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A Telescope The Size Of The Earth
Neil Blender writes "From this article: "Astronomers have fashioned an Earth-sized virtual radio telescope that can distinguish celestial features 3,000 times smaller than the those observed by the Hubble Space Telescope. The device, which uses atomic clocks and a custom supercomputer to link together radio dishes on three continents, is the most powerful radio observatory ever, according to scientists." Some parts of the custom supercomputer use linux and IDE RAID."
This is a radio telescope and planets aren't radio sources (although civilisations on them may be)
resolution is a function of the aperture size of the telescope. In hubble's case, this is 2.5 meters (according to space.com). I don't remember what this function is, but it has to do with the wavelength of the signal too. Something along the lines of d/lambda. And you get a resolution of angle out of it because you don't know the distance to your target.
Note that this will be the maximum theoretical resolution, Hubble is probably less. (and that I could be wrong, but I'm pretty sure about the aperture to resolution relation).
Check the article at SpaceFlight Now.
The Next Generation Space Telescope is planned to be placed in L2 orbit.
I know that they have optical telescopes that do this now. Keck Observatory come to mind. Here is a link to a page that describes what they are doing and the resolution they are getting. The VLT (Very Large Telescope) is another example of combining the beams of multiple telescopes.
the technique is several decades old and the article is essentially contentless.
array of radio telescopes scattered around the whole earch can act like a single telescope if we combine the signal coherently. this can be done by connecting them together in real time (e.g. VLA in New Mexico) or offline (e.g. VLBA). Both VLA and VLBA are run by NRAO. if you want to do offline, you need to preserve amplitude, phase and timing information. atomic clocks are used for time stamping and supercomputers are used to combine signal. this simulates a large telescope whose lens is mostly opaque, save for few dots! the technique is really old (originated in late 60s, early 70s) and has been well mastered for more than 20 years. so there is absolutely nothing new in the article. depending upon the scientific relevance, many global telescopes participate in these experiments. in some cases, only US telescopes (VLBA which is scattered from hawaii to virgin islands) participate, which creates somewhat smaller effective telescope size. some experiments have beed done using space based radio telescopes which increases effective size even further (by the time, the space telescope became operational in late 90s, i left astronomy, so don't know the results).
the supercomputer which combines signal is made up of custom chips and uses custom OS. linux part is quite small and it comes into picture well after the data has been pre-processed (raw data sizes could be few terrabytes a day while processed data is only few gigabytes).
While I don't doubt the value a radio telescope might have for planetary research, I'm willing to bet you're thinking about something akin to being able to see the individual cells on Pathfinder's solar-array on the surface of Mars from a telescope mounted here on Earth.
Anyone know the _optical_ resolution for maximum "zoom" on Hubble...?
A really good telescope will usually be limited by diffraction effects (the fact that the telescope is of finite size causes light being focused to blur out a bit as it passes through the telescope aperture).
A back of the envelope calculation suggests that the diffraction-limited resolution of the Hubble (at 2.5m) for 500 nm light is about 0.2 microradians (letting it resolve features ten million kilometres wide at Alpha Centauri, five light-years away [give or take], or letting you read a typewritten letter at 5 km).
A radio telescope typically operates on wavelengths on the order of a tenth of a metre (as a gross approximation; it's really an order of magnitude in either direction from there, if I understand correctly). The largest radio telescope dish on the planet is about 300m wide, giving a diffraction-limited resolution of about 0.3 milliradians, or about three times sharper than the unaided human eye is at optical wavelengths (the equivalent of reading a typewritten letter at about 10 feet).
An interferometric radio telescope with an aperture the size of the planet would have a resolution of about 10 nanoradians, letting it resolve features about 0.5 million kilometres wide at Alpha Centauri [slightly smaller than our sun] (the equivalent of reading a typewritten letter at a distance of 100 km, or the title on a paperback book from low Earth orbit).
If we had a radio telescope with an atomic clock on the moon (about 400,000 km away), we could resolve objects the size of Jupiter in the Alpha Centauri system. If we had a space-based radio telescopes in the Earth-Sun L4 or L5 points (each 150 million km from Earth), we could resolve individual cities on an Earth-like planet.
This is cheap enough to do that we're probably going to put radio telescopes there within the next couple of decades. Any planet with a magnetosphere within 50-200 light years would be detectable, and we'd have detailed maps of magnetic effects on the surfaces of every star within a thousand light-years.
Properly done interferometry can make it so this telescope array approaches the angular resolution of a telescope that was actually X thousand miles across, but it of course doesn't give it the same light gathering capability (sensitivity). So it won't be able to see anything new, only resolve much better what telescopes could already see. Important, but really only half the benefit of building larger telescopes.