Finer Views to Come From European Radio Telescope

UTRECHT, THE NETHERLANDS--In the quest to image ever-fainter and more ancient galaxies, Dutch radio astronomers this week unveiled preliminary plans to build the world's largest radio telescope--a gargantuan device that would combine images from 34 far-flung elements.

The biggest existing radio interferometer--a set of linked radio telescopes--is the Very Large Array (VLA) in New Mexico, which already yields detailed pictures of distant galaxies. To do better, "you need ... a large collecting area," says Netherlands Foundation for Research in Astronomy (NFRA) director Harvey Butcher. So radio astronomers at eight institutes in Australia, Canada, China, India, the Netherlands, and the United States want to get 75 times more surface area than the VLA by building a Square Kilometer Array Interferometer (SKAI) for an estimated $150 million. At that size, say proponents, SKAI could image dim events from the early history of the universe with more detail than the Hubble Space Telescope.

The project's planners already have a rough sketch for the SKAI: 34 elements, each with the same surface area as a 200-meter dish, spread out over a radius of 150 kilometers. The institutes are now each working on a design for these elements. Ideas range from building large dishes in natural geological depressions to suspending receivers on balloons. The design that the NFRA and the Australia Telescope National Facility unveiled this week is by far the most unconventional. They propose that each of the 34 elements consist of several hundreds of thousands of small, flat radio receivers. Linked together electronically, the elements would home in on specific objects by detecting phase differences--slight differences in the timing of the radio waves reaching the receivers, which depend on the angle from which the waves are arriving. That approach would avoid interference, for example, from a passing communications satellite.

The consortium will decide on a final design, and a site for SKAI will be selected within a few years, after which the institutes will seek funding from their governments. If they're successful, they hope to begin construction by 2005.