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M1/M3 Front Surface Work Begins

M1/M3 Front Surface Work Begins

Wednesday, December 2, 2009

The LSST 8.4-meter mirror blank has undergone its final rotation and integration with the polishing cell at the Steward Observatory Mirror Lab in preparation for front surface optical processing. Significant progress has been achieved since January 2009, when initial rear surface processing commenced. The outer and inner diameters were centered about the cast core geometry and finished to specification; the 25-mm thick backplate has been polished flat with additional core hole polishing at 24 hardpoint locations to increase load capacity; six hardpoint wedges have been attached to provide mirror positioning and interface to the telescope cell; 156 loadspreaders were assembled and bonded to the backplate to support and safely distribute bending forces throughout the mirror; and 146 precision thermocouples were bonded to the mirror front, back, and mid-plane locations to guide polishing and eventual on-telescope thermal control. The mirror and polishing cell will now be moved under the Large Optical Generator to begin generating and eventual polishing of the M1/M3 surfaces. The cast mirror contains an excess 234-mm of glass over the M3 surface (2.3 m3 or 11,000 pounds) which must be removed. Generation via fixed abrasive wheels will be followed by loose abrasive polishing with stressed lap tools until final mirror figure is achieved. The M1/M3 dual surfaces are scheduled to be complete in January 2012. 

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Image Credit: 
Paul O'Connor BNL/LSST

Financial support for LSST comes from the National Science Foundation (NSF) through Cooperative Agreement No. 1258333, the Department of Energy (DOE) Office of Science under Contract No. DE-AC02-76SF00515, and private funding raised by the LSST Corporation. The NSF-funded LSST Project Office for construction was established as an operating center under management of the Association of Universities for Research in Astronomy (AURA).  The DOE-funded effort to build the LSST camera is managed by the SLAC National Accelerator Laboratory (SLAC).
The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.   




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