Giant Mirror Mounting and Metrology
Primary Mirror Mounting and Metrology progress was reported at the most recent GMT1 Quarterly Review, held on April 24, 2007, at the University of Arizona’s Steward Observatory Mirror Lab in Tucson, Arizona.
Tucson, AZ. GMT’s first 8.4 meter mirror segment is currently inverted, the rear
surface having been machined and polished. The installation of
loadspreaders is being completed. The loadspreaders are
triangular metal frames that serve as an interface between the mirror
glass and the actuators that position the mirror.
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| Charlie Hull views loadspreader installation on the inverted 8.4 m mirror segment. |
The polishing cell, a structure designed for securing the mirror
during polishing, is being readied, and plans for processing
the front surface are underway. Generating procedures for the highly
aspheric front face will be first tested on a large piece of granite before grinding the mirror.
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| The Polishing Cell is made ready for the 8.4 m mirror segment. |
The 3.8 meter fold sphere mirror, which will be used for testing the
8.4 meter GMT primary mirror segments, has had rear surface preparation
completed, and its loadspreaders are being installed. The
polishing cell for the fold sphere is ready, and the LOG (Large Optics
Generator) is nearly ready to receive the fold sphere.
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| Steve Shectman inspects installation of loadspreaders on the 3.8 m fold sphere mirror. |
The steel structure of the test tower has been completed and metrology equipment will be installed over the next nine
months. The next Quarterly Review is scheduled for July 26, 2007. At that
time, we should see the mirror right-side up again, and the beginning
of the 18 month process of grinding and polishing the front face.
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| View of 8.4 m mirror polishing cell positioned under the test tower. |
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| Looking up the completed test tower structure. |