Scientists at South Pole Get Best View of Jupiter's Show : Astronomy: Endless night and temperatures of 80 below zero are ideal for telescopes, if not for humans.

TIMES SCIENCE WRITER

In a frozen wilderness where explorers once died for the sake of a penguin's egg and chunks of petrified wood, Hien Nguyen is collecting spectacular images of a fire in the sky.

At the South Pole--atop an ice pack two miles thick, where it is drier than the Sahara and colder than parts of Mars--astronomers like Nguyen this week are getting what may be the clearest view on Earth as Jupiter and a comet clash in the heavens overhead. While their colleagues at other major observatories around the world contend with rain, fog, pollution and viewing opportunities constrained by daylight, Nguyen and his colleagues at the South Pole Station can be assured of pristine darkness throughout the celestial encounter.

At this time of year, the sun at the South Pole never rises and Jupiter never sets, because the station is centered on the axis of Earth's rotation.

As the death rattles of comet Shoemaker-Levy 9 on Jupiter ignited blazing fireballs and dark storms larger than Earth itself, almost the entire staff of the station huddled together in the cold by Nguyen's small infrared telescope to marvel at the sight before them.

"For the first time, the whole station felt like we were together," Nguyen reported Tuesday via a satellite link.

Nguyen, who fled from Vietnam to Southern California in 1981, is among 26 scientists spending the six months of continuous winter darkness under the blue geodesic dome of the National Science Foundation's South Pole Station. Now a research associate at the University of Chicago, he is the station science leader.

The spreading bruise of debris and superheated gases left in Jupiter's southern hemisphere by Monday's explosion of a two-mile-wide comet fragment now rivals the 300-year-old "Great Red Spot" as the most prominent feature on the planet's immense surface, astronomers said. The red spot measures 20,000 by 8,000 miles.

Two more comet fragments hit Jupiter on Tuesday. The white-hot glow from one impact--that of Fragment K--was at least three times the size of Earth. Starting today, three more large fragments were to slam into the planet's upper atmosphere, hitting the same spot over a period of 20 hours.

"You'll have three--boom, boom, boom," said planetary scientist Heidi B. Hammel, who is leading the scientists analyzing the images from the Hubble Space Telescope. "You are going to have one heck of a mess."

By Tuesday, the South Pole Infrared Explorer Telescope (SPIREX) that Nguyen is operating had detected five of the nine comet fragments that had struck Jupiter, he said in an interview conducted via electronic mail.

"For this particular event, our polar site is unique since the sky is continuously dark during the impact period," he said. "Had this occurred during the summertime, our detector would be immediately saturated by the shining sky background and probably would not be able to detect Jupiter itself, let alone the explosions."

Conditions are so extreme--the temperature Monday was minus 80 degrees Fahrenheit, with 25 m.p.h. winds drifting snow over the telescope--that the atmospheric impurities and water vapor that blur most astronomical images froze out of the air.

The frigid atmosphere over the South Pole contains less than one-tenth the water vapor found over the Mauna Kea observatories in Hawaii, one of the best telescope sites in use.

Infrared light, an invisible form of energy radiated by any hot object, is more easily detected in the bitter chill. Because the telescope also is more sensitive when it is refrigerated, the small 24-inch SPIREX instrument is yielding some of the most dramatic and important images of the impacts on Jupiter.

"The atmosphere at the pole is many times more stable and transparent than for the best mid-latitude infrared observatories," said John P. Lynch, the National Science Foundation's director of polar aeronomy and astrophysics. "Because of the cold, dry atmosphere and the cold telescope itself, a two-foot telescope at the South Pole might be comparable to a 30-foot telescope--like the Keck at Mauna Kea--at those infrared wavelengths."

"That is an awfully extreme thing to say, but that is what the numbers show," Lynch said.

The science foundation-funded Center for Astrophysical Research in Antarctica set up the infrared telescope earlier this year as part of a five-year, $20-million effort to transform the pole into a center for astronomy and astrophysics. A larger telescope is scheduled for construction there later this year.

Mark Hereld, the principal investigator for the SPIREX project at the University of Chicago, spent two months at the pole earlier this year assembling the telescope facility from 14,000 pounds of parts, computer equipment and infrared sensors.

In Chicago this week, Hereld's only contact with Nguyen during the comet encounter is an intermittent computer link that depends on two aging satellites. The satellites have strayed far enough from their original orbits to be briefly visible at the pole every day, when they can be used as relay stations.

Nguyen never expected to end up at the South Pole.

He fled Vietnam by boat when he was 17, leaving behind his mother and much of his family. He settled in Torrance long enough to learn English at El Camino College, then received a physics degree from UC Berkeley and went on to Princeton University for his graduate work. He moved to the University of Chicago in 1993.

Eventually, he hopes to set up a planetarium and a major observatory in his native country. University officials are encouraging the project.

"He went from being a refugee afloat on a boat on the China Sea to being a Princeton graduate, a University of Chicago post-doctoral fellow, and now science leader at the South Pole," Lynch said.

"That is a real success story."

* SEVENTH HEAVEN: A retired telescope builder has his eyes on the prize. B1

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Seeking a Clear Shot

Astronomers around the world are limited by bad weather and restricted viewing times in trying to photograph the collision between Jupiter and the comet Shoemaker-Levy 9.

Some of the most important infrared images, such as the view of Fragment G, lower right, have come from the South Pole, right, where:

* The SPIREX telescope can keep Jupiter in view 24 hours day.

* The air is so cold, dry and pollution-free that astronomers can count on unusual clarity.

Other ground-based observatories have captured dramatic sequences. The European Southern Observatory in Chile shows the plume rising from the impact of Fragment H Monday.

Sources: National Geographic, Reuter / CARA, AP Photo / ESO

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