The 4.3-meter-diameter (14 foot), approximately 6,700-pound mirror is the heart of Lowell Observatory's new Discovery Channel Telescope. The telescope is under construction at Happy Jack, Ariz., about 40 miles southeast of Flagstaff.

The Discovery Channel Telescope at Lowell Observatory is a joint project of Lowell Observatory and Discovery Communications, Inc.

When fully operational in 2010, the new telescope will be the fifth largest in the continental United States and will allow Lowell astronomers to enter new research areas and conduct existing programs much more efficiently and effectively.

The DCT and the research it enables also will be the focus of ongoing informative and educational television programs about astronomy, science, and technology, airing on Discovery networks.

UA optical scientists will polish and figure the mirror in an exacting, delicate process expected to take about three years. If the mirror were the size of the United States, all the imperfections would be polished down to less than one inch high.

"I'm really pleased to see this major contract being let in Arizona," said Bob Millis, the Lowell Observatory director. "We are all looking forward to working with the University's highly respected College of Optical Sciences in bringing the mirror to completion."

The DCT mirror was cast and fused by Corning, Inc. in Canton, N.Y. to the Lowell Observatory's exacting specifications. It is made of Corning's ultra-low-expansion glass and is only 100 millimeters (four inches) thick.

"These are very important features," said Lowell's DCT project manager, Byron Smith. "The thinness of the mirror helps it cool rapidly at night reducing heat waves that would blur the images." Both characteristics help to ensure the sharpest possible images from the telescope.

"This is a great telescope and a project we're very interested in," said Martin J. Valente, director of OSC's optical fabrication and engineering facility and UA's principal investigator on the project.

"It's a great opportunity to apply our advanced processing and testing technology and also to show our students, from start to finish, what it takes to actually make a deliverable product."

Valente's engineering team has produced very complex optical systems, including large optics that demonstrated technologies for NASA's James Webb Space Telescope, scheduled for launch in 2013, and ESA's Herschel Space Observatory, scheduled for launch next year.

The UA optics team also designed and built an all-metal telescope that launched on the space shuttle several years ago, and fabricated large-faceted fused quartz blocks for the Gravity Probe B experiment that launched last year.

Other projects for government and industry include designing large optical telescopes and telescope subsystems, space-based detectors, and airborne optical instruments.

"We've got a lot of great technical expertise to work on this program," Valente said.

The DCT mirror will be delivered to UA's optical sciences facility at the end of August. Over about the next half year, the engineering team will bond a minimum of 120 pucks to the mirror's convex backside and make a support structure that holds the mirror just as it will be held in the telescope.

The system will ensure the mirror doesn't flex under the force of grinding and polishing.

Next, grinding the mirror to get it closer to the ideal shape will take about five months, Valente said.

Polishing the mirror and "figuring" it - which is the final stage of polishing that will make the mirror accurate to within a fraction of a wavelength of light, or a few millionths of an inch - probably will take another 15 to 18 months, he said.

Optical sciences students, working under the supervision of Jim Burge, co-investigator on the project, will primarily be involved in optical testing.

Burge's group will design lenses that will be used with several systems that will independently test the DCT mirror. Test systems will include a laser tracker and infrared and visible wavelength interferometers.

Finishing a mirror to such extreme accuracy requires a lot of experience and expertise. "We have the facility and personnel to do it," Valente said.

"We have a lot of excellent optical designers, a lot of experience in analyzing data and figuring out what to do to finish an optic."

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