Construction of the primary mirror of the European Extremely Large Telescope E_ELT. This telescope, due to be completed in 2022, will have a 39.3_metre_diameter primary mirror, composed of 798 hexagonal plates. This makes it the largest of the forthcoming next generation of ground_based telescopes. It is intended to search for and study Earth_like planets. The telescope will be built on the Cerro Armazones mountain in the Chilean Atacama Desert, at an altitude of just over 3000 metres.