A large reflector planned by the US, Japan, China, India, and Canada on Mauna Kea, Hawaii, that will operate at visible to mid-infrared wavelengths (0.3–30 μ‎m). It will have a mirror of 30 m diameter consisting of 492 hexagonal segments each 1.44 m wide and is planned to come into operation in 2024.

http://www.tmt.org/ Official telescope website.