From: LARRY KLAES (ljk4_at_msn.com)
Date: Tue May 20 2003 - 06:44:14 PDT
http://www.ajc.com/news/content/news/science/0503/20bigeyes.html
Scientists envision monster telescopes
By MIKE TONER
The Atlanta Journal-Constitution
Astronomers have begun design work on a generation of huge telescopes that will be able to see to the edge of the visible universe -- the latest quantum leap in a science that began nearly 400 years ago when Galileo trained his first telescope on the heavens.
The behemoth observatories planned by European and American astronomers will dwarf today's "big glass" -- towering telescopes that sit on remote mountaintops in Hawaii and Chile -- with huge mirrors that will be up to 100 meters across.
The largest of the proposed projects is called OWL, or the Overwhelmingly Large, Telescope. It would gather more light and use more glass than all of the telescopes professional astronomers have built since Galileo first saw the moons of Jupiter.
Astronomers say the huge advance in observing power will usher in a new age of discovery by enabling them to see the first light of cosmic dawn -- the events that followed the Big Bang some 15 billion years ago.
"With the instruments we are preparing to build now, we will be able to explore the time when the first stars began to form," said Steve Strom, associate director of the National Optical Astronomy Observatory in Tucson, Ariz.
He says there are certain to be major discoveries closer to home, too.
Under a program sponsored by the Association of Universities for Research in Astronomy, Strom is coordinating design of the Giant Segmented Mirror Telescope -- a 30-meter instrument whose primary mirror will be three times the diameter of today's largest telescope.
"These telescopes will be able to image and analyze planets outside the solar system that now can only be detected indirectly," he said. "If we are lucky, we might even be able to see any Earth-sized planets around stars that are in the neighborhood, 10 to 20 light years away."
In the last decade, the combination of NASA's Hubble Space Telescope and ground-based observatories have worked in tandem to study previously unseen black holes, planetary systems forming around other stars, and the birthplace of stars in glowing stellar clouds.
Although the Hubble can "see" a distant object clearly from its place in orbit, only large ground-based telescopes can gather enough light to analyze the object's spectrum to discern what it is made of.
With the launch of NASA's more powerful Next Generation Space Telescope sometime around 2010, astronomers will need even more powerful ground-based telescopes to keep pace with the observations from space -- seeing light emitted billions of years ago to piece together details of the pre-galactic building blocks in a kind of archaeology of the cosmos.
Some plans unclear
It isn't yet clear where the next generation of telescopes will be built, when they will be completed, or who will pay for them. But astronomers on both sides of the Atlantic are pressing ahead with projects that reflect both the collaborative and competitive aspects of big science in the 21st century.
In Europe, two former competitors -- the European Southern Observatory's OWL and a Swedish-led consortium that had been planning a 50-meter telescope -- joined forces this year to build a single 100-meter instrument that will be in the high desert region of Chile or the Canary Islands. The 15-year project could cost $1 billion or more.
Eli Atad of the Royal Observatory in Edinburgh said the new telescope "will revolutionize astronomy with its ability to collect light from faint objects and distinguish details in images never seen before."
Some engineers are skeptical that such a project is technically or economically feasible. But to Europeans, its value is not merely an expansion of humanity's view of the universe. It would also trump what U.S. astronomers are planning.
"There's clearly an element of competition in all this," said Strom. "So far it's healthy, but the Europeans obviously believe our plans for a 30-meter telescope are too conservative."
Even a 30-meter telescope poses major engineering challenges.
The largest telescopes in the world are the 10-meter, twin-domed Keck Telescopes at Mauna Kea, Hawaii, which stand eight stories tall and weigh 300 tons each.
Construction was possible only because the telescopes' giant primary mirrors, too massive to be produced as a single piece, could be assembled as 36 hexagonal segments, each 1.8 meters in diameter.
The 30-meter segmented mirror envisioned by the Tucson group -- and a similar design being pushed by the California Institute of Technology -- would dwarf the Keck in size, complexity and cost.
Even with the telescopes shielded inside an 18-story steel dome, minute vibrations induced by the wind would blur its images to uselessness. Electronic adjustments can correct the jitters, but the precision required exceeds anything in use today.
"It is going to require money, ingenuity and a very sophisticated design," said David Smith, an Atlanta-based engineer who has been a consultant for the project and for other large telescopes around the world.
"The kinds of high-frequency vibrations we're talking about are only on the order of about 1/400,000th of an inch, but the kind of precision needed for a telescope like this is on the order of a millionth of an inch," Smith said.
"It's a tremendously exciting project. It'll be tough, but with a whole lot of technology it might work."
Smith doubts that the Europeans can move, in a single step, from today's 10-meter telescope technology to what would be required for a 100-meter telescope, whose dish-shaped mirror would contain as many as 2,000 highly polished segments.
Cost poses another challenge. The twin Keck telescopes cost $140 million when they were built in the 1990s. Current estimates of a 30-meter telescope are around $700 million, "give or take $100 million," Strom said.
European astronomers say some major breakthroughs in manufacturing efficiency will be needed if such an instrument is to be built at all.
That is because the mirrors for their proposed 100-meter telescope would consume more precision optics than have been produced throughout history.
"The construction of a 100-meter telescope would constitute a milestone comparable to that of the invention of the telescope itself," an analysis by the European Southern Observatory concluded.
Funding may be hurdle
Yet, barring unforeseen technical problems, the Europeans think they can have their telescope in operation by 2015.
The timetable for the Americans' 30-meter telescope calls for construction to be completed by 2012.
Financing for the massive projects could be as big a hurdle as the technical challenges.
The estimated $700 million cost of the 30-meter telescope dwarfs the National Optical Astronomy Observatory's annual budget of $25 million.
It would probably be built in Chile, Hawaii or Mexico's Baja California.
The National Science Foundation, the primary U.S. funding agency for big science, spent only $126 million this year on all of its major construction projects.
Cal Tech, which built the Keck observatory with money from the Keck Foundation, is actively seeking private funding for its own version of a 30-meter telescope: the CELT, or California Extremely Large Telescope.
Control of such an important project by a single institution, however, could leave outside astronomers without access to a unique observing tool.
"Projects of this size are going to require combined public and private money both to build and to operate," said Strom. "The science and politics of these telescopes are going to be an equal challenge."
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