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The US ELT Program

The National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab), the Giant Magellan Telescope Organization, and the Thirty Meter Telescope International Observatory (TIO) are working collaboratively to develop a U.S. Extremely Large Telescope Program (US-ELTP).  The vision of the US-ELTP is to allow scientists to look more deeply and more precisely into the night sky than ever before. The dual hemisphere model will provide access to 100 percent of the night sky to make the next generation of discoveries about our universe.

USELT strategy

The US-ELT Program will provide all sky access and
a unique suite of instruments to the US science community.

The combined apertures of TMT and Giant Magellan Telescope are comparable to that of the single European ELT, but for many scientific programs, access to two telescopes and a diverse instrument suite offers clear advantages. All-sky coverage enables observation of relatively rare phenomena (e.g., the number of observable rocky planets in the habitable zone is predicted to be small), unique targets in each hemisphere (e.g., Magellanic Clouds in the Southern Hemisphere, Andromeda group galaxies in the North), and key survey fields with unique multiwavelength data sets (e.g., GOODS-North and -South; LSST Deep Drilling fields; the Kepler main survey field; ecliptic pole deep survey regions for TESS, Euclid, WFIRST and JWST).

USELT Sky Coverage

Sky coverage provided by the bi-hemispheric US-ELT Program

Together, Giant Magellan Telescope and TMT will access the full celestial sphere, with roughly 50% sky overlap allowing their complementary instrument suites to be used for joint or even simultaneous investigation of many objects. In addition to separation in latitude, their different longitudes create valuable opportunities for time-domain research, especially for rapidly changing phenomena that benefit from high-cadence observations. Finally, two platforms can offer a greater variety of instrumentation than would be available on a single telescope, and more observing hours to support long term variability and large scale programs that would otherwise require many years to complete.



US-ELTP Brochure: 2 Telescopes, 1 System

US-ELT Program Brochure (PDF 3.6mb) 


US-ELTP Astro2020 Brochure (PDF 4.9mb

The ASTRO2020 Decadal Survey

The decadal survey for astronomy and astrophysics is a powerful study that our community uses to drive strategy and vision for the next decade of federally funded transformative science. The 2020 report, Pathways to Discovery in Astronomy and Astrophysics for the 2020s (Astro2020), was published by the National Academies of Science, Engineering, and Medicine on 4 November 2021. We are honored that the community, via the decadal survey, has ranked the US Extremely Large Telescope Program (US-ELTP) as the highest ground-based priority in Pathways to Discovery. Read more.

Download the Public Briefing slides (PDF) from November 4, 2021


What is the Decadal Survey?

Every 10 years, the U.S. National Academies of the Sciences, Engineering, and Medicine convenes a survey committee and supporting study panels to carry out a Decadal Survey in Astronomy and Astrophysics. The overall goal of the Survey is to evaluate the projects and programs that will be prioritized for the coming decade. The Decadal Survey for the 2020 decade began in early 2019 and is referred to as Astro2020.

Did TMT participate in the Decadal Survey?

Yes, TMT, along with its other partners in the US-ELTP presented their science and technical readiness to a Decadal Survey panel in February 2020.

Which organizations sponsor the Decadal Survey?

While the survey is sponsored by NASA, NSF, and DOE, it is driven by input received by the community in the form of white papers. A total of 573 science white papers were submitted as part of Astro2020.

What does a high ranking in the Decadal Survey mean?

A high ranking in the Decadal means that a project has been identified by the science committee as a high-priority research activity for astronomy and astrophysics for the coming decade.