ELT mirror segment wrapped for delivery

This image, taken at a storage facility near Poitiers, France, in December 2023, shows a segment of ESO’s Extremely Large Telescope main mirror, together with its support system, boxed and ready to start its 10 000 km long journey to Chile. Once there, the segments will be coated with a thin layer of reflective silver, and stored in preparation for installation on the telescope. Each segment is close to 1.5 metres across and 5 centimetres thick, and their surfaces have been polished to an accuracy of tens of nanometres — 10 000 times thinner than a human hair. The ELT’s 39-metre mirror will comprise 798 of these segments, plus 133 additional segments to facilitate recoating.