Saint-Benoît (France) (AFP)
A large mechanical arm makes circular movements on a flat piece, hidden by a pink liquid containing tiny grains. In this new Safran factory, it will be polished to an ultimate degree of precision to become part of the mirror of the future giant European telescope.
When a raw part arrives at the Safran site, it has a shape defect of around 100 microns compared to the specifications of the European giant telescope, the size of a hair. Objective: divide this number by ... 10,000.
"Safran's role is to polish mirrors to a state of absolute precision, it is an industry that does not tolerate error," said Martin Sion, president of Safran Electronics, to journalists. & Defense, during the inauguration of the factory located in Saint-Benoît, near Poitiers (Vienne).
Robots and automated manufacturing workshops should enable the French aeronautical group to accomplish this mission. Machines are interconnected, data and programs pass from one to the other.
The new factory, built with the support of the Nouvelle-Aquitaine region, "will allow those who work there to focus on tasks with high added value and society to be more efficient," says Sion.
In a first break-in workshop, the mirror passes successively over several machines, which smooth its surface, give it transparency and its aspherical shape. This is the stage during which the most material is removed, enough to almost fill a jar of 50 centilitres.
- 500 hours of work -
After each material removal, the part is checked in a room located in the center of the factory, where around fifty people work.
Later in the process, a saw, at the rate of 2,000 revolutions per minute, performs a high-precision cutting of the part to give it its final, hexagonal shape. It is constantly sprayed with water to avoid overheating.
"This is a great moment for French technology and research (...). The example of Safran is what we need to develop in the territory of Grand Poitiers", believes Alain Claeys, president of this community urban.
In total, 500 hours of process, divided into sixty steps, are required to manufacture each of the 798 segments that will make up the primary mirror of the giant European telescope and the 133 spare segments.
The finishes are carried out in a clean room where the temperature, humidity and dust are controlled. Employees in full blue overalls will pass each mirror through an ion-machining machine, which sends a beam of ions to scan the material and tear off the excess.
First delivery expected in about a year. The pace will accelerate from 2022, with the production of one piece per day.
- "Discover other worlds" -
When assembled, they will constitute a mirror with a diameter of 39 meters, intended to collect light and then redirect it to other smaller mirrors. Thanks to this equipment, the giant European telescope, which is scheduled to come into service in 2025, is expected to provide unparalleled observation capacity.
"This extremely complex machine will allow scientists to discover other worlds, to understand how galaxies evolve, how black holes form and to see the first stars which were born in the primitive universe", describes Xavier Barcons, director General of the European Southern Observatory (ESO), grouping of 16 countries, at the origin of the project.
The European giant telescope (the Extremely large telescope, ELT) is being built on the Cerro Armazones, a summit of 3,060 m in the desert of northern Chile, country which already shelters the most important telescopes in the world.
At this site, the atmospheric disturbances are particularly weak, making the conditions of observation ideal.
"Europe is proud to be leading this race to build the next generation" of telescopes, according to Barcons.
Two other giant optical telescope projects are underway, the Giant Magellanic Telescope (25 meters in diameter) also built in Chile by an international consortium, and the American TMT (30 meters) in Hawaii.
© 2020 AFP