AGC Glass Europe will deliver a coater for the mirrors of the world’s largest telescope.

Its Plasma Technology Solutions business unit signed a second contract with the European Southern Observatory (ESO) to deliver a coater equipped for the large mirrors (M2, M3, M4 and M5).

The ESO telescope will be installed in the Atacama desert (Chilean Andes) at Cerro Armazones (3,046 m) equipped with a 39-metre segmented primary mirror and additional 4-metre wide large mirrors.

The telescope has the purpose to acquire scientific data to study the universe and through specific observations address certain unsolved problems of fundamental physics, study exoplanets and investigate other objects and phenomena across the universe.

In 2018 AGC was already selected to assemble and install the two magnetron sputtering coaters for the primary mirror segments of the Extremely Large Telescope (ELT).

The third coater is for the additional 4-metre wide mirrors. The magnetron sputtering coaters are important to maintain the performance of the telescope optics.

It is necessary to have the coaters on site for ESO to be able to re-coat the mirror segments regularly with a protected silver layer stack.

The telescope’s location in the Chilean desert knows harsh climate conditions, such as sandstorms, that affect the silver layers of the mirrors, therefore regular recoating is required.

The newly ordered coater will be installed in the dedicated section of the telescope’s technical facility on the Paranal observatory site in Chile within 32 months.

Patrick Van Bortel, VP Industrial & New Businesses of AGC Glass Europe said: “It is a great honour to be selected again by the European Southern Observatory for this ELT Large Coating Plant.

“The coating plant for the segments of the primary mirror, which is also supplied by the team of AGC Plasma Technology Solutions, has arrived in Chile and is ready for on-site assembly.

“The coating plant that is now ordered by ESO will be used for coating the 4-meter wide convex secondary mirror and concave tertiary mirror, as well as the fourth and fifth mirror. That implicates that all large area mirrors of the ELT will be manufactured with coating equipment supplied by AGC.”

The uniformity control of the highly reflective coating over the entire surface of the 4-metre wide mirrors is a challenge for this project.

AGC has proposed a technical solution by including an Online Shimmable Magnet Bar technology in the cathodes that allows superior thickness control of the deposited thin layers.