How to build a giant telescope

Q: Tell us, what does your job as ELT Programme Manager involve?

A: First of all, my job entails continuous concern about the team — I make sure that there are no weak points in the team. I bring in resources. I help people communicate among themselves and make sure they’re sharing the correct information to keep the project going. I’m also always looking ahead. I try to anticipate problems, to see what can go wrong and anticipate what has to happen so I can ensure everything is in place to run smoothly. Broadly speaking, I plan — but on many different levels, from technical to financial to resources.

In order to do all of this, my day-to-day tasks include meeting with people, having discussions, going into offices, trying to understand what’s happening. This means during the core business hours, I’m meeting with people, then after work I write and read emails and essentially do the rest of my work. So it’s a sort of a dual job. Many people support me in this position — I receive a lot of help from my colleagues, the team, because it’s not just me building the ELT! This is fundamental: I’m just one of the pieces in the vast jigsaw puzzle of our team. When we make good progress, it’s thanks to all the people who are putting in the hard work. I’m the one trying to smooth the jagged edges — to eliminate the friction in communication.

Q: Progress with the ELT has advanced significantly. What has been happening recently?

A: In the last three years, we’ve been implementing the plans that were conceived before. I inherited a project that was in good shape to really begin to be physically pieced together, so we’ve translated the design and preparation work into requirements for procuring material. This has been, I believe, very successful work so far. We’ve started the construction; now we’re building. We’re working with industry and building with steel, with Zerodur®, a material used for the mirror blanks. This is a huge recent step — everything is really coming together.

The ELT secondary mirror blank (also known as M2), which was cast by the German company SCHOTT in May 2017. 4.2 metres across and weighing 4.5 tonnes, the glowing-hot mirror blank is now slowly cooling down before being shipped off for grinding and polishing

Credit: SCHOTT/ESO

Q: What are the three biggest challenges we are facing when building the ELT? How are we dealing with them?

A: First of all, nothing like this has been done before. The ELT is the first of its kind. It’s a big machine with very, very stringent requirements in terms of positioning and tracking. We’re putting a giant 3000-tonne piece of steel in a set position and need to move it with extreme precision. This has never been done before. Yes, we have all the simulations and computational analyses to show that we can achieve it, but there’s a big step between simulations and reality. In my opinion, taking this leap is one of the biggest challenges.

Secondly, we have the challenge to keep the team cohesive, to maintain their enthusiasm and their motivation, to keep the communication running smoothly. Without that, forget it! The ELT wouldn’t happen. “We’re building the biggest telescope!” I remind them. “We’re going to change mankind’s knowledge and embark on a new era of astronomy!” That’s what has to keep the team motivated, to keep them wanting to come into the office every single morning to do the work so that when they return home, they’re happy with what they’ve achieved. When you have an enthusiastic team, you can solve all the other technical problems.

I’d say the third challenge is polishing the mirrors. This is something that our industry partners are now putting into practice. We monitor it, but it’s certainly a major hurdle to do all the polishing they have to do, considering that the primary mirror is made of 798 segments and that the other mirrors have complex shapes.

If I can add a fourth challenge, then I certainly can’t miss mentioning the complexity of making the hundreds of the segments of the primary mirror work together in harmony! Phasing these segments and controlling the wavefront is a complex problem that we’re striving to solve.

This artist’s rendering shows a night view of the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere.

Credit: ESO/L. Calçada

Q: Can you share any interesting details about the construction of the ELT that people don’t usually hear about?

A: It’s interesting to note that we often have to come up with solutions to new and unique challenges. The telescope is being built in a highly seismic area, so we have to isolate the telescope from the rock in case of an earthquake. You can’t transfer all of the energy from the earthquake into the telescope or you’d break the mirrors and damage the equipment. But at the same time, the telescope has to be rigidly connected to the rock to ensure it can be correctly pointed, so it performs to its best. So you have two opposing forces. How do you fulfill these two different requirements? Industry is working with us to solve this tricky problem.

Another challenge is controlling all the parts, for example, moving the dome. I mean, can you imagine turning around a 5000-tonne coliseum-sized structure — and controlling it to millimetre precision? We also have to control all of the segments of the primary mirror, which is done by position actuators. These control the positioning between the segments and the main structure. For every ten millimetres of movement, the position actuators need to be accurate to within two nanometres. Two nanometres! It’s like keeping the entire Atlantic ocean so flat that the waves are no higher than the thickness of a one-euro coin.

This artist’s rendering shows the huge segmented primary mirror of the ELT

Credit: ESO/L. Calçada/M. Kornmesser

Q: What excites you most about being involved in this project? What are you looking forward to?

A: We are constructing something that will expand humankind’s knowledge of the Universe. This is absolutely fantastic; it’s an experience that is utterly unique.

One science case that particularly excites me is the possibility of discovering other planets like our Earth. The ELT will allow us to take images and study exoplanet atmospheres. We might be able to find if there is chlorophyll, if there’s life. We’ll have to wait a few years before reaching that but I hope to see it within my lifetime.

Q: Is there anything else you would like to add?

A: I want to emphasise the effort of all the people behind the scenes — all the people within ESO, from those working directly on the project, to human resources staff, to people working in procurement; then the industry people outside ESO; and all the spouses and the families. Together, they make this project happen. As I said, a project like this can take a lot of time from you at night, during the day, weekends, and sometimes unfortunately also at Christmas and New Years. So again, I want to express my appreciation for the incredible hard work that the team puts in, because without them we’re nothing!