Giant Furnace Opens to Reveal 'Perfect' LSST Mirror Blank
LSST Corp. team members assembled Aug. 11, 2008, around the mirror blank that will become the LSST's primary and tertiary mirrors. The outer primary mirror is 27 feet in diameter and the inner third mirror is 16.5 feet and diameter. The fully finished optic will weigh 35,900 pounds and is destined for the LSST, a large survey telescope being built in northern Chile. ((LSST Corp./Howard Lester))
The Large Synoptic Survey Telescope is being built in northern Chile.
The combination primary and tertiary mirror blank cast for the Large Synoptic Survey Telescope at The University of Arizona's Steward Observatory Mirror Laboratory is "perfect," say project astronomers and engineers.
The LSST, or Large Synoptic Survey Telescope, a large survey telescope being built in northern Chile, requires three large mirrors. The two largest of these mirrors are concentric rings that fit neatly onto a single mirror blank.
The Mirror Lab team opened the furnace last month for a close-up look at the cooled 51,900-pound mirror blank, which consists of an outer 27-foot diameter (8.4-meter) primary mirror and an inner 16.5-foot (5-meter) third mirror cast in one mold.
It is the first time a combined primary and tertiary mirror has been produced on such a large scale. No UA giant mirror casting has ever gone smoother, Steward Observatory Director and Regents' Professor Peter Strittmatter said.
Mirror Lab oven pilots continuously monitored the 4-month casting process, which required carefully controlled heating, with the furnace hitting peak temperatures and spinning in March, and carefully controlled cooling. Casting two mirrors as one saved substantial time and money, and produced two mirrors that are permanently and precisely aligned.
The LSST will be the widest, fastest, deepest eye of the new digital age when it begins science operations from Cerro Pachón, Chile, in 2015. It will provide time-lapse digitial imaging across the entire available night sky every three days, mapping the structure of all matter in our dynamic universe and exploring the nature of dark matter and dark energy.
The mirror blank, along with refractory cores that give the blank its "honeycomb" structure, weigh 85,000 pounds. After the refractory material is cleaned out this fall, grinding and polishing can begin. A total 16,000 pounds of Ohara E6 borosilicate glass will be removed from the faceplate and the backplate of the mirror. The fully polished mirror will weight about 35,900 pounds. It is scheduled for delivery in January 2012.
In January 2008, LSST announced receipt of two major gifts: $20 million from the Charles Simonyi Fund for Arts and Sciences, and $10 million from Microsoft founder Bill Gates. These gifts will enable the construction of LSST's three large mirrors.
The LSST research and development effort is funded in part by the National Science Foundation under Scientific Program Order No. 9 (AST-0551161) and Scientific Program Order No. 1 (AST-0244680) through Cooperative Agreement AST-0132798. Additional funding comes from private donations, and in-kind support at Department of Energy laboratories and other LSSTC institutional members.
In 2003, the LSST Corporation was formed as a nonprofit 501(c)3 Arizona corporation with headquarters in Tucson, Ariz. Membership has since expanded to 25 members.
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