March 3, 2000

U.S. astronomers meet at Arecibo to discuss spending, siting and science for mammoth-size, next-generation radio telescope

ARECIBO, P.R. -- It would be one of the largest scientific instruments ever assembled, a radio telescope composed of perhaps 1,000 antennas spread out over more than 600 miles and costing more than $600 million dollars. And it would make possible high-resolution probes of the outer edges of the universe, giving a window on the evolution of galaxies, the birth and death of stars and a detailed portrait of our own solar system.

The global astronomy community has dubbed the new telescope the Square Kilometer Array, or SKA, and it hopes that if funding and technical problems can be overcome, the massive instrument will be focusing its beams on the distant universe within a decade or so.

To attempt to put a pragmatic and realistic face on the huge project, which would be the new generation of low-frequency radio telescope, more than 60 radio astronomers affiliated with the U.S. segment of the international planning effort -- the SKA U.S. Consortium -- held their first meeting Feb. 28 and 29 at Arecibo Observatory, which is managed by Cornell University, through the National Astronomy and Ionosphere Center (NAIC), for the National Science Foundation (NSF).

"The SKA is only going to succeed after a considerable gestation period," said Paul Goldsmith, Cornell astronomy professor and director of the NAIC. But he warned the astronomers that "there must be clear, incremental progress on the project."

Planning for the telescope has been under way since 1997 by institutes in six nations, and Holland, Canada and China have each produced a different telescope design. The U.S. role is to concentrate on designing an array made up of a large number of small antennas -- each acting as a separate radio telescope -- noted the chair of the U.S. Consortium, Jackie Hewitt of the Massachusetts Institute of Technology.

Speakers from Cornell and the nine other members of the U.S. Consortium, as well as the larger astronomy community, described not only the quantum leap in the view of the radio universe that the SKA would make possible, but also issues such as how to prevent radio interference from affecting such a hugely sensitive instrument, how to write the complex software needed to operate the telescope, where to site it and how to pay for it. It is assumed that the United States will bear about one-third of the cost.

Colin Lonsdale of MIT's Haystack Observatory noted that a telescope made up of perhaps 1,000 antenna "stations" would provide superb imaging fidelity, with more accurate calibration than currently possible, with each station capable of imaging objects in many directions simultaneously. The telescope would depend heavily on electronics, he said, requiring about 5,000 kilometers of connecting fiber-optics cable.

Although the telescope's span would be 1,000 kilometers (620 miles), its actual collecting area for radio beams would be only about a square kilometer, or about a half square mile. The antennas would form a type of telescope called an interferometer, in which radio signals from distant objects in the universe are captured by separate antennas and brought together at a central processor. The single image produced would have a resolution equivalent to an image produced by an antenna 1,000 kilometers in diameter.

Because definition improves as a telescope's diameter increases, the SKA would be 100 times more sensitive than today's most powerful radio telescopes, such as Arecibo and the Very Large Array (VLA), west of Socorro, N.M., consisting of 27 antennas arranged in a Y pattern up to 22 miles across. The SKA's collecting area would be an order of magnitude greater than the VLA's.

Where should such a massive telescope be located, particularly since it would have to be expandable up to 1,000 kilometers in some directions? Meeting chair Yervant Terzian, the David C. Duncan Professor of Astronomy and Space Sciences at Cornell, said the project would be handicapped until a site was located. The site, he said, must be relatively free of radio interference and in an accessible region of a politically stable country with no weather extremes. At the top of his list was the Upper Gascoyne-Murchison region of Western Australia. He also mentioned the Southwestern United States.

"How and who makes this decision I have no idea," he said. "But this is not a premature discussion. These sensitivities must be addressed."

Although most of the participants assumed that the telescope would be funded by national agencies such as the NSF, Mike Davis of NAIC, an adjunct professor of astronomy at Cornell, suggested seeking private funding. This, he said, might mean a much slower development period for the telescope, but sections could be put into operation as they were built. "We could grow the SKA into existence with interim use along the way," he said.

Bernard Burke, professor of physics and astronomy at MIT, however, warned that the major technical problems facing the planners were mainly cost-related, which could inflate the project's budget. This is a warning signal, he said, noting that the superconducting supercollider overran its budget and was canceled by the U.S. Congress.

One of the most serious technical problems, radio interference, was outlined by Rick Fisher of the National Radio Astronomy Observatory (NRAO), who said that such a massive instrument would be highly susceptible to radio frequency interference. He spoke about current research into suppressing this radio noise to levels that would allow the SKA to function without interference. "It is going to take years of research before we are down to the levels of sensitivity that radio astronomers will need," he said.

But the window on the universe that the SKA would make possible -- what some called a true radio map of the sky -- held much of the meeting's attention. Cornell astronomy Professor James Cordes said that the SKA would be able to probe "by many factors of 10" more of the universe than is now possible with the Arecibo radio telescope. And it would allow the detection of tens to hundreds more pulsars -- fast-spinning, highly dense stars called neutron stars -- in other galaxies. Possibly it also would answer such questions as "What is the endgame for neutron stars?" and "What is the relation of neutron stars to supernovae?"

Said Cordes, "SKA can dramatically alter our knowledge of galactic compacted objects." Furthermore, said Cornell astronomy Professor Riccardo Giovanelli, "SKA could make important contributions in the field of spiral galaxies still being formed."

Indeed, such high-resolution images would be possible with the SKA that astronomers could make an "extensive survey" of much of the solar system, including the outer planets, asteroids and comets, said Donald Campbell, Cornell astronomy professor and associate director of NAIC. "SKA could actually produce images as good as those from the NEAR spacecraft," which on Feb. 14 became the first spacecraft to orbit an asteroid, he said.

The SKA's importance to space exploration also was noted by Sandy Weinreb of NASA's Jet Propulsion Laboratory, who said that the agency is exploring the possibility of building an SKA-like instrument for its Deep Space Network. Had this been operational last year when the Mars Climate Orbiter spacecraft was lost as it went into Martian orbit, he said, the mission's off-course problems would have been detected and corrected.

The U.S. Consortium members, besides Cornell/NAIC, are the University of California at Berkeley, the California Institute of Technology, MIT, Georgia Institute of Technology, Ohio State University, NRAO, the SETI Institute, Harvard/Smithsonian Astrophysical Observatory and the University of Minnesota.

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