Monday, March 28, 2016

Hiding From Thermal Imaging

I have a friend who spent a lot of time in combat zones in Iraq and Afghanistan. We were talking about the use of technology in combat and eventually mentioned thermal imaging. This technology is used in aircraft, drones, and on the ground. It works quite well. We then discussed how to “hide” from thermal imaging. I became intrigued and did a little research. There is not much in the way to thwart this technology. That’s probably a good thing.
I did find this article from I was impressed with the less technical way these guys explained how to hide from this technology. I’ve included only a portion of their article but would refer you to the complete article here:
“Thermal imaging is the primary method human detection on the battlefield. Whether it be a drone, an Apache helicopter, or an individual soldier, thermal imaging is the best tool available for the job. Thermal imagers work by “seeing” heat. Everything emits thermal energy, dirt, trees, rocks, humans. Thermal imaging is so successful at detecting human beings that it poses a threat to the average citizen. Don’t get me wrong, I feel every citizen should own a thermal imager as well.
In today’s world it is becoming apparent that the average individual citizen is going to under the prying eyes of the government, but what if Joe citizen has concerns about his privacy? I’ve been through countless forums where people are searching for an answer as to how one can hide from thermal imaging. We are even working on a method ourselves (sign up to our newsletter on the right side of the page, we will let you know when it becomes commercially available). While I would like to be the first to develop a product to defeat thermal imaging, I feel that I should share the challenges in doing so. If I am not successful, maybe someone else will be. All of the ideas I’ve run across so far will not work; Space blankets, glass panels, mud, wet suits, none of it works.
The key to evading thermal imaging is the same as any camouflage, just with different parameters. You will not ever “disappear” from a thermal imager, just the same as you won’t disappear just by wearing Multicam or ATACS. In visible camouflage you use colors and specific patterns to do so. You have to blend in and use cover and concealment. You wouldn’t go unnoticed wearing traditional camouflage laying down in the middle of a parking lot, you shouldn’t expect to do the same in thermal. In both examples knowing your surroundings and the characteristics of what is searching for you is the key.
In order to hide from drones and other entities using thermal imaging, you must first understand how it works. Even if you can develop a method to block your thermal signature you must also know how to use basic cover and concealment techniques, as they apply to thermal imaging. It is not that much different that putting on optical camouflage and knowing where to hide, in fact, there are many parallels. Here are some of the specific challenges and characteristics when trying to evade of thermal imaging:
The most obvious issue in evading thermal imaging is dealing with the heat that a human produces. It is impossible to stop the body from producing heat and it is also impossible to inexpensively contain all of the heat the body produces. Expensive thermal cameras, such as the ones in drones and helicopters, sense the actual photons emitted from an object. Less expensive handhelds use a material that measures the differences in temperature. Either one first needs the heat from your body to reach the sensor. If your heat cannot reach the sensor, you cannot be seen. A physical object between you in the camera, such as the roof of your house, a boulder, or a tree will stop the infrared energy from reaching the sensor. The problem is you can’t continually surround yourself with any of these objects. You must, however, put some barrier between your heat and the camera. The above example of the space blanket will reflect heat back to your body and the imager cannot see through it, but if it touches your body the heat will transfer through the material rather quickly (like one second). If an air gap was kept between your heat and the space blanket this would slow this process down.
The Afghans have used wool blankets to mask their signatures from thermal imaging. If they hear a chopper or suspect an eye in the sky is looking for them they will drop on the ground and cover themselves with a the blanket. If the blanket starts out at ambient temperature the amount of time they will reduce their signature varies, depending on the temperature relative to their body heat. This works because the blanket acts as an insulator. As soon as the wool begins to warm they will become visible again. I suspect this method works for mere seconds, but imagine if they had a wool blanket, a space blanket, and another wool blanket. The heat would first have to transfer through the wool. The space blanket would reflect most of the heat back, but some would leak through. The second wool blanket would then begin to heat up compared to the surroundings. This wouldn’t work forever, by any means, but it would give the insurgent one thing; more time.
Masking your thermal signature is the biggest challenge to evading thermal imaging. There are a number of ways to obscure your thermal signature to avoid being detected:
1. Insulating your heat from the imager, such as the wool blanket. The more effective the insulation, the more time you have bought yourself.
2. Spreading your heat over a larger surface area. Your body has a finite surface area, if you can transfer your body heat to a larger object, that object will be cooler. Think of a heat sink.
3. You can vent heat to the atmosphere. The thermal imager cannot see the heat traveling through the air, at least not at the temperatures we are talking about. It would have to be directly to the atmosphere because if the heat were to heat up your cover, that would be noticeable.
4. You can mechanically trap heat.
Note, heat is also relative. If your entire environment is 98.6 degrees, you won’t disappear by any means, but the advantage of the thermal aspect will be lessened.
Note 2, all thermal cameras have what is called a dynamic range. Imagine I had a palette of 10 shades of gray available to me. As the processor of a thermal I have to assign a “color” to each temperature. The standard view would be white is hot and black is cold. If temperatures are relatively uniform, say everything the camera is seeing is between 60-70 degrees, the processor can assign a color for each degree. If the temperatures of the objects in the cameras field of view are vastly different, say 32 degrees on the cold end and 98.6 on the warm end with lots of variations in between (say a sunny winter day) the processor can no longer assign one of the 10 colors to each degree. It must assign a color to a range of temperatures, say 32 to 37 are “black”, 38 to 44 are dark gray and so on. This is a vast oversimplification but it does have an effect on the cameras ability to resolve your temperature. A real world example might be hiding near the top of a ridge. If someone was looking for you from below they would have to include part of the sky in the field of view. The sky is extremely cold, whereas the earth might be a hundred or more degrees warmer.” © 2016 TinHatRanch.
Thanks go out to Tin Hat Ranch .com for their insight. Please subscribe to the Tin Hat Ranch newsletter.
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