Mirrors for the world’s largest optical telescope are on their way to Chile

The segments will travel from France to Chile.
By | Published: December 21, 2023

The first 18 pieces for one of the European Southern Observatory’s Extremely Large Telescope (ELT) mirrors have started their 10,000 kilometer journey from France to Chile. It’s a key step on the way to competing the ELT, according to the European Southern Observatory (ESO).

Each section is  part of the telescope’s primary mirror, named the M1. Once complete, the M1 will hold 798 individual hexagonal pieces. It’s considered to be the world’s largest mirror ever built for an optical telescope at a whopping 39.3 meters in diameter. ESO said the mirror will gather “tens of millions of times” more light than a human eye.

The ESO Extremely Large Telescope 

Once complete, ELT will have five mirrors to help further study the cosmos, including our solar system, exoplanets, stars, galaxies, and black holes. ELT is scheduled to see its first technical light in 2028. The telescope will be 20 km away from the Very Large Telescope on Cerro Armazones.

Polished to perfection 

Safran Reosc, a French company that worked on mirrors for the James Webb Space Telescope, polished the 18 segments before they were sent to the Atacama Desert. Polishing the mirrors was not simple. Safran Reosc used a technique called “ion beam figuring.” A beam of positively charged ions slides across the mirror’s surface to remove any imperfections at the atomic level.

While only 18 segments were shipped out, more are expected for delivery. Last month, Safran Reosc began inspecting the mirror’s 100th piece.

Handle with care: Mirror segments are loaded in France. Credit: ELT
Handle with care: Mirror segments are loaded in France. Credit: ELT

After the mirrors arrive in Chile, each one will receive a thin layer of reflective silver coating before its stored until it’s time for installation- planned for 2027.