Riccardo Giovanelli, right, professor of astronomy, and graduate student Jeremy Darling show a satellite image, obtained with the assistance of the geology department, of the high Atacama region of northern Chile. Nicola Kountoupes/University Photography
One of the best sites on Earth for astronomical observation is a high plateau in the Atacama desert of northern Chile. Last month astronomer Riccardo Giovanelli returned to the area with a survey group for the fifth time to assess the potential for building the world's largest optical/infrared telescope on the bleak, windswept high Andes. Giovanelli, a Cornell professor of astronomy, his graduate student Jeremy Darling and several other Cornell scientists began a survey in the Chajnantor plateau at 16,500 feet in April 1998.
"The results of the survey were pleasantly surprising. The site is even better than we hoped," Giovanelli said.
The results of the survey, which are posted on the Internet http://astrosun.tn.cornell.edu/atacama/atacama.html, will be published in scientific journals when the assessment is completed. Early survey results have already been presented at professional meetings, such as that of the American Astronomical Society in Austin, Texas, in January, where, Giovanelli said, "we had a very good response."
The Cornell administration, said Giovanelli, has been supportive by contributing funds to the site assessment. While funding sources for the telescope construction are still uncertain, it is believed that support will come from private rather than public sources.
The survey investigators also face the uncertainties of personal safety: Giovanelli and his team must be alert to symptoms of high-altitude sickness, which at 17,000 feet can result in acute headaches and nausea. To date, though, the group has not had any major difficulties.
"It's tough until you get acclimated. But in general, I don't think we had problems with thinking clearly or solving problems," Darling said. "Your body just demands more attention up there." Though the surveyors spend up to 10 hours a day at 17,000 feet, they sleep at a safer 8,000 feet in the village of San Pedro.
Altitude, though, would not impede the operation of the proposed telescope because it would be operated by astronomers remotely, from Ithaca. "They would just log on via a computer link and check their data as they come in. They wouldn't have to go to Chile or the control room of the telescope," said Giovanelli.
This desert region also is being considered as the site for other telescopes by astronomical agencies worldwide. These include the U.S. National Radio Astronomy Observatory, which has plans to build a large facility called the Millimeter Array at 16,400 feet.
On their trips to the desert plateau, the Cornell astronomers measure two important atmospheric properties: Optical seeing, which determines the sharpness of celestial images, and water vapor content, which determines the atmosphere's transparency to cosmic infrared radiation.
The first survey for the telescope was made around the site of the proposed Millimeter Array, and the other four were at the summit of Cerro Chico, a minor elevation roughly 500 feet higher. Neither of these sites, Giovanelli said, are considered as the final location for the proposed telescope. They were chosen for testing because they are easily accessible, and the measured conditions would be a "worst case scenario" compared with the summits of nearby mountains near 18,000 feet. Even so, Giovanelli said, from an astronomical viewpoint, Cerro Chico provides higher quality characteristics than any existing observatory on Earth.
The next step in Giovanelli's assessment is to obtain permission from Chilean authorities to take measurements on one of these higher sites, possibly in the second half of this year.
"It is already clear that the high Atacama sites are the best on Earth for astronomy," said Giovanelli. "The only open question is: How good can they really get?"
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