The European Extremely Large Telescope (E-ELT,
officially renamed the Extremely Large Telescope or ELT) is
a 39.3-meter adaptive optics, segmented-mirror-reflecting
extremely large telescope under construction
by the European Southern Observatory on top of Cerro Armazones, Chile
(altitude: 3046 meters), in the Atacama Desert.
When done, it will be the largest optical telescope
ever, by a substantial margin, able to carry out unprecedented
observations.
It is a new site, about 1 km from the existing
Cerro Armazones Observatory,
but it will be operated out of ESO's Paranal Observatory,
which is about 20 km distant.
Ground construction began in 2017 and
as of 2023, first light is targeted for 2028.
Some instruments under development:
MICADO aka ELT-CAM - Multi-adaptive optics Imaging Camera for Deep Observations.
METIS aka ELT-MIDIR - mid infrared imager and spectrograph.
MORFEO - Multiconjugate Adaptive Optics Relay For ELT Observations (formerly named MAORY for Multi-conjugate Adaptive Optics Relay).
MOSAIC aka ELT-MOS - multipurpose multi-object spectrograph, a follow-on to the earlier plan, EAGLE.
ANDES - Armazones high DispersionEchelle Spectrograph: a high resolution high stability spectrograph (former names HIRES aka ELT-HIRES, and a follow-on to an earlier plan called CODEX).
Some concepts published in the past (likely canceled, subsumed, renamed,
or postponed):