Radio dishes activated and collecting

The first 42 radio dishes of the Allen Telescope Array (ATA) are working and collecting data from outer space, according to the University of California, Berkeley and the SETI Institute.

This is the first phase of a planned 350 radio dishes that will each be 6 m in diameter.

"This project represents a potential breakthrough in building large arrays of radio telescopes that are extremely cost effective," said Paul G Allen, Microsoft co-founder whose foundation donated seed money to start the project in 2001.

Seth Shostak, astronomer at SETI in Mountain View, California explained to Radio Comms Asia-Pacific that the project represents a potential breakthrough in building large arrays of radio telescopes that are cost effective because today, the high-performance 'receivers' that are installed at the focus of each of these antennas are only about 1% as expensive as they would have been 20 years ago.

This has changed the approach to radio telescopes from building arrays with only a few dozen antennas, each of which is relatively large, to arrays having hundreds of antennas, each one of which is small.

"The advantage of having hundreds, instead of dozens, of antennas is two-fold: (1) it's much, much faster at making radio pictures of the sky, and (2) it's less expensive," Shostak said.

What sets the array apart from earlier radio telescopes is its ability to collect and analyse more information about celestial objects and do this simultaneously for several projects.

"For SETI, the ATA's technical capabilities exponentially increase our ability to search for intelligent signals, and may lead to the discovery of thinking beings elsewhere in the universe," said Shostak.

The telescope's potential discoveries include a better understanding of exploding stars, black holes and astronomical objects that are predicted but have not yet been seen.

The array claims to be the first panchromatic, wide-angle, snapshot, radio camera ever built.

Beyond its speed and ability to both garner and analyse data, the array is also the first centimetre wavelength radio telescope with the ability to multi-task. While making observations for radioastronomy, it can simultaneously interrogate solar-type stars for artificially produced signals that would reveal the presence of extraterrestrial intelligence.

This new capability increases the time astronomers can devote to large-scale surveys of the stars, as well as expanding the radio frequency band over which they can search.

"The dishes can work over a very wide range of frequencies - from 500 to 11,500 MHz. At any given time, you can simultaneously observe in four different frequency bands," said Shostak.

For SETI, in particular, this means that over the next two dozen years, the array will get a thousand times more data than has been accumulated in the past 45 years.

The ATA uses mass-produced, 6 m diameter radio dishes and commercial telecommunications technologies combined with innovative receiver design, and digital signal processing.

Working together, these small dishes create a telescope with a wide field of view suited to rapidly surveying the sky.

The ATA can also filter out noise from man-made interference that in many radio telescopes would render much of the data unusable.

"To begin with, the location of the ATA, in the Cascade mountains of California, already reduces a lot of interference. There simply aren't many people living in this area, so there are fewer transmitters. The mountains also shield the ATA from the interference coming from California's big cities. But another capability of an array of so many antennas is that it can make a 'negative pixel' on the sky, blacking out interference from sources such as telecommunication satellites," said Shostak.

The full 350-dish array will be completed in about three years.