8.x m is about the largest single mirror that can be cast with current technology. Above that, segmented wins. Giant Magellan[0] will use multiple 8m mirrors to get to ~25m total aperture. The Thirty Meter Telescope[0] and the European Extremely Large Telescope (39m) will be segmented.
The VRO picked the single mirror approach for lower complexity and the ability to lock the primary and tertiary mirrors into one monolithic structure. For this, they accepted some higher fabrication risk.
Source: A friend on the VRO project.
[0] GMT and TMT are at budget risk and TMT faces stiff opposition from Hawaiians who say Mauna Kea is sacred and shouldn't have anything at the summit.
manufacturing challenges aside, isn't there a practical limit to what terrestrial optical telescopes can achieve, given the interference from our atmosphere? I thought things like JWST was the necessary next step in improvement.
JWST was conceived ~30 years ago and there's been a lot of advancement since then. I agree that the atmosphere and the background light from the earth and sky can get in the way of terrestrial telescopes. On the other hand, the ability to build giant apertures AND equally enormous instruments have benefits of thri own. Check out the proposed instruments for the 39m E-ELT at
These things are immense. The METIS is supposed to cover 3-13 microns, an impressive accomplishment through the atmosphere. On top of that they can be upgraded and the data can be offloaded with current technology vs. waiting for lasercomm to eventually bring the bandwidth. Even the Hubble is ultimately limited by the chassis. E-ELT expects to do 15x Hubble's resolution and directly characterize exoplanet atmospheres.
Of course if the sky gets gunked up by infinite comsats, all bets could be off.
I’ve been binging Goldratt lately, so my brain is awash in Theory of Constraints.
It’s okay to use “old” equipment to offload from a bottleneck. Space based telescopes are going to be a bottleneck for the foreseeable future. They have severe maintenance restrictions and the more you task swap them the more frequent that maintenance.
So from a constraint perspective, you use ground based observation to do anything that can be done without a space telescope. Including trying to determine which patches of sky justify time on JWT.
The VRO picked the single mirror approach for lower complexity and the ability to lock the primary and tertiary mirrors into one monolithic structure. For this, they accepted some higher fabrication risk.
Source: A friend on the VRO project.
[0] GMT and TMT are at budget risk and TMT faces stiff opposition from Hawaiians who say Mauna Kea is sacred and shouldn't have anything at the summit.