Stuff in Space

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Tom Ligon
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Re: Stuff in Space

Postby Tom Ligon » Mon Jul 17, 2017 5:25 pm

I've played with the thermal imager a lot. Pointing it to the sky can be quite an education.

The full moon should be quite toasty, as much as 123 C (253 F). Yet, the thermal imager has trouble picking it up. The first time I tried it, I got no indication at all. That was a summer observation. I tried again in winter, and was able to register a blip at about 40 F against a sky that was pegged as cold as the instrument could indicate.

The factor here appears to be water vapor. If it is humid, the atmosphere blocks all heat in the band where this imager works. You absolutely have to be out of the atmosphere for this sort of measurement to have a chance.

Imaging a bee-sized 102 F target at that distance, but in space, has the advantage that the background is at about 3 Kelvins, and the scope is liquid helium cooled.

A star such as Achird is about 20 LY away ... good candidate for life. Yellow star, about 3 B years older than ours. That is about 4.2 E 8 times further away than the moon. So if you could image a half-inch bee at lunar distance, that would suggest you could image an object 3,300 miles in diameter at 20 LY, in infrared, as a blackbody at 102 F. I am impressed.

ladajo
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Re: Stuff in Space

Postby ladajo » Mon Jul 17, 2017 5:53 pm

I did not know about the bee oven thing. That was interesting, thanks!
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

ladajo
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Re: Stuff in Space

Postby ladajo » Mon Jul 17, 2017 5:54 pm

On another note, you would be pretty impressed with what can be thermal imaged on the ground from.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

Tom Ligon
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Re: Stuff in Space

Postby Tom Ligon » Mon Jul 17, 2017 7:18 pm

I only have the single-band instrument, which works at around 10 microns, IIRC. That makes it a good instrument for seeing water vapor. It can image clouds in the dark, and steam looks like flames. But it also blinds it under humid conditions.

FLIR has another one out that works in a band sensitive to hydrocarbons. These can spot a gas leak ... looks like black smoke.

I have several infra-red cameras that require an IR illuminator. These don't show body heat, although they may discern engine heat and can see other too-hot-to-handle objects. These are sensitive to much shorter wavelength.

A friend of mine involved in amateur SETI research has used a microwave receiver to measure temperature of objects. This can be done with a used microwave receiver available for under $200 on e-bay some days, plus a small satellite dish.

An instrument with multi-band sensitivity, on which you can select the bands you wish to use for the purposes of a given image would be a powerful tool. And if I knew how powerful, Ladajo might have to kill me. This 2003 version is obsolete enough to maybe save my scalp.

http://investors.flir.com/releasedetail ... eid=297621

ladajo
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Re: Stuff in Space

Postby ladajo » Mon Jul 17, 2017 10:42 pm

Just imagine what you could do from space with multi-band large array, synthetic apeture, or multiple sensor interferometers...
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

paperburn1
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Re: Stuff in Space

Postby paperburn1 » Tue Jul 18, 2017 9:02 am

Your tax dollars at work
https://www.youtube.com/watch?v=UUHvpszbilc
And we can accurately tell body part temperatures as well.
Litening G4
On a side note you can make a cheap IR camera out of one of your old Digital cameras. Most use a cheaper CCD type camera that picks up IR so all you have to do is tale the Ruby lens filter or film off the lens and bingo you have an IR capable camera.
(some disassemble required so if your Edward hammer hands, do not try this)
I am not a nuclear physicist, but play one on the internet.

ladajo
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Re: Stuff in Space

Postby ladajo » Tue Jul 18, 2017 12:29 pm

I have to agree the new pods and built-ins are really impressive. Even the older stuff was "holy shit!".
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

Tom Ligon
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Re: Stuff in Space

Postby Tom Ligon » Wed Jul 19, 2017 4:00 am

As a kid, I used to worry that somehow people might see my farts. We now have the technology.

My little home survey camera is sufficiently sensitive to show the difference between my bee-stung hand and the other hand. The stung area felt warmer, and the camera verified it. It will show a 0.1C temperature difference.

I can track a cat across the floor by its warm footprints.

krenshala
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Re: Stuff in Space

Postby krenshala » Thu Jul 20, 2017 1:09 pm

We had a FLIR camera at the datacenter I used to work in. We used it to check breaker panels and subfloor power outlets for power issues/faults. It was easy to see which customers were exceeding the recommended 80% amperage on their power circuits based on the breaker temperatures (hmmm ... could it be the breaker that is 20F warmer than everything else in teh panel? I wonder ...).

I've also seen the same model used to check external walls and roof for internal water due to leaks. A very useful check.

Tom Ligon
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Re: Stuff in Space

Postby Tom Ligon » Fri Jul 21, 2017 1:59 am

10 uM is indeed a fun part of the spectrum, and thermal imagers have too many uses to list. I've tracked down electrical shorts and spotted leaks. Also where the cat threw up.

But getting back to satellite junk, is IR the way to spot it?

Using a space telescope, I can imagine that planets might be rather boring in UV, although there's probably some analysis using it that could be informative. But metal objects reflecting light from a nearby sun might stand out pretty well. There are some papers out on "The ultraviolet spectral albedo of ..." Earth, Jupiter, Saturn, etc. Looking at one abstract, you can pick a band where a satellite can't see clouds on Earth. So maybe you could use a band where the planet nearly disappears, but flashy metallic objects shine.

Most modern digital cameras can detect UV, although we usually make efforts to block it as it is usually considered an adverse effect. However, many lenses will pass it at least down to 350 nm. Simple lenses are best. I've got a fixed 50 mm Nikkormat that I've verified (by inducing fluorescence thru it) can pass the light of a 365 nm UV source. By using such a lens with a filter that passes only UV (not cheap but available) it is possible to take pictures in the longer-wavelength end of the UV spectrum. I want to be able to take UV photos of flowers, the way bees see them.

There's a band called vacuum UV that can't penetrate the atmosphere. Not many lens materials, either, although a company I worked for made sensors for vacuum UV, which did have a thin window. It should work with a Newtonian telescope in space, though.

paperburn1
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Re: Stuff in Space

Postby paperburn1 » Fri Jul 21, 2017 12:55 pm

Against the cold background of space IR should work splendidly . As of 2017, the Voyager 1 space probe is about 19 billion kilometers away from Terra and its heat signal is a pathetic 20 watts But as faint as it is, the Green Bank telescope can pick it out from the background noise in one second flat.
I am not a nuclear physicist, but play one on the internet.

Tom Ligon
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Re: Stuff in Space

Postby Tom Ligon » Fri Jul 21, 2017 1:38 pm

paperburn1 wrote:Against the cold background of space IR should work splendidly . As of 2017, the Voyager 1 space probe is about 19 billion kilometers away from Terra and its heat signal is a pathetic 20 watts But as faint as it is, the Green Bank telescope can pick it out from the background noise in one second flat.


We drove past that big dish a couple of weeks ago, then viewed it from a nearby mountain on the Cass railway. They bill it as the largest movable structure on the planet.

IR can detect many space objects you won't spot with visible light, sure enough, but I was thinking of the specific case of orbiting metal around a planet. The presumptions here are:

1. In the habitable zone close to a star broadly similar to ours.

2. Orbiting in higher concentration fairly close to the planet.

3. Emissivity of shiny metal parts is way below most materials, so they don't radiate IR as effectively.

4. But planets, which may radiate strongly in IR, don't radiate as much in UV.

5. IR emissions from objects orbiting close to a planet are insignificant compared to the emissions of the planet.

What I was interested in is a discrimination tool to pick out shiny metal objects in the light of a nearby sun. I suspect they will "pop" in UV. The Voyagers, by comparison, are illuminated by starlight, and their attitude is fairly fixed at this point, so if no glares are pointed this way, they won't be. I believe they spin slowly, but they no longer have the fuel for end-to-end flips (until a few years ago, these were done for magnetometer calibration). I believe both still transmit, so their location is known, and they can be spotted by their microwave transmissions as well as IR radiation.

krenshala
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Re: Stuff in Space

Postby krenshala » Fri Jul 21, 2017 9:47 pm

Assuming "metal detection via UV sensing" works, it seems to me that it would work best when the body being checked is not in conjunction with its local star, which is the opposite of most of the remote (extra-solar) system detection work done so far (as I understand it, anyway). That would minimize "noise" from the star itself in these investigations.

paperburn1
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Re: Stuff in Space

Postby paperburn1 » Sat Jul 22, 2017 2:49 am

With UV would it be us, object, star so most of the light would be reflected back at the star? The objects being between us and the star. maybe a bright UV halo around the star ?
The most probable material (based off of our system) to be usable are oxygen and iron. These elements could be combined to form an iron oxide called hematite, which we humans have used to make mirrors since antiquity. It should be common in most systems. That actually might make a very unique spectral signal coming from the edges star. Once again assuming a dyson swarm and a system similar to SOL.\\ from a planet I need to think about that, to paraphrase "I think we need a bigger telescope"

And agreed as for voyager it a whole lot easier finding something if you know where to look for it; just like my car keys. :D


Edit: where does all that power go? It would not make sense just to beam it back at at the sun , so a power plant of some sort. a gigawatt point of UV /IR somewhere in system? So not circular orbits but maybe elliptics.
I am not a nuclear physicist, but play one on the internet.

Tom Ligon
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Re: Stuff in Space

Postby Tom Ligon » Sat Jul 22, 2017 11:04 pm

Why would metal objects only reflect light back to their sun? My thinking was, they would be like our satellites, with shiny metal structures. There is no particular direction you need to reflect the sunlight, you just need to keep the satellite cool.

If you sit in your back yard on a clear night for a few hours after sunset, you may be surprised at the number of satellites you can see passing over. You could mistake them for planes until you realize they lack nav lights and flashing strobes. Occasionally one will "flare" for a few seconds as a broad expanse of metal reflects the sun straight at you. Satellites passing the terminator fade out over a few seconds. The Iridium series can be very bright. The ISS can be spectacular, and you can make out the shape with binoculars. If you want to try this, check out this website:

http://www.heavens-above.com/

Earth does not have all that many orbiting the Sun. A more advanced civilization might. We have quite a few in LEO, a veritable swarm in sun-synchronous orbit, and a ring in geosynchronous, spaced, last I heard, about every 2 degrees. Earth geosync is far enough out that a system capable of resolving a 3300 mile diameter planet (see 20 LY problem above) ought to be capable of distinguishing flashes in geosync versus the planet. Of course, the geosynchronous orbit depends on the planet's day length and mass.


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