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Proposed Space Telescope Uses Huge Opaque Disk To Surpass Hubble
Required Snark writes NASA has funded a study of a geo-sychrounous orbit telescope that uses a half-mile diameter opaque disk to provide images with 1000 times the resolution of the Hubble. It uses diffraction at the edge of the disk to focus light, resulting in a very high quality image. It's named the Aragoscope, after the scientist Francois Arago, who first noticed how a disk affects light waves. "When deployed the Aragoscope will consist of an opaque disk a half mile in diameter parked in geostationary orbit behind which is an orbiting telescope keeping station some tens to hundreds of miles behind that collects the light at the focal point and rectifies it into a high-resolution image.
'The opaque disk of the Aragoscope works in a similar way to a basic lens,' says CU-Boulder doctoral student and team member Anthony Harness. 'The light diffracted around the edge of the circular disk travels the same path length to the center and comes into focus as an image.' He added that, since image resolution increases with telescope diameter, being able to launch such a large, yet lightweight disk would allow astronomers to achieve higher-resolution images than with smaller, traditional space telescopes."
Looks like the opposite of a pinhole camera
Not "effects" you illiterate dumbshit!!!
FTA:" ....who first noticed how a disk effects light waves."
Affects.
I can't see how that would work, there's only one geostationary track - and you only have to go a mile either side of it to be well out of sync (and no longer geostationary). The only way I can think of to keep relative station with a co-orbiting body is to lead or follow it in EXACTLY the same orbit. That would be a feat of orbital mechanics never before achieved. Even communication satellites have to carry propellant in order to correct their orbits periodically, and no two follow the exact same orbital track - as I think is what is being proposed in TFS.
Political debates have me rolling my eyes so much I think I got optical whiplash. I should sue. - Foamy The Squirrel
Did you even bother to read your link or do you not understand the article? The article you link talks about blocking bright interfering stars using a big shield. TFS talks about using a big disc as a lens with a very long focal length.
that's a star shade to improve contrast.
This focuses based on diffraction, an entirely different concept.
meanwhile, something like thermal expansion would probably ruin it. most diffraction lenses need to be mechanically accurate to within a wavelength of light.
It only effects it when it's in "geo-syncrounous" orbutt.
They may be thinking of using one of the Lagrange points -- geostationary and stable. But, yeah, at least one component (I'd guess the small one) will need some sort of station-keeping propulsion. Ion drive with a big fuel tank?
Actually, a half-mile disk would get some significant thrust from sunlight/solar wind. I don't know whether they could use that for station-keeping, or whether it would just be one more thing for them to fight.
So would a half mile opaque disk actually be visible from Earth in terms of blotting out stars behind it?
Maybe not naked eye visible, but it seems like anything that big might have an observable effect.
Lost at C:>. Found at C.
Definitely not a new concept, although the Boulder group has been doing this type of study for a while. The ultimate cost is immense though, because one has to do formation flying to incredible tolerances.
Double it! Then double it AGAIN!
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A half-mile diameter disk isn't going to be easy to rotate and point in different directions, and considerable motion by the light detector is also going to be required.
Frankly, I think these disadvantages so severely reduce the utility of the telescope that I wouldn't want to deal with it.
Not only that, but a half-mile diameter disk is one heck of a target for random space junk.
--PM
Without googling it, I'd say mile is about 300 meters?!
Which was define by some american scientist back in 1256...
1 mile = 1000 length of the scientists penis?
Am I correct?
This was my immediate reaction to skimming the front-page blurb.
Seriously, differentiation of "effect" and "affect" is neither a difficult nor novel concept. This just reflects editorial laziness, which does call into question in the mind of the audience the quality of information being conveyed.
Never thought this one would be useful...
http://xkcd.com/975/
Since the obscuring disk and the 'camera' have different altitudes, their orbital period is not the same. It will take the constant use of fuel to keep them aligned. How well can they do this? How long can they do this? How will this affect image quality? Will they allow it to drift while taking data? Etc.
Use the moon as your disk, it's much bigger, and it's already there.
It's basically an interferometer - the maximum separation of the telescope's mirror/lens is what gets you resolution. The surface area just makes dim objects brighter. Using a diffraction lens is irrelevant to the interferometry - it's just a way of bending the incoming light.
The catch is, the surface area of your lens needs to be aligned within a fraction of a wavelength of light for interferometry to work. It's been done on smaller optical telescopes and bigger radio telescopes (radio waves are much longer than light waves, so proper alignment is a lot easier). Getting the edges of a half mile diameter ring to remain within less than one wavelength of light from your sensor is going to be very difficult. There are methods to correct for differing distances. But I'd imagine rotating such a large annular scope would induce a lot of micro-vibrations (bigger than a wavelength) which may thwart such methods.
I have a question: Are these mega-scopes just PR exercises or are they necessary instruments? I thought radio astronomy surpassed narrow-band subjective Galilean astronomy decades ago.
.... lead or follow it in EXACTLY the same orbit. That would be a feat of orbital mechanics never before achieved.
The GRACE mission has been doing it for a few years now, tiny fluctuations in gravity can be inferred by the change in distance between the two probes. However it's not a geostationary orbit, just one probe following the other in low orbit. Personally I think it's a genius idea to turn the problem of keeping two probes in sync into a highly accurate gravity probe.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
I'm wondering if you could improve this by having multiple edges?
I'm not a physicist, but does the disc have to be a disc? Would a very thin edge do the job of diffraction? If so, you could block out unwanted light that passes on the "wrong" inner side of the edges with a small disc in front of the telescope.
Then you could have multiple thin edges next to each other and thus get multiple Arago spots. Most of them would be a bit out of focus I guess, but that could probably be handled by software or using something like the lytro camera.
Just a thought - though if it has to be a disc before the diffraction occurs, then it doesn't work.
The problem is that it wouldn't be steerable. It would sweep a slice of the sky rather than track a star
Will "AOL" be painted on the disk in huge letters?
Table-ized A.I.
Especially with one party wanting to divert science to social programs and the other fearful of science or tightwad.
Is it possible to use a big disk for both blocking light and for diffraction, per target object? That way both parties can be right. Win win. (Pardon me for sounding like a PHB there).
Table-ized A.I.
That disk had better be really black. I can imagine light coming up from the sun or earth or the moon giving a nasty background to the image one tries to obtain.Does anyone know how this works? Is the detector somehow focused on the edge of the disk?
It seems like this would only collect light at the rim of the opaque disk -- perhaps this gives sharpness (like a pinhole camera), but wouldn't it have awful light gathering abilities, somewhat like having a really tiny aperture (also like a pinhole camera)? Are they planning to make up for this with extremely long exposure times?
Why does geostationary even matter unless they are pointing it at the Earth?
See Solar Sail Demonstration (The Sunjammer Project)
http://www.nasa.gov/mission_pages/tdm/solarsail/solarsail_overview_prt.htm
What would keep the sun light and solar wind from moving it?
If the disk was made of 2 mil Mylar it would weigh about 65000 pounds.
Maybe having it spin slowly to use centrifugal force to keep it flat.
Being that big, how often is it going to be hit by a meteor?
Is it OK if it has some holes in it?
Does the disk have to be flat? If not, could you use the moon?
Put a satellite around the moon at the correct distance and block out the sun lit side of the moon.
http://www.edmundoptics.com/te... "Huge opaque disk" seems a lot more confusing then calling it a massive lightweight lens.
A disk 1/5 mile with a sensor 10 to 100 miles away (precisely aligned on the axis of the disk) isn't going to be very steerable, especially if the distances from the EDGES of the disk to the sensor all have to match within a half-wavelength in order for the interferometry to work right.
And wouldn't the changing relative positions of earth, moon, and sun cause disturbances in the disk? Is the solar wind sufficiently uniform over distances of 1/2 mile at earth orbit to not be a concern for causing non-uniform disturbances to the disk?
"geostationary" MUST be a mistake in the article. I don't see how the sensor can maintain a 1/2 wavelength position from the disk at a range of 10 to 100 miles unless the sensor is powered (ion drive?) somehow.
The station keeping and vibration might not be a problem - as long as you know what is happening I bet you could digitally correct for it. In fact, that might need to occur in any event, since for the levels of precision, you will probably need to be able to correct for the difference in gravitational forces acting on the ring between sea level and whatever orbit they put it in.
HA! I just wasted some of your bandwidth with a frivolous sig!
"NASA Proposes Huge Opaque Dick"
Aren't they normally opaque?
I cannot visualize this without the proper car analogy. Someone quick! Describe this using cars, Systemd, Hassleton, and women so I know which emotion to feel so I can respond accordingly.
I am lost without the emotional trademarks of FUD andor cars!
How do they propose to cram a 1/2 mile diameter disc into a conventional rocket?
A series of tubes?
as the opaque disk? Just sayin.
If you were, say, a light year from our moon and you had god-like technology(no actual miracles, just really smart and rich) I wonder how detailed you could make the picture.
You don't just want a circular object. You want a series of circular rings at the right intervals to interfere and give an intensity peak where the camera is. This s not as efficient as using a giant mirror, but it could be a lot lighter, and less sensitive to vibrations or distortions out of the plane of the disc. Saturn has a lot of rings. The shepherd satellites within the rings make some pretty complex patterns. It may be possible to use the natural structures. Or maybe we could add a few small moons of our own. The camera would have to lie above or below Saturn to look at the unlit side of the rings.