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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!!!
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
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.
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
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.
Use the moon as your disk, it's much bigger, and it's already there.
1609m roughly so out by a factor of five.
I would presume that the bulk material in the inside has no need for accuracy, only the very rim. The question is more of whether you can have a coiled material that when uncoiled (deployment) can return to a shape with that level of accuracy. I would think it possible, but I really don't know.
I would forsee a super-precise rim with just a small bit of light shielding on its inside, deployed via uncoiling, and then attached to a much stronger, less precise uncoiled ring to which the bulk shielding material (and stationkeeping ion thrusters) are attached. The attachment between the two would need to provide for vibration and tension isolation (even the slowest adjustments in angle of such a huge, thin shield are going to set in motion relevant vibrations, you've got almost no damping - you want the structural ring to deal with those and not transfer them through to the precision ring). Not to mention that your shield will be acting as a solar sail whether you like it or not (unless you're at L2... but then your craft better be nuclear powered).
Your telescope behind it is going to need to do some real precision stationkeeping (either extreme precision on the whole spacecraft positioning, or merely "good" positioning of the whole spacecraft plus extreme precision adjustment of the optics within) . This means long development times and costs to demonstrate that you can pull it off before you actually build the shield. But I would think that also possible - just very difficult. If they take the latter route they could probably demonstrate that here on Earth, which would be a big cost-saver.
Crowd: What do we want? Fry: Fry's dog! Crowd: When do we want it? Fry: Fry's dog!
A mile is the distance where a measurement-unit douche-bag still wont notice the warning shots. A good thing to know.
"His name was James Damore."
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.
1 mile=1.6km
So you're way off the mark.
Political debates have me rolling my eyes so much I think I got optical whiplash. I should sue. - Foamy The Squirrel
.... 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
Are these mega-scopes just PR exercises or are they necessary instruments?
It's just a proposal at this stage, which is coincidentally generating a bit of PR by getting people reading and talking about NASA. As to "necessary," well, none of it's necessary, but the thought of getting 1000x Hubble resolution has got to be at least worth costing up.
I thought radio astronomy surpassed narrow-band subjective Galilean astronomy decades ago.
They're complimentary. You might be able to see "more" in most objective terms from the ground in radio than visible light, but that doesn't mean visible light can't provide information you can't get from radio.
systemd is Roko's Basilisk.
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.
The telescope body, free flying tens to hundreds of miles away, can adjust ti stay in the focus.
Consciousness is an illusion caused by an excess of self consciousness.
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?
Stick the sensor on a boom, like the picture shows. Problem solved.
When our name is on the back of your car, we're behind you all the way!
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!
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!
Spin it fast enough and the rim will form a perfect circle on its own.
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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.
Spinning will provide easily obtainable centrifugal force (acting outwards - stretching the rim). Adding contracting straps ("artificial muscle") in the radial direction will allow to control the shape precisely. (creating outward force (push) would be difficult otherwise).
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