The European Extremely Large Telescope (E-ELT) will be a ground-based astronomical observatory with a 42-meter diameter segmented mirror. The design features a filled aperture mirror with an area of 1,300 m².[1] On 26 April 2010, the European Southern Observatory (ESO) Council selected Cerro Armazones, Chile, as the baseline site for the planned E-ELT.[2] The telescope's "eye" will be almost half the length of a soccer pitch in diameter and will gather 15 times more light than the largest optical telescopes operating today. The telescope has an innovative five-mirror design that includes advanced adaptive optics to correct for the turbulent atmosphere, giving exceptional image quality. The main mirror will be made up from almost 1000 hexagonal segments. If completed it will become the largest of a new generation of Extremely Large Telescopes.

Although with significantly less area and aperture than the E-ELT, the 25 m/368 m² Giant Magellan Telescope and 30 m/655 m² TMT are also targeting 2018 for completion.

European Extremely Large Telescope (E-ELT)

Artist's Impression of the  E-ELT  Design
Organization ESO
Location Cerro Armazones, Chile, near Paranal Observatory
Coordinates 24°35′20″S 70°11′32″W / 24.58889°S 70.19222°W / -24.58889; -70.19222Coordinates:   / -24.58889; -70.19222
Altitude 2701m
Wavelength Optical, near infrared
Built Planned completion: 2018
Telescope style Reflector
Diameter 42 m (138 ft)
Angular resolution 0.001 to 0.6 arcseconds depending on target and instruments used
Collecting area 1300 m2
Focal length 420-840 m (f/10 - f/20)
Mounting Alt/az
Dome Spherical
Website http://www.eso.org/public/astronomy/projects/e-elt.html



  Goals and Planning

The ESO is focusing on this design after a feasibility study concluded the proposed 100 metres (330 ft) diameter Overwhelmingly Large Telescope would cost €1.5 billion (£1 billion), and be too complex. Current fabrication technology limits single mirrors to being roughly 8 metres (26 ft) in a single piece. The next-largest telescopes currently in use are the Gran Telescopio Canarias and Southern African Large Telescope, which each use hexagonal mirrors fitted together to make a mirror more than 10 metres (33 ft) across. The E-ELT would need to use a similar design. In addition, the E-ELT would also need to use techniques to work around atmospheric distortion of incoming light, known as adaptive optics (AO).

Project E-ELT has the aim of observing the Universe in greater detail than even the Hubble Space Telescope. A mirror of approximately 42 metres (138 ft) would allow the study of the atmospheres of extrasolar planets.[citation needed] The E-ELT is now planned in the Astronet Infrastructure Roadmap, and “is currently going through a Phase B study that will end with a Final Design Review of the whole facility in 2009/2010. This Phase B study includes contracts with industry to design and manufacture prototypes of key elements like the primary mirror segments, the adaptive fourth mirror or the mechanical structure. It also includes concept studies for eight instruments.”[3]

Because of the competition with some similar projects (in particular the Thirty Meter Telescope and the Giant Magellan Telescope), “the decision for the construction of the European ELT cannot be deferred later than 2010.”[3] The construction period is estimated to be 7–8 years leading to first light around 2018. The design phase of the 5-mirror anastigmat (€57M) is fully funded within the ESO budget, and the construction cost is estimated to be €960M (including first generation instruments). “About €350M for the construction phase are available within the existing budget integrated over a period of ten years. One of the goals of the preparatory phase is to study the possibilities for additional funding. Additional activities on the organisation of the project and the mission design are supported through a €5M FP7 grant.”[3]

The Future European Extremely Large Telescope.

Diagram of the E-ELT primary mirror.

The E-ELT from above.

The E-ELT and VLT sizes compared with Brandenburg Gate.

E-ELT compared with one of the four existing "unit telescopes" at Cerro Paranal (Chile).

Telescope at work, with its dome open and its record-setting 42-metre primary mirror pointed to the sky.


Model of the gigantic and intricate structure inside the enclosure of the E-ELT.

Eight different instrument concepts and two post-focal AO modules are currently being studied, with the aim that two to three will be ready for first light, with the others becoming available at various points over the following decade.[4] The instruments being studied are:

  • CODEX: a very high resolution optical spectrograph[5]
  • EAGLE: a wide-field, multiple integral field unit near-infrared (NIR) spectrograph, with multi-object adaptive optics[6]
  • EPICS: a optical/NIR planet imager and spectrograph with extreme AO[7]
  • HARMONI: a single field, wide-band spectrograph
  • METIS: a mid-infrared imager and spectrograph
  • MICADO: a diffraction-limited near-infrared camera
  • OPTIMOS: a wide-field visual multi-object spectrograph
  • SIMPLE: a high spectral resolution NIR spectrograph

The two post-focal AO modules currently being studied are:

Night-time panorama of Cerro Armazones, the site selected in April 2010 for the European Extremely Large Telescope


On 26 April 2010, the ESO Council selected Cerro Armazones as the site for the planned E-ELT.[2]

Other sites that were under discussion included Cerro Macon, Salta, in Argentina; Roque de los Muchachos Observatory, on the Canary Islands; and sites in South Africa, Morocco, and Antarctica.

  See Also


  1. ^ http://www.eso.org/public/astronomy/teles-instr/e-elt_num.html
  2. ^ a b "E-ELT Site Chosen". Europe: ESO. 26 April 2010. http://www.eso.org/public/news/eso1018/. Retrieved 26 April 2010. 
  3. ^ a b c Astronet, 2008, The astronet Infrastructure Roadmap: A Strategic Plan for European Astronomy, p. 43
  4. ^ "E-ELT Instrumentation". http://www.eso.org/sci/facilities/eelt/instrumentation/index.html. Retrieved 2009-10-29. 
  5. ^ Pasquini, Luca; et al. (2008). CODEX: the high-resolution visual spectrograph for the E-ELT. SPIE. doi:10.1117/12.787936. http://www.eso.org/sci/libraries/SPIE2008/7014-52.pdf. 
  6. ^ "EAGLE: the Extremely Large Telescope Adaptive Optics for Galaxy Evolution instrument". http://eagle.oamp.fr/spip/. Retrieved 2009-10-29. 
  7. ^ Kasper, Markus E.; et al. (2008). "EPICS: the exoplanet imager for the E-ELT". Adaptive Optics Systems - Proceedings of the SPIE, Volume 7015. SPIE. pp. 70151S-70151S-12. doi:10.1117/12.789047. http://adsabs.harvard.edu/abs/2008SPIE.7015E..46K. 

  External Links

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Categories: Telescopes | Astronomical observatories in Chile | European Southern Observatory