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New MMT mirror moves up mountain

By Sean McLachlan
Arizona Daily Wildcat
March 24, 1999
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Arizona Daily Wildcat

Photo courtesy of the Multiple Mirror Telescope Observatory The University of Arizona and the Smithsonian Institution built a vacuum dome on top of Mt. Hopkins. The dome will create a fine metal mist that will give the Multiple Mirror Telescope a reflective surface.

UA astronomers and engineers heaved a sigh of relief yesterday as a flatbed truck carrying the new mirror for the Multiple Mirror Telescope reached the summit of Mount Hopkins after a hair-raising, 13-mile trek up a narrow, winding mountain road.

"It's a nasty road with hairpin turns...one of the most hairy drives you can imagine," said Chris Impey, a University of Arizona astronomy professor.

The truck carrying the 10-ton mirror crawled up the road at three to four miles an hour, carefully negotiating turns that often face sheer cliffs. Parts of the road are unpaved and lack guardrails.

The 6.5-meter mirror is part of a $20 million upgrade for the observatory sponsored by the Smithsonian Institution and the UA. The new mirror will replace the six smaller ones in use since the facility opened in 1979.

The original mirrors, when used together, formed the equivalent of a 4.5m mirror.

The new mirror will have more than twice the light gathering capacity of the previous ones, Impey said.

Impey, who studies distant galaxies and quasars, said astronomers want telescopes that can gather as much light as possible to make faint objects more visible.

Astronomy professor Marcia Rieke, who studies the infrared emissions of celestial objects, says the improvements would be especially important for her research.

Rieke is looking forward to using the telescope's infrared spectrometer with the new 6.5m mirror.

Construction and delivery delays for the new mirror meant that the spectrometer had to be fitted onto the old multiple mirrors. Since it was not designed for a for them, stray light decreased performance, Rieke said.

With the new mirror, the spectrometer will be as much as 400 percent more efficient, she said.

"It's going to be fabulous," she said.

The mirror will be lifted into the telescope on Thursday, said Smithsonian spokesman Dan Brocious.

After it is in place, Brocious said, the mirror will be coated with a reflective aluminum surface.

A dome will be fixed over the mirror and aluminum bars inside will be jolted with an electric current. As electricity arcs between the bars, they will give off a fine mist of metal and coat the mirror's surface with a layer of aluminum that is one single molecule thick.

The surface will be so delicate that the natural oil on a fingertip would be enough to corrode the metal. The surface cannot be touched or cleaned, but will be given a new coating every year, Brocious said.

Impey said that the mirror will need to go through numerous tests before being available for observations, but astronomers should get their first look in August or September.