Skip to Content
Home US-ELTP About Why Two?

Why Two?

Two Telescopes, One System

Humanity’s understanding of the Universe is expanding at an unprecedented rate, and new fundamental questions are arising as a result of this progress. Answering these questions requires making new observations currently impossible with existing facilities and instead employing the next generation of highly advanced, ground-based, extremely large optical telescopes.

The US Extremely Large Telescope Program (US-ELTP) is a joint endeavor of NSF’s NOIRLab, the US national center for optical astronomy, and the organizations building the Giant Magellan Telescope and the Thirty Meter Telescope.

The Power of Two

With a combined light-gathering power comparable to any other current or planned telescope, the US-ELTP will realize extraordinary scientific and societal benefits, delivering more than twice the science, twice the sky, twice the night, twice the technology, and twice the outreach of a single telescope. The combined system will provide unique access to the entire sky with a level of precision and sensitivity never seen before. The US-ELTP will maintain US leadership in observational astronomy well into the next generation and beyond.

  • Twice the Science — The US-ELTP will deliver significantly more scientific output than a single telescope would achieve. With twice the amount of data collected, the US-ELTP will make ground-breaking discoveries and shape our understanding of the Universe.
  • Twice the Sky Coverage — With one telescope in the northern hemisphere and one in the southern hemisphere, the US-ELTP system will be able to observe the entire night sky with a sensitivity and resolution unrivaled by any existing telescopes on the planet. This means that researchers will be able to observe rare and interesting objects wherever in the sky they occur, something not possible with a single telescope.
  • Twice the Night — The two US-ELTP telescopes are separated not only in latitude but also in longitude. When the Chilean night is ending for the Giant Magellan Telescope, the Hawaiian night is entering its prime for the Thirty Meter Telescope. Astronomers will be able to take advantage of the extended night and be nearly twice as likely to have a telescope in the dark when needed to rapidly follow up on a new discovery.
  • Twice the Technology — The US-ELTP combines two sophisticated methods of making extremely large segmented-mirror telescopes with state-of-the-art adaptive optics systems and a diverse suite of scientific instruments. This technology development will continue US leadership in astronomy technology innovation and provide a solid foundation for future technologies and technical spin-offs to come.
  • Twice the Outreach — With engaged communities surrounding each US-ELTP telescope, there will be twice the opportunities for outreach, STEM education, and community engagement. The individual and combined efforts of the three US-ELTP partners will enable the combined team to employ a community-based model of astronomy to build deeper connections with traditionally underserved communities

More than twice the benefit

The US-ELTP enhances all these benefits by optimizing tasks, leveraging existing investments, joining forces where most needed, and achieving greater efficiency and depth than any partner could accomplish on its own.