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Global Internet Telescope Tops Hubble's Resolution
satorchi writes "
The Arecibo Observatory
together with the
European VLBI Network have used the internet to make a
real-time transatlantic synthesis telescope. Data from the individual telescopes was transfered via the internet, and processed in real time by the central processing station at the Joint
Institute for VLBI in Europe. 9 terabits were transfered during the 20 hour experiment, and the resulting synthesised telescope had a resolution of 20 milliarcseconds, about 5 times better than the Hubble Space Telescope (HST). This level of detail is equivalent to picking out a small building on the surface of the Moon!"
we can look for the place where the moon landings took place to finaly debunk all those sceptics ?
Oh, no room for Bender, huh? Fine! I'll go build my own lunar lander, with blackjack and hookers. In fact, forget the lunar lander and the blackjack. Ahh, screw the whole thing!
-- look sir droids...
9 terabits in 20 hours is slightly over 131 Mb/sec. Most of the telescopes were in Europe, but even assuming the Arecibo telescope generated three quarters of the traffic, 100 Mbit should be a drop in the bucket going across the Atlantic.
This method of merging data from multiple telescopes is equivilent to tiling together all the images from all the spectators at an event.
You get more information because of a larger number of eyes.
This principle has been known about for years and years, it just seems that the software/hardware to synchronise this and pull it off is coming into standard use.
From the article:
Until now, VLBI has been severely hampered because the data had to be recorded onto tape and then shipped to a central processing facility for analysis. Consequently, radio astronomers were unable to judge the success of their endeavours until weeks or months after the observations were made. The solution, to link the telescopes electronically in real-time, now enables them to analyse the data as it arrives. This technique, naturally called e-VLBI, is now possible as high-bandwidth network connectivity has become a reality.
liqbase
The comparison between Hubble's and Arecibo's resolution is misleading. The hubble telescoope operates in the viewable spectrum of light, while Arecibo and VLBI do radio astronomy. Radio waves are several magnitues longer, so it's even more difficult to get the same resolution. But since the frequencies are lower, too, it is possible to synchronize several telescopes using interferometry.
Interferometry is done at ESA's VLT with up to four telescopes and mirrors with a precision of about 10nm in the viewable spectrum, at a distance of about 100m. But here, we have a distance of several thousand kilometers, so the signals are digitalized and put together at the computer. This is difficult because it's really hard to synchronise the time -atom clocks are not precise enough. Hence the synchronisation is done "so that it fits best", not using any precise clock. (I don't think this is any easier to do, kudos to the scientists at arecibo and VLBI!)
Very simply, this aperture synthesis experiment is not the same as being able to resolve a house on the moon, unless the house was emitting radio waves. Optical aperture synthesis is harder, but it has been done, at COAST, among others.
Owl tried to think of something wise to say, but couldn't.
Interferometric telescopes can drastically increase the resolution as compared to single-tube telescopes.
Having two scopes one mile apart, as far as resolution is concerned, is equivalent to having a single one-mile-wide mirror (in essence; the previous poster is correct in his argument about atmospheric distortions & other problems).
The problem is that the amount of light collected is still based solely on the sum of the surface areas of the mirrors-- not the effective area.
If not enough light (or radio waves, in this case) is collected to trigger the CCDs, the object throwing out the radiation simply won't be detected.
Incidentally, the Keck telescopes in Hawaii work this same way, but with a much shorter baseline. It helps that, at two miles above sea level, they're above much of the atmosphere, and that they both have fairly large mirrors to begin with.
For more information about how they work, Google lists plenty of resources.
Allegedly real newspaper headline from 1998:
Man Struck by Lightning Faces Battery Charge
Here's some math to explain what a resolution of 20 milliarcseconds really means.
:)), that is.
1 arcsecond = 1/3600 degrees
Therefore, 20 milliarcseconds = 20/3600000 degrees = (20/3600000)/360*2pi radians
Delta = arctan(diameter/distance)
where Delta stands for angular diameter. This formula is the basic definition of angular diameter. (Note : This formula automatically implies that the units of angular diameter are same as the unit of a plane angle, i.e. radian/degree)
Taking tan function on both sides we get
tan Delta = diameter/distance
Since resolution of the telescope is (20/3600000)/360*2pi radians we get
tan ((20/3600000)/360*2pi) = diameter/distance.
Now,
tan ((20/3600000)/360*2pi) = 9.69627362*10^-8,
This means that
9.69627362*10^-8 = minimum diameter/distance
which can be restated as
distance*9.69627362*10^-8 = minimum diameter
By substituting distance as required, we can obtain the diameter of the smallest observable object at that particular distance.
For example, taking (mean) earth-moon distance as 385,000 km we get
minimum diameter for an object on the moon to be observable = (385,000*9.69627362*10^-8) km = 0.0373306534 km = 37.3306534 m (approx.)
All math was done using Google's calculator and all formulae/definitions are from Wikipedia.
Disclaimer : I may have misinterpreted/misued the formulae so the above results are open to mistakes.
Mod this up anyway, I'm sure somebody will find my mistakes, if there are any (I hope not