Optics Shop Installs New Stressed Lap and Polishing Machine

Another Step Toward the World's Most Advanced Solar Telescope

At noon on Friday, Feb. 28, a crowd of more than 80 faculty, staff and students rustled around the Meinel Building's basement-level optics shop, surrounded by bulky stands of complex optical machinery. In the background, a video screen looped footage of a large device polishing the glass surface of an enormous telescope mirror.

A crowd of OSC and Steward Observatory staff listen to the featured speakers at a reception celebrating new equipment in the Optical Engineering Fabrication Facility

The group was invited to the University of Arizona College of Optical Sciences Optical Engineering and Fabrication Facility to celebrate the impressive integration of a new 60 cm stressed lap and 4.5 m computer-controlled polishing machine, key equipment for the successful completion of the 4 m primary mirror of the Daniel K. Inouye Solar Telescope. As Jeffrey Kingsley, director of projects, engineering and technical services at OSC and the UA College of Science's Steward Observatory, said, "We're really thrilled about it." (Photos from the event are now available.)

Kingsley began the noontime reception by explaining its purpose: applauding the wide variety of skills needed to make the new equipment, and thus the DKIST, a reality. Bruce Cook, OEFF program manager, continued the program. "One word keeps coming to mind," he said of the project and its amazing team. "That word is 'wow.'"

Audience members check out the new stressed lap at the OEFF receptionThe DKIST, which was renamed from "Advanced Technology Solar Telescope" in December in honor of the late senator from Hawaii, is funded by the National Science Foundation and overseen by the Association of Universities for Research in Astronomy. When completed in 2019 on Mount Haleakalā on the island of Maui, it will be the world's most powerful ground-based solar telescope — and its existence is only possible through the unique capabilities of OSC and the Steward Observatory.

Noting this year's commemoration of the college's 50th anniversary, professor of optical sciences and astronomy Jim H. Burge underscored the optics shop's role in its history. Its current breadth of research, which impacts health care, communications, defense and more, formed around the nucleus of the fabrication facilities. "We make stuff," Burge said. "We make the stuff that nobody else can make — some of the most challenging optics in the world." Previous collaborations between the OEFF and Steward Observatory have included components of the Large Binocular Telescope, the Giant Magellan Telescope and the Large Synoptic Survey Telescope.

A close-up view of the new computer-controlled polishing machine in the optics shopBurge then described the importance of the new equipment in particular. The computer-controlled polisher replaces a machine built 40 years ago by Steward Observatory engineers, and the stressed lap features two innovative elements: an orbital stroking mode and a pressure-sensing mat that explicitly calibrates polishing force and allows unprecedented levels of accuracy.

The DKIST mirror requires such remarkable accuracy. While it is more than 13 feet wide, thermal constraints limit it to a mere three inches thick. It is also extremely aspheric and nonsymmetric, requiring active shape control to fit its surface. No mirror has ever been made with such steeply changing curvature — and, again, it is only possible thanks to the unique equipment and expertise at the OEFF.

 Speakers Jeffrey Kingsley, Bruce Cook, Jim H. Burge and Thomas L. Koch

Other specialized OEFF facilities include a temperature-controlled environment, an instrument shop, a small optics shop, a 35 m vertical test tower and a newly installed freeform generator.

To close the luncheon, Dean of the College of Optical Sciences Thomas L. Koch applauded the coming-together of the OSC and Steward Observatory communities. Being exposed to this culture of "making things," he said, was "an amazing opportunity, an amazing experience and, frankly, a lot of fun." Before releasing those present to pizza and further discussion, he asked them to act as ambassadors, across campus and around the world, for such new and challenging projects.

UPDATE: March 19, 2014—A crane pulled up to the optics shop hatch on Tuesday to deliver some very special cargo: the final glass blank for the DKIST's primary mirror. (The stressed lap and computer-controlled polishing machine described above were tested on a prototype blank.) The new glass will be grinded, polished and measured over the course of a year and then sent to its final destination on the island of Maui.

Photos of the delivery are now available.