: 8 min
Looking into deep space... one step beyond!
Cathy loves astronomy, and science in general. She wants to become an astrophysicist and live her dream, by discovering the secrets of the Universe thanks to the world's biggest telescope, ELT, to be built in the mountains of Chile. Through this new story from Safran, learn how the skilled people at Safran Reosc, the world leader in high-performance optics for land-based astronomy, polish the super-size mirrors needed for telescopes such as the ELT.
A passion, a dream…
Today, Saturday, October 10, the Optics Graduate School is holding an open house which has attracted a number of young visitors, all passionate about science and astronomy. One of them, Cathy, hopes to be chosen for a master's program at the renowned Charles Fabry Laboratory, working with the prestigious chair in Ultimate Photonics. Created by Safran in partnership with the lab, this research and training chair is dedicated to the latest advances in nano-photonics and quantum optics.
She explains her aspirations to the professor who greets her at the open house:
My dream is to become an astrophysicist and discover new exoplanets. One day, I hope I'm lucky enough to be able to use the largest telescope in the world for now, the Gran Telescopio de Canarias!
That seems to awaken the professor's interest, and he replies,
Ah, yes, the one at the Roque de Los Muchachos observatory at Las Palmas in the Canary Islands… I know it well! But there will soon be an even bigger one: I suppose you've heard about the huge new European telescope, the ELT (Extremely Large Telescope), to be installed on Cerro Armazones mountain in Chile. First light is expected in 2024. So we have to wait another seven years before these distant exoplanets, until now invisible to the eye, unveil their secrets.
The most powerful telescope in the world
Yes, of course I've heard that it will be the most powerful telescope in the world,
says Cathy with a smile.
All I have to do is move to South America.
The professor calls up computer-generated images of the future telescope on his tablet and continues his explanations:
The ELT features a totally innovative design, with five mirrors. It has both three aspherical mirrors and also two deformable mirror surfaces that will correct the effects of atmospheric turbulence, as if the telescope were out in space, away from the atmosphere.
The French company Safran Reosc, a subsidiary of Safran Electronics & Defense, was chosen by the European Southern Observatory (ESO) to produce all the segments in the primary M1 mirror, to polish the M2 secondary and the M3 tertiary mirrors and also the thin sheets of glass making up the M4 adaptive mirror.
As he scrolls through the images on his screen, he continues:
Look, here's the 39-meter primary mirror that will capture light and direct it to the other mirrors. It will comprise 798 hexagonal segments, each measuring 1.5 meters, and polished to a very high degree of precision. Safran Reosc has to produce all these segments by 2024. The light will then be sent to the M2 mirror, installed 60 meters over the M1. Measuring 4 meters in diameter, the M2 will be the largest convex mirror ever built. Lastly, the M4 mirror, a concentration of opto-mechanical precision, will be in charge of correcting the image imperfections due to atmospheric disturbances, no matter how small.
Expertise unrivaled worldwide
Cathy moves closer to examine the picture of the future M4 secondary mirror, made up of six segments.
It looks like petals,
she says, as the professor enlarges the image and explains:
Yes, the mirror is made of six extremely thin petals of a vitroceramic material, barely 2 millimeters thick. Its optical surface has to be shaped very precisely, to within a few nanometers, and thickness cannot vary more than a few microns.
Safran Reosc meets these exacting specifications by using very-high-precision polishing robots. The company's engineers start by polishing the front surface to the required tolerances, then work on the back side to gradually reduce the thickness to the specified size. In fact, each petal will take several months to finish.
Cathy seems more than ever lost in her dreams…
No doubt that with this giant telescope, we'll be able to analyze the atmosphere of new exoplanets, and detect any traces of gas on some of them.
The professor nods in agreement, adding,
If any telescope is capable of this type of discovery, it will be the ELT!
As he takes leave of Cathy with a friendly handshake, he tells her:
Here, you'll find all the information you need to register for the program in this application pack. I hope we'll meet again very soon – perhaps in Chile!