ESO's ELT: A Journey to Revolutionize Our Understanding of the Cosmos

Sunday - December 24 2023, 01:57 UTC - 11 months ago

The European Southern Observatory's Extremely Large Telescope (ESO's ELT), is being pieced together to unveil the mysteries of our universe. It has been crafted from the collaborative efforts of multiple companies from Europe and Chile, and will boast a colossal mirror with a diameter of over 39 meters. With its first light scheduled for 2025, it marks an exceptional technological achievement, featuring advanced devices, and unprecedented data capture capabilities.

The world’s largest optical telescope is being pieced together to life. The first 18 segments of the European Southern Observatory’s Extremely Large Telescope (ESO’s ELT) main mirror, dubbed the M1, have commenced their 10,000-kilometer journey from France to Chile.

Once finished, the ELT will boast a colossal mirror comprising 798 individual hexagonal segments, making it the largest telescope mirror in the world with a diameter of over 39 meters. The complexity of crafting such a mammoth mirror was such that it could not be created as a single piece.

The final stage in the production of M1 mirror segments, polishing, was entrusted to Safran Reosc, the world-leading optical systems manufacturer based near Poitiers, central France, according to a press release. Safran Reosc dedicated a building completely refurbished to work on this complex task, developing new automation workflows and measurement techniques to meet the high standards of polishing the ESO’s ELT requires, with surface irregularities of the mirror reduced to under 10 nanometers, less than one-thousandth of the width of a human hair.

To meet this end and ensure that astronomers get the best views, the company leveraged a technique called ion-beaming figuring, which involves a beam of ions sweeping across the mirror's surface, eliminating irregularities one atom at a time.

A remarkable pace of production. On November 1, 2023, the 100th segment emerged from Safran Reosc’s production line, marking an achievement for the series production of high-precision optics. Although only 18 segments have been shipped so far, the has met its production rate targets of four segments per week and has set sights on increasing it to five weekly segments soon.

Bringing the ELT to life has brought forward a collaboration of multiple companies across Europe and Chile. From the casting of mirror segments by the German company SCHOTT to the delicate segment supports crafted by Dutch company VDL ETG Projects BV, each contribution underscores the international nature of this endeavor. The German-French FAMES consortium played a crucial role in developing and manufacturing sensors with nanometric accuracy, while the German company Physik Instrumente designed and produced actuators capable of positioning each segment with nanometric precision. The responsibility of transporting these segments to their final destination in the Atacama desert was given to Danish company DSV.

Grand vision and future challenges. As the polished mirror segments make their way to the ELT’s construction site in the Atacama Desert, the telescope promises to tackle some of the most significant astronomical challenges of our time. From its strategic location, ESO's ELT will delve into the mysteries of the universe, making unprecedented discoveries once operational later this decade.

From our solar system and exoplanets to stars, galaxies, and black holes, the ELT will explore diverse celestial phenomena and revolutionize our understanding of the cosmos. M1, the ELT’s primary mirror, is designed to capture "tens of millions of times" more light than the human eye.

Scheduled for its first light in 2025, ESO’s ELT marks an exceptional technological achievement, featuring cutting-edge optical systems, advanced devices, and unprecedented data capture capabilities.