For years the ELT has been the most anticipated and most challenging project the European Southern Observatory has ever embarked upon. Constructing this 39-metre mega telescope is only possible by building on ESO’s long history in pioneering astronomy and engineering, and in bringing countries together to work on ambitious projects. Far from an isolated project, the ELT will become an integral part of the large family of telescopes at ESO’s observatories in Chile. Although smaller in size, these telescopes are giants that have paved the way for the ELT and its almost inconceivable capabilities in imaging and collecting data from our Universe.

Essential for the ELT’s spectacular imaging quality is the incorporation of active and adaptive optics technology including (but not limited to) precise position actuators, multiple sensors, deformable mirrors and laser guide stars. Active optics, the system which allows the mirrors of a telescope to retain perfect shape and position, was first successfully introduced on ESO’s New Technology Telescope (NTT) at La Silla Observatory in 1989 and has been deployed in ESO’s telescopes ever since. Engineers at ESO and elsewhere have also made strides in developing adaptive optics for ESO telescopes, a technology that compensates and corrects for the distortion caused by atmospheric turbulence. Important advancements in adaptive optics came with ESO’s Very Large Telescope (VLT), which revolutionised astronomy and telescope design when the first of its four 8.2-metre telescopes began operations on 25th May 1999. Of particular importance are the VLT’s laser guide stars, which are used by the telescopes’ adaptive optics system to perfect image quality.  

Active and adaptive optics systems developed for ESO telescopes have been improved upon and fully integrated into the ELT’s design, as have other technologies and knowledge gained from the NTT, the VLT and other telescopes and instruments ESO has developed and operated. Engineering and technological advances have been improved and scaled-up to be implemented on the ELT, allowing for far greater optical quality and imaging power than would have been possible without standing on the shoulders of other ESO giants. 

The ELT will become the biggest sibling in ESO’s fantastic family, working with ESO’s other telescopes, which together can observe the Universe in a wide range of wavelengths, to achieve the best science possible. For example, when one telescope spots something unusual or unexpected, follow-up observations can occur rapidly to confirm and obtain more detail on the discovery by the other telescopes at ESO’s La Silla and Paranal Observatories. ESO’s partnerships in observatories such as ALMA (the Atacama Large Millimeter/submillimeter Array) or the future Cherenkov Telescope Array (CTA), which observe the skies at wavelengths other ESO telescopes cannot access, further allow astronomers to expand and deepen studies of our Universe. Welcoming the ELT into the ESO family expands this opportunity further, giving humanity a front row seat to the best observations of the most pressing science taking place each night. 

Another example of this synergy between the ELT and other ESO telescopes, is that the 39-metre machine will be operated from the same control room as other telescopes at the Paranal Observatory. The ELT is being built just 23 km from Cerro Paranal.

More powerful than all professional ground-based optical telescopes in the world combined, the ELT builds on all of ESO’s hard work. Thanks to fruitful worldwide collaborations between ESO’s sixteen member states and its host state of Chile, the ELT has become one of the largest projects ever undertaken in astronomy and will allow ESO’s large and unique family to revolutionise our view and understanding of the Universe.