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Overwhelmingly Large Telescope Closer to Reality
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.
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!
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?
I have been pwned because my
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
There is no cryptographic solution to the problem where the intended receiver and the attacker are the same entity.
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.
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?
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 ?
When will I end this grieving ? When will my future begin ?
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.
Easy, just find enough blonde girls...
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.
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.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
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.
That what was all this school was for... to teach us how to solve our own problems. -- janeowit
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 doubt, therefore I may be.
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...
- 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.OWL telescope sounds to me like something out of SpaceBalls.....obligatory semi-OT quote:
....jammed.
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.
HELMET Jammed? Raspberry.
There's only one man who would dare give me the raspberry. Lone Starr!
Mod away
Sent from your iPad.
A nearby star system in proximity of Alpha Centauri
- We are the slashdot. Resistance is futile. Prepare to be moderated -
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.
I'm a loner Dottie, a Rebel.
and we're told we have to move. Today the OWL gets funded. Coincidence?
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.
Troc's dubious podcast and blog: http://www.trocnet.net
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 is the source.
So maybe I did oversimplify.
That what was all this school was for... to teach us how to solve our own problems. -- janeowit
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!
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.
Catch it with something that is also moving that fast.
Because of the huge cost involved in such a project and the increasing risk of orbital debris 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."
Actually, depending on the size of the object (and assuming that a magnet would be attracted to it), 10km/s is no problem. 10km/s is relative to a fixed point. All you would have to to is attach the magnet to an object also going 10km/s for the magnet to latch on, then just slowly brake.
My original argument against the magnet idea is that not everything is attracted to magnets, regardless of how powerful the magnet is.
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.
The problem is far from solved. You still have the problem of holding that shape (be it 2 or 3-D) to telesope-level quality. Whether that is easier for the 2-D shape or not depends on the support system and active optics (if any). Obviously they see advantages in going with the 2-D surfaces, but the problem is basically almost as hard.
I recall from an astronomy talk they manuafactured at the site. It becomes economial when making hundreds of sub-mirrors for the five scopes.
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.
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
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.
The Anti-Blog
Well, there's no such thing as a stable orbit for anything in our solar system, period. The Moon itself is moving away from Earth gradually due to tidal effects, and none of the planetary orbits are predictable (including Earth's) for more than 100 million years or so due to chaotic instabilities in the equations of motion when you have more than 2 bodies involved...
But for orbits in the range 300 to 1000 km or so from the Moon's surface, orbital decay due to the various effects of Earth, Sun, and gravitational anomalies becomes small enough that you can expect to stay in orbit for a year or more without any extra orbital maneuvers. This isn't actually so different from Earth, where orbits close to the surface decay quickly due to the atmosphere. See a NASA technical report on the lifetimes of close orbits for more information...
Energy: time to change the picture.
http://www.eso.org/projects/owl/
Yay! Another huge telescope here in Chile! :D
--- Sueños del Sur - a webcomic about four young siblings
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:
In Soviet Russia, sig types you!
Deep-space Overwhelmingly Large Telescope.
(DOLT).
Sometimes boldness is in fashion. Sometimes only the brave will be bold.
Like existing large mirrors it will have an active (air) suspension that continuously corrects for any temperature and gravitational effects.
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