The clean room at the MMB

View of the clean room at the Paranal Mirror Maintenance Building (MMB). In here, two crucial steps of the recoating process of the VLT’s mirrors take place. In the foreground is the machine which removes the aluminium layer from the surface of the mirror by chemical washing. In the background is the vacuum chamber where the surface of the mirror is covered with a new layer of aluminium. This process is necessary to keep the mirrors clean and to preserve their optical quality. Each of the four 8.2-metre mirrors is recoated every 18 months.