Thirty Meter Telescope

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Thirty Meter Telescope (Proposed)

Rendering of the Thirty Meter Telescope design as of 2012
Location Mauna Kea Observatory 13 North[2][3]
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[4]
Altitude 4,050 m or 13,290 ft[3]
Wavelength Near UV, visible, and Mid-IR (0.31–28 μm)
Built planned (est. completion 2018)
Telescope style Segmented Ritchey–Chrétien telescope
Diameter 30 m or 98 ft
Collecting area 655 m2 or 7,050 sq ft[3]
Focal length f/15 (450 m)[3]:52
Mounting Altitude/azimuth
Dome Spherical calotte
Website www.tmt.org

The Thirty Meter Telescope (TMT) is a planned ground-based large segmented mirror reflecting telescope, proposed to be built on Mauna Kea in Hawaii. The telescope is proposed to be much larger than existing telescopes (though the planned European Extremely Large Telescope's mirror is 30% larger), and designed for observations from the near-ultraviolet to the mid-infrared (0.31 to 28 μm wavelengths). In addition, its adaptive optics system would help correct for image blur caused by the atmosphere of the Earth, helping it to reach the potential of such a large mirror.

The telescope was given approval by the state Board of Land and Natural Resources in April 2013,[5] and is now awaiting a determination by the Intermediate Court of Appeals of the State of Hawaiʻi.[6]

Science case

Mauna Kea and surrounding islands from space[1]

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:[7]

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

Observatory design

The TMT began in the 1990s as the California Extremely Large Telescope, and due to a positive response continued to be developed.[8] 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).[9]

Telescope

Thirty Meter Telescope design (late 2007)

The centerpiece of the TMT Observatory will be a Ritchey-Chrétien telescope with a 30 meter diameter primary mirror. This mirror will 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.

A 3 m secondary mirror produces an unobstructed field-of-view of 20 arcminutes in diameter with a focal ratio of 15. A flat tertiary mirror will direct the light path to science instruments mounted on large Nasmyth platforms.

The telescope will 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.

The TMT moving mass (including instruments) is almost 2000 tonnes.

This design descends from the successful W. M. Keck Observatory.

Adaptive optics

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

Early-light capabilities

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.[10]
  • 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

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)

Location

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.[11][12] 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 was very likely to be doing so in Chile, and if both next-generation telescopes were in the same hemisphere, there would be many astronomical objects that neither could observe.

Approval talks

Mauna Kea silversword near summit

The telescope was given approval by the state Board of Land and Natural Resources in April 2013.[13] However, at one point there was opposition in Hawaii to the building of the telescope,[14] 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,[15] and to the fact that Mauna Kea is a sacred site for the Native Hawaiian culture.[16][17] 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.[18] 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.[19] "

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.[20]

Partnership

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.[21] Construction is expected to commence immediately thereafter, leading to initial science operations in 2018.[21] 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.[22]
  • In 2009, the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) joined TMT as an Observer.[23][24]
  • 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.[25][26]

Japan, which has its own large telescope at Mauna Kea, the 8.3-metre Subaru, is also a partner.[27]

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

Funding

The telescope cost was estimated in 2009 to be $970 million[28] to $1.2 billion;[11] 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

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

References

General

  1. http://www.tmt.org/foundation-docs/TMT-DSC-2007-R1.pdf
  2. http://www.astro.utoronto.ca/acura/en/index.html

Specific

  1. ↑ Hawaii January 29, 2014
  2. ↑ Thirty Meter Telescope Selects Mauna Kea, TMT Observatory Corporation, 2009-07-21, retrieved 2009-07-24 
  3. ↑ 3.0 3.1 3.2 3.3 Thirty Meter Telescope Construction Proposal, TMT Observatory Corporation, 2007-09-12, p. 29, retrieved 2009-07-24 
  4. ↑ Sanders, Gary H (2005-01-11), [79.03] The Thirty Meter Telescope (TMT) Project, p. 17 
  5. ↑ "Massive telescope to be built in Hawaii". 3 News NZ. April 15, 2013. 
  6. ↑ http://bigislandweekly.com/sections/news/uncertain-future-mauna-kea.html
  7. ↑ http://www.tmt.org/sites/default/files/TMT-DSC-2007-R1.pdf
  8. ↑
  9. ↑ http://www.tmt.org/foundation-docs
  10. ↑ "IRIS Home Page". Irlab.astro.ucla.edu. 2010-10-05. Retrieved 2013-07-31. 
  11. ↑ 11.0 11.1 Schmidt, Klaus (July 22, 2009). "Hawaii chosen to host world's largest telescope". Space Fellowship. Retrieved 18 October 2010. 
  12. ↑ McAvoy, Audrey (July 21, 2009), "World's largest telescope to be built in Hawaii", Washington Post 
  13. ↑ "Massive telescope to be built in Hawaii". 3 News NZ. April 15, 2013. 
  14. ↑ "Hearing on Hawaii Thirty Meter Telescope to continue next week - Pacific Business News". Bizjournals.com. 2011-08-19. Retrieved 2013-07-31. 
  15. ↑ "Summit Ecosystems — KAHEA". Kahea.org. Retrieved 2013-07-31. 
  16. ↑ "Sacred Landscape — KAHEA". Kahea.org. Retrieved 2013-07-31. 
  17. ↑ "Hawaii Tribune Herald". Hawaii Tribune Herald. Retrieved 2013-07-31. 
  18. ↑ "For the Love of Mauna Kea — KAHEA". Kahea.org. Retrieved 2013-07-31. 
  19. ↑ http://www.state.hi.us/dlnr/swat/Land/Ch13-5.pdf
  20. ↑ "TMT Takes Step Towards Construction after Approval by the Board of Land and Natural Resources | Thirty Meter Telescope". Tmt.org. 2013-04-13. Retrieved 2013-07-31. 
  21. ↑ 21.0 21.1 Thirty Meter Telescope operations page, TMT Observatory Project, retrieved 2010-10-12 
  22. ↑ "Thirty Meter Telescope". Tmt.org. 2009-04-01. Retrieved 2012-08-06. 
  23. ↑ "Thirty Meter Telescope". Tmt.org. 2009-11-17. Retrieved 2012-08-06. 
  24. ↑ "China, India to jump forward with Hawaii telescope". Associated Press. Retrieved January 12, 2012. 
  25. ↑ "Construction of 30-meter optical telescope to begin next year". The Economic Times. 23 January 2013. Retrieved 23 January 2013. 
  26. ↑ "China, India to work for largest telescope". The Hindu. Retrieved January 13, 2012. 
  27. ↑ "India Joins Thirty Meter Telescope Project | Thirty Meter Telescope". Tmt.org. 2010-06-24. Retrieved 2012-08-06. 
  28. ↑ Mann, Adam (November 16, 2009). "Titanic Thirty Meter Telescope Will See Deep Space More Clearly". Wired. Retrieved 18 October 2010. 

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