October 30, 2018 - On the morning of October 25th, at the Richard F. Caris Mirror Lab on the University of Arizona campus, the LSST Primary/Tertiary Mirror (M1M3) was successfully lifted out of its transport container and onto the M1M3 Cell. The mirror lift was performed with a special lifting fixture, outfitted with 54 vacuum pads, that was designed specifically to safely lift and lower the 37,000 lb (16,780 kg) glass monolith. The M1M3 Mirror was lifted onto the Cell, interfacing successfully with the 355 static supports (wire rope isolators), that hold it above the upper surface of the mirror cell.
In order to minimize the risk of damage to the glass, the M1M3 Mirror will only be lifted in this manner this four times during the entirety of LSST construction and operations. This lift was the second; the first lift occurred in February of 2015, when the Mirror’s fabrication was complete and it was lifted into its protective transport container. The third lift will occur when it’s time to put the Mirror back into its protective box for transport to Chile, and the fourth will integrate M1M3 and the Cell for the last time in the LSST summit facility. Once M1M3 is integrated with the Cell at the observatory site, it will not be removed from the Cell again—not even for coating. The M1M3 Mirror can be coated while installed on the Cell, thanks to an internal cylindrical vacuum barrier. When rolled into place under the Coating Chamber lid using the transport cart, the Cell takes the place of the bottom half of the Coating Chamber, allowing a vacuum to be drawn and the M1M3 Mirror to be coated.
Over the next few weeks, work in the Mirror Lab will focus on the integration of the Mirror and Cell, which includes installing hardpoints, actuators, and electronics. These activities will be followed by functional testing of the assembled system. The Mirror is scheduled to move under the Mirror Lab’s interferometery tower for optical testing in January, 2019.
