Of DAS, EOTS etc..

Cockpit, radar, helmet-mounted display, and other avionics
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jetblast16

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Unread post04 Aug 2016, 03:04

To give you an idea about military-grade laser designation considerations...

Original source: http://www.dtic.mil/ndia/2004armaments/ ... nators.pdf

4.1 pounds with batteries
(3.6 pounds w/o)
- 40 mJ/pulse
- 10-20 Hz
- 20 nsec pulse width
- >1 hour operation per set
of batteries
-Beam Divergence < 400uRad
- Two (2) Systems Constructed


My calculations could be wrong but with the above specs, that's about 2 MWs (megawatts) per pulse, with a pulse width of 20 nanoseconds.
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hornetfinn

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Unread post04 Aug 2016, 07:06

Very true jetblast. Even though the lasers are "eye-safe", they can still be dangerous to the eyes and there is a reason why laser protection goggles exist. Higher powered lasers emit a lot of energy and can damage the eye and the probability increases the more exposure there is like in training. EOTS likely uses something like this or something even more powerful:

http://goo.gl/hyPRRW

With up to 300 mJ of energy per pulse in tactical situations and up to 90 mJ of energy in training, means very high energies can be reached which means danger to eyes. Especially the tactical wavelength and power is bad for the eyes and I'd bet dropping real bombs means using tactical setting even in training as laser receivers in bombs might not see training wavelength. Maybe the current restrictions are based on tactical energies and wavelengths and restrictions might be lowered as more experience is gained and systems and procedures mature?
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KamenRiderBlade

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Unread post09 Aug 2016, 15:51

Is the threat of the F-35's IR laser designator blinding people in a real issue?
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SpudmanWP

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Unread post09 Aug 2016, 18:23

No, it's the same safety restrictions that cover Lightning ATP and Sniper ATP when they first get certified.
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count_to_10

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Unread post09 Aug 2016, 22:36

jetblast16 wrote:To give you an idea about military-grade laser designation considerations...

Original source: http://www.dtic.mil/ndia/2004armaments/ ... nators.pdf

4.1 pounds with batteries
(3.6 pounds w/o)
- 40 mJ/pulse
- 10-20 Hz
- 20 nsec pulse width
- >1 hour operation per set
of batteries
-Beam Divergence < 400uRad
- Two (2) Systems Constructed


My calculations could be wrong but with the above specs, that's about 2 MWs (megawatts) per pulse, with a pulse width of 20 nanoseconds.

40 mj 10 to 20 times a second is less than 1 W.
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Unread post10 Aug 2016, 08:48

Make sure you differ correctly on Mega (M) and milli (m) - that's a whopping difference.
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hornetfinn

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Unread post10 Aug 2016, 08:50

SpudmanWP wrote:No, it's the same safety restrictions that cover Lightning ATP and Sniper ATP when they first get certified.


While they use "eye safe" lasers, there is really no truly eye safe laser although they use wavelengths humans can not see. Modern systems use 1.54 µm wavelength in training modes with reduced output power. This wavelength is fairly safe for the eyes, but not totally without danger, so some restrictions are likely needed. 1.06 µm wavelength used for combat can be really bad for the eyes even for short exposures. Of course eye safety is not the top priority in those situations... My hunch is that those cited restrictions apply for tactical wavelength and power levels and are going to be reviewed and lowered for training wavelengths and power levels. Maybe they want to be sure that nobody accidentally uses tactical settings for training and procedures must be approved.

More about the issue:
http://www.laserfocusworld.com/articles ... tions.html
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hornetfinn

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Unread post10 Aug 2016, 09:09

count_to_10 wrote:
jetblast16 wrote:To give you an idea about military-grade laser designation considerations...

Original source: http://www.dtic.mil/ndia/2004armaments/ ... nators.pdf

4.1 pounds with batteries
(3.6 pounds w/o)
- 40 mJ/pulse
- 10-20 Hz
- 20 nsec pulse width
- >1 hour operation per set
of batteries
-Beam Divergence < 400uRad
- Two (2) Systems Constructed


My calculations could be wrong but with the above specs, that's about 2 MWs (megawatts) per pulse, with a pulse width of 20 nanoseconds.

40 mj 10 to 20 times a second is less than 1 W.


40 mJ 20 times a second equals 0.8 Ws (Watt Second) or 0.8 Joules as Joule equals Watt Second. That much power is sustained for one second, very small amount. 40 mJ for 20 nanoseconds however means there is 2 megawatts of energy in each pulse. Since the pulses are so very short, there is enormous amount of power in them (peak power). Average power is very low due to very long time between pulses. In this it is less than 1 Watt.
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popcorn

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Unread post13 Oct 2016, 12:15

So how would the F-35''s sensor suite fare against these?
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blindpilot

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Unread post13 Oct 2016, 22:11

popcorn wrote:So how would the F-35''s sensor suite fare against these?


These decoy balloons influence imaging for prior target scheduling and deployment processes rather than actual guided targeting. In truth for tactical targeting a black box sitting like a refrigerator on the ground, with thermal management and signals emission would be more effective than the balloons during an attack.

Which sort of answers your question. While classified, the F-35's sensor fusion algorithms and sensor "data" would likely be effective against these distractions for targeting requirements. This is a strength of sensor fusion, in that the display-targeting is not "raw data" output.The weakness might be the Red October syndrome where Jonesie says, "When it gets confused it runs home to momma - magma displacement," but the system probably would NOT call it a "Mig-31," or "Missile truck" It would be "magma," worse case.

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Unread post13 Oct 2016, 23:48

Good point. Those seem more relevant vs previous gen aircraft. The F-35's fusion engine has much finer discrimination matching sensor input vs. those 600+ parameters in it's library.
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arian

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Unread post17 Oct 2016, 01:55

I'm not so sure about that. The radar in SAR mode would probably recognize these as real targets and ID them accordingly. You'd need a thermal sight to tell that they are decoys because usually these balloons will have a small motor providing inflation (otherwise they deflate). EOTS is not a thermal imager, correct? Also decoys can be made from wood, metal or other materials which may even fool thermal imagers. And at 100km range, I'm not sure there's a thermal imager that would work (with EOTS one could probably easily visually ID these at 100km+, judging by some of the videos of F-35 EOTS)

But you are correct, so these would be really targeted at satellite and UAV surveillance.
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Dragon029

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Unread post17 Oct 2016, 03:01

The decoys don't need a motor, they just need a compressed gas canister that triggers upon deployment.

EOTS also is a MWIR sensor, meaning it is a thermal imager, same as the DAS.
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arian

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Unread post17 Oct 2016, 03:26

Dragon029 wrote:The decoys don't need a motor, they just need a compressed gas canister that triggers upon deployment.

EOTS also is a MWIR sensor, meaning it is a thermal imager, same as the DAS.


In that case, EOTS would probably recognize these as fakes. Although, at extreme ranges shown for EOTS (like that video form Las Vegas where it is looking at extremely fine detail out to 70+km), could it use its thermal sensor or simply be relying on visual?

Not an answer anyone would know, or be willing to share, I understand. But in general, I'd imagine ranges for thermal sensors will be a lot lower than ranges of visual sensors.
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Unread post18 Oct 2016, 04:07

Again, it's a MWIR sensor; there is no visual sensing capability in it (although Advanced EOTS will add multispectral capability, which infers MWIR + SWIR + visual); the Vegas video is also at a slant range of a little over 90km.

I'm not 100% certain whether visual has a longer or shorter range than IR either; the atmosphere is more opaque to IR, but IR disperses less in the atmosphere.
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