Did you know ...

... TMT's dome is incredibly compact and efficient!  

Even though TMT’s mirror is more than 13 times larger in surface area than Gemini’s, its dome is only slightly bigger—about 20% in height. In fact, it’s the smallest dome among the three Extremely Large Telescopes. This graphic compares the heights of these domes with that of Gemini, a well-known 8 meter telescope. TMT’s dome has a smooth, curved design that helps reduce wind shake, which can blur images. By keeping the telescope steady, TMT can capture sharper, clearer views of the universe. Plus, its shape and color were chosen to help it blend in better with the surrounding environment.

The TMT mirror has 90% of the surface area of its diameter collecting light, as opposed to 82% for the E-ELT and 70% for GMT.

... TMT is ideally suited for finding extrasolar planets!

Its diffraction-limited point spread function, which determines how precisely the telescope focuses light from a distant star, makes it particularly effective for detecting planets orbiting close to their host stars—one of TMT’s primary science objectives.

The central core of a telescope’s point spread function becomes narrower as the primary mirror diameter increases. Since the E-ELT has the largest mirror, it produces the narrowest core, while Keck, with a smaller mirror, has the widest core. However, not all light is concentrated in the core; some spreads into rings and side lobes.

TMT’s aperture has the smallest gaps, resulting in a smoother and more uniform diffraction pattern than the other telescopes with larger gaps. This well-structured diffraction pattern enhances TMT’s ability to detect planets closer to their host stars with greater precision, accuracy, and clarity.

... TMT's optical design is highly efficient.

TMT uses three mirrors to direct light from the sky to its instruments, whereas the European Extremely Large Telescope (E-ELT) uses five or even six mirrors. With fewer mirrors, TMT loses less light, ensuring more light reaches the instruments for analysis. GMT uses at least two mirrors for its direct Gregorian focus and three mirrors for its folded Gregorian instruments.  

This efficient design also helps reduce thermal emission from the telescope itself—since all objects emit a faint glow in the near-infrared. By minimizing this unwanted background noise, TMT improves its ability to observe the faintest and reddest light in the universe with greater clarity.

... TMT’s preferred Maunakea, Hawaiʻi site is the world’s premier location for adaptive optics!

Adaptive optics corrects for most of the atmospheric distortion that blurs images, allowing ground-based telescopes to capture images even sharper than those from space-based telescopes.

The table to the left compares key site characteristics for TMT on Maunakea, the E-ELT, and GMT, with highlighted boxes showing the best values for astronomical observations. Many of these characteristics are directly linked to adaptive optics performance and clearly show TMT’s preferred site on Maunakea the best in the world for adaptive optics!

... TMT makes the most out of its mirror!

A telescope’s mirror diameter helps determine how sharp its images are, but it’s the collecting area, the part of the mirror that actually gathers light, that lets astronomers study the faintest objects in the universe. TMT’s 30 meter primary mirror is designed with minimal gaps between segments and a smaller central shadow from its secondary mirror, allowing it to collect light as efficiently as a 28.4-meter unobstructed mirror.

Each of the ELTs has a unique design tailored to its scientific goals. The Giant Magellan Telescope (GMT), with its 25.4 meter segmented mirror, is optimized for certain observing strategies but has more space between its segments, resulting in a light-collecting area similar to that of a 21.3 meter unobstructed mirror. The European Extremely Large Telescope (E-ELT), with the largest mirror at 39 meters, achieves a collecting area equivalent to a 35.3 meter unobstructed mirror.

TMT’s efficient optical design was purposefully chosen to maximize the science return from its full aperture, ensuring exceptional sensitivity and the ability to observe some of the faintest and most distant objects in the cosmos.

... TMT’s design takes advantage of a 100+ year legacy of building and operating the biggest and best optical and IR telescopes in Northern Hemisphere.

TMT builds on over a century of experience, through its partner institutions, in designing and operating the world’s leading optical telescopes, from the 200 inch Hale, to the 8 meter class Subaru and Gemini, to the twin 10 meter Keck telescopes. This shared legacy of innovation, engineering, and management excellence is embedded in TMT’s design. With its 30 meter mirror and powerful adaptive optics, TMT will be up to 200 times more sensitive than today’s 8 meter class telescopes, an evolution made possible by 100+ years of progress in building the best optical-IR telescopes.

... TMT is built for speed.

Every second counts when you’re operating a billion dollar observatory. That’s why the Thirty Meter Telescope is designed for exceptional operational efficiency, minimizing downtime between observations and maximizing time spent collecting science data.

TMT can acquire a new target, including adaptive optics setup, in under 5 minutes, even when switching between major instruments like IRIS and MODHIS. By comparison, the E-ELT advertises a 6 minute target switch, and GMT aims for under 10.

TMT is also primed to chase fleeting cosmic events, perfect for following up discoveries from surveys like the Vera Rubin Observatory.

More time on target. More science per second.

... Spending on TMT is invigorating the American economy.

The Thirty Meter Telescope is a global collaboration with a major U.S. impact: $136 MILLION invested across as many as 34 states from 2020 through 2024 alone! And more investment is on the way.   We're proud to bring non-taxpayer, international investment into the U.S. to support American jobs and innovation.

... TMT is ready for NSF's final design phase.

The National Science Foundation (NSF) conducted a readiness review of the U.S. Extremely Large Telescope Program (US-ELTP), a collaboration between TMT, NOIRLab, and GMT. The report said hands down that TMT is ready to advance to its final design phase (FDP):

“The [review] panel found that both GMT and TMT were sufficiently ready to advance to FDP.”  

The report goes on to say,

“The current panel believes both projects have met the requirements to proceed to FDP once a governance framework is agreed on.”  

We look forward to continuing our work with NSF and the US-ELTP as we move into the NSF's final design phase.

... TMT found the sweet spot between image clarity and field of view.

In adaptive optics (AO), there is a tradeoff: correct a wide area and lose sharpness, or focus on sharp images over a narrow region.  TMT chose the right balance based on its driving science case: mapping the stars around the black hole at the center of the Milky Way. TMT’s design was driven by one of the most demanding scientific goals in astronomy: mapping the orbits of stars near the supermassive black hole at the Milky Way’s center. This requires sharp images across a moderate-size and crowded field — a challenge tailor-made for NFIRAOS, TMT’s first-light adaptive optics system.

NFIRAOS uses advanced multi-conjugate adaptive optics (MCAO) to deliver high Strehl* ratios (70%) across a 30-arcsecond field, with effective correction out to 2 arcminutes. MCAO corrects for multiple layers of the sky at the same time which allows it to somewhat overcome the sharpness vs. field of view tradeoff.  This makes it exceptionally well-suited for deep imaging in crowded stellar fields where precision over a moderately sized field of view is critical.  Doing so provides an exquisite correction over the region that matters for the Galactic center.  As you can see in the picture on the right, TMT’s MCAO (the image in the lower right) offers the resolution of Laser Tomography AO (LTAO) over a much broader corrected field of view.  

The Giant Magellan Telescope (GMT) uses ground-layer adaptive optics (GLAO) to improve seeing over a wide 25 arcminute field in the visible (wavelengths less than 1 micron). While GLAO corrects a larger field of view than MCAO, the correction is modest.  The  Strehl ratios with GLAO double the Strehl ratios without, but the Strehl ratio is still less than 0.01% at a wavelength of 0.5 microns. That is a long way from diffraction-limited imaging. The GMT also has a laser tomography adaptive optics (LTAO) in the near infrared (wavelengths longer than 1 micron) to achieve high image quality near the center of the field, but performance drops off quickly as the field of view increases. The European Extremely Large Telescope (E-ELT) is also developing an MCAO system that they have optimized to cover a wider field than TMT’s NFIRAOS, but at the cost of lower Strehl ratios (roughly 50% for E-ELT compared to roughly 70% for TMT at a wavelength of 2 microns), a clear example of the tradeoff between area and precision.

TMT’s AO strategy is deliberately science-focused: it doesn’t aim for the widest field, it delivers the sharpest images over the area critical for its science. The other telescopes have chosen different compromises based on the science and technology they will be doing; together the three ELTs cover many different AO types. By maximizing the image quality over a wide field of view, TMT ensures the best conditions for a variety of studies involving dense fields of stars over a scientific field of view.

* Imagine an image taken from a perfect telescope with no atmosphere in the way. That's our ideal. The Strehl ratio tells us how close a real telescope image, affected by the atmosphere and other imperfections, gets to that ideal. It’s measured as the ratio of the peak of an observed image of a point source (the point spread function or PSF) divided by the peak from a theoretical perfect image. 100% is perfect and 0% means the image is not corrected at all. Neither extreme is possible in the real world.  Even JWST has a Strehl ratio of 83% at a wavelength of 2 microns, and the Strehl ratio of a 30 m telescope in typical Maunakea conditions with no AO is really small, about 0.1% at a wavelength of 2 microns, but not zero. So, a higher Strehl ratio means a sharper, more corrected image. (The telescope diameter also contributes to resolution, so here we’re concentrating on telescopes of the same diameter.)