The mirror maintenance building

View of the southern facade of the Mirror Maintenance Building (MMB) at ESO’s Paranal Observatory. The two main doors are closed in this picture. Through the one on the left, the VLT’s 8.2-metre primary mirrors (M1s) are carried inside the coating plant. The one on the right is the door of the maintenance area for the VLT’s 1.8-metre Auxiliary Telescopes (ATs). The white dish on the left is a dummy of the M1 mirrors. It is a copy of the giant main mirrors, made of concrete instead of Zerodur, and with the same mechanical characteristics as the M1. It is used as a substitute for the real mirrors in different kinds of tests.