Researchers at Ohio State University (OSU) are building a radio array, composed of 64 tiny antennae, as a prototype for telescopes that may revolutionize the search for extraterrestrial intelligence (SETI) and radioastronomy in general.

At roughly 100 square centimetres, each antenna is so small that its field of view extends from horizon to horizon, unlike dish-shaped antennas, which focus on a small portion of the sky. Eight antennae have been installed, with four already operating full-time. The team expects the entire array to be in place this autumn.

A telescope built this way could monitor the whole sky continuously over a wide range of radio frequencies. Not only might it pick up transient signals from extraterrestrial life, but it might also spot short-lived astrophysical phenomena missed by other instruments.

The project, funded by the California-based SETI Institute, has so far cost less than $200,000. “We're working with a 64-element array because that's large enough to get into some of the technical issues, but small enough that we can put it together at a reasonable cost,” says the principal investigator Steven Ellingson, an electrical engineer at OSU. “Our main goal is to figure out how to build and operate an entirely new kind of telescope.”

One lesson that has already been learned, says Ellingson, is that, rather than trying to form images of the entire sky, “it's more efficient to use modern signal-processing techniques to figure out when and where something interesting is happening, and then focus on just that part of the sky”.

The prototype is called Argus, after a Greek mythological hero with 100 eyes. The urban setting of Columbus, Ohio, is far from ideal for astronomy, which is why the array is intended primarily as an engineering test-bed, rather than a front-line observational tool.

Nevertheless, Argus can still make valuable contributions to radio astronomy. The instrument could, for instance, detect bright, ephemeral events such as supernovae and advise other observatories on where to point their telescopes.

X-ray and gamma-ray bursts are another good example, says Frank Briggs, a radio astronomer at the University of Groningen in the Netherlands. “We can learn new things about these phenomena by looking at the radio signals they emit, as well as at the X-rays and gamma rays.”

Such an array could have tremendous potential, says Kent Cullers, a physicist at the SETI Institute — provided that costs can be kept down. The main expense for a larger, more sensitive instrument, perhaps linking a million antennae, would be the computing power tying them together, rather than the antennae themselves. “If computing costs keep coming down, this could well be the telescope of the future,” says Cullers.