Something like NG’s MESA takes 10 seconds to do a full sweep…
See http://www.northropgrumman.com/Capabilities/MESA/Documents/mesa.pdfhttp://
Sorry, but fraction of seconds is really nonsense.
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i think you should read it more careful
. Rotodome AEW systems have higher drag antenna configurations and are limited by mechanical scan rates of 10-12 seconds. In contrast, the MESA radar has variable scan rates and instantaneous target revisit rate to satisfy diverse mission priorities
or look at the APG-81 testing video
do you see the gray beam, these are target revisiting beam ( area that radar have scanned and detect target, can be instantaneous revisit for tracking) estimated the gray area accounted for 2/5 total FoV of APG-81, and it done that in 1.2 seconds, and not only detecting targets it kniw their heading as well, so it would take about 2-2.5 seconds for APG-81 to scan it’s whole FoV
RWR detect radar way before the radar detects their target, hence the planes are flying straight like they do 99% of the time.
RWR doesn’t always detect enemy’s radar before themselves get detected ( even though they have the advantage that the signal only have to travel one way)
Firstly, modern AESA implement several method to make their signal appear like background noise to enemy’s RWR ( due to the fact that they change frequently every second , have random scanning pattern,compress their pulse .. etc)
http://www.mar.mil.br/caaml/Revista/2007/Ingles/10-Pag40.pdf
http://www.emrsdtc.com/conferences/2004/downloads/pdf/tech_conf_papers/A14.pdf
also radar receiver have much better gain than RWR receiver allowed them to detect weaker signal. Here are reason why radar antenna have better gain :
1. RWR antenna typically has a gain of about 0 dB due to wide angular coverage. Fighter AESA radar has a gain of roughly 40 dB. This means instant 40 dB advantage to the radar.
2. Radar can operate at much narrower bandwidth as it knows the frequencies it uses and RWR does not and has to operate at much wider bandwidth. RWR receivers have a sensitivity in the region of -40 to -60 dB while radar receivers have a sensitivity is roughly about -100 dB with digital receivers achieving even better sensitivity like -120 dB.
This can give additional 50 to 80 dB advantage to radar depending on exact design of the systems involved. As AESA has a very wide total bandwidth, RWR must cover that very wide bandwidth leading to much less sensitivity. As the radar signal has a quite narrow bandwidth and radar can process only very narrow bandwidth giving large advantage in sensitivity. For AESA the advantage can be for example in the 60 to 80 dB range.
3. Radar can code or modulate the signal so that it achieves significant processing gain over RWR. Either phase or frequency modulation/coding can be used. As radar knows the coding, it can filter out the signal from noise using matched filters. The RWR can’t know the coding and this gives the radar another big advantage in total gain. This is called Processing gain and it can be tens of decibels. The more complex the coding the larger the processing gain of radar is. Modern AESA radar using Digital Beamforming can use very complex coding schemes and basically only processing power and software is the limit here. A simple calculation about processing gain is dividing the spreading bandwidth (bandwidth where the signal is spread) with actual signal bandwidth.
4. When the radar main beam is not directly pointing towards the RWR, then it will only be seen through sidelobes. Given that sidelobe level can be lower than -50 dB in AESA radars (about -20 to -30 dB in fighter MSA/PESA radars), this gives the radar a healthy advantage against RWR/ESM systems which it’s not painting. This means RWR will only see very short flashes of main beam and makes it more difficult for the RWR to work effectively.
Calculated together, radar can suddenly have well over 100 dB advantage over RWR system through mainlobe and over 150 dB advantage otherwise. There are ways for RWR/ESM systems to get some of that back and of course the race is never ending. RWR/ESM system can use more directional antenna, more sensitive receivers and higher processing power.
also it worth noting that to measure range the ELINT aircraft will have to perform specific maneuver ( S shape maneuver, that will show it’s side aspect RCS to the enemy) , and as we know, all aircraft, even the Stealthy one have huge side aspect RCS ( around 20-30 dBsm or 100-1000 m2) . Modern AESA radar on fighter would have no trouble detect and track target with rcs = 30 to 40 dBsm from 300-400 km, so even though in theory, if both side receiver have equal gain, RWR can detect radar from longer distance than the radar can detect it ( since radar signal have to travel 2 ways) , in reality the ELINT aircraft will be detected as soon as it attempt to maneuver to collect data for passive ranging
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Only for head on closing (or the solution doesn’t converge for obvious mathematical reasons)
fighter have radar on their nose, and most BVR fight will happen with fighters of 2 side fly at opposite direction, into the merger
. Anyway it takes a single S-manoeuver to reach <10% accuracy according to http://subs.emis.de/LNI/Proceedings/Proceedings154/gi-proc-154-222.pdf
well in the table it specific say the range error is from 24-40 % for 15 seconds geolocation ( the longer they do it, the smaller the error is)
and the S maneuver will only work if the enemy fighter fly straight and doesn’t change their heading, fly at constant speed
remember that side aspect RCS of any aircraft is very high, the ELINT aircraft if wasn’t detected by enemy radar earlier will be detected the moment it perform the S maneuver
So after detecting the ELINT aircraft, all enemy pilot have to do is changing their heading according to the heading of ELINT aircraft ( if the ELINT aircraft turn left, you turn left, if the ELINT aircraft turn right, you turn right, accelerate or decelerate to make your speed not constant)
that will neutralise ELINT aircraft passive ranging ability
Hard to track a target if you don’t scan it regularly, isn’t it?
Thank god actual radar scan their targets every second or so
actually turn off radar most the time and only turn on radar for a few seconds is a common tactics among SAM crew to negate SEAD aircraft effectiveness
(and even AESA take tens of second to fully scan the battlefield. Fraction of seconds? Really? Can you be even more out of tune with actual radar performance?)
APG-81take about 2 sec to detect about 19 targets
https://youtu.be/CRkpFsXz9yk
something like SPY-1 with huge processing power will be alot better, fraction of a second doesn’t seem far from reality
0.1° is the typical performance of an intererometric receiver in the X-band. See http://www.phys.hawaii.edu/~anita/new/papers/militaryHandbook/sig-sort.pdf.
Even the Gripen NG RWR is quoted as better than 1° if fitted with interferometric antennas, see http://saab.com/globalassets/commercial/air/electronic-warfare/radar-warning-receivers/bow/bow-product-sheet.pdf.
Iam sorry, you probably misunderstanding my question, the question is : where does it state that Spectra have better than 0.1 degree accuracy
How suddenly Spectra have 10 times better accuracy than ELINT system on EA-18G, F-22, Gripen-NG?
and seriously, Gripen-NG still mostly in concept state, it use a lot of future technology for its radar and RWR, like the GaN modules, how can rafale that have been buit like 10-15 years before somehow have an ELINT sensor that is 10 times more accurate ?
That’s a sensor fusion issue, sensor fusion in the F-22 is actually quite limited (everything is slaved to the radar, it’s a hierarchical architecture like in the Typhoon and Gripen, unlike the cooperative architectures found in the Rafale or the F-35).
F-35 have better sensor fusion than F-22 because they was designed that way, and LM themselves claim it have better sensor fusion than F-22
but do you have any evidence to support the theory that Rafale have better sensor fusion than F-22, Typhoon, Gripen-NG?
( to be fair i don’t think F-35 have better sensor fuse than Gripen-NG either)
BTW, yet another paper discussing something that you claim is not possible (air-to-air passive ranging)…
Anyway, this entire discussion started because you made the claim that a bearing-only sensor cannot be use to estimate range. You were wrong and your entire posts are nothing but smokescreens to hide that very simple fact.
yes my original claim that air to air passive ranging is not possible is wrong , but the debate here have shown that single ship passive ranging by ELINT sensor doesn’t work at long range due to very inaccuracies, it also very easily negated by enemy’s tactics, Spectra isn’t a trump card conquer all like the Rafale fan prefer to believed
Modern EW systems can determine the bearing of a signal with a very high degree of accuracy. This can certainly allow BVR shots under some circumstances, but not with the same precision afforded by a proper radar track. Such a shot would need to be shorter ranged, and would suffer from reduced probability of kill. (not to mention generally reduced situational awareness if the shooting aircraft were really operating entirely passively. )
Boeing has also discussed using multiple Growlers operating cooperatively to passively triangulate a target, determining its location, heading, and velocity in real-time. The limitation here is that it requires multiple Growlers.
http://aviationweek.com/awin/us-navy-aims-curb-enemy-jamming
So is it possible to employ the sorts of entirely passive tactics that people spend so much time here talking about? Yes… but we are talking about cutting edge stuff here that would almost certainly require multiple aircraft acting cooperatively using both very capable EW systems and very capable data-links and they would still probably want to supplement that information with an IRST or perhaps an active sensor.
Very cool stuff, but not a magic “win” button for air combat, especially if your adversary is using similarly advanced tactics where some elements in a flight are emitting, while others are operating passively.
i mentioned that method in my first post too 😎
but here we taking about single ship geolocation ability of Spectra again air target
1) Planes tend to flight at constant speed (unless you want to argue that 60 seconds of flying straight is unusual in a fighter plane)
fighter tend to accelerate when they detect enemy aircraft, and not all fighter have the same cruise speed and acceleration rate
2) Planes tend to flight straight (unless you want to argue that the typical fighter change headings several times per minute)
to perform the range measurement method we are talking about here
the ELINT aircraft have to perform maneuver that creates changing in bearing with enemy for calculation ( fly zick zag side to side) , side RCS of fighters are extremely high ( could be several hundred m2 even for small fighter ), thus the ELINT aircraft will appear very clear on enemy fighter’s radar screen when it try to maneuver to collect data for range measurement
Example : the ceasna have RCS about 0 dbsm head on but about 20 dBsm from the side
a steath fighter without RAM have about – 10 dBsm head on, but from the side that increased to around 30 dBsm
Su-27 with RAM have frontal RCS about 10 dBsm but side RCS over 40 dBsm
and since it not uncommon for fighter to point it nose and fly toward to enemy direction, the ELINT will have a really hard time collecting data because the enemy’s heading changing constantly
everytime the ELINT aircraft try to fly zigzag
3) It’s hardly unexpected that a plane will use its radar for at least a minute (hard to track a target or scan airspace without turning the radar on)
they can easily turn radar on for 1-2 seconds and turn off and wait 10-20 seconds before turning their radar on again ( iam not even talking about AESA radar here, these things have LPI and can scan the whole battle space for fraction of a second )
4) Nope, heading is not known at first
in the simulation example, it said that, heading is assumed to be known at all time
1) Depends on the relative positions, in most cases specific manoeuvers aren’t needed
it said in the paper that the ELINT aircraft must maneuver in a certain way to allow passive geolocated target
in head on situation the bearing will the the same regardless of range so if you dont perform specific maneuver it not possible to measure range
2) 1 mrad resolution = 0.06°, similar to the interferometric chain of the Rafale in the X-band (<0.1° accuracy)
can you posted a link to support this comment ? where does it say Spectra have 0.1 degree accuracy? even the ASQ-218 on EA-18G only have 1 degrer accuracy, ALR-94 have 2 degree accuracy
and 0.06° is like 10 times better than 0.1
3) 20% is after 15s, it converges to a couple % after a minute.
and enemy cooperative for the whole time?
As written in the article, RMSE = Root Mean Square Error.
I.e. the difference between estimated range and actual range squared (normalized of course). So the 0.2 reached after 20 seconds is the equivalent of 10% error on the estimated range. One can easily see how the error gets smaller the more bearings are measured.
ok so RMSE is the error? , so why the error get bigger in the graphics the longer you take to geolocated enemy? ( after 15 second point the error actually get higher)
This would be classified info. So either you’re committing treason or you’re talking about stuff you know nothing about…
according to LM advertising, their ALR-94 required APG-77 ranging capabilities to perform an Air to air Aim-120 shot
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