Hubble Accuracy Surpassed By Earthbound Telescope 87
randuev writes "A high-speed adaptive optics system helped the Large Binocular Telescope (on Earth) to beat the accuracy of the Hubble Space Telescope's observations. 'A special sensor detects atmospheric distortions in real time and controls the mirror to adjust its position to compensate, effectively canceling out the blurring. The mirror can make adjustments every one-thousandth of a second, with accuracy to better than ten nanometers.' Now, that's what I call real-time. This nifty trick multiplied the Strehl ratio (optical quality) of the LBT by about 80 times. The new system was tested in May and June, so hopefully we'll soon see more space around us in higher resolution on Google Sky."
Impressive! (Score:2)
Wait. Nevermind.
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If your space telescope is experiencing significant camera shake then you've got bigger problems.
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Nope. Except for the basics, deblurring algorithms are usually highly application specific. The one you link to only handles motion blur caused by the camera moving and requires six axis motion tracking.
Before Hubble was repaired, a different, more general deblurring algorithm was used to help correct the distortion from the bad lens.
Although, many of the atmospheric distortion correction methods require a guide star. If no guide star is available one is created by shining a powerful laser up into the at
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Sounds good (Score:2, Interesting)
This doesn't mean we'll see better Deep Field images does it?
I know they used super new adaptive optics but it wont increase the amount
of light collected.
Re:Sounds good (Score:5, Informative)
While this does mean that it could possibly make some Deep Field images. There is still another problem that makes this possibly intractable. The atmospheric absorption of some wavelengths means that it might still not be able to see certain areas in the spectrum effectively; this could prevent it from being able to produce nice deep field images like the hubble. However this ability to resolve objects that much better means that it could most certainly be effective at searching for planets.
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However this ability to resolve objects that much better means that it could most certainly be effective at searching for planets.
That touches on what I was thinking, even if it's more powerful than Hubble the true beauty of all this is we now have two fantastic devices that can be working concurrently!
Several limitations to Adaptive Optics (Score:5, Insightful)
There are several limitations to adaptive optics, which are by no means a cutting edge technology for large observatories any more. Just about every telescope being built or upgraded today are having adaptive optics fitted.
One major limitation is that the adaptive optics are only good for small fields of view since you're using a single guide star to calibrate the disturbances in the atmosphere you're correcting. So they are not good for imaging multiple objects or even large single objects (like a single galaxy). Another is that since you're not in orbit like Hubble you have to wait for the planet to rotate, so a deep field would take much longer anyway.
When we lose Hubble we lose some unique capability. Even successor telescopes that don't work in optical light will not fill that void. Adaptive optics will only be useful in some circumstances whereas Hubble would have been useful in the general case. Oversimplifications like this story don't belong on a techy site like slashdot.
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That is why they build MCAO which means multi-conjugate adaptive optics, most often with laser guide stars. It allow for much greater isoplanatic field of view. This is done using (typically) three sensors and the adaptive mirrors projected to different heights in the atmosphere. I wouldn't say is a done deal but it's certainly quite far along and several telescopes are equipped with this stuff. I'm not sure how much real science has yet been done with this technology though but the improvements I've seen m
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There are several limitations to adaptive optics, which are by no means a cutting edge technology for large observatories any more. Just about every telescope being built or upgraded today are having adaptive optics fitted.
Yeah but these are really, REALLY good adaptive optics.
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When we lose Hubble we lose some unique capability. Even successor telescopes that don't work in optical light will not fill that void. Adaptive optics will only be useful in some circumstances whereas Hubble would have been useful in the general case. Oversimplifications like this story don't belong on a techy site like slashdot.
What I don't understand is why we don't have a direct successor to Hubble. James Webb will be an infrared satellite, not visible light, so I don't see how it's a direct successor (IANAA I Am Not An Astrophysicist). I know of no other satellites that overlap but improve Hubble's coverage. Yes, I understand that today, adaptive optics beat Hubble, but Hubble was launched in 1990. Twenty years later the ground-based coverage bested space-based, but what could we conceivably learn from a visible-wavelength orb
Re:Several limitations to Adaptive Optics (Score:4, Informative)
So the answer to the first question is, infrared and near infrared are the wavelengths most useful for meaningful astronomy, because they allow astronomers and cosmologists to see through clouds of interstellar dust and gas to the interesting stuff in the clouds, and the interesting stuff hidden behind those clouds. That's why Hubble has both visual and infrared technology on-board. As well, infrared spectroscopy will tell us which nearby planets have the kind of chemistry that indicates the possibility of life. Due to water vapor, the atmosphere is virtually opaque to these frequencies so they must be viewed either from extreme altitude (balloon or very high flying jets), or space.
The color images that Hubble produces from visual light are in fact heavily altered and do not reflect what the human eye would perceive. Typically the colors being recorded are from the light emitted by Hydrogen, Sulfur, and Oxygen. Hydrogen and Sulfur both emit light in the Red optical spectrum, and if they were presented as the color the human eye perceives would blur together. Instead, the Hubble images view Hydrogen as Red, and Sulfur as Green with Oxygen providing the blue. This gives rich full color images rich in detail and visually stunning color. Images from infrared telescopes are used in exactly the same way, you just can't see those colors. So the representation in either case is not "real".
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Oversimplifications like this story don't belong on a techy site like slashdot.
Sure they do, because they give people like you a chance to fill in the details. I came here looking for a comment exactly like yours.
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The big difference between ground-based telescopes using active optics or adaptive optics to obtain diffraction-limited images, and the Hubble taking advantage of the lack of an atmosphere to obtain diffraction-limited images is that Hubble can do this over a large field of view whereas ground-based telescopes can only do this for extremely small fields. This is because the coherence length of the turbulence cells in the atmosphere that are responsible for atmospheric blurring (called seeing) are very smal
Re:Sounds good (Score:4, Interesting)
Probably not. It's not that the binary telescope isn't capable of doing Deep Field work, but the deepest of the deep imaging shots took Hubble keeping its optics focused on a single, apparently dark area of the sky for literally months. Deepest sky search took up most of the Hubble's lifespan during the last few years, and many other projects had to be put on the back burner. Administering big science involves trying to share time fairly for many projects, and I'd bet that many of the first time slots scheduled on the new version of the binary array are promised to the people who were bumped from the Hubble when it became apparent it was a good tool to investigate the very early universe. Other time is doubtless already reserved for those non-cosmologists who want to do other important astronomical things, such as exoplanet searches and resolving what's possible in visible wavelengths of our own galactic core. There's also a need sometimes to do visual backup observation when the orbiting infra-red or x-ray scopes find something unexpected in their wavelengths, and how much time could be borrowed or traded around for this depends on just how weird the other observations are.
Re:Sounds good (Score:4, Informative)
More please!!! (Score:2)
I hope they keep up the pace of developments like these, I would like to see some good pictures of planets outside our solar system in my lifetime...
Re:More please!!! (Score:5, Informative)
Alas, there's no way around the Rayleigh criterion: http://en.wikipedia.org/wiki/Angular_resolution [wikipedia.org]
We're not going to construct one-hundred-kilometer size telescopes any time soon.
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When it comes to funding - probably pretty much impossible; at least when it comes to "any time soon" / "in my lifetime".
Anyway, the really sexy thing for now will be destructive interferometry (or some starshade, whatever) of light from a star & spectroscopy of the planet; we should be able to notice a biosphere. And, over many observations, images not too dissimilar to current Pluto ones should be relatively easy, that's not so bad.
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When it comes to funding - probably pretty much impossible; at least when it comes to "any time soon" / "in my lifetime".
As the AC pointed out,
Isn't that exactly what telescope arrays are for?
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How does a big, complex system help with funding problems?
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In fact creating a baseline in space with telescopes millions of miles apart is perfectly doable. Even more interesting is placing an optical assembly on a distant planet like Pluto, and using the gravitational distortion around the sun as a primary lens. It should be possible to create an optical telescope of such design, whose primary lens is nearly half a million miles in diameter. Of course you'll have to eclipse the star in the middle, but that should be relatively easy.
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There's no particular barrier to the construction of interferometers of such aperature in space, especially at longer wavelengths. You don't actually need to control the separation precisely: just measure it.
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The problem of separation is what put on hold few recent plans for such missions, indefinitely (until it will be figured out, if practically possible)
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I didn't mean to imply that the task was trivial: just that there is no fundamental barrier. It is not necessary to construct multi-kilometer sized structures in order to have multi-kilometer aperatures. You would use a laser interferometer to measure the separation and then use your adaptive optics technology to compensate for the changes in it (which sho
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Well, if the precision needed surpasses practical approaches possible to us, that's moderately close to fundamental, as far as seing it soon goes... Or perhaps, at the least, you'd probably need zero drag spacecraft; while doing it with a large part containing mirrors plus including all the "portholes" for incoming and outgoing (to the hub) light...fun.
There are certainly good reasons why one ESA mission [esa.int] was put on hold (without managing to determine if what they want to do, with only 3 spacecraft, is techn
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My idea (which I assume others have already thought of) is to use two unconnected spacecraft. Don't try to rigidly control the separation: measure it and
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Yeah, that's what the linked ESA mission was about... (well, not two but three/four, depending how you want to count - a problem of similar scope anyway; and also about which my example was - I assumed it was clear with "outgoing light" pathway and "hub" parts) Didn't really seem to simplify things.
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> Yeah, that's what the linked ESA mission was about...
The article makes it sound like they were planning on trying to station-keep to within a fraction of a wavelength rather than using active optics to compensate for drift which is what I had in mind (very precise station-keeping would still be needed, though).
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But that's dynamically basically equivalent, from the perspective of a spacecraft obviously not anchored anywhere (interference relies on timing of signals); especially considering that single observations, collecting those scarce photons, take a long time.
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I would use a movable mirror to compensate for drift. If you could get the drift down to centimeters per hour you could still make fairly long continuous observations. You should also be able to combine multiple observations, each made after resetting the compensator. If you could get the drift rate low enough and/or tolerate short enough individual observing periods the compensator could be fairly small.
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But with movable mirror one would still need to dump the momentum somewhere; counterweight, reaction wheels (ESA mission would probably use those, too, it's mostly a no-brainer; OTOH ion engines, with their very finely metered output, could be perhaps better, simpler & allowing more continuous work...maybe still not enough, apparently) - that still needs dumping accumulated displacement or rotation via thrusters/etc.
And "centimeters per hour" would be several orders of magnitude too big; especially when
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I mean centimeters per hour before compensation: zero afterwards, until the compensator saturates and has to be reset. However, if the ion engines can be as good as you say they could be combined with a short-range movable mirror compensator ("active optics"). The ion engines would handle "gross" stationkeeping with perhaps a few millimeters of jitter which would then be compensate
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To elucidate: I'm visualizing two spacecraft, one with a movable mirror capable of adjusting the path of the light coming from the other by perhaps +- 1 meter. Rockets would be used to get the rate of change of the distance between the two spacecraft down to perhaps 1 cm/hr and then be shut off. You'd then start observing, using a laser to measure the spacecraft seperation and moving the mirror to compensate as it changes. This would give you a hundred hours or so of continuous observation before the m
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Actually the Terrestrial Planet Finder-Interferomete, TPF-I, (as opposed to TPF-Coronograph), studied both a fixed length deployable structural interferometer and a four telescope + beam combiner = five spacecraft mission. The latter was downselected for a pre-phase A mission, due to the larger telescopes available to a spacecraft which didn't require a deployable boom, and the ability to fine-tune the spacecraft separation to best tune in individual targets. The larger telescopes (4 m) were the deciding
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So I was right. Others did think of it.
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So I was right. Others did think of it.
Yep. The idea has been around for a long time. Radio interferometers have used moving delay lines for a long time. SIM was planning on using moving delay lines in the 90s. CHARA uses moving delay lines.
No, I didn't. I was not consulted.
I meant "you" in the general sense of /., and the resulting pressure on Congress. Go back and read the /. threads at the time, lots of Hubble fanboy-ism, and that sentiment carried on to Congress. Hubble is expensive to maintain an
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Well, yes, moving delay lines are bloody well obvious: the Q4 radar used them in the 1950s (and others probably used them earlier). I meant the idea of using two unconnected spacecraft and compensating for drift instead of attaching the telescopes to a rigid beam or attempting perfect stationkeeping. I didn't think that was original with me (as you confirmed).
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For some reason what you describe doesn't quite fall in line with how the very similar ESA free-flying project, which seriously researched joining forces with NASA effort, apparently says as one of its ending conclusions "we would still need to determine if this is even feasible with ~available tech"...
Re:More please!!! (Score:4, Interesting)
: using the sun as a gravitational lens. Sure, it need a spacecraft to go 13x times farther than any spacecraft ever did, but we would get gorgeous pictures. Some people say this may be our only way to ever observe directly exo-planets in details. I am not sure if it enters in the "practical within my lifetime constraint" but if you have 50 more years to go, I wouldn't rule it out.
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I don't hold much hope, even though I do have a fair chance of living at least 50 years more (also, imagine repositioning / between acquiring one planetary image times for this thing). Oh well - determining atmosphere & surface spectrum plus some rough rotational color map should be here relatively soon; and plenty fun, considering the possibility of discovering alien biospheres (with such event always having a slight chance of motivating us, but I most likely won't see the effects of this one)
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I dont know if things have changed but when I last read anything about adaptive optics it involved sending
a laser beam into the atmosphere. You'd have to be away from air traffic to do that these days.
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You'd have to be away from air traffic to do that these days.
Or have a TFR in place. Bloomington-Normal, IL has a university that is constantly doing atmospheric work with a laser, and they have a standing TFR in place (which doesn't really make it a temporary flight restriction, but I don't file them *shrugs*).
Sarcasm, right? (Score:3, Informative)
In case my sarcasm detector is giving a false positive, the answer is you don't need adaptive optics for a mirror diameter of 30 cm or less, because at those sizes you get more blurring from diffraction than from atmospheric effects.
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As Jeff Goldblum said in Jurassic Park, 'scientists will find a way.'
uh.... he said "life finds a way", implying that the scientist's assumptions will be proven false, and their efforts will have been proven ineffective.
Better than the Hubble, but... (Score:5, Interesting)
It's great that atmospheric distortion can be largely eliminated, but just wait until we get some improved optics into space. Hubble has produced wonderful images, but the James Webb Space Telescope is going to be a phenomenal upgrade.
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Hubble has produced wonderful images but the James Webb Space Telescope is going to be a phenomenal upgrade.
Finally astronomers can put aside the childish, obsolete visible light spectrum and focus in on what really matters: infrared.
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It's not like (many) Hubble images have much in common with reality, with their long exposures, et al...
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Ah, the treachery of images. This is not a galaxy.
What a testament to the HST... (Score:5, Insightful)
...that it was more than 20 years ahead of any Earth-bound telescope when it launched.
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The only modifications that was done to the optics was the installation of "glasses" to correct the shape of the lenses involved, iirc. The computer hardware was later updated to make it usable beyond its original design expectations.
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The various refurbishment missions have done a lot more than just correct for the flaw in the primary mirror. Most of the instruments have been replaced with newer instruments over Hubble's lifespan. In many ways Hubble is almost a completely different observatory from what was launched.
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...and probably 10 years behind spy sats on which it was based? (to be fair, "20 years ahead" in some things, too)
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> ...and probably 10 years behind spy sats on which it was based?
Astronomical telescopes and spysat cameras have little in common (not nothing, but little).
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"Astronomical telescopes and spysat cameras" - yeah. But "Hubble and Keyhole" - probably somewhat more than little. The same main manufacturer of both spacecraft and apparently the same mirror diameter are strong hints... (the astro cameras of course are fairly specific; but the general tech, CCD, was of might interest for spysats; and Hubble could, and have done so rarely, image the surface)
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AFAIK, adaptive optics is of no use in space.
On top, sending a telescope of this size on a rocket, would probably require TNG level technology. (TOS level only if Scotty is around with some duct tape)
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Don't forget that HST's launch was delayed by 4 years due to the Challenger explosion. Make that "over 24 years ahead."
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I admit i clicked on that, despite suspecting it was spam.
Well... I couldn't figure out whether the guy is a genius artist or an entertaining retard.
Either way, there is something about it - it's a website that Eric Cartman could have set up, and that's no small thing.
Not bad ... (Score:2)
All Kidding aside, High fives to everyone involved. This is some cool tech.
it's resolution that's better, not accuracy (Score:4, Informative)
The adaptive optics increases the resolution of the telescope by eliminating the refractive errors caused by atmospheric turbulence. And the basic resolution of the LBT is better because its 8.4m mirrors are over 3 times the diameter of the 2.4m Hubble mirror.
The ideal would be a larger mirror in space, such as the James Webb telescope is to be if it works.
[Disclaimer: I eat lunch with LBT engineers, so I know way too much about the gory details of getting 600 magnetic actuators to work together without breaking glass.]
Watch the documentary (Score:3, Informative)
not in the IR though (Score:4, Informative)
Much of astronomy is being pushed by the need to image deeply in the infrared. For example, to discover the most distant objects in the universe, you need to use near- and mid-infrared wavelengths (because objects that are far away are receeding rapidly, hence redshifted). And for this, mostly what you want is raw photon count, not sharpness (although that would be a "nice-to-have" someday).
Unfortunately (for astronomy), the atmosphere absorbs heavily in the infrared wavelengths (aside from a few windows, which give us our passpands), and as a result, a 1 meter telescope in space still beats an 8 meter on the ground, in almost every respect (putting cost aside for a moment...).
At least for infrared work...
Deep field work (Score:1)
There are lots of comments about Hubbles deep field images, which are really impressive but Hubble is only a 2.4m telescope and the standard on the ground today is 8-10 m. The light gathering power is more than 10 times that of Hubble and what Hubble could do in one month, these telescopes can do less than a week. The James Webb telescope will be able to do lots of impressive stuff but the resolution and lots of the science has come down to earth. There are several ongoing +30m projects such as for example
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Not in the infrared.
Ah! My only weakness! (Score:1)
Did They Use Forth? (Score:2)
Good news, everyone! (Score:2)
Meh. Wake me when they invent the smelloscope.
Or install a telescope on the moon.
And a webcam. How could would it be to have a webcam on the moon pointing at Earth. It would take the narcissism of internet technology to the global scale. Too bad it would probably just show us all masturbating.
But seriously i think such a webcam would generate great interest.