Arecibo Joins Forces with Global Antennae to Simulate 6,800 Mile Telescope
Written by Ian O'Neill
The Arecibo Observatory in Puerto Rico has joined forces with telescopes located in North America, South America, Europe and Africa to create the observing power of a radio telescope 6,800 miles (nearly 11,000 kilometres) in diameter. This collaboration is called the Express Production Real-time e-VLBI Service (EXPReS) project, and on May 22nd, the system went "live" with all antennae observing the same part of the sky. This is an historic project where international collaboration has resulted in the most powerful radio telescope system available to date…
May 22nd heralded the first live demonstration of the EXPReS project that used radio telescopes from four continents. e-VLBI stands for "electronic Very Long Baseline Interferometery" and the system has the huge benefit of taking real-time observations. Data from the EXPReS project is transmitted to the central signal processor at the Joint Institute for VLBI in Europe (JIVE) in Holland, where speeds of data-streaming have exceeded Arecibo's previous record four times over. Apart from being an acronym fest, the e-VLBI, EXPReS, JIVE collaboration will observe the cosmos with a resolution of 100 times better than the worlds most advanced optical telescopes.
So how can a single radio telescope dish with a diameter of 6,800 miles be simulated if the project has telescopes scattered around the planet? This is where the clever technique called Very Long Baseline Interferometery (VLBI) comes in. If you have multiple telescopes observing the same radio source in the cosmos simultaneously (and using very precise atomic clocks as a guide), the distance (or base-line) between observatories will simulate the effect of using a telescope with a diameter of that distance. The resolution of the observation is improved when the interferometer has several observatories working as one. Traditionally, the radio signal received at each antenna was recorded on a magnetic tape and then shipped to a central processing facility. The results of a campaign usually took weeks to be compiled. By using the e-VLBI system, recording data at the telescope site can be bypassed and transmitted real-time to the central processing facility along with the other telescopes observing the same source. Results are now available in a matter of hours – essential rapid processing when fast astronomical processes (such as supernovae) are in progress.
"These results are very significant for the advance of radio astronomy. It shows not only that telescopes of the future can be developed in worldwide collaboration, but that they can also be operated as truly global instruments." – Huib Jan van Langevelde, JIVE Director.
The EXPReS project is funded by the European Commission and aims to connect 16 of the world's most sensitive radio observatories. In the middle of this collaboration is the JIVE processor so real-time data processing can help astronomers achieve very quick results and react to transient radio sources.
Sources: Physorg.com, Arecibo Observatory
Filed under: Astronomy, Observatories
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June 10th, 2008 at 4:35 pm
I think I've asked this question a few other places, but I'm still not sure about the answer:
Will it be possible to do this trick a telescope on the Moon in concert with ones on Earth? Or will the lack of points in between be a problem?
Also – if it *is* possible how good a telescope is needed? Would a robotic mission that just laid out an array of wires on the surface give enough information to be useful or would a proper, pointable, parabolic desk be necessary?
June 10th, 2008 at 6:03 pm
Maybe I'm getting a little tired here – but wouldn't a dish on the Moon coordinated terrestrially be a little impractical because its distance from the Earth varies and it's not in a static orbit? Hmmm….
Nice catch, Ian!
"We'd like to teach the world to hear… In pefect harmony. We'd like to buy the world a dish… And keep it company."
June 10th, 2008 at 6:52 pm
Moving dishes would be a challenge. Maybe some math superheroes in concert with interplanetary hackers would whip up an algorithm that could handle it. That source code would scare the bejesus out me, for sure, for sure.
Someday, we have dishes locked in a constellation around the solar system, locked together and recording, then lasering their data to a Central Data Center in a spot maybe at the L5 point of the Earth-Moon system. A virtual disk light hours across. That would talk some scary math, even if the relative distances were stable!
I would call it, the Children of the Sun Interferometer.
June 11th, 2008 at 1:49 am
Simply amazing.
I'm sitting here, and I find myself wondering:
"How long will it be before we have radio telescopes in orbit at the solar L3, L4 and L5 points, and have those dishes operatingin concert with this array".
I mean, think about it, the resolving power of a dish 1AU in diameter.
Okay, so I get the difficulties involved, but if we did something like combine it with the Pulsar 'GPS' that was mentioned at one point.
I wish someone would get on with the Square Kilometer Array though.
June 11th, 2008 at 3:05 am
Coordination of e-VLBI with lunar and/or space-based antennae would not be prohibitatively difficult. As long as there were coordinated time stamps on the data, the coordination could even be accomplished after the fact, if necessary.
June 11th, 2008 at 4:28 am
The only real issue of coordination between a lunar dish (supposedly fixed) and a terran dish would be that they would face the same direction (and pick up the same signal) only once in every 25-ish hours (I don't feel like doing the math right now to get the exact number).. It would be better if we had two dishes in orbit around their respective bodies, like Vanamonde suggested..
I had heard a rumor years ago that one project was supposed to shoot a dish out to one of the L5 points.. dunno how thats coming or if it would be true.
June 11th, 2008 at 5:25 am
Yes, a Precision Spacecraft Formation – Nano-Precision, Photon Tether Formation Flight (PTFF – http://www.baeinstitute.com/tech_precFormation.html) – technology already developed by BAE institute, and using laser photonic propulsion, may come handy for space fleet interferometers.
June 18th, 2008 at 9:45 pm
The precise location of satellites could be determined with little effort. The only problem I can forsee with including them in an array including ground based telescopes is that the atmosphere may have an effect on the wavelength being viewed and it might take some specialized software to compute the difference between space and ground observations. The problem currently with a space based array is having them looking in the same spectrum since most of them are specialized in the wavelengths they are viewing. But overall, it is probably an idea that bears some looking at in the future if we plan to continue on increasing the power of telescopes to see the universe with more clarity. With some of the plans for upcoming space telescopes being set up as arrays, it might be worth reconsidering the future of the Hubble telescope if it could be tied into the arrays for even a minor amount of time and provide a significant increase in the resolution.