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First stone laid as Construction work begins on World's Largest Telescope

26 May 2017


Artists impression of the complete ELT
(Credit: ESO)

A ceremony marking the laying of the first stone of the European Southern Observatory’s (ESO) Extremely Large Telescope (ELT) has taken place at ESO’s Paranal Observatory in northern Chile, close to the site of the future giant telescope. This milestone marks the beginning of the construction of the dome and main telescope structure of the world’s biggest optical telescope, and ushers in a new era in astronomy.

In attendance was the President of the Republic of Chile, Michelle Bachelet Jeria, Tim de Zeeuw, Director General of ESO, Roberto Tamai, the ELT Programme Manager, and Andreas Kaufer, the Director of the La Silla Paranal Observatory.

Highlights of the ceremony included the sealing of a time capsule prepared by ESO. The contents include a poster of photographs of current ESO staff and a copy of the book describing the future scientific goals of the telescope.

In her speech, the President emphasised: “With the symbolic start of this construction work, we are building more than a telescope here: it is one of the greatest expressions of scientific and technological capabilities and of the extraordinary potential of international cooperation.”

Tim de Zeeuw from ESO said: “The ELT will produce discoveries that we simply cannot imagine today, and it will surely inspire numerous people around the world to think about science, technology and our place in the Universe. This will bring great benefit to the ESO Member States, to Chile, and to the rest of the world.”

With a main mirror 39 metres in diameter, the Extremely Large Telescope (ELT) will be the largest optical/infrared telescope in the world and will take telescope engineering into new territory. It will be housed in an enormous rotating dome 85 metres in diameter — comparable in area to a football pitch.

The ELT will be the biggest “eye” ever pointed towards the sky and may revolutionise our perception of the Universe. It will tackle a wide range of scientific challenges, including probing Earth-like exoplanets for signs of life, studying the nature of dark energy and dark matter, and observing the Universe’s early stages to explore our origins. It will also raise new questions we cannot conceive of today, as well as improving life here on Earth through new technology and engineering breakthroughs.

The ELT is one of the biggest global science collaborations in history and includes an £88 million investment by the UK government. UK industry has already won over £10 million worth of contracts from the E-ELT and that figure is expected to at least match the UK government’s investment by the time construction is complete.

The most recent UK success has been the appointment of Teledyne e2v, based in Chelmsford, who have been awarded a multi-million euro contract to design and produce a set of Large Visible Sensor Modules for use on the telescope. In order for the telescope to capture the Universe in exquisite detail, the ELT will use highly sophisticated adaptive optics systems which will enable it to adjust for changes in the atmosphere above it. Each sensor, with a size of 800 x 800 pixels, will employ Teledyne e2v’s CMOS technology to permit the ELT’s adaptive optics systems to make tiny adjustments around 700 times a second to compensate for variations in Earth’s atmosphere. This will ensure that the resulting astronomical images — of exoplanets, distant galaxies and everything in between — will benefit from the highest resolution possible.

Other elements of the ELT project involving the UK include a team made up of members from the University of Oxford and STFC’s UK Astronomy Technology Centre leading on one of the first instruments for the telescope, a spectrograph called HARMONI. This instrument will provide the ELT with a sensitivity that is up to hundreds of times better than any current telescope of its kind.

The ELT is targeted to see first light in 2024. The laying of the first stone marks the dawn of a new era of astronomy.


Becky Parker
STFC Media Officer
Tel: 07808 879294

Notes to editors

The dome will have a total mass of around 5000 tonnes, and the telescope mounting and tube structure will have a total moving mass of more than 3000 tonnes. Both of these structures are by far the largest ever built for an optical/infrared telescope and dwarf all existing ones, making the ELT truly the world’s biggest eye on the sky.

One year ago, ESO signed a contract with the ACe Consortium, consisting of Astaldi, Cimolai and the nominated sub-contractor EIE Group, for the construction of the dome and telescope structure (eso1617). This was the largest contract ever awarded by ESO and also the largest contract ever in ground-based astronomy.

The Teledyne e2v contract will last for four years, and consists of two stages. In the initial phase, sample sensors will be designed and manufactured to demonstrate proof of concept. Then a total of 28 sensors will be manufactured at Teledyne e2v’s site in Chelmsford, UK, most of which will be installed in planned ELT instruments and others will be deployed when needed. 

More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile.

ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor.

At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.


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