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Space Science

Overwhelmingly Large Telescope Closer to Reality 223

Posted by timothy from the see-zits-on-gerbils-from-alpha-proxima dept.
An anonymous reader submits: "The 100m OWL telescope proposed a few years ago by the European Southern Observatory group (ESO) may actually be built. Currently, the largest aperture for a telescope is the Very Large Telescope (VLT) at a 'very tiny' 16.4m by comparison. This monster is predicted to have a light gathering resolution of about 40 times the Hubble Space Telescope and a sensitivity several thousand times greater. Among many other things, it should be powerful enough to detect and gather spectroscopic data of extra-solar planets in order to determine the atmospheric composition and any signatures for life, like oxygen." We mentioned the OWL in this previous article too.
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Overwhelmingly Large Telescope Closer to Reality More

Overwhelmingly Large Telescope Closer to Reality

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  • How can a scientific article use such a fool multiplier as billion ?
    (english vs US vs old vs new vs ...)
    Please use comprehensible multipliers.
    If in doubt, use popwer of ten!
    • If in doubt, use popwer of ten!

      Is that like ppreview?

      (Umfff - the sound of tongue in cheek.)
    • How can a scientific article use such a fool multiplier as billion ?

      I'm not US and in my native language the billion would indeed be 10^12. But billion is worldwide understood as 10^9, also in various scientific literature.

      Besides anyone dumb enough to think they might have meant the 10^12 (i.e. one trillion), shouldn't be reading the article anyway.

      For those interested the notation comes from the prefixes mi, bi, tri and so forth representing the common one, two and three, but the US formula is 10^(3+3*X) where as the european formula is 10^(6*X) where X is the prefix number. From there you can see how the million is same for both formulas, but the following quantitys differ quite significantly.

      It's not once or twice that I've seen the US budjet (few trillions, i.e. 10^12) been poorly translated to my native language also as our trillions, making the error quite enormous (10^3*6 == 10^18).

  • Active and adaptive correction (Score:4, Interesting)

    by ObviousGuy ( 578567 ) <ObviousGuy@hotmail.com> on Tuesday July 09, 2002 @05:51AM (#3848189) Homepage Journal
    A space-based telescope wouldn't have to compensate for atmosperic disturbances...

    What is the space station for, if not for this kind of thing? Vanity?
    • ...Getting a 100m telescope up there...

      • Re:Not easy... (Score:3, Funny)

        by troc ( 3606 )
        Such large telescopes should be built on the moon. It's a great excuse to go there, they could be huge, we could build interferometers etc etc.

        Troc

        PS Just not too near the nuclear waste dumps that will explode in 1999. Erm.

    • The larger an object is in orbit, the more likely it is to be damaged by random chance and debris. We really need to clean up earth orbits before we start putting more stuff up there.

      Should we have more space-based telescopes? Absolutely. But for now, it's much cheaper and safer to have large telescopes down here, even if they do have to account for atmospheric distortion.

      • also, the location in the atacama has negligible atmospheric disturbance, as outlined in the article.

      • We really need to clean up earth orbits before we start putting more stuff up there.

        How about placing it in orbit around something else then, like the moon. It'll cost more, and be harder to repair, and have 'lag' on communications. But if the earth orbit is that 'polluted' it could be an option

        • How about placing it in orbit around something else then, like the moon. It'll cost more, and be harder to repair, and have 'lag' on communications. But if the earth orbit is that 'polluted' it could be an option

          Unfortunately, the much larger gravitational pull of the Earth would drag whatever we put in orbit around a smaller planetary body than the Earth itself (like the moon) into the Earth's own orbit. Oops.

          • Then isn't it strange that the earth actually has a moon?

            Wouldn't the much larger gravitational pull of the Sun drag whatever we put in orbit around the earth (like the moon, or sattelites) (the earth beeing a smaller planetary body than the Sun itself) into the Suns own orbit. Oops. Maybe we should shoot down the moon since it's not supposed to be there?

            I usually try to counter my own arguments before posting anything, then it's less likely that I post something that someone will reply to by making me look like a fool. Maybe you should consider doing the same?

            • If I remember correctly (wherever I heard it that is, not the event), the moon was formed out of part of the earth, in a collision with a massive body. Imagine a liquid droplet held together under it's own gravity, and then a splash!

              • That's one of the theories anyway

                The two others that I can remember was that it formed at the same time as the earth, or that it came flying past (like a comet) and was 'captured' by the earths gravity

                I don't know what is the 'accepted' theory though

          • Not necessarily - remember that although the Earth is much more massive than the Moon, it would also be much further away. Gravitational force is proportional to mass/(distance^2). I admit the Earth's pull would have to be taken into account, but I'm sure stable lunar orbits exist (didn't the Apollo modules orbit the Moon for a few days?)

            What I'd like to know is whether it would be sensible to put a telescope at one of the Lagrange points - points where the Earth's pull on an object is exactly equal to the Moon's.

            • There would be no problem of the earth pulling anything out of a stable orbet around the moon.
      • We really need to clean up earth orbits before we start putting more stuff up there.

        But how do we do that? These things are moving pretty fast. For a low Earth orbit, the speeds is about 10 km/sec (36,000 km/h), while a geosynchronous orbit (higher up) is only about 200 m/sec.

        How can you clean something up which is moving that fast?

        • My crazy thought was something akin to satellites with "butterfly nets". Even at 200m/sec, that's still a completely acheivable speed - you just have to apply energy to the problem. You have a satellite cruise out there and capture debris, coming up from behind it so as not to be damaged by high-speed impact; then drop it into the atmosphere over the ocean, where most (if not all) of it will burn up.

          The satellite could use a fairly simple capture process, and could be refueled and prepared for it's next round by shuttle or at ISS.

          But maybe I'm oversimplifying.

          • The misconception here is that space is cubic, and even the region in earth orbit where most satellites are places has a volume exceeding that of the earth. It is HUGE. This makes the odds of collision, given that we have "only" placed a few thousand objects up there, ever, very remote. Granted, airliners occasionally crash into each other, too, and people do win the lottery...
          • Problems:
            • Finding the debris
            • Burning lots of fuel to change course to the debris, more to slow down upon approach
            • Burning HUGE amounts of fuel to slow down the combined mass enough to put both objects into a decaying orbit
            • Burning more fuel to put the capture device back into stable orbit again after release
            You use lots of fuel (that has to be lifted into orbit) and take out only one object. You could attach little computer controlled rocket/gyro kits to pieces to send them down by themselves. That would eliminate the fuel needed for the capture device to regain orbit, but it's still a lot.
            • Finding the debris: well it all within about 22,000km of the surface of the earth. Burning lots of fuel to change course to the debris, more to slow down upon approach: I was thinking that we could send up some big magnets the would either change there orbit (into or away from the earth) or they would stick to the magnets. you could have then controled from the ground and they would be like... vacum cleaners (every pun intended), being able to turn them on and off at the flick of a switch (i know tech isn't perfect...) you could turn it off if they get near something important. I know that they would have to be BIG and POWERFUL but you could have it on half the day and recharging half the day. spin some around the center and some around the pole's.
              • I was thinking that we could send up some big magnets
                You are assuming that the debris is metal and that the metal is ferrous. Both things (especially the latter) can not be assumed.
                • this is true, but i think that the majority would be and that would be a start. the rest is anybodys guess. But here is an intresting question, who would pay for it? the US and Russian space programs are older and they have been throwing stuff up there for the last 40 years....would the US and Russia pay for the clean up of near orbit space?
          • A satellite compared to the total volume of space it is moving through is insignifigantly small. Even something we might consider large on Earth is a teeny tiny spec in space. The chance a satellite in a geosynchronus orbit is going to impact a piece of debris is very very small. The biggest dangers don't lie in the same orbit as the satellite anyhow, the biggest dangers come from debris with radical orbits. Anything with a stable geosynchronus orbit is going to be moving at the same velocity so your bird isn't going to rear end the bird ahead of it like a car would rear end someone on the freeway. It is the bolt with the 5000m/s escape trajectory that happens to be intersecting the satellite's flight path that is the danger. A net or some other shielding does little good unless you suround the satellite with it and then your satellite is a very expensive paper floating rock.

          • Notes from NASA:

            What's orbiting in our near-Earth space environment?
            Orbital debris in the near-Earth space environment is made up of micrometeoroids and man-made debris. The man-made debris or space junk consists mainly of fragmented rocket bodies and spacecraft parts created by 40 years of space exploration. These objects number in the millions and orbit the earth at hypervelocities averaging 10 km/s (22,000 mi/h).

            From the White Sands Hypervelocity Impact Test Facility. The Orbital Debris article [nasa.gov] is the source.

            So maybe I did oversimplify.

        • You just need a good targeting system. Great practice for "Star Wars." A big laser would be nice too. Seems anything that doesn't run on 5V DC circuits is beyond some people here. ;o)
        • How can you clean something up which is moving that fast?

          Catch it with something that is also moving that fast.

    • Re:Active and adaptive correction (Score:1, Insightful)

      by Anonymous Coward
      Even with atmospheric disturbances that have to be compensated, I'd think getting the same sensitivity from an orbiting scope would be more expensive than buiding it down here.

      I'd split the question:
      1) what can the Hubble do that a 100m scope down here can't?
      2) what can a 100m scope do that the Hubble can't up there?

      The answers will probably point out that each has its pros and cons.
    • Sure but the power consumption might be a problem.

      Hubble's mirrors are heated to 70 degrees fahrenheit to avoid warping. If they would have to do that to a football field sized mirror, it'l take a nuclear reactor.

      • it'l take a nuclear reactor

        Aren't we orbiting one?
        • Yeah. I shall write to Greenpeace now! And my member of parliament. This "sun" thing should be stopped before it goes nova. I mean it's giving us all skin cancer, it's why we need air conditioning - which contributes to global warming and has resulted in loads of CFCs in the atmosphere - which has resulted in the holes in the ozone layer - which is allowing the sun's HARMFUL rays onto our litle planet.

          That sun thing is the main danger we face for solar-system exploration too, dammed solar flares would just cook an astronauts outside the Van Allen radiation belts. It's uncontrolled fusion reactors like these that will result in the eventual heat-death of the universe.

          I think the sun is a Communist, Capitalist plot to sell more sunglasses. ;) (for the humo(u)r impaired)

          Troc
    • In the last 15 years, our ability to compensate for such disturbances has increased enormously. However, the cost of shooting a megatelescope into orbit is still very high. Option a continues to look more and more attractive.
    • First of all the space station is not the place where you want your extremely sensitive telescopes. I guess that the pointing of the telescope would be lost if an astronaut did so much as breathing.

      Second, there is now and in the foreseable future no way to launch a telescope the size of a football-field into orbit. Think about the costs: Hubble, with a primary mirror of only 2 meters, costed several billions for the launch and all the maintance flights. The OWL would cost the same order of magnitude and would give you a diameter of 100 meter!

      It is true that some wavelengths (x-ray, UV, far IR) can only be viewed in space, but the visible and near IR can convienently be viewed from earth. (If you have the adaptive optics working.)

      Just my 2 eurocents.

    • How much more would it cost to build a 100m filled aperture in space? Lots more because launching to low earth orbit is very expensive, much more expensive than doing multi-conjugate adaptive optics from the ground.

      Space does bring unique capabilities even in the adaptive optics era, since the atmosphere is opaque at many wavelengths. Hence the need for space-based X-ray, ultraviolet, and mid- and far-infrared telescopes. In this sense Hubble is an aberration (pun intended), in that its doing from orbit what can be done from the ground. But adaptive optics was nowhere near as developed when it was launched. The other benefit Hubble gets is low background, which makes it more sensitive, but when compared to a 100m telescope, that doesn't make a lot of difference.

      Likely to be online before OWL is CELT [caltech.edu]- the CalTech Extremely Large Telescope.

      And Hi from the ESO Guesthouse in Chile!
  • I would have thought that a bigger space based telescope would be better. Although, at 5000m, its halfway there (at least in terms amount of atmostphere above), and probably cheaper.

    Wouldnt a large array of telescopes in a grid give you just as much resolution these days? You can integrate the images from lots of smaller mirrors pretty easily in software, and a small mirror is much easier to make than a big one.

    Michael

    • Re:Better in space? (Score:1, Interesting)

      by Anonymous Coward
      Wouldnt a large array of telescopes in a grid give you just as much resolution these days? You can integrate the images from lots of smaller mirrors pretty easily in software, and a small mirror is much easier to make than a big one.

      You mean like the VLT (very large telescope)?

    • The mirror is made of smaller mirrors - a single 100 meter mirror wouldn't be able to support it's own size and would break/warp.

      would be made of 1,500 hexagonal segments and would use some of the clever computer techniques - active and adaptive optics - that further improve resolution.

    • Re:Better in space? (Score:5, Informative)

      by TMB ( 70166 ) on Tuesday July 09, 2002 @06:13AM (#3848247)
      I would have thought that a bigger space based telescope would be better.

      One is being planned [stsci.edu]. However, there's absolutely no way you're going to put a mirror that big in space. So if you care more about number of photons and less about resolution (for example, if you're taking spectra of distant point sources like quasars or planets), it's better (and cheaper!) to do it from the ground.

      [TMB]

      • (for example, if you're taking spectra of distant point sources like quasars or planets)

        Er... that didn't come out quite right. Let's try again: "if you're taking spectra of faint point sources like planets or distant quasars". :-)=

        [TMB]

    • If by "array of smaller" you mean optical interferometry, then yes, you can, and its being done, (at the Keck observatory on Mauna Kea, and at Mt. Wilson, for example), but it is anything but "easy". Also, although it does give you equivalent _resolution_ of a single giant telescope, it only gives you the light-sensitivity of each of the smaller ones.
      Building a f*ckinghyouge telescope like the one the article talks about is really more about being able to see extremely _faint_ objects, and get enough light from them to do spectral analysis etc., than resolution. Although the fantastic resolution you'll get certainly is very nice too.

    • Re:Better in space? (Score:3, Insightful)

      by Betelgeuse ( 35904 )
      You can integrate the images from lots of smaller mirrors pretty easily in software

      Actually, that's hideously hard. Despite the suggestion made (by both the people running the VLT along with the /. post), I don't know that anyone has actually used either Keck or the VLT in multi-telescope mode for "real science". It turns out that optical interferometry is much harder than radio interferometry (see the VLA [nrao.edu]) and no one has successfully done it in any sort of regular way yet (I believe that they've done it once on Keck and once using two of the VLA telescopes, but never using all four).

      In short, people are discovering that doing optical interferometry is REALLY hard and building one, large telescope saves a lot of headaches (but, of course, is a lot more expensive).

      Finally, having a telescope in space really does help out a lot for getting better resolution, but there is something to be said for large telescopes on the ground. They are able to gather more light and, hence, able to get a higher signal-to-noise ratio than a smaller, space-based telescope.
      • Optical aperture synthesis is working quite well from the ground at specialist observatories. COAST [cam.ac.uk] gets fringes from 5 telescopes and synthesises a baseline of 67m, while CHARA [gsu.edu] has achieved fringes from 2 telescopes separtaed by 400m. It has 6 telescopes in all. The combination of beams is, however, not done in software because we don't have instruments capable of recording the detailed phases of a beam of light, as can be done in the radio. All these optical interferometers use light pipes and mirrors on trollies to match path lengths and to directly combine the beams of light coming from the sub-telescopes.

        The key with these projects though is that they all use small sub-telescopes, so can only observe fairly bright objects. Still, it can give you images of the surface of a star like Betelgeuse [cam.ac.uk].
        Getting to fainter objects means going to larger apertures for the sub-telescopes, and that brings problems. With the small telescopes the wavefront across them is affected in the same way by the atmosphere, so things are coherent when they're combined. With a large aperture (like the VLT primaries at 8m) the wavefront is not the same across the mirror, so this needs to be corrected before the individual telescopes can be combined. This is a major sticking point that has taken a long time to sort out. The corrections needed still limit these systems to quite bright obejcts, though.
        • Very well put. I guess that I wasn't very exact in what I said. Putting large (>5m) telescopes together to do interferometry and "real science" just isn't really possible yet.
    • Wouldnt a large array of telescopes in a grid give you just as much resolution these days? You can integrate the images from lots of smaller mirrors pretty easily in software, and a small mirror is much easier to make than a big one.

      Not really. Interferometry is wonderful for some types of works, but it only detects differences between two beams. This is cool if you're trying to discover new objects and such, but if you want to see them... take spectral measurements, etc. then you need an actual solid mirror.

  • right on... (Score:4, Funny)

    by australopithecus ( 215774 ) on Tuesday July 09, 2002 @05:56AM (#3848203)
    in case funding falls through in the middle of construction, the mirror can also be used to fry a turkey in under ten seconds...
    pass the giblets.

    • Hmm.. math. (Score:2, Funny)

      by plaa ( 29967 )
      in case funding falls through in the middle of construction, the mirror can also be used to fry a turkey in under ten seconds...

      The sun deposits about 340 W/m^2 energy on the Earth. Say the mirror is round with a diameter of 100 meters, so we get an area of about 8000 m^2 -- a heating power of 2.7 Megawatts.

      Say the turkey weighs 10 kg and is made up of only water (a reasonable estimate) and is at 20C. Let's boil it up to 100C. The change of 80 degrees takes about 80C*10kg*4200J/kgC = 3.3MJ of energy, so you could heat it up from room temperature to boiling point in just a bit over a second.

      So if the turkey is frozen, then ten seconds sounds a reasonable time. Just hope it warms up on the inside too, or you'll get a deep-fried ice-turkey. :-)
      • I don't know about the energy side, but on the cooking side, it'd take about 12 hours to cook a turkey at 100C, and it would be extremely dry. Turkey cooks around 180C or 350F, a 10Kg turkey would probably take five hours to cook.

        I suspect our turkey here would be an extremely blackened turkey still frozen inside. Mmm... fried turkey popsicles....

      • Forget turkeys...this would be a perfect way to char-broil steaks, and it would only take a quick pass underneath it to be cooked to perfection (yum yum). Also, I would highly recommend wearing asbestos gloves while doing this.

        Wait a minute, asbestos, charbroil, asbestos, charbroil...Well, then again you are prolly going to get cancer from either the charred steak, the asbestos, or the insane amounts of UV radiation... Looks like cancer is the big winner.

  • Naming convention (Score:5, Funny)

    by NicolaiBSD ( 460297 ) <spam@NoSpAM.vandersmagt.nl> on Tuesday July 09, 2002 @05:58AM (#3848207) Homepage
    So how are we going to call the next generation of large telescopes? The Even More Overwelmingly Large Telescope? The Incredible Supa-Dupa Overwelmingly Huge Motherf***ing Telescope?
    We are bound to run out of comparatives soon, then all we'll have left is the Largest Large Telescope and then what?

  • exposure time (Score:4, Insightful)

    by selderrr ( 523988 ) on Tuesday July 09, 2002 @05:58AM (#3848209) Journal
    I wonder what the exposure time of such a 'space photo' is... probably something in the order of minutes ?
    In that case, how do they handle stuff like an overflying plane ?
    • I'd imagine that the field of view of such a telescope is rather narrow, to say the least. Additionally, the site is probably well away from important air routes, and would likely have an agreement with the air traffic control people to route aircraft away from where the telescope is looking.
    • okay about planes, but what about satelites ??? Our skies are stuffed with them. Must be quite a pain for those telescopes ! A bit like a dove crapping in your eye when you're watching the skies without scopes.
      • Looking at a nearby star system means your field of view SO narrow its like the odds of that gnat in your laboratory flying RIGHT into the business end of your electron microscope (though actually these scopes usually have sealed specimen chambers) It isn't likely...even though the satellite can be "seen" somewhere in the sky where the telecope is looking, the optics are focused so that rays of light from anywhere but the objective simply do not come into play.
    • Actually, according to this [eso.org] there is only about 1 second of exposure and field of view of about a few micro-arcseconds so it will probably not be that big of a deal. Plus since it is going ot be based probably in Chile, are there a lot of plans flying over the Chilean Atacama Desert anyway?
    • Swiss air traffic control just orders the planes to crash into each other; keeping the air above southern europe free of aircraft.

    • Re:exposure time (Score:5, Informative)

      by gmarceau ( 119282 ) <dnys2v4dq1001@sneakemail.com> on Tuesday July 09, 2002 @08:43AM (#3848640) Homepage
      The farther you try to look, the longer the exposure. For instance, the deep field pictures that came back from Huble some years ago had a few days of exposure time. Of course, you better have a mighty solid research project to justify monopolising the telescope for such long times while other labs are waiting for their turn.

      Powerful telescopes are built on top of high montains and away from air routes, but not for the reason you think. The field of view of telescope is so narrow, you don't have to worry about things crossing in the way. Rather, monitors lights on the tips of air planes would generate enough background lighting to screw an exposure. Those devices realy are that sensitive to light. In fact, telescope operators tend to play trick on neibouring villagers, telling them on which days they forgot their porch light on. The lights leave a tale tell background whiteness on the pictures.

    • The second graphic on one of the pages compares the estimated exposure time from the different telescopes and compares the pixel arc secs as well.

      The VLT clocked in at pixel .20 arc secs for a ~16x16 pixel image that took just over 10 minutes to recieve (for a bluish blob).

      The OWL is estimated to recieve the same image except at a ~1.6 Megapixel size at pixel .0005 arc secs for the same area, but at crystal clear resolution (by comparison) in about 1 seconds time.

  • 5000m? (Score:1, Interesting)

    by morty4321 ( 590088 )
    Now how the heck would they manage to transport a 100m mirror to a mountain peak at 5000meters? I seem to recall when they built the first VLT that the mirror has to come in one piece and transporting a 100m mirror to that location would the way I see it, be a job only superman can do.

    • Re:5000m? (Score:2, Insightful)

      by australopithecus ( 215774 )
      The mirror, much like the US 10-metre Keck telescopes in Hawaii, would be made of 1,500 hexagonal segments and would use some of the clever computer techniques - active and adaptive optics - that further improve resolution.

    • Re:5000m? (Score:2, Funny)

      by roalt ( 534265 )
      Now how the heck would they manage to transport a 100m mirror to a mountain peak at 5000meters?

      Easy, just find enough blonde girls...

    • I recall from an astronomy talk they manuafactured at the site. It becomes economial when making hundreds of sub-mirrors for the five scopes.

  • Already obsolete (Score:2, Interesting)

    by Anonymous Coward
    Although it sounds great, it'll take more than 15 years to build from the start of the construction project - so we're talking at least 20 years.

    By then, it is predicted that computing will have advanced enough to build a globally-large coordinated telecope ("GCT").

    GCT is where the 'scopes are situated anywhere on earth, and computer processing converges the images into one single image. This highly distributed method will require a degree of measurement so far unprecendented. But given the next generation of atomic clocks and earth rotation measurement, it'll be very reasonable.

    The advantage is spacing. Since the telescopes can be located anywhere on earth, minor local variances of weather are, for all intents and purposes, irrelevant. In addition, even space-based telescopes (Hubble) could participate in the system.

    And a GCT system uses many devices, so if any one is unavailable, the others will still operate, resulting in very high availabilty.

    Finally, a GCT is relatively inexpensive. I estimage it'll take about $100,000 per site. Just a rough guess, but not unreasonable. That's lots less than OLT.

    Therefore, I conclude that OLT is merely a way for to amass large grants, and not a way to do better science.
    • Although it sounds great, it'll take more than 15 years to build from the start of the construction project - so we're talking at least 20 years.

      By then, it is predicted that computing will have advanced enough to build a globally-large coordinated telecope ("GCT").

      Yes, but by the time we can build a GCT, we'll only be ten years away from building a massively distributed telescope made of billions of tiny nanobots floating in space gathering photons and performing massively complex calculations with quantum computing methods. So we might as well just all wait around until then.

      • Yes, but by the time we can build a GCT, we'll only be ten years away from building a massively distributed telescope made of billions of tiny nanobots floating in space

        Yes, but by the time we can build billions of tiny nanobots floating in space, we'll only be ten years away from nano-engineering the asteroid belt itself into a telescope 3 AU in diameter.

        But we would want to do that because given another 10 years we could instead nano-engineer the asteroid belt to fire telescopes out in a sphere expanding at 10,000 MPH, or roughly 1 AU per year.

        But why do that when in another 10 years we'd be able to fire the telescopes out at 0.1% of lightspeed, expanding at roughly 63 AU per year.

        But why bother with that when 10 years later we'll just be able to fire probes towards all of the nearest stars at 1% of lightspeed. Actually you can go through several decades of faster and faster probes becuase even a slight increase in speed will trim more than 10 years off the trip.

        But then within another 10 years we'll be able to transfer human conciousness into the probes. But then within another ten years we'd just be able to fold space itself. But then in another ten years we'll be so advanced that we'll already know everything making the trip pointless.

        Please fasten your seatbelts - we are now approaching the technological singularity. Enjoy the ride.

        -

    • Re:Already obsolete (Score:2, Informative)

      by photonic ( 584757 )
      As far as i know this is complete BS. Globally combining telescopes with just accurate clocks and a lot of computing power only works for radio telescopes. They measure frequencies in the GHz regime, which means you can measure the phase of your signal with respect to an atom clock. Correlating the recorded signals from the various telescopes can then be done by computer.

      Combining telescopes in the optical domain (frequency ~10^14 Hz) is only possible by correlating in the optical domain with an interferometer. This means you need optical delay-lines [eso.org] (VLTI) of maximum some hundred meters or fibers [hawaii.edu] (OHANA) of maximum a few kilometers.

    • not the point (Score:2, Informative)

      by El Puerco Loco ( 31491 )
      Although it is possible to improve resolution of optical telescopes with interferometry, separation of the instruments is limited to tens of meters because the light from each must be combined physically. Anyway, the point of having a telescope this large is not to improve resolution, but light-gathering ability. A mirror this large would be able to see much dimmer objects than any realistically sized space telescope. This telescope should be able to see further into deep space than any but radio telescopes. Most of the work will be done in the infrared, because light from objects that far away is red-shifted well away from the visible spectrum.

    • Apples and oranges (Score:4, Informative)

      by hubie ( 108345 ) on Tuesday July 09, 2002 @09:48AM (#3848951)
      You are confusing two different operating modes in astronomy. What you are describing is globally coordinating telescopes to provide continuous coverage of an object (when the object sets for one telescope, it is in view for another). This is particularly useful for object that change appearance on reasonable timescales (such as Cephid variables) and you want to accumulate a nice, continuous data set. The fact that you are using telescopes spread out over the globe does not mean that you now have an effective aperture as big as the globe. Your light gathering ability and angular resolution are still only as good as each individual telescope.

      The purpose of the 100m telescope is just that, to build a very large aperture telescope. This will increase your light gathering ability and angular resolution. This you cannot accomplish (as another poster suggested) in the same manner that they do with radio astronomy (i.e., time-tag the data and put the picture together later during post-processing) because you'll never get accurate enough clocks to make those measurements.

      Consider that to make a decent image you need an optic that is accurate to a fraction of a wavelength (lets use 1/10 to make the math easier). To make a radiotelescope image you are dealing with wavelengths of about a meter, so you need to tag the wavefront to about 10 centimeters, which given the speed of light is 3x10^10 cm/s, means you need clocks that are synchronized to a few hundred picoseconds. You can do this with atomic clocks. However, in the light band, if you have a wavelength of 500 nm, you need to tag your wavefront to about 50 nm, which means you need to synchronize your clocks to about 10^-16 seconds. I don't know what kind of improvement you are expecting out of the next generation of atomic clocks, but it isn't going to be six orders of magnitude. And I'll even go out on a limb and suggest that you aren't going to have clocks that accurate in our lifetimes.

      A 100m telescope is good science any way you look at it.

  • determine the atmospheric composition

    I hope that they find a planet with an atmoshpere that indicates life. Watching the media, politicians, religious leaders and mad scientists then would be the show of the milennium.

    Less exciting but still good would be the discovery of some planet that's a good candidate for terraforming, if we had the option to leave this solar system - would we? And who would pay?

    • Even if we did find life or a planet that could be terraformed its not going to happen until we find a cheap quick way to travel across the vast distances of space.

      And on Terraformin: There are various theories [google.com]
      on how Mars could be terraformed and how we could get there with current technology but I don't see too many people jumping in rockets to go and do it.
  • Ok, suppose this telescope is built and later another, even larger, telescope will be build. How on earth are we going to name it then?

    Improbable Large Telescope ?

  • What about the Square Kilometer Array [ucalgary.ca]? I know, it's a radio telescope, but it's bigger!
  • OWL telescope sounds to me like something out of SpaceBalls.....obligatory semi-OT quote:

    RADAR TECH. I'm having trouble with the radar,
    sir.

    HELMET What's wrong with it?

    RADAR TECH. I've lost the bleeps, I've the lost
    the sweeps, and I've lost the creeps.

    HELMET The what?

    SANDURZ The what?

    HELMET And the what?

    RADAR TECH. You know. The bleeps, the sweeps, and the creeps.
    HELMET (to Sandurz) That's not he's lost.

    RADAR TECH. Sir. The radar, sir. It appears to
    be....

    Jam starts dripping down the screen.

    RADAR TECH. ....jammed.

    HELMET Jammed? Raspberry.
    There's only one man who would dare give me the raspberry. Lone Starr!

    Mod away
  • and we're told we have to move. Today the OWL gets funded. Coincidence?
  • The subject of this article says:
    see-zits-on-gerbils-from-alpha-proxima
    I expect what you ment is Proxima Centauri, the closest star to Earth (other than the Sun, obviously). I believe it is also known as Alpha Centauri C, as it is a third star in the Alpha Centauri system.
  • Teach me to read before my morning coffee: I read that as Overwhelmingly Large Testicle Closer to Reality. Nothing says "good morning" like shockingly large testicles.

  • Not just bigger - smarter too (Score:5, Informative)

    by Richard Kirk ( 535523 ) on Tuesday July 09, 2002 @08:39AM (#3848625)
    The news article left out all the interesting engineering bits. If you read it, it just sounds like yet another bigger telescope, big deal, so they are always getting larger, yada yada.

    I have ground an eight-inch mirror. If you rub two glass plates with carbo between in a random fashion, the grinding and polishing process naturally produces a spherical surface. We actually want a parabolic surface, but the difference on an f8 mirror of this size is about half a wavelength. You can do this parabolizing by the same back and fourth process, but by pressing down a bit harder on the end of the stroke, to remove more material from the centre of the plate on top. It's a wonderfully low tech process that gives a very accurate result.

    Now, if you scale up the mirror, then things get harder. The errors in a larger mirror scale up, so you have to take off many wavelengths thickness,so people have to use interferometers and computer controlled polishing machines.

    Adaptive optics made parabolization easier. If your mirror is made up of segments that are a bit smaller than my eight inch mirror, then the differences between a spherical element and a paraboloidal element are no longer worth worrying about.

    When you get to the size of the OWL, the difference in a 10 cm tile between a spherical surface and a flat surface is hardly worth worrying about. You could use float glass if it came in stress-free 10cm squares. You can make accurate plastic elements that would do the job. If you can stamp out computer controlled mirror elements, then maing a mirror the size of a football field no longer seems so impossible.

    The next big thing is to make the telescope track a celestial object. This thing is going to be about the size of the great pyramid, and the mirror has to stay in shape to a fraction of a wavelength. They reckon they can do it for a billion (10e9) euros. I remember (maybe wrongly) that the Mount Palomar telescope cost about 400 million dollars, back in the late twenties, early thirties.

    I am not sure yet that the thing can be built for the price, but it is beginning to look like it might. Cor, juice!

  • One of the most interesting and controversial yet least known upcoming space telescope projects currently on the drawing boards at NASA's JPL [nasa.gov]. The tentatively named the Spacebourne Ultra Viewer should more than triple the size of the proposed Next Generation Space Telescope [stsci.edu].

    Because of the huge cost involved in such a project and the increasing risk of orbital debris [nasa.gov] the telescope will be sheathed in a special alloyed sleeve. The sleeve itself is so massive that it is estimated it will take 3 shuttle flights to lift its segments. Detractors of the project say that while the sleeve does provide excellent protection that fact is more than offset by decreased mobility by making the craft ungainly and impractical to manoeuvre. Another concern is that the huge size of the telescope will interfere with the viewing instrumentation on other nearby space instruments.

    However project director Harold Mann responded to the criticisms by saying "Sure my SUV blocks other's view, has terrible fuel efficiency, and handles like shit, but hey if there's a collision it'll be the other guy who gets creamed, especially if it's one of those dinky Japanese models, and in America that's how we like it."

  • I heard an OWL talk at the Denver Astronomical Society late last year. In the back of my mind I was comparing to Hubble. Both have 20-30 year planned lifetimes and similar imaging resolution resolutions. ESO-OWL is planning about $100 million a year for construction and operation. Hubble spent $1.5 in initial construction and launch, had two $0.5 billion servicing/upgrade shuttle mission in 1994 and 2002, with a final one planned around 2008. Hubble also has an annual data archiving and analysis budget. I found the total lifetime costs to be comparable.
  • Hands down, OWL is probably the coolest Earth-based telescope that might actually be built. But it's not the pinnacle of possible telescope technologies.

    One idea that researchers in the field have been bouncing around is to construct a space-telescope at a distance of 550 AU out from the sun, and in solar orbit. This is well beyond the heliopause, and in the interstellar medium. At this particular distance, the 'scope could use the Sun as a gravitational lens.

    Theoretically, if we parked Hubble there, it could resolve surface features of an Earth-sized planet orbiting a nearby star. A 1-meter telescope in this orbit could use parallax to directly measure the distance to most stars in the Milky Way as well. It could also resolve individual, ordinary stars in distant galaxies.

    So that'd be, like, the coolest telescope you could build :-)

    Some links:

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