Thirty meter telescope

Thirty Meter Telescope
(postponed)

Artist's rendering of proposed telescope
Organisation	TMT International Observatory
Location(s)	(This is a proposed project) for Mauna Kea Observatory, Hawaii, United States
Coordinates	19°49′58″N 155°28′54″W / 19.8327°N 155.4816°W / 19.8327; -155.4816Coordinates: 19°49′58″N 155°28′54″W / 19.8327°N 155.4816°W / 19.8327; -155.4816
Altitude	4,050 m or 13,290 ft
Wavelength	Near UV, visible, and Mid-IR (0.31–28 μm)
Built	Postponed
First light	est. 2022 (prior to permit problem)
Telescope style	Segmented Ritchey–Chrétien telescope
Diameter	30 m or 98 ft
Secondary dia.	3.1 m or 10 ft
Tertiary dia.	2.5 m × 3.5 m or 8.2 ft × 11.5 ft
Collecting area	655 m2 or 7,050 sq ft
Focal length	f/15 (450 m)
Mounting	Altazimuth mount
Enclosure	Spherical calotte
Website	www.tmt.org
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The Thirty Meter Telescope (TMT) is a proposed astronomical observatory with an extremely large telescope (ELT) that has become the source of controversy over its planned location on Mauna Kea in the US state of Hawaii. Construction of the TMT on land which is claimed to be sacred to Native Hawaiian culture and religion, attracted international coverage after October 2014, when construction was temporarily halted voluntarily due to protests. While construction of the telescope was set to resume on April 2 and later on June 24, 2015, it was blocked by further protests each time. While it was approved by the Board of Land and Natural Resources, the State Supreme Court of Hawaii invalidated the TMT's building permits in December 2015, ruling that due process was not followed when the board approved the permits. Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain may be the alternative site if construction cannot go forward in Hawaii. The TMT will be the last area on Mauna Kea on which any telescope will ever be built.

Scientists have been considering ELTs since the mid 1980s. In 2000, astronomers considered the possibility of a telescope with a light-gathering mirror larger than 20 meters in diameter. The technology to build a mirror larger than 8.4 meters does not exist; instead scientists considered using either small segments that create one large mirror, or a grouping of larger 8-meter mirrors working as one unit. The US National Academy of Sciences recommended a 30-meter telescope be the focus of U.S. interests, seeking to see it built within the decade. Scientists at the University of California and Caltech began development of a design that would eventually become the TMT, consisting of 492 segmented mirrors with nine times the power of the Keck telescope. Due to its immense light-gathering power and the optimal observing conditions which exist atop Mauna Kea, the TMT would enable astronomers to conduct research which is unfeasible with current instruments. The TMT is designed for near-ultraviolet to mid-infrared (0.31 to 28 μm wavelengths) observations, featuring adaptive optics to assist in correcting image blur. The TMT will be at the highest altitude of all the proposed ELTs. The telescope has government-level support from several R&D spending nations: China, Japan, Canada and India.