Flagstaff, Ariz. – Lowell Observatory and the University of Arizona’s College of Optical Sciences (OSC) have finalized a $3 million, three-year contract to complete the Discovery Channel Telescope primary mirror.
The 4.3-meter-diameter (14 ft.), approximately 6,700-pound mirror is the heart of Lowell Observatory’s new Discovery Channel Telescope (DCT). The telescope is under construction at Happy Jack, Ariz., 40 miles southeast of Flagstaff.
The Discovery Channel Telescope at Lowell Observatory is a joint project of Lowell Observatory and Discovery Communications, Inc. (DCI). When fully operational in 2010, the new telescope will be the fifth largest in the continental U.S. 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, 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 Lowell Observatory’s exacting specifications. It is made of Corning’s ultra-low-expansion (ULE) glass and is only 100mm (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 Next Generation Space Telescope (James Webb Space Telescope) scheduled for launch in 2013 and the European Space Agency’s Far Infrared Space Telescope (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 – will probably take another 15 to 18 months, he said.
Optical sciences students, working under the supervision of optical sciences professor Jim Burge, co-investigator on the project, will be primarily 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.”
Lowell Observatory and Corning, Inc. announced completion of the primary mirror blank in October 2005. Building of a road to the DCT site near Happy Jack began in November 2004 and construction of the telescope enclosure and an auxiliary support building commenced in mid-September 2005. Thanks, in part, to an exceptionally mild winter, progress on the buildings and other site infrastructure has been rapid.
The Discovery Channel Telescope is located within the Mogollon Rim Ranger District of the Coconino National Forest. U.S. Forest Service staff and officials have been supportive of the approximately $40-million telescope project. end
About Lowell Observatory
Lowell Observatory is a private, non-profit research institution founded in1894 by Percival Lowell. The Observatory has been the site of many important findings including the discovery of the large recessional velocities of galaxies by Vesto Slipher in 1912-1914 (a result that led ultimately to the realization the universe is expanding) and the discovery of Pluto by Clyde Tombaugh in 1930. Today, Lowell’s 19 astronomers use ground-based telescopes around the world, telescopes in space, and NASA planetary spacecraft to conduct research in diverse areas of astronomy and planetary science. Lowell currently has four research telescopes at its Anderson Mesa dark sky site east of Flagstaff, Arizona, but its main headquarters continues to be the Observatory’s original home on Mars Hill overlooking downtown Flagstaff. Tours of that historic facility, nighttime viewing sessions, and other educational programs are offered to the public daily throughout the year. Visit www.lowell.edu.
About The University of Arizona Optical Sciences Center
The University of Arizona’s College of Optical Sciences is recognized internationally for its innovative and unusually comprehensive research programs. Research encompasses a broad set of technologies and techniques for exploiting the properties and applications of light and touches virtually every field of science and all modern industries. Visit http://www.optics.arizona.edu/. The Optical Systems Development and Fabrication section of The Optical Sciences Center at The University of Arizona is a full function optical design and fabrication facility. This department, headed by Martin Valente, houses a large optics shop, a small optics shop, opto-mechanical engineering facility and instrument shop, optical generation equipment, and optical testing equipment. Visit http://www.optics.arizona.edu/opt_fab/.
About Discovery Communications
Discovery Communications, Inc. is the leading global real-world media company with operations in 170 countries and territories reaching 1.4 billion cumulative subscribers. DCI’s over 100 networks of distinctive programming represent 28 trusted brands including Discovery Channel, TLC and Animal Planet. DCI’s other properties consist of Discovery Education and COSMEO, a revolutionary online homework help service, as well as Discovery Commerce, which operates more than 100 Discovery Channel Stores in the U.S. Discovery brings the real world to the whole world through its global multiplatform initiatives including Discovery Travel Media, Discovery Mobile and multiple broadband services. DCI’s ownership consists of four shareholders: Discovery Holding Company (NASDAQ: DISCA, DISCB), Cox Communications, Inc., Advance/Newhouse Communications and John S. Hendricks, the Company’s Founder and Chairman. More information about Discovery and its businesses can be found at www.discovery.com.
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