[wthomp]

My understanding is that the AO system for GMT is going to pose quite a challenge. A big topic of ongoing research is dealing with “petaling” where the separate primary mirrors in phase due to the atmosphere.

For combining the projects, it does seem like that may be the only option funding wise, but it’s hard to imagine what the resulting observatory would look like. Maybe it would have to be a completely new design?

[OldGuyInTheClub]

Thanks for the pointer. I am interested in instrumentation so I'll look up the AO papers. Naively it seems like that would be an issue whether the primary is a few large segments or a lot of small ones.

If the resulting project winds up as a redesign, it would presumably add years to the project and that will only increase costs. Some philanthropic organizations and partner countries will see their generosity go for nothing which won't help matters. EELT will be operational in that time and getting results.

I also wonder about the growing LEO satellite problem. I get that these enormous telescopes have narrow fields-of-view compared to Rubin and similar wide-field survey facilities. The possibility of these being overwhelmed by spaceborne light pollution seems very real.