MMB-coating-chamber

The Mirror Maintenance Building (MMB), a large and complex structure that has been constructed next to the base camp, at the foot of the Paranal mountain. In order to hold the large VLT mirrors, this coating plant has a diameter of 9.4 metres. It is used to cover the large mirror surfaces with a thin layer of highly reflecting material (normally aluminium, maybe silver at a later stage), thus ensuring that nearly 100% of the photons from celestial objects impinging on the mirror may also be recorded by the sensitive telescope instruments.

Due to the unavoidable deterioration of this reflective layer, for instance oxidation and abrasion by airborne particles, the mirrors must be re-coated at intervals of some years.