From The Lab: Paris Observatory's role in building the world's biggest telescope

The Extremely Large Telescope (ELT), which is currently being built in the Atacama desert in Chile, will be the  biggest telescope ever built.Its primary mirror will be 39 metres in diameter, which is slightly less than the size of the Arc de Triomphe in Paris, while it's main structure will weigh 3700 tonnes.Overall, the telescope will use five mirrors to obtain sharp images of the Universe.

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The Extremely Large Telescope is being built in the Atacama Desert in Chile. ESO

One of the key parts of this telescope, which is part of the European Southern Observatory (ESO) is an imager called MICADO (Multi-Adaptive Optics Imaging Camera for Deep Observations).

MICADO will allow the ELT to take images of distant galaxies, individual stars, and help search for exoplanets( planets outside our solar system).

A hypnotic golden spiral. The #galaxy NGC 4254, also known as Messier 99 captured by European Southern Observatory (ESO). pic.twitter.com/q5susqUBY9

— Space (@redditSpaceView) March 18, 2022

The Space and Astrophysics Instrumentation Research Laboratory (LESIA) of the Paris Observatory in Meudon is leading a group of French laboratories and institutes in developing MICADO's first-light adaptive optics system.

Speaking about adaptive optics, LESIA's Yann Clenet expalined that in order to observe distant or faint objects from the Earth, scientists need large telescopes such as the ELT.

"However, ground-based observations suffer due to the turbulence of the atmosphere which degrades the quality of the images. So to compensate for this effect of the turbulence, the adaptive optics system was devised," Clenet said. 

He said ELT's first-light adaptive optics system consists of a sensor that is able to measure the deformation of the light.

The second subsystem consists of corrective optics made up of mirrors with actuators - a machine that is responsible for moving and controlling a mechanism -  below their surface. These actuators move the mirrors' surface to make the image better.

The third component is a powerful computer which decides what commands should be sent to the mirrors.