The Large Synoptic Survey Telescope (LSST) primary/tertiary (M1M3) mirror cell is a 25-ton, 9-meter x 9-meter x 2- meter steel weldment that supports the 19-ton borosilicate M1M3 monolith mirror on the telescope and acts as the lower vessel of the coating chamber when optically coating the mirror surfaces. The M1M3 telescope mirror cell contract was awarded to CAID Industries, Inc., of Tucson, Arizona in October 2015. After the mirror cell final acceptance in October 2017, the integration of the mirror support system started. The M1M3 cell assembly with the surrogate mirror will take place in a dedicated controlled-environment area at CAID Industries. All components of the mirror support system that were developed and tested by the LSST Telescope and Site M1M3 team at the NOAO offices in Tucson have been moved to CAID premises and have been integrated into the cell by a team of LSST, CAID and Richard F. Caris Mirror lab personnel. After completion of the cell integration and its assembly with the surrogate, a test phase that includes zenith and offzenith testing for the mirror support system will be carried by the LSST team. These tests aim to verify that the active support system components, mirror control, and software are performing as expected and the mirror support system is safe for the next step, the M1M3 cell to borosilicate glass assembly and tests at the RFC Mirror Lab of the University of Arizona.
The Large Synoptic Survey Telescope (LSST) primary/tertiary mirror is an 8.4-meter cast borosilicate monolith. The hardpoints form a hexapod that is used to define the location of the M1M3 relative to the mirror cell, as the pneumatic figure actuators, which support the mass of the M1M3 during operation, are unable to define position. The hardpoints must have high stiffness, precise displacement control, and features to limit loads in all six degrees of freedom in order to protect the mirror. Assembly of the hardpoints and verification of the hardpoints and their requirements was undertaken in the summer and fall of 2017.