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The Thirty Meter Telescope (TMT) will be a ground-based astronomical observatory with a 30m diameter segmented mirror capable of observations from the near-ultraviolet to the mid-infrared (0.31 to 28 microns). High spatial resolution (so-called diffraction-limited) images will be created using adaptive optics systems. TMT will be more sensitive than existing ground-based telescopes by factors of 10 (natural seeing mode) to 100 (diffraction-limited mode). If completed on schedule, TMT will be the first of the new generation of Extremely Large Telescopes.

Thirty Meter Telescope design (late 2007)

Science Case

A Detailed Science Case [1] for TMT is available.

TMT will be a general purpose observatory capable of investigating a broad range of astrophysical problems including:

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

Observatory design

A complete description of the TMT Observatory design can be found in the TMT Construction Proposal (2007) [2].

Telescope

Thirty Meter Telescope design (late 2007)

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

A 3m 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 shape of each mirror will be controlled actively.

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 moving TMT moving mass (including instruments) is almost 2000 metric tons.

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

Adaptive Optics

Integral to the observatory is a multi-conjugate adaptive optics system. This MCAO system will measure atmospheric turbulence by observing a combination of natural (real) 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 micron, almost 10 times better than the [[Hubble Space Telescope]].

Scientific instrumentation

Early-light capabilities

When TMT science operations begin, three instruments will be available for scientific observations.

The Wide Field Optical Spectrometer (WFOS) will provide 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 will enable long-slit observations of single objects as well as short-slit observations of hundreds of objects simultaneously. WFOS will use natural (uncorrected) seeing images.

The Infrared Imaging Spectrometer (IRIS) will be mounted on the observatory MCAO system and be capable of diffraction-limited imaging and integral-field spectroscopy at near-infrared wavelengths (0.8 – 2.5 μm).

The Infrared Multi-object Spectrometer (IRMS) will allow 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 to be deployed during the first decade of science operations. These plans will be 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 (0.0005 arcsecond) astrometric imaging 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

In cooperation with AURA, the TMT project has recently completed a multi-year site evaluation program.

The sites included in this program were:

  • Cerro Tolanchar, Antofagasta Region, Republic of Chile
  • Cerro Tolar, Antofagasta Region, Republic of Chile

The final TMT site selection decision will be based on a combination of scientific, financial, and political criteria. Local cultural sensitivities will also be an important part of any TMT site decision.

Partnership

The TMT Observatory Corporation is a partnership between:

  • Association of Canadian Universities for Research in Astronomy (ACURA) [3]

The current US$ 80 million, five year design and development program is planned for completion in 2009. Construction is expected to commence immediately thereafter, leading to initial science operations in the second half of the next decade. 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.

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

See also

References

  1. http://www.tmt.org/foundation-docs/TMT-DSC-2007-R1.pdf
  2. http://www.tmt.org/news/TMT-Construction%20Proposal-Public.pdf
  3. http://www.astro.utoronto.ca/acura/en/index.html


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