ON this mountain top high above Arizona's Sonoran Desert, white domes house an array of telescopes - minarets at a Mecca of modern astronomy.
Run by the National Optical Astronomical Observatories (NOAO) in nearby Tucson, the Kitt Peak facility hosts more than 500 scientists a year. They come to take advantage of the site's Venetian-glass viewing conditions.
At least they have until now.
Possible budget cutbacks in Washington threaten to close some of the telescopes here - and, scientists say, could imperil the future of ground-based astronomy in the United States.
Because several major projects are just getting under way that were launched with government help, researchers note that any less largess from Washington will undermine their ability to carry out the initiatives - and plumb the secrets of the cosmos.
They believe the cutbacks could also discourage a new generation of scientists from entering the field, and will prohibit the upgrading of telescopes crucial to keeping the US in forefront of research. Already, the prospect of less funding for astronomy is touching off a fight within the overall science community over the divvying up of federal funds.
``It is unrealistic to think that there isn't a very major problem,'' says Vera Rubin, an astronomer with the Carnegie Institution.
The funding flap comes at a time when public fascination with astronomy remains high, say scientists, because it tries to answer age-old questions about the universe and its origins. Often, astronomy is the only science course college students take.
Yet federal money for science is being shifted from basic research into ``strategic'' fields, such as chemistry and material science. When stacked up against disciplines with more direct impact on the economy, ``astronomy does not map very well,'' says Hugh Van Horn, director of the National Science Foundation's division of astronomical sciences.
Within the NSF, a shift in budget priorities has already been evident. Last year President Clinton requested a 5.5 percent increase for the NSF's division of astronomical sciences, Dr. Van Horn says. By early summer, Congress had boosted the NSF's appropriation to 13.5 percent. But when the money was divvied up internally in the organization, astronomical sciences ended up with only a 0.2 percent increase.
Now, Van Horn says, there is talk of a possible 1 to 5 percent cut in the federal budget. ``People tell me that maybe even those numbers are too small,'' he adds.
The budget squeeze comes at a time when the NSF is underwriting half of the International Gemini Project, a pair of telescopes to be run by the NOAO that will boast 8-meter (38-foot) mirrors and the latest in technology. One will sit atop a mountain in Chile and the other in Hawaii.
The aim is to give US astronomers more opportunities to observe the entire sky - northern and southern hemisphere. The $176-million project includes Britain, Canada, Chile, Brazil, and Argentina as partners, with the US picking up 50 percent of the construction costs. Once on line, the NSF's will fund $5.5 million a year of the operating budget.
NEARLY 50 percent of astronomers, largely from smaller universities, rely on the NOAO facilities for telescope time. At the same time, private institutions with large investments in their own telescopes are turning to the NSF for grants to upgrade their instruments.
A National Research Council study commissioned by Van Horn laid out a grim picture for the future of ground-based astronomy under flat budgets. The panel of astronomers who prepared the study, released last week, gave the highest priority to Gemini.
Although it held that the full impact of Gemini on astronomy budgets will not be felt until 1998 and 1999, it concluded: ``With level funding, we see no alternative but to face the necessity of major reductions in the NOAO operations.''
The smaller telescopes at the Kitt Peak National Observatory would have to be either closed or sold to private institutions. And operation of the largest telescope on the mountain, the 4-meter Mayall Telescope, would be severely limited. ``A large number of astronomers whose only access to front-line research tools is through the NOAO telescopes will be unable to carry our their research, and US science will suffer,'' the report concludes.
``This is a grim scenario,'' says Richard McCray, a University of Colorado astronomer who chaired the panel.
Sidney Wolff, the NOAO's director, agrees. She points out that the four small instruments in question play a valuable role in selecting objects for larger telescopes to study. That task will become even more important as the 8-meter Gemini telescopes come one line, she says.
Meanwhile, prospects for individual researchers moving into the field are uncertain. ``The number of astronomers has grown by 40 percent in the last decade, while the number of grants from the NSF has remained dead flat,'' McCray says.
This creates several problems, astronomers say. It discourages promising talent from entering the field in the first place. It has also led to a growing group of itinerant astronomers - researchers who try to survive by hopping from grant to grant.
Nor does the prospect of fewer opportunities to use telescopes help. At Kitt Peak, for instance, at least one-third of those using the telescopes that may close are graduate students gaining research experience.