Thirty Meter Telescope

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Thirty Meter Telescope (Under construction)
Top view of tmt complex.jpg
Rendering of the Thirty Meter Telescope design as of 2012
Organization TMT International Observatory
Location Mauna Kea Observatory 13 North[1][2]
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[3]
Altitude 4,050 m or 13,290 ft[2]
Wavelength Near UV, visible, and Mid-IR (0.31–28 μm)
Built 2014-2020[4]
First light est. 2022[4]
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[2]
Focal length f/15 (450 m)[2]:52
Mounting Altitude/azimuth
Dome Spherical calotte

The Thirty Meter Telescope (TMT) is a ground-based large segmented mirror reflecting telescope under construction on Mauna Kea in Hawaii. The telescope is designed for observations from near-ultraviolet to mid-infrared (0.31 to 28 μm wavelengths). In addition, its adaptive optics system will help correct for image blur caused by the atmosphere of the Earth, helping it to reach the potential of such a large mirror.

Amongst existing and planned extremely large telescopes, the TMT will have by far the highest altitude, and will be the second-largest telescope after the E-ELT, both of which use arrays of small 1.44 m hexagonal mirrors — a design vastly different from the large mirrors of the LBT or GMT.[5] The TMT is the only such telescope with government-level support from the three largest R&D spending nations: United States, China, Japan — as well as other top R&D nations including Canada and India.[6]

The telescope was given approval by the state Board of Land and Natural Resources in April 2013,[7] as well as the Intermediate Court of Appeals of the State of Hawai'i.[8] Construction of the telescope began on July 28, 2014[9] and the dedication and ground-breaking ceremony was held on October 7, 2014.[10]

Science case[edit]

Mauna Kea and surrounding islands from space[11]

TMT would be a general purpose observatory capable of investigating a broad range of astrophysical problems. A science case prepared by the TMT Foundation outlines the following aims for the observatory:[12]

By design, TMT complements the scientific capabilities of the James Webb Space Telescope and Atacama Large Millimeter Array.

Observatory design[edit]

The TMT began in the 1990s as the California Extremely Large Telescope, and due to a positive response continued to be developed.[13] The project changed its name to Thirty Meter Telescope in 2003-4 as the scope of development partners evolved, including a merger with the Canadian VLOT project and the GSMT.

A description of the TMT Observatory design can be found in the TMT Construction Proposal (2007).[14]


Thirty Meter Telescope design (late 2007).

The centerpiece of the TMT Observatory is to be a Ritchey-Chrétien telescope with a 30-metre (98 ft) diameter primary mirror. This mirror is to be segmented and consist of 492 smaller (1.4 m), individual hexagonal mirrors. The shape of each segment, as well as its position relative to neighboring segments, will be controlled actively.[citation needed]

A 3-metre (9.8 ft) secondary mirror is to produce an unobstructed field-of-view of 20 arcminutes in diameter with a focal ratio of 15. A flat tertiary mirror is to direct the light path to science instruments mounted on large Nasmyth platforms.[citation needed]

The telescope is to have an altitude-azimuth mount. This mount will be capable of repositioning the telescope between any two points of the sky in less than 5 minutes, with a precision of 2.0 arcseconds or better. Once the celestial object is acquired, the telescope will track its motion with a precision of a few milliarcseconds.[citation needed]

The TMT moving mass (including instruments) is almost 2000 tonnes.[citation needed]

The design of the facility descends from the successful W. M. Keck Observatory.[citation needed]

Adaptive optics[edit]

Integral to the observatory is a Multi-Conjugate Adaptive Optics (MCAO) system. This MCAO system will measure atmospheric turbulence by observing a combination of natural (real) stars and artificial laser guide stars. Based on these measurements, a pair of deformable mirrors will be adjusted many times per second to correct optical wavefront distortions caused by the intervening turbulence.

This system will produce diffraction-limited images over a 30 arcsecond diameter field-of-view. For example, the core of the point spread function will have a size of 0.015 arcsecond at a wavelength of 2.2 micrometers, almost 10 times better than the Hubble Space Telescope.

Scientific instrumentation[edit]

Early-light capabilities[edit]

Three instruments are planned to be available for scientific observations:

  • Wide Field Optical Spectrometer (WFOS) providing near-ultraviolet and optical (0.3–1.0 μm wavelength) imaging and spectroscopy over a more than 40 square arcminute field-of-view. Using precision cut focal plane masks, WFOS would enable long-slit observations of single objects as well as short-slit observations of hundreds of objects simultaneously. WFOS would use natural (uncorrected) seeing images.
  • Infrared Imaging Spectrometer (IRIS) mounted on the observatory MCAO system, capable of diffraction-limited imaging and integral-field spectroscopy at near-infrared wavelengths (0.8–2.5 μm). Principal investigators are James Larkin of UCLA and Anna Moore of Caltech. Project scientist is Shelley Wright of the University of Toronto.[15]
  • Infrared Multi-object Spectrometer (IRMS) allowing close to diffraction-limited imaging and slit spectroscopy over a 2 arcminute diameter field-of-view at near-infrared wavelengths (0.8–2.5 μm).

Additional first-decade capabilities[edit]

For planning purposes, TMT has developed concepts for an additional six instruments, which it proposes to be deployed during the first decade of science operations. These plans have been reviewed and updated on a roughly bi-annual basis starting in 2010.

In no order of preference, planned additional scientific capabilities include:

  • Extremely high contrast (1 part in 108 @ 1.65 μm) exoplanet imaging and spectroscopy at near-infrared wavelengths
  • Diffraction-limited echelle spectroscopy (resolving power ~ 25 000) at near-infrared wavelengths (1.0–2.5 μm)
  • Diffraction-limited imaging and echelle spectroscopy (resolving power ~ 50,000) at mid-infrared wavelengths (8–28 μm)
  • High precision (~0.01 arcsecond) astrometric imaging and (<<0.001 arcsecond) astrometry at near-infrared wavelengths (1.0–2.5 μm)
  • Multiple integral-field unit spectrometers deployable over a 5 arcminute diameter field-of-view, each with individual adaptive optics correction, at near-infrared wavelengths (1.0–2.5 μm)


Mauna Kea peak

In cooperation with AURA, the TMT project completed a multi-year evaluation of five sites:

The TMT Observatory Corporation board of directors narrowed the list to two sites, one in each hemisphere, for further consideration: Cerro Armazones in Chile's Atacama Desert, and Mauna Kea on Hawai'i Island. On July 21, 2009 the TMT Board selected Mauna Kea as the preferred site.[16][17] The final TMT site selection decision was based on a combination of scientific, financial, and political criteria; ESO is also building a very large telescope E-ELT, and is doing so in Chile. If both next-generation telescopes were in the same hemisphere, there would be many astronomical objects that neither could observe.

Approval talks[edit]

The telescope was given approval by the state Board of Land and Natural Resources in April 2013.[7] However, there was some opposition in Hawaii to the building of the telescope,[18] based on potential disruption to the fragile glacial environment of Mauna Kea due to construction, traffic and noise, which is a concern for habitat disruption of several species,[19] and to the fact that Mauna Kea is a sacred site for the Native Hawaiian culture.[20][21] Hawaiian cultural practitioners cite impacts to indigenous cultural practice, while recreational users have argued that construction harms the scenic viewplane, and environmentalists are concerned that irreparable ecological damage may be done by construction. All three groups are represented amongst the petitioners opposing the TMT.[22] According to State of Hawaiʻi law HAR 13-5-30, eight key criteria must be met before construction can be allowed on conservation lands in Hawaiʻi. Among other criteria, the development may not “cause substantial adverse impact to existing natural resources within the surrounding area, community, or region,” and the "existing physical and environmental aspects of the land must be preserved or improved upon.[23] "

The Hawaii Board of Land and Natural Resources conditionally approved the Mauna Kea site for the TMT in February 2011. The approval has been challenged; however, the Board officially approved the site following a hearing on February 12, 2013, and the TMT Foundation anticipates that construction will begin in April 2014.[24]

The construction phase began on July 28, 2014.[25]

A groundbreaking ceremony on October 7, 2014 was disrupted by protesters.[26]


Sunset over four current telescopes of Mauna Kea Observatories. From left to right: Subaru, the two Kecks, and IRTF

The TMT Observatory Corporation is a partnership between:

The current US$80 million, five-year design and development program is planned for completion in 2012.[27] Construction is expected to commence immediately thereafter, leading to initial science operations in 2018.[27] The Gordon and Betty Moore Foundation has committed US$200 million for construction. Caltech and University of California have committed an additional US$50 million each. TMT is actively seeking additional major partners for the construction and operations phase.

  • In 2008, the National Astronomical Observatory of Japan (NAOJ) joined TMT as a Collaborating Institution.[28]
  • In 2009, the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) joined TMT as an Observer.[29][30]
  • In 2010, a consortium of Indian Astronomy Research Institutes (IIA, IUCAA and ARIES) joined TMT project as an observer. The observer status is the first step in becoming a full partner in TMT and participating in the engineering development and scientific use of the observatory (Subject to approval of funding from Indian Government).
  • In 2012, India and China became partners, with representatives on the TMT board. China and India will pay a share of the telescope construction costs, expected to top $1 billion.[31][32]

Japan, which has its own large telescope at Mauna Kea, the 8.3-metre Subaru, is also a partner.[33]

TMT has received design and development funding from the following public and private organizations:


The telescope cost was estimated in 2009 to be $970 million[34] to $1.4 billion;[16] the funding had not been completely raised by mid-2011, although $100 million had already been spent on design, engineering and site-assessment work.


Comparison of nominal sizes of primary mirrors of the Thirty Meter Telescope and some notable optical telescopes (click for detail)
Hubble floats free after its 2009 servicing

At wavelengths longer than 0.8 μm, adaptive optics correction would enable observations with ten times the spatial resolution of the Hubble Space Telescope. TMT would be more sensitive than existing ground-based telescopes by factors of 10 (natural seeing mode) to 100 (adaptive optics mode). If completed on schedule, TMT could be the first of the new generation of Extremely Large Telescopes.

See also[edit]




  1. ^ Thirty Meter Telescope Selects Mauna Kea, TMT Observatory Corporation, 2009-07-21, retrieved 2009-07-24 
  2. ^ a b c d Thirty Meter Telescope Construction Proposal, TMT Observatory Corporation, 2007-09-12, p. 29, retrieved 2009-07-24 
  3. ^ Sanders, Gary H (2005-01-11), [79.03] The Thirty Meter Telescope (TMT) Project, p. 17 
  4. ^ a b Callis, Tom (29 July 2014). "TMT to begin construction". West Hawaii Today. 
  5. ^ Anderson, Mark (13 March 2014). "The Billion-Dollar Telescope Race". Nautilus. New York: NautilusThink. 
  6. ^ "Megascope member". Seven Days. Nature (paper) 516 (7530): 148. 11 December 2014. India announced on 2 December that it will become a full partner in the Thirty Meter Telescope.... 
  7. ^ a b "Massive telescope to be built in Hawaii". 3 News NZ. April 15, 2013. 
  8. ^ Jamie Winpenny (2013-06-26). "The Uncertain Future of Mauna Kea". Big Island Weekly. Retrieved 2014-03-11. 
  9. ^ Next-Generation "Thirty Meter Telescope Begins Construction in Hawaii". TMT. 
  10. ^ Beatty, J. Kelly. "Work begins on Thirty Metre Telescope". Australian Sky & Telescope (Odysseus Publishing Pty Ltd) (83): 11. ISSN 1832-0457. 
  11. ^ "Hawaii : Image of the Day". Retrieved 2014-03-11. 
  12. ^ "Thirty Meter Telescope Detailed Science Case : 2007". Retrieved 2014-03-11. 
  13. ^ "UC Santa Cruz astronomers forge ahead on giant telescope project". Archived from the original on 2002-02-20. 
  14. ^ "TMT Foundation Documents". Archived from the original on 2009-08-23. 
  15. ^ "IRIS Home Page". 2010-10-05. Retrieved 2013-07-31. 
  16. ^ a b Xin, Ling (October 9, 2014). "TMT opening ceremony interrupted by protests". Science. Retrieved 10 October 2014. 
  17. ^ McAvoy, Audrey (July 21, 2009), "World's largest telescope to be built in Hawaii", Washington Post [dead link]
  18. ^ "Hearing on Hawaii Thirty Meter Telescope to continue next week - Pacific Business News". 2011-08-19. Retrieved 2013-07-31. 
  19. ^ "Summit Ecosystems — KAHEA". Retrieved 2013-07-31. 
  20. ^ "Sacred Landscape — KAHEA". Retrieved 2013-07-31. 
  21. ^ "Hawaii Tribune Herald". Hawaii Tribune Herald. Retrieved 2013-07-31. 
  22. ^ "For the Love of Mauna Kea — KAHEA". Retrieved 2013-07-31. 
  23. ^ "Conservation District". Retrieved 2014-03-11. 
  24. ^ "TMT Takes Step Towards Construction after Approval by the Board of Land and Natural Resources | Thirty Meter Telescope". 2013-04-13. Retrieved 2013-07-31. 
  25. ^ "Next-Generation Thirty Meter Telescope Begins Construction in Hawaii" (Press release). TMT Observatory Corporation. 27 July 2014. 
  26. ^ Callis, Tom (7 October 2014). "TMT groundbreaking disrupted". Hawaii Tribune-Herald. 
  27. ^ a b Thirty Meter Telescope operations page, TMT Observatory Project, retrieved 2010-10-12 
  28. ^ "Thirty Meter Telescope". 2009-04-01. Retrieved 2012-08-06. 
  29. ^ "Thirty Meter Telescope". 2009-11-17. Retrieved 2012-08-06. 
  30. ^ "China, India to jump forward with Hawaii telescope". Associated Press. Retrieved January 12, 2012. 
  31. ^ "Construction of 30-meter optical telescope to begin next year". The Economic Times. 23 January 2013. Retrieved 23 January 2013. 
  32. ^ "China, India to work for largest telescope". The Hindu. Retrieved January 13, 2012. 
  33. ^ "India Joins Thirty Meter Telescope Project | Thirty Meter Telescope". 2010-06-24. Retrieved 2012-08-06. 
  34. ^ Mann, Adam (November 16, 2009). "Titanic Thirty Meter Telescope Will See Deep Space More Clearly". Wired. Retrieved 18 October 2010. 

External links[edit]