FLIR , IRST in air to air mission

Cockpit, radar, helmet-mounted display, and other avionics
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popcorn

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Unread post05 Oct 2018, 11:14

It forms an image and can target.a specific section of said image.
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hornetfinn

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Unread post05 Oct 2018, 13:23

falcon.16 wrote:I have a question; Missiles with IIR are harder to fool using countermeasures as flares. Missiles bring IIR inside its cone, but how does it know which is the heat source they need attack? are they using a database or some similar?

Because if a flare is a very hot source than plume of the engines, the most normal mssiles will go to the flares...it does not matter if it has IIR...


IIR missiles have imaging seeker which means they see the image of the target aircraft (or other platform) and also the flares. At longer ranges it can not differentiate between them, but that doesn't matter as target and flares are so close to each other in any case. When it gets closer, it sees them in detail and it can pretty easily tell flares from aircraft as they have totally different visual (in IR though) shape. IIR seekers are not confused by hotter objects as they are not heat seekers (like older IR missile seekers). They are imaging systems operating in thermal wavelengths. For them higher temperature is bit like brighter color.

Flares will have very little effect on IIR seekers unless they can almost totally mask the target aircraft from seeker. IMO, this is why latest flare dispensers dispense a lot of flares to make things difficult even for IIR seekers to handle.
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ricnunes

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Unread post05 Oct 2018, 20:36

hornetfinn wrote:Sorry, I missed your question here earlier. Thales site itself claims it's FSO infrared image:
https://www.thalesgroup.com/it/search-m ... search=FSO

Of course it could be an error but it's also sometimes really difficult to tell image from thermal imaging system and monochrome TV system. It depends how the TI system is set up and configured. For example the used wavelength and what temperature range it operates affects the image qualities a lot. Naturally system resolution, sensitivity and image processing does as well. There are number of other things that affect the image quality and appearance, so it can be deceiving. This particular picture can well be from either the IIR or TV system. Thales site says it's IR image, but of course that might be an error as well.


No problem hornetfinn.

Yes, I understand that some of the newer IIR imagery has some very , very good definition which makes them very well suitable to perform ID.
However there are still quite noticeable differences between a very good IIR imagery and an even a "not so good" TV (light spectrum) imagery.

For example and looking at the F-35 EODAS video that lrrpf52 posted and while (according to his post) some paint scheme differences could be noted on IIR imagery (like the 'ED' letters on the F-16), these differences are very subtle and (judging by the video) they apparently can be seen or better observed while the "motif" (object) is at a very close range, this by actually being close to the sensor or by being on a "zoomed-in" image and at longer ranges these differences don't seem to be that noticeable at all.
This contrasts with the big differences of coloring seen on that Rafale FSO image (and the "motifs" are not that "close"), namely on the aircraft below (Mirage 2000) which is what I would expect to see on a light spectrum imagery (TV).

Moreover, if that Rafale FSO image would be IIR than we would see a major difference on the engine area in which if the image was "Black-Hot" (IMO the only possibility for that image to be IIR) than we would see a major black coloring, this again in the engine area. This again is not the case and specially notice again, the lower aircraft (Mirage 2000).

Another difference that I notice between a very good IIR imagery and any TV imagery is the edges of an object. Even in very good IIR imagery (like the F-35 EODAS) the object edges always seem to be kind of a "bit rough" or to be more precise quite "pixelated" which contrasts with TV imagery. The aircraft edges on that Rafale FSO image seem IMO to be much closer to what I would expect to see in TV imagery as opposed to IIR.

So yes, I inclined to agree that this is probably a caption error by Thales.
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Unread post08 Oct 2018, 13:25

ricnunes wrote:
hornetfinn wrote:Sorry, I missed your question here earlier. Thales site itself claims it's FSO infrared image:
https://www.thalesgroup.com/it/search-m ... search=FSO

Of course it could be an error but it's also sometimes really difficult to tell image from thermal imaging system and monochrome TV system. It depends how the TI system is set up and configured. For example the used wavelength and what temperature range it operates affects the image qualities a lot. Naturally system resolution, sensitivity and image processing does as well. There are number of other things that affect the image quality and appearance, so it can be deceiving. This particular picture can well be from either the IIR or TV system. Thales site says it's IR image, but of course that might be an error as well.


No problem hornetfinn.

Yes, I understand that some of the newer IIR imagery has some very , very good definition which makes them very well suitable to perform ID.
However there are still quite noticeable differences between a very good IIR imagery and an even a "not so good" TV (light spectrum) imagery.

For example and looking at the F-35 EODAS video that lrrpf52 posted and while (according to his post) some paint scheme differences could be noted on IIR imagery (like the 'ED' letters on the F-16), these differences are very subtle and (judging by the video) they apparently can be seen or better observed while the "motif" (object) is at a very close range, this by actually being close to the sensor or by being on a "zoomed-in" image and at longer ranges these differences don't seem to be that noticeable at all.
This contrasts with the big differences of coloring seen on that Rafale FSO image (and the "motifs" are not that "close"), namely on the aircraft below (Mirage 2000) which is what I would expect to see on a light spectrum imagery (TV).

Moreover, if that Rafale FSO image would be IIR than we would see a major difference on the engine area in which if the image was "Black-Hot" (IMO the only possibility for that image to be IIR) than we would see a major black coloring, this again in the engine area. This again is not the case and specially notice again, the lower aircraft (Mirage 2000).

Another difference that I notice between a very good IIR imagery and any TV imagery is the edges of an object. Even in very good IIR imagery (like the F-35 EODAS) the object edges always seem to be kind of a "bit rough" or to be more precise quite "pixelated" which contrasts with TV imagery. The aircraft edges on that Rafale FSO image seem IMO to be much closer to what I would expect to see in TV imagery as opposed to IIR.

So yes, I inclined to agree that this is probably a caption error by Thales.


With EODAS and EOTS we are talking about MWIR detectors and that gives quite different imagery from LWIR detectors (which FSO IR channel very likely uses). You can not really compare the images of different wavelengths directly. MWIR cameras have peak emission at relatively high temperatures and therefore the it can be better for the detection of jet exhaust or jet plume signatures with high thermal contrast against ambient temperatures. LWIR on the other hand has the peak emissions at approximately room temperature which means it can detect colder objects better especially against cold sky background. On the other hand it's far less sensitive to high temperatures (without special filters) and cuts off at fairly low temperatures. An object which has the surface temperature of 70 degrees Celsius and another with 700 degrees Celsius can look as equally hot in LWIR as it can for example measure temperature range between 0 and 50 degrees Celsius. This means a jet exhaust and jet wing can have equal signature in LWIR while having very large difference in MWIR. In MWIR the 70 degree C object would look like cold object and 700 degrees C object as very hot and bright object.

I do agree however that it might well be caption error by Thales. But at the same time I've seen imagery from thermal imagery which is very close to that image. Also imagery from older systems is usually far less pixelated as they are read and displayed using analog signals instead of digital interfaces. We have to remember than both FSO and Pirate in Eurofighter were developed during 1990s and their technology is pretty old by now.

For example Pirate IRST in Eurofighter does have only IR channel and it seems to give rather similar images like that F-4 in the datasheet:
http://www.leonardocompany.com/document ... nload_file

Engine area is not any brighter than the rest of the aircraft here either.
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Unread post08 Oct 2018, 17:39

Yes, its possible to see differente colour on engines/tail and airframe on the phantom image.
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Unread post08 Oct 2018, 20:50

@hornetfinn,

Thanks for your reply.
And also thanks for the link (regarding PIRATE).
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Unread post08 Oct 2018, 22:23

Just to add something about toveri hornetfinn's peak emission pertaining LWIR vs MWIR, it's pretty easy to compute the wavelength, assuming aircraft behave more or less like black bodies : https://en.wikipedia.org/wiki/Black-bod ... cement_law

If some aircraft edges were at 100°C = 373K for example, you'd get the wavelength for peak emission at 7.77 microns, which would be near the border between MWIR and LWIR at 8 microns : https://en.wikipedia.org/wiki/Infrared# ... e_infrared
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Unread post09 Oct 2018, 06:24

viper12 wrote:If some aircraft edges were at 100°C = 373K for example, you'd get the wavelength for peak emission at 7.77 microns, which would be near the border between MWIR and LWIR at 8 microns : https://en.wikipedia.org/wiki/Infrared# ... e_infrared


Yes, but a hotter 200° C part of the jet will still emit more intense LWIR radiation than the 100° C area. The peak wavelength gets shorter as temp goes up, but the longer wavelengths are still gaining intensity.
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Unread post09 Oct 2018, 08:47

ricnunes wrote:@hornetfinn,

Thanks for your reply.
And also thanks for the link (regarding PIRATE).


No problem, hope I can help. Here is another picture which shows the difference in MWIR and LWIR as they took the image at the same time:
Image

For example the jet exhaust plume of that passanger jet is clearly visible in MWIR and not much is seen in LWIR. Of course there are differences even within each infrared band and different systems using different technologies (like detector materials, imaging methods, cooled/uncooled, optics, signal processing, optical filters).
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Unread post09 Oct 2018, 10:58

Dunno if useful (on topic), but its worth remindin that there are presently two "plug and play" versions of OSF (OSG and OSF IT). The former has IR channel and was organized like that :

Image

The former, FSO IT is devoid of IR channel. The heat constraints on first models were found to be too high in a such a small volume. The IR IRS part being done by MICA IR sensors and eventually damocles pod. (T of IRST part being performed by - and /or damocles pod)

Presently Thales is working on FSO IR (linked to Indian market), with a brand new IR channel called OSF-IR.

All in all the most modern in Europe presently shold be skyward, as pirate (i think, i should check maybe) and OSF will have upgrades within few years.
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Unread post09 Oct 2018, 11:59

castlebravo wrote:
viper12 wrote:If some aircraft edges were at 100°C = 373K for example, you'd get the wavelength for peak emission at 7.77 microns, which would be near the border between MWIR and LWIR at 8 microns : https://en.wikipedia.org/wiki/Infrared# ... e_infrared


Yes, but a hotter 200° C part of the jet will still emit more intense LWIR radiation than the 100° C area. The peak wavelength gets shorter as temp goes up, but the longer wavelengths are still gaining intensity.


True, but the detector has can only handle finite amount of radiation before they are "filled" (saturated) and this is fairly low in LWIR case. This means that 200° C object usually looks pretty much the same as 100° C object. Of course it's possible to have higher temperature range in LWIR cameras, but that makes them less sensitive which is bad for long range detection.
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Unread post09 Oct 2018, 13:35

hornetfinn wrote:
No problem, hope I can help. Here is another picture which shows the difference in MWIR and LWIR as they took the image at the same time:
Image

For example the jet exhaust plume of that passanger jet is clearly visible in MWIR and not much is seen in LWIR. Of course there are differences even within each infrared band and different systems using different technologies (like detector materials, imaging methods, cooled/uncooled, optics, signal processing, optical filters).


Thanks again hornetfinn for the reply and more precisely for that comparison picture.

However and after reading your very insightful posts together with the great pictures that you posted, I'm still (and probably more so) convinced that picture from Thales is TV and nor IR.
I guess that another reason for this is the cloud details. In that picture from Thales, the clouds have a level of detail that I've yet to see on IR cameras/sensors and only observed on TV cameras/sensors.
Moreover it's interesting (and I believe we can all agree here) that in case that Thales picture is actually IR than it could only be LWIR, right?
But it's also interesting by looking at your latest posted picture, that clouds seem to have a far better detail in MWIR compared to LWIR (but sill less than that picture from Thales).

In the meanwhile I found this I believe, interesting site about the FSO which belongs to one of its manufacturers (Safran):
https://www.safran-electronics-defense. ... /optronics

There we can read the following:
The "front sector optronics" (FSO) system is a passive electro-optical sensor developed for the Rafale multirole fighter. Safran Electronics & Defense is responsible for the infrared search & track (IRST) and forward-looking infrared (FLIR) part of the FSO, while Thales provides the daytime video channel and laser rangefinder


So from what I gather, Safran manufactures the IR part of FSO while Thales itself manufactures the TV part (and also the laser rangefinder) of the FSO.
So why would Thales show/advertise the FSO part which is not manufactured by them?

This indeed sound like a caption error. Perhaps they meant something like: "TV image of in-flight aircrafts from FSO system." but perhaps because the FSO is predominantly an IR sensor (IRST) they put Infrared instead of TV (caption error)? :?
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Unread post09 Oct 2018, 13:54

Ricnunes, I do concur with your points and agree with you that the FSO image in Thales site is most likely TV image. Just wanted to point out some details about imaging infrared systems.

Aasm, thank you for those details about FSO system. I think FSO IR channel will come back when they put modern components inside it with vastly lower power and cooling requirements. Resolution and sensitivity will likely be much better than with the old system.
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Unread post09 Oct 2018, 17:47

hornetfinn wrote:Just wanted to point out some details about imaging infrared systems.


Which again, I appreciate and thank you! I really learned a lot more about IR sensors/cameras (namely the principles behind MWIR and LWIR) due to your posts, so and again thanks :thumb:
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Unread post09 Oct 2018, 19:09

I also enjoyed learning a bit more about these systems. hornetfinn is definitely an asset to the boards.
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