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Corning Ships Second Gemini Mirror Blank

May 9, 1997

Project Update - GEMINI Telescope

Corning Ships Second GEMINI Mirror Blank

On May 13, 1997, one of the largest glass objects ever created, the GEMINI II telescope mirror blank, will leave Corning's Canton, N.Y. plant as it makes its way to the port of Ogdensburg for a transatlantic voyage to France for polishing.

Corning Incorporated announced successful completion of the fmal fabrication phase for the mirror blank on May 1. The mirror blank, measuring over 26 feet in diameter and approximately 8 inches thick, is the second of two identical blanks being produced for the GEMINI 8-Meter Telescopes Project. The project is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the National Science Foundation.

This Gemini telescope will be located on the 8895 ft. summit of Cerro Pachon, Chile, and is scheduled to be in operation by 2000.

Fabrication of the Gemini II mirror blank began at Coming's Canton, N.Y., plant in 1992. Coming fusion sealed individual hexagons of its ULE* (ultra-low expansion) glass into one monolithic, flat, mirror blank. Fusion sealing was performed at temperatures over 1700 C (3100 F) in an expanded facility built to fabricate the mirror blank.

After fusion sealing, the 33-ton blank was lifted, turned over, and ground flat on both surfaces. Then it was sagged - that is heated and slumped - to a nominal contour (concave-convex shape). Coming also ground all the mirror's surfaces and machined a center hole.

The GEMINI mirrors are among the world's largest monolithic mirrors. Corning's large mirror expertise created the world's largest mirror blank, for the Subaru Telescope for the National Astronomical Observatory of Japan.

Established in 1851, Corning Incorporated creates leading-edge technologies for the fastest growing segments of the world's economy. For communications and communications-related industries, Coming manufactures optical fiber, cable and components, high-performance glass and components for televisions, and other electronic displays and equipment; advanced materials for environmental, industrial, and scientific markets; and consumer products. Corning's total revenues in 1996 were $3.7 billion.

Editor's Note: ULE is a trademark of Coming Incorporated.