Engineers praise quality of LSST mirror blank

September 3, 2008--The single-piece primary and tertiary mirror blank cast for the Large Synoptic Survey Telescope (LSST) is "perfect," say its project astronomers and engineers.

September 3, 2008--The single-piece primary and tertiary mirror blank cast for the Large Synoptic Survey Telescope (LSST) is "perfect," say its project astronomers and engineers. The design for the LSST, a large survey telescope being built in northern Chile, requires three large mirrors. The two largest of these mirrors are concentric and fit neatly onto a single mirror blank. The single-piece primary and tertiary mirror blank emerged from the oven at the University of Arizona's Steward Observatory Mirror Lab (Tucson, AZ), where team members gathered to celebrate this major milestone.

The Mirror Lab team opened the furnace for a close-up look at the cooled 51,900 lb mirror blank, which consists of an outer 27.5-ft-diameter (8.4 m ) primary mirror and an inner 16.5 ft (5 m) 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.

The LSST, to be located at Cerro Pachon, will probe near space (examining the Solar System in great detail) and galactic space (mapping the Milky Way), and--perhaps most exciting--will probe much farther off, looking for signs of dark energy and dark matter. It will have a 9.6-square-degree field of view and a 3.2 gigapixel camera that will allow coverage of about 10,000 square degrees of sky every three nights; six wavelength bands will be covered, spanning wavelengths from 325 to 1050 nm. First light is scheduled for 2014.

In January of this year, LSST announced receipt of two major gifts: $20 million from the Charles Simonyi Fund for Arts and Sciences, and $10 million from Bill Gates. These gifts are being used to enable the construction of LSST's three large mirrors. The finished mirror is scheduled to be delivered in 2012.

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