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CMU helps fund large telescope in S. Africa
Saturday, July 11, 1998 By Byron Spice,Science Editor, Post-Gazette
Carnegie Mellon University astrophysicists say the makers of the film Godzilla had it right: Size does matter. That's why they are raising $6 million to help build one of the world's largest telescopes.
The telescope, the South African Large Telescope, or SALT, will be built near Sutherland, South Africa, about 230 miles northeast of Cape Town. When finished in 2003, it will be the largest telescope in the Southern Hemisphere.
Being assured of observing time on a large telescope is critical to the young astrophysics department Carnegie Mellon has assembled over the last couple years, Richard Griffiths, professor of astrophysics, said yesterday as the university announced its commitment to the project.
And the $20 million telescope has been adopted by the fledgling democratic government of South Africa as a flagship for its scientific programs.
"By American standards, this is not a big program," acknowledged Robert Stobie, director of the South African Astronomical Observatory, who was in Pittsburgh this week for meetings at Carnegie Mellon. "But in South Africa, this is big science."
SALT will be a twin of Penn State University's Hobby-Eberly Telescope, an unusual design that began operation this summer at the McDonald Observatory in Texas.
Both telescopes feature giant, segmented mirrors measuring almost 36 feet across. But unlike almost every other major telescope, the mirror is not designed to track stars across the sky. Instead, the primary mirror is mounted at a fixed angle; only its air-cushioned base can rotate.
"We don't point at any object in the sky," Griffiths said. "We allow the sky to drift by and focus on the stars and galaxies that come into view."
The trick, Griffiths explained, lies in the design of the secondary, or tracking mirror that sits above the primary mirror. This mirror, the focal point of light collected by the primary mirror, can move in six dimensions, moving up, down, side to side, yawing, rolling and pitching to keep a celestial body in focus as it moves across the sky.
Whereas a conventional telescope, such as the world's largest optical telescopes, the Keck Telescopes on Hawaii's Mauna Kea, can track a single object all night long, the Hobby-Eberly and South African telescopes can track objects no more than an hour or two. That is plenty of time for most observations, Griffiths said.
Keeping the 90-ton primary mirror stationary keeps costs low -- about five times lower than the Keck telescopes.
"It's bargain astrophysics," agreed Frank Tabakin, chairman of physics and astronomy at the University of Pittsburgh.
Pitt astrophysicists would love to invest in SALT as well, although they have yet to convince university administrators to sign on. The university's long-established astrophysics group is growing, but it needs the same access to large telescopes that Carnegie Mellon seeks, Tabakin noted.
Plans to invest $8 million in the Magellan Telescope on Las Campanas in Chile, which had been championed by former Pitt Chancellor J. Dennis O'Connor, were shelved when the university decided to concentrate its fund raising on a convocation center and other projects.
Griffiths acknowledged that, despite its commitment to SALT, Carnegie Mellon has yet to raise a penny of its $6 million goal. He said he isn't sure where the money will come from, although he noted telescopes have often benefited from individual philanthropists.
Last month, the South African government committed $10 million over the next five years, based in part on letters of intent from Carnegie Mellon, Rutgers University and institutions in Poland and Germany.
Khotso Mokhele, president of South Africa's Foundation for Research and Development, said ground can't be broken until more partners sign on. But, given the priority the South African cabinet has placed on SALT, "we cannot afford to linger for long," he added. He plans to hire a project manager after his return to South Africa and hopes to have construction underway by March 31.
"If we can have 80 percent (of the commitments) by the end of November of this year, we'll have a much better Christmas," he said.
Astronomy has a long history in South Africa, Stobie said, but until 1972 the country's largest telescopes were located near large cities, where light pollution had made them nearly useless.
The telescopes, including a 1.9-meter telescope that was the largest in the Southern Hemisphere when it was built 50 years ago, were relocated to the Karoo region, to what became the South African Astronomical Observatory. The Karoo is a semi-arid desert where nothing grows that is larger than a bush, and sheep farming is the major industry. The skies are dark and clear.
New, large telescopes in Australia and Chile long ago eclipsed the South African scopes and, when he became observatory director six years ago, Stobie made the construction of a large telescope his highest priority.
When the new democratic government took power in 1994, there was concern that a government faced with deficiencies in basic education, housing and health care would consider astronomy a luxury, Stobie noted. The government in 1996, however, identified astronomy and physics as priorities not only for South Africa, but for the continent as well. Astronomy was seen not only as an important fundamental science, but also as a way to spur students to study science.
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