ARCHIVED - Supercomputer aids deep probes of space
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February 09, 2009— Ottawa, Ontario
NRC is playing a vital role in upgrading the world's biggest radio telescope, the Very Large Array (VLA) at the U.S. National Radio Astronomy Observatory near Socorro, New Mexico. When its upgrade, begun in 2001, goes online in 2012, the radio telescope will be known as the Expanded VLA.
As part of this $100 million project, the NRC Dominion Radio Astrophysical Observatory (DRAO) in Penticton, British Columbia, is designing and building a highly specialized supercomputer called a "correlator." The correlator uses a unique, patented NRC technology called wideband digital architecture (WIDAR) to process the very wide bandwidth signals with far more efficiency and flexibility than possible with the VLA's original correlator.
"The upgrade is actually a bargain in radio telescope terms," says Dr. Sean Dougherty, Group Leader, DRAO at the NRC Herzberg Institute of Astrophysics. "Especially since a prototype of the correlator tested in August, 2008 showed amazing results already far beyond the capability of the VLA."
"The technology behind the VLA is 30 years old. Our goal is to replace the 1970s electronics to improve its overall capability," he says. "And NRC is the world's leader in high-density digital design."
The VLA's original 25-metre dishes will remain, but the electronics are being replaced with state-of-the-art modern digital electronics to improve performance. The new correlator, worth about $20 million, is one of the world's fastest special-purpose supercomputers at the moment.
The correlator receives a data stream from the VLA's 27 dishes that is equivalent to 48 million simultaneous phone calls, then performs 10 million billion calculations per second to combine the data from each of the telescopes. The amount of information the NRC device can handle at one time, and its ability to process it in many different ways, will give radio astronomers the power to make almost any type of observation they can conceive.
Dishing on radio astronomy
In addition to developing exotic electronics for radio telescope arrays, NRC is also finding ways to make parabolic reflector dishes less costly, yet more accurate. The accuracy of a dish affects its ability to collect the weak radio signals from outer space.
NRC researchers have blended existing moulding processes with new materials and special manufacturing tricks to build dishes relatively cheaply and easily. The complexity of their process falls somewhere between common "wet-layup" fibreglass processes used to make ordinary boats and exotic carbon fibre techniques used in the latest aircraft.
So far, NRC researchers have built very lightweight 10-metre parabolic dishes, with an average surface deviation of just half a millimetre. This involves laying high densities of carbon fibre around a foam core in a mould, sealing everything in a giant plastic bag and using vacuum pumps to draw liquid polymer evenly through the fibres.
Dean Chalmers, a mechanical engineer at DRAO, says NRC's process is being developed for the Square Kilometre Array (SKA), which is projected to start construction in 2012 and go online in 2018. The SKA will be located in the Southern Hemisphere, where radio interference is low and its 10-metre diameter dishes can aim straight at the galaxy's heart. With up to 3,000 identical dishes, spread across a square kilometre, this array will be the world's largest.
"Our dishes are very light and very stiff, which reduces wind deflection, and very temperature-stable, making them more accurate under more conditions than metal dishes of the same size," says Chalmers.
Radio telescopes form pictures of the universe using parabolic dishes to sense radio energy from stars and other deep space objects. Just as there are limits on how large a glass telescope lens can be made before it sags and distorts under its own weight, there are practical limits to the size of a parabolic dish. But astronomers can use an electronic technique called interferometry to connect or "array" two or more small dishes to create radio telescope arrays that act like one huge dish, with correlators processing and comparing the signals they receive. If the dishes are 36 kilometres apart, a telescope's effective aperture — the size of its "eye" — is 36 kilometres wide.
Dr. Dougherty says the NRC correlator is made of 256 custom printed circuit boards, produced in Ottawa by BreconRidge Manufacturing Solutions. These boards are the biggest yet made: each board is 28 layers thick, weighs nearly five kilograms, and holds more than 1.5 kilometres of copper circuits and up to 12,000 components. These boards generate so much heat they need massive cooling fins that weigh another seven kg each.
"Canada is gaining a reputation for expertise in such specialized supercomputers," says Dr. Dougherty. In fact, NRC recently designed a similar device for the James Clerk Maxwell Telescope in Hawaii. And NRC is in the running to design an even larger supercomputer for the new, super-sized Square Kilometre Array (SKA), which will harness data from 3,000 dishes at once, making it the most powerful radio telescope ever built. Still being planned, the SKA will be located in the Southern Hemisphere, where it can aim at the centre of our galaxy.
In pushing the boundaries of electronics design, NRC is helping to expand knowledge about our universe, and Canadian manufacturers are breaking through old limits to gain expertise in cutting edge manufacturing techniques for large scale high-density electronic designs.
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