First segments of ELT’s main mirror arrive in Chile

16 January 2024

After a 10 000 km journey across the world, the first mirror segments of ESO’s Extremely Large Telescope (ELT) have safely arrived in their next home, the ELT Technical Facility at ESO’s Paranal Observatory in the Chilean Atacama Desert. A total of 18 segments (out of 798) of the telescope’s main mirror (M1) successfully made the trip from Europe to South America, first arriving in Chile at the Antofagasta Terminal International (ATI) port last week. 

Once complete, the ELT’s M1 will be over 39 metres across, making it the world’s largest eye on the sky. Such scale means that the mirror can’t be cast in one piece, thus, 798 hexagonal segments will work together to form M1. An additional 133 will be produced to facilitate the segments’ recoating. 

Embarking on a remarkable voyage that began near Poitiers, France, where the ELT segments were finished, they then traveled by road to the port of Le Havre. On 17 December 2023, these vital components of the ELT set off across the ocean. They arrived at the port of Antofagasta and continued their long journey on dry land, reaching ESO’s Paranal Observatory on 12 January 2024. There, ESO engineers performed extensive inspections to confirm they did not suffer any damage during transport.  

With the segments at Paranal, the next phase in this intricate process involves the coating of the mirror segments in the ELT Technical Facility to give them their highly reflective finish, a process that will be reiterated on each segment every 18 months once the ELT begins observations. This monumental telescope, once operational later this decade, is poised to tackle the most profound astronomical challenges of our time, promising groundbreaking discoveries that were once unimaginable. 


Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670

About the Announcement



A white and blue lorry, or truck, labelled Hapag-Lloyd is captured on a grey concrete road which stretches off into the distance in the centre right of the photo. A dusty, beige ground sits on either side. The pastel blue daytime sky is in contrast above. To the right of the lorry, a brown roadside sign has an image of a telescope dome with the words Cerro Paranal.
Next stop, Paranal
Outside a white building to the left of the photo, a person in construction clothing and a protective helmet is working on a large white box with the ESO logo — four stars around the letters E, S, O on a blue background — on it. In the blurry background is another white building.
A special delivery for ESO
Looking in the open back door of a lorry, or truck, three large white boxes fill the lorry bed, surrounded by white air bags. Two people with protective helmets stand in the truck bed, while six others stand on the ground below, everyone with their backs to the camera. In the distance, brown ground juts up with a white building sitting atop under a blue sky.
Unloading the first shipment of the ELT main mirror segments
Inside a large warehouse made of a metal structure with white siding, white boxes with the ESO logo — four stars around the letters E, S, O on a blue background — are lined up in a row stretching off into the background. To the left, tall metal and orange shelves sit empty.
ELT mirror segments as far as the eye can see
A group of about 40 people stand on beige concrete in front of a large white building and a lorry, or truck, labelled Hapag-Lloyd. There are many hands in the air and many expressive faces. This scene is complemented by a light but vivid blue daytime sky.
A joyous day at the ELT’s Technical Facility
Inside a large white warehouse, five people in protective lab coats, masks, and hair nets stand around a metal, hexagonal object, suspended above the ground.
ESO engineers inspect an M1 segment


Unboxing mirror segments
Unboxing mirror segments