Liquid Nitrogen (LN2) Pour Filled Dewar Cameras

[Fraser]

Interesting. As you can tell, this is not the sort of thermal imager I normally deal with. It definitely had the Risley Prism system though.

[coppice]

Interesting. As you can tell, this is not the sort of thermal imager I normally deal with. It definitely had the Risley Prism system though.

Interesting. I thought LANTIRN was late enough that it would use a full image sensor. Either way, its not like the ground mapping line scanners. They only have a single pixel sensor, spinning on the edge of a vertical disc, sweeping the ground below. As the plane moves forward they achieve a raster scan. The electronics needs to manipulate the geometry of the scan, to allow for the actual forward speed of the plane, and may do the image manipulations needed to correct for the plane's attitude as well.

[Fraser]

I just found the detail on the LANTIRN system and I can confirm that the unit I advised on was part of the navigation pod and provides a forward thermal view of the terrain that is presented to the pilot on the HUD. It all gets very confusing with the various similar looking pods, some with fixed heads, others with moving ball heads and modern versions doing the job of both the navigation and targeting pods in a single unit. As I said, not my area so this is uncharted territory for me beyond the basic design of the thermal imaging camera core.

https://www.oocities.org/capecanaveral/5415/lantirn.html

From the provided information I can also confirm that the pod contained an “environmental control” section so that was likely why it had fluid pipes in the camera section.

Fraser

[coppice]

I just found the detail on the LANTIRN system and I can confirm that the unit I advised on was part of the navigation pod and provides a forward thermal view of the terrain that is presented to the pilot on the HUD. It all gets very confusing with the various similar looking pods, some with fixed heads, others with moving ball heads and modern versions doing the job of both the navigation and targeting pods in a single unit. As I said, not my area so this is uncharted territory for me beyond the basic design of the thermal imaging camera core.

https://www.oocities.org/capecanaveral/5415/lantirn.html

From the provided information I can also confirm that the pod contained an “environmental control” section so that was likely why it had fluid pipes in the camera section.

Fraser

If its specifically described as terrain imaging, it must have been for ground hugging missions at night. Mechanically scanned imagers usually have a rather low refresh rate. I wonder what this one achieves? A pilot needs something good if they are following the terrain at high speed.

[Fraser]

The image presented to the pilot appears decent but no idea of the frame rate. I attach an example image and, as you say, it appears to be for low level operations. We had better shut down this interesting ‘conversation’ now as we are way off topic for this thread

Thanks for your insight into military aircraft thermal imaging systems 

Fraser

[coppice]

Thanks for your insight into military aircraft thermal imaging systems 

If you are interested in thermal imaging, this is the killer application. 

[CatalinaWOW]

I just found the detail on the LANTIRN system and I can confirm that the unit I advised on was part of the navigation pod and provides a forward thermal view of the terrain that is presented to the pilot on the HUD. It all gets very confusing with the various similar looking pods, some with fixed heads, others with moving ball heads and modern versions doing the job of both the navigation and targeting pods in a single unit. As I said, not my area so this is uncharted territory for me beyond the basic design of the thermal imaging camera core.

https://www.oocities.org/capecanaveral/5415/lantirn.html

From the provided information I can also confirm that the pod contained an “environmental control” section so that was likely why it had fluid pipes in the camera section.

Fraser

If its specifically described as terrain imaging, it must have been for ground hugging missions at night. Mechanically scanned imagers usually have a rather low refresh rate. I wonder what this one achieves? A pilot needs something good if they are following the terrain at high speed.

Frame rate, scan speed and sensitivity are a trade space.  Many scanners of the era achieved frame rates well above the effective frame rate of a human pilot (20-60 fps range).

The rotating wedge system can generate a large number of scan patterns with the interesting property of widely varying scan rates over the field.  Thus information can be gathered over a large field of view with a small number of detectors, and very high quality, data information provided over a small region. 


For MrSheep - Just about every cooling gas imaginable has been used for cooling infrared systems.  Helium for systems that need really low temperatures, Neon for slightly less demanding cases.  Nitrogen and argon are widely used, and for roughly similar temperatures.  Nitrogen is widely available and cheap, argon has desirable thermodynamic properties.  Oxygen is rarely used because of fire danger, but compressed and dried air is sometimes used in cryostats.  There are even systems that use Freon and CO2.

[Fraser]

I will see whether I kept the images of the F-15 navigation pod and start a new thread about it as such might be interesting to forum members. It is not often that we get to see the inner workings of military thermal imaging systems, albeit older technology in this case.

Fraser

[Fraser]

I have found the images of the LANTIRN Thermal navigation pod internals  I am having some doubts about posting such in the public domain though ! The unit was dated 2001 so not exactly ancient technology. Posting technical pictures and details of an F-15 related thermal imaging technology may not be the brightest of ideas. I was surprised that the scrap dealer obtained a complete pod that was actually unused stores stock with only 4 hours on its cooler. When discussing the more advanced thermal imaging technologies we do have to consider why such is not already documented in the public domain.

Anyway, apologies to the OP for the off topic discussion. Now back to the topic of LN2 cooled cameras 

I own two LN2 cooled cameras, the AGA 680 thermal microscope and the AGA 780 series portable thermal imaging scanner. Neither will ever see LN2 again as they are museum pieces. I did look into sourcing LN2 and what the costs would be. Sadly in the UK, unless you are well connected with a Technical University, it is actually quite hard to obtain small quantities of LN2 on an ad-hoc basis. The storage Dewars are quite expensive as well. It quickly became apparent to me that the cost of providing LN2 for my two antique cameras far exceeded any benefit of getting them running. The situation with the LN2 cooled Amber cameras is very different though. Those cameras are worth the cost and effort of the LN2 sourcing and associated equipment. I was not previously aware of the need to refresh the vacuum on the dewars of those detector housings and was similarly unaware of the extensive equipment requirement to pull that vacuum to the required level. As has already been stated, these cameras are well suited to science roles where LN2 and associated vacuum pumps are more common. I will stick to Stirling coolers and can understand why the Stirling mechanical cooler was such a welcome development for many industrial users of cooled thermal imaging systems. We actually had an AGEMA THV880 scanning thermal camera upgraded to a Stirling cooler by AGEMA in Sweden. We were one of the first to have that upgrade installed and it cost a small fortune.

Pictures added…

AGEMA 880 LN2 model
AGEMA 880 with Stirling Cooler upgrade mounted on rear
AGA 780 series portable LN2 cooled system
AGA 680 LN2 cooled camera …. Early thermal imaging ! Not exactly small or light in weight !

Fraser

[MrSheep]

Fraser, yeah I didn't know that I needed high vacuum equipment either until I read the manual. You learn something new everyday haha 

Also yeah it is kind of a hassle to source LN2. It is easier if you live near colleges or universities as the always get it by the truck load. However not sure how willing they are to give it to you when you are not part of the department. I have however been able to source some near me via welding supply shops. Not all of them have it but some do so you have to do some research and some calling to find some. I know Airgas and Praxair sell it. But the prices near me are a bit too high $10/L. Luckily I found a store that was less at $5/L

I will prob not use the LN2 cameras as much as well but will from time to time because I do want to play around with them more.

[MrSheep]

Cool video on servicing a LN2 Detector system 
Although I do question is it safe to just pull the vacuum port like that. I at least pump mine down to rough vacuum (5mbar) before I attempt to remove the plug.