Keck Telescope Opens New Door to Heavens : Astronomy: The facility is dedicated in Hawaii. When fully functional, it will be the largest of its kind in the world.

Scientists gathered Thursday atop a dormant volcano on the Big Island of Hawaii to celebrate the dawn of a new era in astronomy.

The $94-million Keck Telescope, the first--and some say the boldest--in a new generation of superscopes, was dedicated during ceremonies on top of Mauna Kea. In a Hawaiian tradition, ground was “blessed” for a twin scope that will carry the study of the heavens to new heights.

Eighteen of the 36 hexagonal mirror segments that will make the Keck the largest telescope in the world have been installed. When completed, the scope, with a diameter of 10 meters, is expected to dominate the field of astronomy for several years.

The nearby sister scope, Keck II, scheduled to be completed by 1996, will be able to operate independently or in concert with Keck I to create a telescope about eight times more powerful than the largest scopes in the world today.

“We are the first of a new generation of large telescopes,” said Edward C. Stone, chairman of California Assn. for Research in Astronomy, which is building the Keck Observatory primarily with funds from the W. M. Keck Foundation.

The association is composed of Caltech, of which Stone is vice president, and the University of California. The University of Hawaii will also have access to the observatory because it owns the site, widely regarded as the premier astronomical site in the world.

The Keck uses a radically different technology than any of the great telescopes now under construction. Its 36 segments will be continually adjusted so that they act as a single mirror twice the diameter of the Hale Telescope on Mount Palomar, which has dominated the field of astronomy for nearly half a century.

But the Keck’s reign as the world’s largest telescope may be short-lived. European scientists have begun construction of an observatory in Chile, with its centerpiece four telescopes, each 8.2 meters in diameter, linked to eight one-meter telescopes. Combined, the observatory will act as a single telescope with a diameter of 190 meters. Unlike the Keck’s 36 segments, each of those telescopes will have a single primary mirror.

Meanwhile, Japan has embarked on its most ambitious program in ground-based astronomy. Japan has set aside $300 million for a 7.5-meter telescope, to be built on Mauna Kea, which will use an extremely thin primary mirror that can be warped into the correct shape.

The various approaches, and the complexity of the Keck design, have precipitated strong debates within the astronomical community over which course is wisest. But Stone and Jerry Nelson of UC Berkeley, the primary designer of the Keck, are confident that time will prove the value of the segmented mirror.

“I’m quite pleased with the way it is going,” Nelson said during a recent interview on Mauna Kea.

Stone described the technology as “open-ended.” “We have not taken it to its natural limit,” he said. “There’s no reason why one could not build a 15-meter segmented mirror.”

When large telescopes are built in space, or on the moon, they will most likely use segmented mirrors because huge mirrors cannot be launched, Stone added.

While ground-based telescopes are limited by disturbances in the Earth’s atmosphere, so much progress has been made eliminating atmospheric distortion that some scientists believe earthbound telescopes may eventually produce images as sharp as those from space scopes.

The new field of adaptive optics has emerged in recent years, allowing engineers to design systems that subtract atmospheric disturbances from the images produced by ground-based telescopes, thus overcoming some of the disadvantages that argue for putting telescopes in space.

The Keck will be equipped with adaptive optics, and scientists hope that its images will rival those from the Hubble Space Telescope in terms of sharpness.

Space-based telescopes will always have one advantage over their larger cousins on the ground: Those in space are able to study the universe by examining light that gets filtered out by the Earth’s atmosphere and never reaches telescopes on the ground.

But the new generation of large ground-based telescopes have one profound advantage over the Hubble. They are many times larger than the orbiting observatory, and thus can collect much more of the light that does penetrate the atmosphere. That allows long-term studies of dim objects, which can reveal the distance of the objects.

This special ability could someday allow scientists to answer one of the most baffling questions of astronomy: How did the universe, which presumably began with a big bang, evolve into its present complex structure?