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Mirror with ULE® glass will help capture deepest, widest image of universe ever

Mirror with ULE® glass

December 2018

CANTON, N.Y.-- Corning’s glass arrived at the summit of Cerro Pachón, Chile, last week to help unravel the mysteries of the universe as part of a mirror for a new telescope. Data and images from the telescope will answer some of humankind’s deepest questions about the heavens: what’s out there and how did it get there. It will scan the sky for evidence of dark matter, catalog the solar system through high-resolution photos, and provide information about the structure and formation of the Milky Way.

“Discoveries that will be written about in history books are being enabled by our materials and processes,” said Larry Sutton, product line manager, advanced products.

The telescope, known as the Large Synoptic Survey Telescope, currently under construction, will conduct a 10-year survey that will deliver a motion picture of half the sky using a tennis-court sized primary mirror, two additional mirrors, and the world’s largest digital camera. Corning’s glass will play an important role as the telescope takes the deepest, widest image of the universe in history.

“It’s big science,” Larry said.

The Corning glass that arrived was a 3.4-meter disc of ULE®, or ultra-low expansion glass, part of a secondary mirror in the system. A 70-inch disc of Corning’s HPFS® glass is also used in the camera system. The glass for the mirror required precise engineering for a unique application, but ULE has also proven to be incredibly versatile over its 75-year history. Applications range from ground-based astronomy to semiconductor chip manufacturing with extreme ultraviolet lithography.

The glass for this mirror started as a boule, or a discrete chunk of glass, made through Corning’s vapor deposition process. The boule was created by depositing a pure form of silica in layers. From that, six individual segments of glass were created, like pieces of a pie. They were then sealed together.

ULE glass has a near-zero coefficient of thermal expansion, which is a measure of how an object’s size changes with temperature. Even when exposed to the shifting temperatures of the sky from day to night, the glass holds its shape, which helps prevent image distortion.

“It’s the most stable material in the world,” said Mary Edwards, product engineer and program management, about ULE.

Corning was awarded the contract for the mirror glass in 2007 and LSST is expected to be operational in 2022. Financial support for LSST comes from the U.S. National Science Foundation, the U.S. Department of Energy, and private funding raised by the LSST Corporation. 

This project drew on Corning’s core technologies in glass and optical physics, combined with vapor deposition, one of its best-in-the-world manufacturing platforms. Corning’s other involvement in space has included providing window glass for every crewed American spacecraft, as well as mirror glass for the Gemini, Hubble, and Subaru telescopes.

“We’re excited to be part of another major milestone in astronomy,” said Cassandra Taliaferro, business director, optical materials and technology. “On its 75th anniversary, ULE glass continues to amaze the world as it remains at the cutting edge of science.”


Photo credits, top to bottom: M. Park/Inigo Films/LSST/AURA/NSF, Gianluca Lombardi