The Thirty Meter Telescope as seen on its proposed site on the summit of Maunakea. (Credit: TMT International Observatory)

Name Thirty Meter Telescope
Site Maunakea, Hawaii, United States (proposed)
Full collaboration members Caltech, Department of Science and Technology of India, National Astronomical Observatories of the Chinese Academy of Sciences, National Institutes of Natural Sciences/National Astronomical Observatory of Japan, National Research Council Canada, University of California
Estimated first light 2026
Wavelength Near-ultraviolet, visible, near- and mid-infrared (0.31 – 28 μm)
Primary mirror aperture 30 metres
Total collecting area 655 square metres


The Long Range Plan (LRP) prepared in 2000 for the Canadian Astronomical Society (CASCA) identified the Very Large Optical Telescope project as a highest priority. A decade later, LRP 2010 confirmed this priority, and the Canadian astronomy community is now on track to realising this goal, with the Thirty Meter Telescope (TMT). Such a telescope will be able to see farther and better than ever before and as a result work well with the upcoming ground- and space-based missions such as the Square Kilometre Array (SKA) and the James Webb Space Telescope (JWST), Hubble’s successor.


The most recent decade has launched the era of Extremely Large Telescopes, or ELTs. These are the next logical step from the current fleet of today’s largest telescopes that have mirrors on the order of 8 to 10 m in diameter. The sheer magnitude of these projects requires international collaboration to leverage the knowledge and technological resources of several countries to build these facilities.

In the case of the TMT, over half the world’s population will be backing the facility through their countries’ involvement. Astronomers, engineers and scientists from Canada, the United States, China, India and Japan have joined together to design a scientific program to answer key questions about the structure and evolution of the Universe, search for exoplanets and life beyond the Earth and conceive and deliver the facility needed to accomplish this program. Canada’s involvement is at a level of 15%. The TMT project builds upon the vast experience of many of its partners in the conception and construction of telescopes and astronomical instruments. Furthermore, as with all astronomy projects, this gargantuan project will lead to many technological spinoffs that all partners will benefit from.


The TMT will study the Universe through both visible and infrared light. Following the success of current large segmented-mirror telescopes such as the Keck 10-m telescopes, the TMT’s primary mirror will consist of 492 hexagonal glass segments that each measure approximately 1.44 meters across. The telescope will have a 30-m total aperture. In order to make good use of this massive mirror and perform high-resolution photometry and spectroscopy, the TMT will rely on cutting-edge adaptive optics (AO) technology developed at the National Research Council (NRC) in Canada.

In addition to using very advanced AO technology, the TMT must be located at a carefully chosen site with specific atmospheric characteristics. In 2003, the TMT collaboration undertook the most comprehensive site testing campaign ever carried out for a new observatory over the course of five years to determine the best site for the TMT. Five candidate sites were initially considered in Chile, Mexico and on the summit of Maunakea in Hawaii. In 2009, the TMT collaboration selected Maunakea as the preferred site at an altitude of 4,100 metres to build and operate the TMT. Following issues in the 2010s with the TMT’s construction permit, the TMT collaboration identified Roque de los Muchachos Observatories in the Canary Islands, Spain as an alternative site to Maunakea


An artist’s concept of the TMT primary mirror which will consist of 492 hexagonal segments. (Credit: TMT International Observatory)

The telescope will be housed in an enclosure designed by Dynamic Structures, a Canadian company that has already been involved in the design and construction of most of the world’s largest observatories including the Canada France Hawaii Telescope and the Gemini North and South observatories.


An astronomical facility the size and caliber of the TMT must be designed to answer fundamental questions across a wide range of astrophysical fields including:

  • Fundamental Physics & Cosmology
  • Early Universe, Galaxy Formation and the Intergalactic Medium
  • Supermassive Black Holes
  • Milky Way and Nearby Galaxies
  • Stars, Stellar Physics and the Interstellar Medium
  • Formation of Stars and Planets
  • Exoplanets and the Search for Life
  • Our Solar System
  • Time Domain Science

With its impressive light-amassing potential, high-resolution capabilities and planned suite of cutting-edge instruments, the TMT will allow astronomers to study the farthest reaches of the Universe, up to the “dark ages” when the first sources of light were formed. Furthermore, it will enable the study of objects such as galaxies and massive black holes through time. It will also help astronomers better detect and characterise exoplanets, and may even lead to the first detections of biosignatures beyond Earth.


An artist’s concept of the TMT at night with its laser guide star system illuminated. (Credit: TMT International Observatory)


  • June 2003: Founding of the TMT Observatory Corporation by its partners: the Association of Canadian Universities for Research in Astronomy (ACURA), the University of California and the California Institute of Technology.
  • January 2008: The National Optical Astronomy Observatory of Japan joins the TMT collaboration as a participating member.
  • March 2009: Completion of the five-year Design Development Phase; $300 million secured for the project.
  • July 2009: TMT Board of Directors selects Maunakea in Hawaii as the preferred site for the observatory.
  • November 2009: The National Astronomical Observatories of the Chinese (NOAC) Academy of Sciences and the Indian Institute of Astrophysics (IIA) join the TMT collaboration as observers.
  • April 2013: The Hawaiian Board of Land and Natural Resources grants a building permit to the TMT project.
  • Octobre 2014: A ground blessing ceremony for the TMT is conducted on-site.
  • December 2014: India formally joins the TMT collaboration as a participating member.
  • March 2015: The TMT receives a Notice to Proceed regarding the project’s construction.
  • December 2015: Following a set of oral arguments presented to the Supreme Court against the construction of the TMT on Maunakea, the Hawaii Supreme Court revokes TMT’s construction permit.
  • March 2016: TMT officials begin studying alternate sites for the project in the event the observatory cannot be built on Maunakea. The Observatory del Roque de Los Muchachos in La Palma on the Canary Islands is selected soon after.
  • October 2018: Following a series of hearings, challenges and reports about Maunakea as the TMT’s site that began in 2016, the Hawaii Supreme Court affirms the TMT’s construction permit for Maunakea by majority decision.
  • June 2019: The TMT’s enclosure is completed and ready to be shipped from Canada.

The following timeline includes several planned steps that are subject to change.

  • June 2020: The enclosure installation set to begin on the TMT site.
  • March 2021: The telescope structure is completed and ready to be shipped from Japan.
  • February 2022: The installation of the observatory enclosure is completed.
  • September 2022: The secondary mirror is completed and shipped to the observatory.
  • November 2023: The observatory facility building is completed.
  • March 2024: The tertiary mirror is completed and shipped to the observatory.
  • October 2025: A first on-sky test of the primary mirror is performed using 40 segments at prime focus.
  • April-June 2026: Scientific instruments are ready for commissioning.
  • October 2026: An on-sky test with the full primary mirror with all 492 segments aligned and phased on sky is performed.
  • November 2026: First light using the AO system and the IRIS instrument
  • July 2027: First light completed. The TMT is ready for science!

For more information on the Thirty-Meter Telescope, please visit