The 2,454th Meeting of the Society

February 11, 2022 at 8:00 PM

Via Zoom Webinar

The ESO’s Extremely Large Telescope

Challenges and Progress on the World's Largest Telescope

Roberto Tamai

Programme Manager
European Southern Observatory

About the Lecture

Of the three very large telescope projects currently underway, the European Southern Observatory’s Extremely Large Telescope (the EELT) has the largest aperture, involves the most mirrors and has the most complex light path, involving five distinct mirror assemblies.  After overcoming several difficulties and a number of delays – not surprising for such a complex project – substantial progress is being made on the telescope in Europe and on site in Chile.  Indeed, construction of the EELT is now proceeding at full speed with more than 35 large industrial contracts in place to build the telescope and observatory infrastructure, and four agreements with consortia of astronomical research institutes to develop the first suite of scientific instruments.

The first structural concrete for the foundation has been poured at the Cerro Armazones site in Chile.  A large facility has been built a few miles away on Cerro Paranal to host a large fraction of the ELT Assembly Integration and Verification work, as well as future mirror maintenance activities.  In Europe, many pieces of hardware have been fabricated.  Prototypes, qualification and validation models of critical components have been produced, including nanometric-precision M1 mirror position actuators, M1 mirror edge sensors and M1 mirror segment supports.

Many components are now in the serial manufacturing phase and deliveries of components are underway, including several hundred M1 mirror segment blanks and M1 segment supports, the M2 and M3 mirror blanks, and a full set of petals for the M4 mirror, to name a few.  In addition, the designs of the scientific instruments have also progressed well.  All of them have passed Preliminary Design Review and are heading towards Final Design Review.  The project is now fully funded and the First Scientific Light is expected for the end of 2027.

This lecture will discuss the design of the ELT, summarize the current status of the construction project, and briefly outline the science that the telescope will undertake once it is completed.

Selected Reading & Media References

General information on the ESO/ELT can found at

More technical information is provided at

About the Speaker

Roberto Tamai is Program Manager for the European Southern Observatory’s Extremely Large Telescope project (ESO’s ELT), also referred to as the European Extremely Large Telescope (EELT).  Previously he served as Deputy Director of Engineering at the European Southern Observatory, and before that as Head of the Technology Division at ESO.

Among other engagements in his long and distinguished career at ESO, Roberto served as Project Engineer on the ESA Hypersonic Plasma Wind Tunnel Project at the Italian Aerospace Research Center, as a Mechanical Engineer at ESO’s Paranal Observatory, and as head of Engineering and then Deputy Director of ESO’s La Sillia-Paranal Observatory.

Roberto was educated at Naples University Federico II and then at the University of California, Berkley.