> With our current technology, we can build ELT on Earth for a fraction of the cost of putting it in orbit.
That's going to change soon. The reason the ELT needs individually adjustable panels is to provide corrections for refraction in the atmosphere as it swirls around. A space-ELT doesn't need that (well, maybe some cheap slow actuators to set the focus on a large non-rigid mirror).
As the cost of launches drop, we will hit a point where it is cheaper to put the telescope in space where you don't need those expensive atmosphere correctors.
Every 30-meter-class telescope uses segmented mirrors, because nobody knows how to make a single, monolithic 30-meter-diameter mirror.
It's only barely technically feasible to construct these 30-m telescopes on the ground. The idea that they can be constructed in space is just fanciful.
Yes, but in space the segments don't need real-time corrections for atmospheric effects (and the whole structure doesn't need to be built to withstand the strong winds at the top of a mountain). The idea that you can't build that in space is just naive.
That's going to change soon. The reason the ELT needs individually adjustable panels is to provide corrections for refraction in the atmosphere as it swirls around. A space-ELT doesn't need that (well, maybe some cheap slow actuators to set the focus on a large non-rigid mirror).
As the cost of launches drop, we will hit a point where it is cheaper to put the telescope in space where you don't need those expensive atmosphere correctors.