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The Square Kilometer Array
EyesWideOpen writes "A very ambitious project to build the world's largest radio telescope, named the Square Kilometer Array or SKA, is in its early design stages. As its name suggests the SKA will be one square kilometer in size if it gets built. The SKA consortium (consisting of Cal Tech, Cornell, SETI, the Max Planck Institute and Beijing Astronomical Observatory to name a few) hopes to build the telescope by 2010. "If they succeed the SKA will be so big and precise it will jump the world's current best, the American Very Large Array in New Mexico, by a factor of 100, both in sensitivity and resolution." It's interesting to note that the project is based on technology that will only exist in three, five or seven years -- to account for data rates of tens to hundreds of terabytes per second and storage in the petabytes -- so they're counting on Moore's law to hold true."
This just means more data units for the SETI virus.
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It's interesting to note that the project is based on technology that will only exist in three, five or seven years -- to account for data rates of tens to hundreds of terabytes per second and storage in the petabytes -- so they're counting on Moore's law to hold true.
Moore's law only talks about cost, not about maximal hardware performance. If Moore's law doesn't hold, the project will only be much more expensive, but still possible.
DNA is the ultimate spaghetti code.
Instead of relying on super-powerful transmissions from the aliens, as we do now, we could detect, for the first time, signals at the same strength as our own and "listen" to most of our own galaxy for them.
This is truly new, and means a SETI "hit" comes into the realm of the probable, IMO. The link is to the "SETI" page on the SKA site. It's down a couple of levels and jargonized, so I don't think I deserve a redundant mod... but you're the boss!
Given that the wavelength of 'visible' light is approximately half a million times shorter than radio wave wavelengths, the collecting area has to be much larger to get the same antennae gain.
An interesting corollary of this is that the naked eye is (very roughly) as powerful (at visible light wavelengths) as Arecibo is (at radio wavelengths). See the The seti league pages for more info...
Simon.
Physicists get Hadrons!
I'd like to see you get the material for a square kilometre of telescope into space. Maybe once we actually get that space elevator, but not until.
:-) does matter
It's important for a radio telescope to be large (see my other post). Size (at least here
Simon
Physicists get Hadrons!
If this will ever get funded (they recently got some money to make first studies) it will be a telescope the size of half the Netherlands. This is of course not a filled aperture, but a sparse one operating at very low frequencies (10-250 MHz, on both sides of the FM frequencies). It will consist of some hundred small "antenna parks" spread around the country and uses a lot of computer power to generate images. It could be a precursor for SKA.
karma police: arrest this man, he talks in maths; he buzzes like a fridge, he's like a detuned radio. [radiohead]
I believe a petabyte is 1,000 GigaBytes, or 1,000,000 MegaBytes... No, a Petabyte is 1024 Giga Bytes... See http://www.tuxedo.org/~esr/jargon/html/entry/quant ifiers.html or do a search on google...
As with all pure science efforts, the benefit comes from learning something. Knowledge isn't just a means to an end, but is an end in and of itself.
Not everything worth doing can be monetized.
Learn to spell: nickel, missile, lose, solely, amendment, speech, kernel, probably, ridiculous, deity, hierarchy, versus
If God doesn't want to be found, then she won't be. I mean... that's why she's God!
Any sufficiently advanced civilization is indistinguishable from Gods.
What's the difference between what is referred to as the baseline in a VLBA, and what we're talking about here? If you increase the baseline, you increase the "aperture", right? But that doesn't increase the sensitivty, right? Is the real advantage of a huge array of dishes designed and operated as one telescope (as opposed to an ad hoc assembly) the things that are involved in this story -- i.e., data communication bandwidth and control?
I ask this because I had kind of taken for granted that the real future of radio astronomy was going to be something like an array made out of many dishes in very high orbits...
If God doesn't want to be found, then she won't be.
True, assuming you believe that God is omnipotent. The real question is, what are its motives and why does it hide? I naturally mistrust anything with that much power.
"I have opinions of my own, strong opinions, but I don't always agree with them." -- George H. W. Bush
Fortunately it's only compared to the VLA in regards of resolution. Single radiotelescopes have no chance in hell to get to extreme resolutions. Resolution is all in the diameter, or baseline. Nothing you can do about, it's just basic physics. Fortunately you can have big holes in your telescope, or inversely just a few parts of the surface. Excactly the principle of the VLA and VLBI in radio frequencies and the VLTI for light. You can even find a simulation applet here
In fact the earth itself is getting too small to get more resolution. Going into space is indeed being looked into, but not in the sense of a satellite like the Hubble orbiting the earth. That would hardly be worth the effort where radio astronomy is concerned. Having a baseline as long as the distance between the earth and the moon, now that would be an improvement. Plus, if it's built on the side that's always turned away from the earth, the telescope will be shielded from all the annoying interference created by all the radiochatter on earth, while it's still possible to look at the same piece of sky as an earth based telescope.
In the visual spectrum, Darwin from ESA looks set to become the next record holder . A first technology demonstration/development flight in the form of SMART-2 is currently under development.
The brochure doesn't actually say how they're going to do it - it puts forward some suggestions but none of these seem definite yet. A single one million square-kilometre dish would be quite something!
:-)
The difference between a single dish and a synthetic aperture of two dishes (as far as I understand it anyway) is that increasing the baseline to get the synthetic aperture will increase the resolving power of the telescope, but since you've only doubled your collecting area's size, it won't increase the amount of signal that you get. So yes, higher resolution, much the same sensitivity.
There is also a critical dimension to an interferometer (ie: a synthetic aperture radio telescope) which determines what such a telescope can look at. The angular presentation of the object you're studying must be small in comparison to twice (IIRC) the distance between the two dishes you're using for the interferometer, because you're using the phase difference in the signal arriving at both dishes to infer the resolution you gain. You can't look at objects which extend beyond this limit because the phase starts to overlap. Or so I think, anyway. You might want to ask your ex
One other point is that you can do the same interferometry trick between any two nodes in the array. In fact you can do it to (all nodes)factorial and get as much data as possible. The superposition of all of this would take a fair amount of CPU though...
Simon
Physicists get Hadrons!
ALL THESE WORLDS ARE YOURS--EXCEPT EUROPA.
ATTEMPT NO LANDINGS THERE.
blakespot
-- Heisenberg may have slept here.
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> How do you know this is something worth doing?
>
> Or is it just a matter or "because we can build
> something bigger, we should"?
Larger telescopes = the ability to see farther.
So a more apt question would be "Should we explore further, just because we can?"
Isn't the answer obvious?
A very small number of people actually explore our planet and universe. Most of the rest of us sit home and watch them do it on the Discovery Channel or National Geographic specials, and are amazed. The rest prefer the Home Shopping Network and say "who cares about the rest of the universe when we have cubic zirconia?"
> Isn't this what led to the Escalade and the Excursion?
Wow, you're actually comparing bigger and better scientific instruments to ever-larger SUVs?
Eventually, larger telescopes will probably allow us to see the edge of the universe.
They will probably allow us to image planets around other stars.
Then continents on those planets.
Who knows what else we will see. Cities?
As we understand them today, the laws of physics confine us to traveling within our own solar system, but we have the ability see much, much farther. Aren't you interested?
When the international community is involved in the project, however, a more precise name like "The Square Kilometer Array" is used. Of course, Americans have no idea what a kilometer is, so American magazine Wired refers to it as "this huge radio telescope." Now I can visualize it.
When the U.S. government attempts to top this ten years from now, I'm sure they'll call it "The Very Unprecedented Array in Afghanistan"
No. There hasn't been a single installation so far with a more than a 1/30 km of collecting area.
Juputier is because it has a large magnetic dynamo, but the other solar system planets are not.
No, the more apt question is how much of our resources should we spend on exploration (meaning science). Of course, I think it should be more than we spend now.
Also very important is, of that amount, how much do we put into big science projects, and which ones... do we put it into big telescopes, massive accelerators, fusion devices, proteonomic surveys, earth observing satellites, or which? Since there isn't an infinite amount to spend, unfortunately choices have to be made. Even more unfortunately, too many these days are made by politicians.
The proper place of politicians in this issue is how much of our finite government resources should be spent on public science projects, not which projects.
The only good weather is bad weather.
Hum, keep in mind that this is a RADIO telescope array. So you can't "see" further with it, you can "listen" better...
What are you talking about? There are lots of radio images around.
Whether it's "audio" or "video" depends only on whether you're using a point detector (like a radio receiver or a photodiode for visual light) or a spread out detector (like a lens or an array of point detectors).
You wouldn't believe how increasingly difficult it is to do decent Radio Astronomy these days. Heck, the processor in your laptop or desktop is likely radiating right in "L" band (about 1.4 GHz). We thought big hulking monitors were bad until we measured the E/M interference from flat panel displays (it's bad). We're struggling to deal with the onslaught of laptops, 802.11b wireless equipment, PDAs and the like at places like Green Bank. And don't even start to talk about Iridium...
I speak for myself, not my employer.
-- This
- Fraught with uncertainty or doubt; undecided.
- Arousing doubt; doubtful: a dubious distinction.
- Of questionable character: dubious profits.
The search for microbes was dubious, too. Just for instance.If, by your definition, people only attempted "real science" we would never accomplish anything.
Education is the silver bullet.
What's the difference between what is referred to as the baseline in a VLBA, and what we're talking about here? If you increase the baseline, you increase the "aperture", right? But that doesn't increase the sensitivty, right? Is the real advantage of a huge array of dishes designed and operated as one telescope (as opposed to an ad hoc assembly) the things that are involved in this story -- i.e., data communication bandwidth and control?
:), then the resolution will be dictated by how big Australia is. About 1 milliarcsecond, or about 1000 times better than the average pre-interferometer resolutions you could get with optical telescopes on the ground, and 100 times better than hubble, keeping in mind that a radio telescope of the same size as an optical telescope will always have a resolution many thousands of times less (the ratio of the wavelength of optical light to radio light).
Interferometers are very differnt beasts to normal radio telescopes. Single dish scopes look at a single area of the sky, and their sensetivity is proportional to the collecting area (square of diameter). Their angular resolution is proportional to the diamater. When I say the are pointing at a single area of sky, the telescope is actually looking at one point the size of the angular resolution - you may choose to look for a long time, gathering a spectrum (or looking at a pulsar) of that single point, or you may scan the telscope back and forth slowly to generate an image (with resolution equal to the angular resolition of the telescope).
With interferometers, you have a bunch of telescopes. The fundamental unit is no longer a single dish - it is now every combination of 2 dishes. At ATNF narrabri, there are 6 dishes, so there are 15 combinations (5 + 4 + 3 + 2 + 1) (I remember once having to step through each baseline individully, for each frequency for each observation we made, for each.... something else, to mitigate some interference manually, to get the best possible image I could generate for some nifty work I was asked to do) of pairs. The resolution is now a function of the distances between all the pairs.
You generate an image immediately, by getting the fourrier transform of the signals from the pairs, as the earth rotates. To generate the optimal image, with an East West synthesis telescope (such as Narrabri) where the X -resolution is (almost) the same as Y-resolution, you have to let the earth rotate a half turn, ie you sit there imaging for 12 hours. I have gotten away with observing for 4 before, but that was a very specific project. Other telescopes can sometimes do a "snapshot" mode, where you observe for a few minutes or hours, without too much loss of information. But basically, you don't have to scan the telscopes anymore, the centre of the image is where you point the telescopes, and the size of the image can be as big as the resolution would have been if you were using just one telescope.
The resolution you get is effectively from the farthest separated dishes, and the biggest structure you can see is from the resolution of the closest dishes (this all comes from the fact that you have to perform an inverse fourrier transform of the data coming from the pairs, and there are bits missing from the fourrier plane, where there aren't telescope pairs). With a single dish, you can see structures of any size bigger than the resolution. But an interferometer is missing all these bits where telscopes aren't situated, and in particular, has effectibely a hole in the middle of the "telescope" the size of the distance between the closest dishes. So there is an upper limit on the size of structures you can see (as well as a lower limit).
So occasionally, there have been tricks where you combine the high resolution data from interfereters with the low resolution data from a single dish, and you generate a very accurate and imformative image. This was done for generating a map of the Large Magellanic Cloud (no URL handy). But this needs a lot of work and telescope time, both hard to come by.
The sensetivety goes only as the size of the physical collecting area. So 1 square kilometer indeed is much better than the previous 1/30 or so sqaure kilometers we have had in a single setup. Note that, if the telscope is set up in Western Australia, (where I certainly hope it will
I apoligise in advance for confusing you all, but it is kindof a complex topic, and no doubt my head will explode now as well!
> named the Square Kilometer Array or SKA
Truly, this is One Step Beyond.
Please take some time to study the subject before you call people stupid. It has been mentioned in other replies that size is very important in radio astronomy. The larger the base line, the better the resolution. Furthermore, the SKA is only the begin. The next project is already planned. It's called LOFAR and it will have a baseline of 100 km. This will give an extremely high resolution and will be impossible to lift into space.
Furthermore, the success of the Hubble space telescope you mention is not all the it's cracked up to be. With modern adaptive optics techniques that compensate for seeing errors, land based telescopes are (in certain areas) superior to Hubble.
Last but not least, research done in the developement of the Dutch Open Telescope has shown that much of the seeing errors are actually caused by temperature difference close to the ground, so by using a dome-less telescope on a special high platform can reduce seeing tremedously, without even having to resort to adaptive optics techniques. All these techniques can be employed for a fraction of the cost of a space based telescope.
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