Question about thermal sight

[exsonic01]

If this question was already asked, please delete or close this post. I searched, but I just couldn't find exact answer that I want. 

 

Usual advertisement or catalog of companies/providers for thermal IR night vision are so fantastic. They claim that you can see through the darkness, even with heavy wind + heavy rain or thick fog.

But some claims that is more or less exaggerated. Who is right?

 

At the same time, in the CMBS world, I also see the all faction's tanks and vehicles with IR sight have trouble to detect / clarify the target in night with pouring rain or heavy fog. In both condition, (night + downpour and night + heavy fog) I checked that T90AM and M1A2 Abrams had difficulties to fully detect each other when it was greater than 2km. Also around 2km or less, longer times were required to detect each other for both tanks (not ? icon) to shoot, than clear day condition. All veteran, +1 leadership, excellent motivation. I personally felt that the fog condition was slightly worse than downpour condition. (But that personal impression might be wrong) 

 

Is this realistic depict of thermal visions under bad weather condition? and how those thermal visions 'restricted' by weather? Their maximum distance to detect in IR wavelength limited? Or bad weather make too much noise or make the signals weak, so that the crews inside the vehicle feels hard to detect the enemy? I'm just very curious and confused, because all those thermal vision companies claim that their product can see 100% same with the day at any condition. 

Edited May 12, 2015 by exsonic01

[panzersaurkrautwerfer]

Everything absorbs or reflects heat to some degree.  This includes dust, rain water, fog etc.  The more sensitive a thermal optic, the better it "sees" through this interfering barrier, but if that barrier is especially thick, especially at ranges it will struggle to make out targets. 

 

In terms of darkness, and most common weather types, the adverts have it right, the dark and stormy night you're looking through your thermals, you're still finding targets, but like, during monsoon season in Korea we'd occasionally have to cease fire because the targets were too hard to make out*

 

Basically realistically it should degrade performance somewhat.  To what degree, I'm uncertain, I've never sat in combat conditions in a monsoon and looked for something at 2 KM+.  But thermals do suffer some reduced performance in the heavy rain, or dense fog at range.  

 

*Before someone jumps on that, it's worth noting range targets are much less obvious on thermals than real vehicles.  They're just plywood that rests on a concrete heating pad before being presented for holing.  On very wet days the plywood gets saturated, and the pad has a hard time getting as hot as it should.  Add those degraded targets to reduced thermals performance, and it's usually enough to call for a cease fire until the worst of the monsoon passes and returns merely to "GOD EVERYTHING IS SOAKED" level heavy rain.  Things like tanks, wheeled vehicles, and other AFVs remained pretty obvious at sub 1500 meter ranges regardless of downpour.  

[Apocal]

Is this realistic depict of thermal visions under bad weather condition? and how those thermal visions 'restricted' by weather? Their maximum distance to detect in IR wavelength limited? Or bad weather make too much noise or make the signals weak, so that the crews inside the vehicle feels hard to detect the enemy? I'm just very curious and confused, because all those thermal vision companies claim that their product can see 100% same with the day at any condition. 

 

Moisture has an insulating effect, so as humidity climbs, your thermals degrade. I don't know how you would put a good number on it, but the effect is real. If they are seriously claiming 100% across all conditions, they are absolutely lying. What they can reasonably claim is that thermal works better than Mark 1 Eyeball or image intensifying systems, which can be rendered pretty damned well useless by overcast nights or dense fog.

[exsonic01]

Everything absorbs or reflects heat to some degree.  This includes dust, rain water, fog etc.  The more sensitive a thermal optic, the better it "sees" through this interfering barrier, but if that barrier is especially thick, especially at ranges it will struggle to make out targets. 

 

In terms of darkness, and most common weather types, the adverts have it right, the dark and stormy night you're looking through your thermals, you're still finding targets, but like, during monsoon season in Korea we'd occasionally have to cease fire because the targets were too hard to make out*

 

Basically realistically it should degrade performance somewhat.  To what degree, I'm uncertain, I've never sat in combat conditions in a monsoon and looked for something at 2 KM+.  But thermals do suffer some reduced performance in the heavy rain, or dense fog at range.  

 

*Before someone jumps on that, it's worth noting range targets are much less obvious on thermals than real vehicles.  They're just plywood that rests on a concrete heating pad before being presented for holing.  On very wet days the plywood gets saturated, and the pad has a hard time getting as hot as it should.  Add those degraded targets to reduced thermals performance, and it's usually enough to call for a cease fire until the worst of the monsoon passes and returns merely to "GOD EVERYTHING IS SOAKED" level heavy rain.  Things like tanks, wheeled vehicles, and other AFVs remained pretty obvious at sub 1500 meter ranges regardless of downpour.  

 

Moisture has an insulating effect, so as humidity climbs, your thermals degrade. I don't know how you would put a good number on it, but the effect is real. If they are seriously claiming 100% across all conditions, they are absolutely lying. What they can reasonably claim is that thermal works better than Mark 1 Eyeball or image intensifying systems, which can be rendered pretty damned well useless by overcast nights or dense fog.

 

Great thanks to detailed and helpful answers with some real experiences.  

 

I checked some data, found that the IR wave for thermal visions - far-IR (8-13 micrometer)and mid-IR (3-5 micrometer) - can be degraded by pouring rain or dense fog. IR is also light, and it is natural to be adsorbed by liquid/vapor phase water. If it is normal or weak rain, than thermal vision might looks ok or just slightly interfered, but like you mentioned, pouring rain or squall can degrade the maximum range of IR / thermal vision by 1/3 of normal day ability. And panzer, you are right, downpour in Korean rainy season is sometimes just crazy.  

   

Far-IR (8-13 micrometer) is stronger against liquid water (=rain) than mid-IR, but it is weak against vapor anyway. This means the dense fog can interfere possibly all IR range. Question cleared  

[Pat O]

 Non Game experience. Thermals are great when your looking for badguys in non standard equipment. Fighting another developed army though you really have to get that PID. Unsure if the developers did this on accident but it can be real hard to tell the difference with tons of similar equipment out there. When training with or against folks in the miles game that were at the same techno level it was a real bit**. so I think it adds a bit of realism to the feel of being a unit commander moving chess pieces. Just my two cents. Great question though and likewise great answers from the previous posters.

[John Kettler]

exsonic01,

 

While I can't speak to how things are for modern thermals, other than generally, I can tell you that thermals can be environmentally degraded to the point where the target disappears altogether. Circa 1980, I was at Hughes, which made the TOW ATGM and the TOW Night Sight. We had a bunch of math types who were doing some modeling but knew squat about what they were modeling. Our TOW guy, Bob Siegrist, who was instrumental in getting TOW into the Army originally while in it, decided to give them some field experience in the California winter. Weather was bad, with patchy cold fog where I was and socked in withdark clouds and some rain for everyone. They set up a TOW launcher (no TOW) with AN/TAS-4 FLIR Night Sight on a hill about a kilometer from where I was being TC on a bailed National guard M48A5. These geniuses, to the great mirth of our guy, set up in the mud rather than on the road! So they're peering down at me through this weather, and I've got a reservist driver, and we're maneuvering on the floor of a dry reservoir. They have me. They have me. More fog rolls in, and the rain really starts coming down. I'm gone! Pandemonium ensues on the radio. How can an entire tank disappear? They are freaking out. The rain lets up a little. They have me--until the heavens really open up, after which, I'm not there at all until the test was ended. Bob later told me our brilliant mathematicians looked like frozen drowned rats. Common sense isn't! Would add that tanks in such conditions, absent a heater, are brutal places, especially with no working radio and yours truly with a handheld radio poked out of a cracked hatch and cold rain running down the collar. All respect to the tankers!

 

AN/TAS-4 was a very early 8-12 micron FLIR with, compared to today's systems, a very poor MRT (Mean Resolvable Temperature). When it comes to MRT, you want as small a number as possible, for it is the IR analog of resolving power of optics. The better the MRT, the easier it is to find a target by being able to separate it out from the background temperature. Also, the TOW Night Sight had nothing like the zoom capabilities of the astounding stuff on the Abrams and Bradley. I tell you these things, not as a performance predictor in CMBS, but as a real world example of environmental degradation of FLIR performance. I guarantee you today's systems do much better than the now-fossil trying to find me, but fog and rain assuredly will negatively affect their performance, too. A tank that is itself cold and has only begun moving, as seen from the front, offers very little for a FLIR to see, as opposed to that lovely hot engine when viewed from the flank.

If you really want to explore the real world impact of environmental effects on modern FLIR performance, may I commend to your attention this Institute for Defense Analyses study, which should prove most informative?

 

A Tutorial on Electro-Optical/Infrared (EO-IR) Theory and Systems, by Koresky, Nicoll, Taylor

https://www.ida.org/~/media/Corporate/Files/Publications/IDA_Documents/SED/ida-document-d-4642.pdf

 

Regards,

 

John Kettler

[Stagler]

Knowing CM as well, I bet that the temperature and time of the map your playing on affects them also, with the night water clincher effect and radiometric crossover influencing detection at morning and evening hah.

Edited May 13, 2015 by Stagler

[John Kettler]

Stagler,

 

Full grog marks! I never encountered the first term, but I understand the second. Regarding the first, if you're talking about reradiation after diurnal insolation ends, then I believe I understand your point. I have an upstairs room with a west looking main exterior wall. This thing is a murderous reradiator which often forces me to put on the AC just to keep it from going over 80 in here.

 

You anticipated something I was about to say which neatly depicts the crossover phenomenon. During the Vietnam War, the US Navy deployed the revolutionary Hughes TRAM (Target Recognition Attack Multisensor) on the A-6 Intruder. The FLIR in it provided all sorts of wonderful new capabilities, including being able to see which fuel tanks were full and which weren't in attacking POL storage complexes, so the most damage could be done during a strike. Things were not so great, though, when it was discovered the crossover effect could make a huge highway bridge we were trying to kill simply disappear from the FLIR display. Talk about ruining a bomber pilot's day!

Regards,

John Kettler

[exsonic01]

exsonic01,

 

While I can't speak to how things are for modern thermals, other than generally, I can tell you that thermals can be environmentally degraded to the point where the target disappears altogether. Circa 1980, I was at Hughes, which made the TOW ATGM and the TOW Night Sight. We had a bunch of math types who were doing some modeling but knew squat about what they were modeling. Our TOW guy, Bob Siegrist, who was instrumental in getting TOW into the Army originally while in it, decided to give them some field experience in the California winter. Weather was bad, with patchy cold fog where I was and socked in withdark clouds and some rain for everyone. They set up a TOW launcher (no TOW) with AN/TAS-4 FLIR Night Sight on a hill about a kilometer from where I was being TC on a bailed National guard M48A5. These geniuses, to the great mirth of our guy, set up in the mud rather than on the road! So they're peering down at me through this weather, and I've got a reservist driver, and we're maneuvering on the floor of a dry reservoir. They have me. They have me. More fog rolls in, and the rain really starts coming down. I'm gone! Pandemonium ensues on the radio. How can an entire tank disappear? They are freaking out. The rain lets up a little. They have me--until the heavens really open up, after which, I'm not there at all until the test was ended. Bob later told me our brilliant mathematicians looked like frozen drowned rats. Common sense isn't! Would add that tanks in such conditions, absent a heater, are brutal places, especially with no working radio and yours truly with a handheld radio poked out of a cracked hatch and cold rain running down the collar. All respect to the tankers!

 

AN/TAS-4 was a very early 8-12 micron FLIR with, compared to today's systems, a very poor MRT (Mean Resolvable Temperature). When it comes to MRT, you want as small a number as possible, for it is the IR analog of resolving power of optics. The better the MRT, the easier it is to find a target by being able to separate it out from the background temperature. Also, the TOW Night Sight had nothing like the zoom capabilities of the astounding stuff on the Abrams and Bradley. I tell you these things, not as a performance predictor in CMBS, but as a real world example of environmental degradation of FLIR performance. I guarantee you today's systems do much better than the now-fossil trying to find me, but fog and rain assuredly will negatively affect their performance, too. A tank that is itself cold and has only begun moving, as seen from the front, offers very little for a FLIR to see, as opposed to that lovely hot engine when viewed from the flank.

If you really want to explore the real world impact of environmental effects on modern FLIR performance, may I commend to your attention this Institute for Defense Analyses study, which should prove most informative?

 

A Tutorial on Electro-Optical/Infrared (EO-IR) Theory and Systems, by Koresky, Nicoll, Taylor

https://www.ida.org/~/media/Corporate/Files/Publications/IDA_Documents/SED/ida-document-d-4642.pdf

 

Regards,

 

John Kettler

Thank you so much John, I will happily read this pdf in some time. Thank you. 

[John Kettler]

exsonic01,

 

You're most welcome. I, too, need to read it, having had only time to skim it. Looked pretty impressive.

 

Regards,

 

John Kettler