European Extremely Large Telescope

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.
• HARMONI aka ELT-IFU - wide-band spectrograph.
• 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 Dispersion Echelle 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):

• EPICS - NIR spectrograph.
• OPTIMOS - wide-field multi-object spectrograph.
• SIMPLE - high-resolution NIR spectrograph.