Starlink satellites that are already impacting astronomy. Yay....? https://www.skyandtelescope.com/astronomy-news/starlink-sate...
I think that while there's perhaps more difficulty and more cost - there's probably a lot more advantages to having these in space.
No atmospheric interference/absorbtion issues. No ground-based light interference from nearby cities. No weather or time of day observing restrictions. No issues with trampling sacred/sensitive indigenous sites. Able to get very very large synthetic apertures combining telescopes in earth + lunar orbit. (Plus sol-earth lagrange points too, I guess)
Starlink seems to be the first to exploit the drastically lowered launch costs to launch a lot more stuff into space at once.
Large-aperture ground-based telescopes have huge advantages over space telescopes in many technical areas (and disadvantages in others). Eliminating them would be a huge blow to astronomy.
We won't get space based manufacturing until we can put a ton of things in space - things that likely be much larger and a whole lot more visible than Starlink satellites.
I don't think requiring that we can put a 30M telescope in space be the requirement before we can put things into space.
Also, as very-much-an-amateur my understanding is that a single 30m element isn't necessarily the only way to get very large telescopes.
One approach is what JWST is using, using folding mirror segments, another is tying together multiple telescopes that are distant from each other, where the distance between them is the effective aperture.
Of course, I'm sure there's drawbacks and issues with those approaches too.
At the moment, the vast majority of telescopes are on Earth. There is a role for space telescopes, but the total number of them could be counted on a few hands. Space telescopes are an extremely precious and limited resource, used basically only for things that absolutely cannot be done from Earth.
We can sit here and dream about building 30-meter telescopes in space some day, but that day is a very long way off. My guess is that even far in the future, if you're given X amount of money to invest in astronomy, you will still want to invest a large percentage of it in ground-based telescopes, because your money goes a lot father on the ground for most problems.
> a single 30m element isn't necessarily the only way to get very large telescopes.
No existing or planned telescope uses a single 30-meter element. I think the largest primary mirror is 12m. All the planned 30-meter-class telescopes are segmented.
There's no "just" about it, I'm aware of that, and I know it's not a case of taking existing scopes and shoving them into space.
> There is a role for space telescopes, but the total number of them could be counted on a few hands. Space telescopes are an extremely precious and limited resource, used basically only for things that absolutely cannot be done from Earth.
This is, in large part, because of the cost of launching and maintaining them. Satellite launch prices have come down dramatically in the last 20 years. If Starship becomes a reality, then it'll come down even further.
If we're actually to ever get off this planet as a species, then dramatically lowering the cost of getting stuff into orbit is a necessity.
I sympathise with Astronomers who're concerned about the impact on their ability to do science today, but its a bit like people complaining about the first interstates highways being built. Yep, we're going to demolish some houses, and make some places a bit noisier.
I'm hoping that someone will decided to invest their billions of dollars into mining and manufacturing in space to demonstrate that it's actually possible, and likely incredibly profitable.
Once that happens, we can make really stupidly large telescopes in-orbit.
https://en.m.wikipedia.org/wiki/Orion_(satellite)
It is estimated the highly classified Orion signal inteligence satellites currently in geostationary orbit have radio reflecting dishes of more than 100 m in diameter.
I don't think it's that far off, the primary mirror for Hubble was 2.4m and the big telescopes you're talking about are made up of mirror segments around 10m in size. The Falcon 9's payload fairing is 5.2m diameter and 13m long and the proposed Starship fairing would be 9m diameter by 19m high. SpaceX is currently proving they are capable of sustaining a rapid launch cadence and have already proved they're capable of docking with the ISS. If someone built a modular space telescope, they'd be the first ones to call to get it into orbit for assembly.
Cost has been a severe bottleneck to getting science into space for so long that we seem to have become convinced that it will always be so. These Starlink launches are the first real steps in proving that it need not be so.
The cost to build JWST, a 6.5-meter space telescope, is over $10 billion. The ground-based telescope costs 1/10th as much and has 20x the collecting area (and 4.5x the resolution). Unlike the space telescope, the ground-based telescope can be periodically upgraded with new cameras, spectrometers, and other scientific instruments.
Space telescopes have a place in astronomy, but they're no substitute for ground-based telescopes.
Weight allows you to put many more scientific instruments on the same telescope (fiber-fed spectrometers, intregral-field spectrographs, imagers, coronagraphs, etc.) In order to put an instrument on a space telescope, you have to miniaturize it and make it light, and you have to decide before launch what instruments to put on the telescope. In contrast, on the ground, you're not nearly as weight- and size-constrained, and you can upgrade the instruments on a telescope every several years. There are decades-old telescopes still in use, retrofitted with modern sensors.
And?