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  • ESOesoastronomy@mastodon.social
    Oct 14, 2026, 12:03 PM

    However the coating does not last forever:

    ➡️ Once the telescope is operating, two segments a day will need to be exchanged to receive a fresh reflective layer, work that our team at Paranal will do throughout the entire ELT operation lifetime.

    ➡️ To make this possible without ever leaving a hole in the mirror, 133 additional segments have been produced (that is, a total of 931), so that a segment can be taken out for recoating and be immediately replaced.

    📷 Safran Reosc/ESO

    3/4

    A diagram showing the status of the primary mirror of ESO’s Extremely Large Telescope as of 27 September 2026. A large mirror diagram uses blue, green and yellow hexagons to indicate segments that have been shipped, packed or are still in production. A central chart shows 558 segments shipped, 317 packed and 56 in production, while a smaller diagram on the right shows the status of the exchange set.
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  • ESOesoastronomy@mastodon.social
    Oct 14, 2026, 12:03 PM

    While more than half the segments with their supports have now arrived in Chile, most other segments are either en-route or packed and ready to be shipped, with a remaining few in production. This means that, in the coming months, all segments will be in Chile.

    4/4

    📷 ESO/A. Russell

    A view of the main structure of ESO’s Extremely Large Telescope from above. There is circular shape at the base with a tall metal post, joined to surrounding metal beams by five long horizontal metal supports. There is a twelve-sided metal structure at the top, with a gap in its centre, which the surrounding beams attach to.
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  • Ross of Ottawaottaross@mastodon.social
    Oct 14, 2026, 12:45 PM

    @esoastronomy how much do the segments weigh? Is there a whole series of customized handlers and lifting gantries/carts perhaps for moving them around?

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  • ESOesoastronomy@mastodon.social
    Oct 14, 2026, 1:51 PM

    @ottaross Each segment weighs 250 kg, including the supports. And yes, we have a segment manipulator specially designed to handle this. It will be mounted on a crane that can position it directly above the desired segment. This segment will be then pushed above the rest and grabbed by the manipulator. We're currently testing this device at our headquarters in Germany, stay tuned... ;-)

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  • DessiniFabDessiniFab@piaille.fr
    Oct 14, 2026, 12:54 PM

    @esoastronomy Bonjour, quand est-ce que le ELT pourra fonctionner ? est ce qu'il pourrait faire de l’interférométrie avec le VLT ?

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  • ESOesoastronomy@mastodon.social
    Oct 14, 2026, 1:56 PM

    @DessiniFab Hi! The first observations with a test camera are planned for 2029, and the first observations with the actual scientific instruments for late 2030.

    The ELT and the VLT won't work together interferometrically, but some ELT instruments will (independently) complement the capabilities of the VLT Interferometer.

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  • ESOesoastronomy@mastodon.social
    Oct 14, 2026, 1:40 PM

    @tamme Good question! You can divide the main mirror into 6 radial sectors or petals. Each sector has 133 segments, which are slightly different from each other, but identical to the 133 segments of all the other sectors. That's why in addition to the 798 segments that make up the full mirror there are 133 extra ones – the "exchange sector" you see in the image in post 3 of this thread. Every day we'll remove two segments from the mirror and replace them with their counterparts from this set.

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