The Trials and Tribulations of the Thirty Meter Telescope

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A few weeks back I wrote about the many, many, many things that need to be taken into consideration when it comes to designing, building, and installing a single instrument on a world-class observatory. Building a cutting-edge facility is hard. And that’s when you can actually build it.

A story came up this week involving the extremely beleaguered Thirty Meter Telescope (TMT), a proposed superlative astronomical instrument that, as of yet, has barely seen any actual construction happen in the nearly eleven years since its groundbreaking ceremony. So what is TMT? What is the controversy? And what are some potential solutions?

Join me as I take a brief, shallow dip into the extremely deep waters that are the trials and tribulations of the Thirty Meter Telescope. 

Big Ol’ ‘Scope

When we call this thing the Thirty Meter Telescope, we are referring to the diameter of its primary mirror. The more surface area a telescope’s primary mirror has, the more sensitive it can be (there are other factors that affect sensitivity, some of which we’ll get into later). So where would a thirty-meter-wide mirror rank in today’s astronomical facilities? Simple. There is nothing the size of TMT operating today. In fact, there’s nothing even close.

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The largest mirror currently in operation is installed on the Gran Telescopio Canarias, which is 10.4 m (34 ft). So when we’re talking about building TMT, we’re talking about building something with three times the diameter as any single mirror in use today (there are a few facilities, such as the Very Large Telescope or the Large Binocular Telescope, that make use of multiple fairly large mirrors next to each other, which is a way of getting around having a single very large mirror for some applications). That, to put it mildly, is a lot of sweet, sweet astronomical real estate.

TMT will also feature adaptive optics to help deal with distortions from Earth’s atmosphere and be able to observe in a range of wavelengths, primarily focusing on the visible part of the spectrum, but with infrared and UV capabilities too. In short, it’s designed to be the kind of astronomical powerhouse that can be used to solve a wide range of cosmic mysteries. It would be a key player in Earth’s fleet of premier observatories.

So that’s why we want to build it. And if you’re going to build something so big (its dome will be 180 feet, or 55 m, high and twice as wide as the telescope itself) and so very eye-wateringly expensive (all that astronomical greatness doesn’t come cheap and construction will cost over $1 billion), you want to make sure it’s going somewhere it can do the most good.

Location, Location, Location

Not all astronomical sites are created equal. For instance, the Museum of Science sits at sea level on the coast of New England. This is a terrible observing site. Being at sea level means we’ve got the entirety of the atmosphere between us and the stars, being on the coast means we get all kinds of cloudy weather blowing in off the ocean, and being in New England means we’re swimming in humidity (the more water in the air, the more it moves) for a good chunk of the year. It’s basically the opposite of what you want for a good observing site: high, dry, and clear.

This description fits what are often reckoned as the best observing sites on our planet: the Chilean high desert and the dormant volcano Maunakea in Hawaii, each already home to a number of extremely prolific observatories. The recently opened Vera Rubin Observatory and the under-construction Giant Magellan Telescope, for instance, chose Chile.

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The consortium building TMT, which consists of research facilities from Canada, the US, Japan, China, and India, considered Chile as well as a number of other sites around the world as possible homes for TMT. In the end, though, Hawaii beckoned and in 2013 Maunakea was announced as the future home of this massive facility.

Maunakea is high, the highest point in Hawaii at 13,803 ft (4,207 m) above sea level (fun fact, if you were to measure it from its peak to its base on the ocean floor, it’s taller than Mount Everest). It’s dry, receiving an average of less than 8 in (20 cm) of rain per year. And it’s clear, with on average 300 nights a year receiving observation-worthy weather. What’s more, from its latitude of about 19.8 N, it can not only see the entire northern celestial hemisphere, but the vast majority of the southern one as well. From an astronomical standpoint, it’s pretty darned perfect. 

Controversy

A groundbreaking ceremony was held in October 2014 and since then…well, not much. There are lots of folks who are not fans of putting TMT on Maunakea, for a variety of reasons. The one that gets the most attention is the importance of the mountain to Native Hawaiian religion.

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Please be aware that I have no personal experience or knowledge of Native Hawaiian religious beliefs. What I’ve read is that Hawaii’s volcanos are all considered sacred, and as the highest of them Maunakea is the most sacred of all, a home to the gods. The University of Hawaii at Hilo’s website describes it as a centerpiece in the story of Hawaii’s creation (That site also says that it should be written as Maunakea. The name means “white mountain”. Spelling it the way I’ve always seen it, Mauna Kea, apparently refers to a generic white mountain, while Maunakea refers to this specific mountain. I will refer to it thusly from now on).

But while that point of contention tends to get the most press, probably due to often being written up as “culture vs. science” or “history vs. progress” to get clicks, there have also been numerous ecological concerns raised about building a truly gigantic edifice in a fragile alpine ecosystem. Past reports looking at the existing observatories on Maunakea found that inadequate waste disposal and chemical spills have damaged surrounding habitats.

It’s worth noting that there have been protests against the placement of telescopes on this sacred ground since construction began on the first big dome, the Canada-France-Hawaii Telescope, in 1973. But no previous protests have reached the strength of the ones against TMT, with activists making concerted efforts to block the roads to the site. All construction has been effectively halted since 2015.

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Any number of attempts have been made to make it possible for construction to resume. These attempts run the full gamut from trying to arrest all the protesters and dismissing their claims in court to offering to tear down some of the existing telescopes to lessen the overall effect on the mountain. From time to time it has seemed like some sort of compromise could be reached, but progress has been minimal enough that the National Science Foundation has dropped its support for TMT, putting the project at risk of full cancellation.

What To Do?

One potential solution to the problem is simply to give up on Maunakea. And there’s a very, very good reason to consider this: Spain would just looooove to give TMT a home! Not actually in Spain though. Sitting about 60 miles (100 km) off the coast of Africa are the Spanish-owned Canary Islands, one of which is the island of La Palma. And it’s possible La Palma could, maybe, become the TMT’s actual for real permanent home.

La Palma was one of the sites initially considered for TMT before Maunakea was chosen. The highest point of La Palma sits 7,874 ft (2,400 m) above sea level and hosts a raft of telescopes of its own (including, as you may have guessed, the Gran Telescopio Canarias mentioned earlier). In the face of the resistance on Maunakea, the consortium behind TMT started looking at La Palma as a possible secondary site in 2019. Just last week Spain offered up $471 million (€400 million) to help build the telescope on La Palma. Spain really wants TMT.

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Now to be clear, there is a reason why Maunakea was initially chosen over La Palma. Being at a much lower elevation, La Palma is not nearly as good a site for a telescope of TMT’s magnitude as Maunakea. It’s not so high, not so dry, and not so clear. It also can’t see as much of the southern hemisphere sky. Scientifically, building TMT there would be a net loss over building it on Maunakea.

But sweet Carl Sagan, it’s sure looking like the dang thing isn’t gonna get built at all right now! Yes, building it on La Palma isn’t as good as building it on Maunakea—but it’s better than not building it at all! Between a world with no TMT and one with a TMT in the Canaries, I know which one I prefer as an astro nerd.

This story is still playing out. It’s entirely possible at this stage that TMT will remain only a lovely astronomical dream. Or maybe, just maybe, years down the road we’ll be admiring gorgeous pictures taken by one of the biggest observatories ever constructed, perhaps taken from Maunakea or perhaps taken from La Palma. We’ll have to wait and see, but my fingers are crossed!