The Maunakea Spectroscopic Explorer in the current location of the Canada France Hawaii Telescope at sunset. (Credit: Doug Simons, CFHT Corporation)

Name Maunakea Spectroscopic Explorer
Site Maunakea, Hawaii, United States
Collaboration members Australia, Canada, France, Hawaii, China, India
Estimated first light 2029
Wavelength Visible and near-infrared (0.36 – 1.8 μm)
Primary mirror aperture 11.25 metres
Total collecting area 78.5 square metres


The Canada France Hawaii Telescope (CFHT) has been a pillar of astronomy on the summit of Maunakea since it began operations in 1979. Due to its privileged site, the CFHT has enjoyed decades of arguably the best air quality for astronomical observations in the world. As more and more large aperture optical telescopes are being built, the idea of revitalising the CFHT into a modern observatory with a large segmented-mirror telescope began to take shape. This project was first conceived as the Next Generation CFHT as a grassroots proposal in the Canadian Astronomical Society’s (CASCA) 2010 Long Range Plan (LRP). The National Research Council (NRC) of Canada undertook an initial feasibility study to determine the strength of the case for such a facility specialising in multi-object spectroscopy. This Maunakea Spectroscopic Explorer (MSE) project has since seen interest from an enlarged collaboration of international partners interested in taking the CFHT into the next era of ground-based telescopes via this route.


The MSE project enjoys a larger collaboration than the CFHT, bringing together Canada, France and Hawaii from the latter with the addition of Australia, China and India.

One of the key motivations for this project is to enable efficient follow-up of objects of interest found within the catalogues of the next-generation of survey telescopes. The Sloan Digital Sky Survey (SDSS) Telescope was a precursor to the era of large survey telescopes we are currently in which includes the Square Kilometre Array (SKA), Gaia, Euclid and the Large Synoptic Survey Telescope (LSST). The latter will be imaging the entire Southern sky ever three days, but has a fairly weak spectroscopic component, as is the case for most survey telescopes. The MSE will be able to provide optical and near-infrared spectroscopy for these imaged survey objects, and will help identify a smaller subset of objects that merit detailed study by specialised facilities such as the suite of extremely large telescopes being constructed in the next decade, including the Thirty Meter Telescope.


Since the MSE would be located in the same spot as the CFHT, the dome housing this 11.25-m telescope cannot be substantially larger than the one currently housing the 3.6-m CFHT. In order to do this, the CFHT’s rotating dome will be replaced by a Calotte enclosure — much like the one that will be constructed for the Thirty Meter Telescope — which is only 10% larger than the current size. The MSE enclosure would likely be designed and constructed 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, the Gemini North and South observatories and the upcoming Thirty Meter Telescope.

The MSE would use an altitude-azimuth telescope with a segmented 11.25-m primary mirror. Each of the 60 segments would measure 1.44-m across. The observatory would also make use of a wide field corrector design to both enable a wide field of view of 1.5  square degrees for the telescope and a reduction of atmospheric refraction in order to make the most out of the MSE site’s incredible image quality. Science instrumentation would be planned for both high-resolution spectroscopy (R = 20,000 to 30,000) and low- to mid-resolution spectroscopy (R = 2,000 to 6,000). Each mode would allow the collection of up to 4,000 spectra at once for efficient spectroscopic follow-up of multiple astronomical objects.


A cutaway view of the Maunakea Spectroscopic Explorer, showing the 11.25-m telescope in the new  Calotte enclosure. (Credit: Doug Simons, CFHT Corporation)


The MSE team has developed a Detailed Science Case which lays out the key science ambitions of 263 scientists representing the MSE community using this transformational facility. Broad areas of interest include:

  • Exoplanets and Stellar Astrophysics
  • Chemical Nucleosynthesis
  • The Milky Way and Resolved Stellar Populations
  • Astrophysical Tests of Dark Matter
  • Galaxy Formation and Evolution
  • Active Galactic Nuclei and Supermassive Black Holes
  • Cosmology

As described in the Detailed Science Case, major pillars in the MSE science program include (i) the ultimate Gaia follow-up facility for understanding the chemistry and dynamics of the distant Milky Way, including the outer disk and faint stellar halo at high spectral resolution (ii) galaxy formation and evolution at cosmic noon, via the type of revolutionary surveys that have occurred in the nearby Universe, but now conducted at the peak of the star formation history of the Universe (iii) derivation of the mass of the neutrino and insights into inflationary physics through a cosmological redshift survey that probes a large volume of the Universe with a high galaxy density.


The MSE project completed its conceptual design phase, which began in 2016, in January 2018. The preliminary design phase should be ongoing until 2020, with the detailed design phase being completed by 2023 at which point the construction permit will hopefully be approved. Science operations should begin in 2029. The entire MSE project is currently estimated at $500M USD.

For more information on the Maunakea Spectroscopic Explorer, please visit