by Erik Starman
The DKIST Primary Mirror has been successfully aluminized in preparation for installation into the Telescope Mount Assembly. The 4-meter diameter, 75-mm thick mirror is made from Schott Zerodur glass with a weight of 3.3 metric tons. Despite the large size of the mirror, it requires only a tiny amount of aluminum (less than an ounce) to coat the surface. The aluminum coating provides a highly reflective surface required for the optical and infrared wavelengths at which DKIST will operate.
The operation kicked off in early April with the transport of the mirror in its shipping box from DKIST to the Air Force Maui Optical Station Mirror Coating Facility (MCF). Once at the MCF, the mirror was lifted with its whiffletree support from the box onto the wash cart. Handling of the mirror is done with extreme care due to the extremely thin profile for its size. After installation on the wash cart, the mirror was prepared for washing by installing a gutter around the perimeter for liquid waste collection and installing a gantry assembly to the cart to provide a work platform. Next the mirror was cleaned in several stages which included a mild soap wash, followed by a chemical scrub and acid rinse. Finally, after a thorough rinse with deionized water, the glass was dried with cleanroom wipers and given a final buff with pure ethanol.