Problem is that it makes the system very large, fixed and easy to target. It also makes them very expensive and thus limited in numbers. Useful to defend some key infrastructure but otherwise limited in applications.
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