Friday, June 6, 2008

Biggest Eyes on the Universe Get Makeover

Bigger and Better
Bigger and Better

In astronomy, size matters. And for decades radio astronomers have been able to boast that they had the largest telescopes on the planet.

They still do, with some now virtually the size of continents. But until recently the technology used to run them was getting pretty clunky and outdated.

An international effort is now underway to upgrade the world's giant radio telescopes with 21st century technology. The improvements will increase their sensitivity up to 10 times, opening up whole new heavenly realms. At the same time, new and more specialized radio telescope arrays are being built to peer into the universe's earliest star-forming era.

21st Century Radio

"We're leapfrogging several generations of technological progress," said Fred K.Y. Lo, director of the National Radio Astronomy Observatory (NRAO).

The flagship of NRAO is the almost 30-year-old Very Large Array (VLA) near Socorro, N.M., which combines the waves of 28 radio telescopes, each 25 feet in diameter, that are spread out over the desert to create a virtual telescopic dish the size of a small city.

VLA is undergoing a total upgrade, starting with the key element in radio telescope arrays -- the computer correlator that blends all the radio data from all the dishes.

Arrays of radio telescopes combine the radio waves they collect to vastly enhance the resolution of their cosmic images. This has been possible -- and necessary -- for decades because radio waves from space can be more in the range of tens of meters long. That makes them both easier to line up and combine than visible light waves, which are only millionths of a meter long. But combining radio waves also makes for less sharp, lower resolution images.

"Radio waves are very long and so you need very large telescopes," said Rick Perley, who is working on the 21st century Expanded VLA, or EVLA.

To illustrate: A meter-wide visible light telescope is a couple of million times wider than the wavelength of light it gathers. It's analogous to having a computer monitor with lots of very high-density pixels -- that makes for a sharper image. Visible light telescopes can resolve a piece of sky just a few arc seconds across -- at least 60 times a smaller patch of sky than can be resolved with the human eye.

Because radio waves are millions of times longer than visible light, a collecting dish of a 10-meter radio telescope might only resolve an area of sky the size of the moon. The only way to counteract this is by aiming lots of widespread radio telescopes at the same thing and combining their light -- gather a lot more pixels, in other words -- to sharpen the image.

For this reason one of the most important upgrades for the VLA and other radio telescopes is the correlator, which synchronizes all the light from all the radio dishes to create a single high-resolution radio image. The EVLA correlator is being built by Canadian researchers and engineers. Like most new computers, it will be able to handle more data much faster.

Original here

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