UC Berkeley, SETI Institute join forces to build the world's largest telescope devoted principally to the search for extraterrestrial intelligence

By Robert Sanders, Public Affairs

BERKELEY-- The University of California, Berkeley, and the SETI Institute have teamed up to design and build an array of 500 to 1,000 radio telescopes whose primary task will be to seek out signals from civilizations elsewhere in our galaxy.

Rather than construct one large and expensive radio telescope like the famous dish at Arecibo, Puerto Rico, or even an array of many large, custom-built telescopes like the Very Large Array in New Mexico, the UC Berkeley/SETI Institute team will explore the use of many inexpensive antennas similar to those used for backyard TV reception. By electronically coupling many dishes together, a large "radio ear" can be constructed at a fraction of the cost of more conventional approaches. The project is estimated to cost less than $25 million, and could be completed by 2004.

"This represents a paradigm shift in the design and construction of radio telescopes," said Jill Tarter, science team leader for the Institute's current SETI (Search for Extraterrestrial Intelligence) program. "We hope to demonstrate that a premium instrument need not have a premium price."

UC Berkeley researchers emphasize, though, that the novel array will be spectacular for radio astronomy, too. Because of its unique construction, the telescope could be used simultaneously for SETI and other radio astronomy observations.

"The instrument we want to build will have unique capabilities for observing objects from the solar system to the edge of the Universe," said Leo Blitz, director of the UC Berkeley Radio Astronomy Lab and professor of astronomy. "Our goal is nothing short of standing the way radio astronomy has been done up to now on its head."

The array will eventually comprise a total collecting area of 10,000 square meters, or one hectare (2.47 acres), hence the project's current name, the One Hectare Telescope, or 1hT. When completed, the 1hT will be among the world's largest radio telescopes. By comparison, the Arecibo telescope, which is the world's largest, is 1,000 feet in diameter and has a collecting area of about 73,000 square meters (about 18 acres).

Once completed, the 1hT will be the world's largest observing facility devoted substantially to SETI. SETI observations require not only a large collecting area-to find the weak signals expected from a transmitter many light years away-but also highly sophisticated digital receivers to scrutinize millions of radio channels.

For SETI observations, dedicated time on large radio telescopes is scarce and expensive. The result for SETI is less than optimal; at best, SETI scientists are able to scan only a few hundred star systems per year. The 1hT would allow this number to expand at least tenfold. In the Milky Way Galaxy alone, there are an estimated 400 billion stars.

"UC Berkeley has one of the world's premier radio astronomy programs, along with first-rate programs in engineering and computer science, " said Tarter. "Together, we can design and build an instrument for that will have no peer for this type of work."

The first goal will be to build a prototype composed of perhaps a dozen small radio dishes at UC Berkeley's Hat Creek Observatory, located near Mt. Lassen in northern California. The Hat Creek Observatory is the site of the ten-telescope array now operated by UC Berkeley, called BIMA (Berkeley-Illinois-Maryland Array). Once the 1hT concept has been proven and the electronics are working, the team would embark on the construction of an array of up to 1,000 telescopes, probably also at Hat Creek. The number of telescopes will depend on the ultimate size of the individual dishes, which could be 12 feet or 18 feet in diameter, whichever provides the most cost-effective solution.

The design concept of the 1hT should significantly reduce the cost of construction, according to UC Berkeley and SETI Institute researchers. A comparably sized instrument, the 300-foot Green Bank Telescope now under construction at the National Radio Astronomy Observatory in West Virginia, will cost at least $75 million. The 1hT, whose sensitivity at the frequencies of interest to SETI will be similar to the Green Bank Telescope, is predicted to cost less than one-third as much as that instrument. The smaller telescopes of the 1hT would also be much less expensive to maintain.

Unlike conventional radio telescopes, the 1hT is also scalable. By adding new dishes to the array, the 1hT could be made larger at relatively low cost. And while damage to the collecting surface of a traditional radio telescope is expensive and time-consuming to repair, the individual dishes of the 1hT can be replaced quickly and cheaply.

UC Berkeley's lead astronomer on the 1hT project, Professor of Astronomy William "Jack" Welch, plans to support a targeted SETI search in addition to conducting observations of star-forming regions. The newly-appointed Watson and Marilyn Alberts Chair for SETI at UC Berkeley, Welch said that the 1hT team will begin the search with 1,000 nearby sun-like stars and gradually moving outward to encompass 100,000 then one million candidate stars in our galaxy. The team will search for strong signals at a single frequency - like radar or radio broadcasts from Earth - as well as pulsed signals that repeat. The 1hT computer system will conduct an analysis, to be performed eventually by a receiver on a mass-produced integrated circuit chip, designed to alert researchers immediately to signals of interest. Funds for the 1hT will be raised from private sources under the direction of the SETI Institute. The Institute's Project Phoenix is currently the world's largest privately supported radio astronomy enterprise, with an annual budget of more than $3 million.

Blitz and Tarter note that the 1hT would also prove the feasibility of an even larger array of telescopes-perhaps as many as 100,000-with a total collecting area of a square kilometer, or one million square meters. This so-called Square Kilometer Array (SKA) is being developed as a major international collaboration for radio astronomers in the next century. If built, the SKA would surpass Arecibo as the world's largest radio telescope.

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