European
Southern
Observatory

About | Timeline
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2025 (planned)
Dome complete

ELT's dome is completed.

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2025 (planned)
Technical first light of the ELT

ELT has its technical first light.

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2025 (planned)
Main mirror segments installation

ELT's main mirror segments are being installed.

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2025 (planned)
M4 adaptive unit complete

ELT's M4 mirror is completed. Its diameter is 2.4 metres

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2024 (planned)
Tertiary mirror complete

ELT's tertiary mirror is completed. Its diameter is 3.75 metres.

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2023 (planned)
Telescope structure complete

ELT's telescope structure is completed. Its weight is 2800 tonnes.

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2023 (planned)
M5 mirror complete

ELT's M5 mirror is completed. Its diameter is 2.7 x 2.1 metres

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2022 (planned)
Secondary mirror complete

The ELT's secondary mirror is completed. With a diameter of 4.25 metres, the secondary mirror will be the largest in the world.

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2021 (planned)
First main mirror segment polished

The first of the 798 segments for the ELT primary mirror is polished.

2025 (planned)
Dome complete
2025 (planned)
Technical first light of the ELT
2025 (planned)
Main mirror segments installation
2025 (planned)
M4 adaptive unit complete
2024 (planned)
Tertiary mirror complete
2023 (planned)
Telescope structure complete
2023 (planned)
M5 mirror complete
2022 (planned)
Secondary mirror complete
2021 (planned)
First main mirror segment polished
2019
First 18 ELT Primary Mirror Blanks Arrive at Safran Reosc
May 2018
Dome and main structure start
9 Jan 2018
First ELT main mirror segments successfully cast
25 May 2016
Contract awarded for construction of dome and main telescope structure
10 Dec 2015
Agreement Signed for MAORY
28 Sep 2015
Agreement Signed for METIS
23 Sep 2015
Agreement Signed for HARMONI
18 Sep 2015
Agreement Signed for MICADO
4 Dec 2014
Green light given for ELT construction
19 Jun 2014
Part of Cerro Armazones peak flattened to make space for ELT
14 Mar 2014
Construction begins on road to Cerro Armazones
27 Oct 2013
Land around Cerro Armazones donated to ESO for the ELT site
11 Jun 2012
ESO Council approves ELT programme
13 Oct 2011
ESO and Chile sign agreement on ELT
26 Apr 2010
Cerro Armazones selected as site for ELT
11 Dec 2006
Green light given for detailed ELT study