Are ground-based telescopes obolete?

[Mitchz95]

With the advent of truly reusable launch vehicles, two things are very likely to happen over the next decade or two:

1) Launching stuff into space is going to be way cheaper than ever before.

2) There's going to be a LOT more stuff in orbit. We all saw the concerns about what effect Starlink would have on astronomy. Even if Starlink itself turns out to be not a big deal, we know Kuiper is coming soon and presumably lots of other mega-constellations will follow.

With these in mind, it seems likely that we'll soon have both the desire and the ability to launch space telescopes more commonly, and to higher orbits as well. So does this mean ground-based telescopes, like the controversial one planned in Mauna Kea, obsolete in the near-term?

[Bill Phil]

I don’t think so.

Building space hardware of any sort is difficult and will remain so for some time.

Even if launching is cheap the actual spacecraft itself will likely be expensive.

I don’t think space telescopes will rival the sheer size of ground telescopes for some time. I think we’d need a mature space manufacturing industry for that. Maybe not but even now there are quite a few 20 to 30 meter telescopes under construction. Quite a lot of astronomy is done with already existing installations so I expect the bigger telescopes to be very useful in the coming decades. 

[Gargamel]

Simply, No. 

[Wjolcz]

Nope. Adaptive optics can be really precise. Not only that but we have interferometry. I don't think measuring time and distance with on-orbit telescopes is doable right now. You could land a couple of telescopes on the Moon and directly image exoplanets.*

*Probably. At least I want to live long enough to see that happen.

[Cunjo Carl]

Getting one of these into space would be an undertaking of Kerbal proportions!

[tater]

Not yet, but they will be, eventually.

It's simply a matter of cost right now. Seeing is better out of the atmosphere, but space telescope projects end up incredibly expensive.

Angular resolution is a function of objective diameter, so you want big telescopes. Once you get better than seeing, then you might as well be in space, but then cost gets higher.

[kerbiloid]

Once they make a mirror construction to be easily built in space, not launched at once or made by hands in orbit.

Say, foldable 10 m wide segments being attached around the existing mirror, then around the bigger mirror, and so on, until the orbital mirror gets 100 m in diameter.
Preferably, self-crawling, self-attaching. Just dock/berth it and wait while it's crawling, attaching, and unfolding.

Edited July 28, 2019 by kerbiloid

[satnet]

19 hours ago, Cunjo Carl said:

Getting one of these into space would be an undertaking of Kerbal proportions!

Actually there is an interesting proposal to use in space construction to build something on this scale. I'm not sure how likely it is to actually be built, but it does allow for some interesting possibilities.

 

Edited July 28, 2019 by satnet
Fixing grammar marred by rewrite.

[kerbiloid]

A tank with viscous material (low-melting alloy or high-melting polymer).
A source of power (solar panels or a mini nuke).
A low-thrust thruster (say, an ion engine).

Switch on the power plant.
Full (but tiny-tiny) throttle of the thruster.
Start rotating this, including the tank..
Start melting the mirror material and sticking it out from the rear end.
Let it keep radially expanding as a pancake, and freezing.
By the thrust of the thruster keep the pancake parabolic.
Cool the mirror.
...
Profit!!!!!! A monolithic parabolic orbital mirror.

Now you can send a hundred of such canisters across the Solar system and get a telescope swarm.
Possibly bad quality would be offset by large quantity.

Edited July 29, 2019 by kerbiloid

[Guest]

Imagine a starlink size constellation but made of small cheap telescopes and pointed outward instead of in. I bet with some fancy ground based processing that would be a super powerful tool for astronomers. 

I wonder what kind of resolution that would give us if used as an interferometer. 

Edited July 29, 2019 by Guest

[DDE]

On 7/27/2019 at 9:44 PM, Mitchz95 said:

There's going to be a LOT more stuff in orbit.

It really, really depends on what kind of telescope we’re talking about.

For some telescopes, you don’t want them to be vulnerable to the Kessler syndrome - or enemy space superiority assets.

[Listy]

The Keck Observatory was built around the same time as Hubble (mid-80's) & probably represented the pinnacle of ground based observatories at the time. It's got a bigger mirror (10m vs 2.4m), cost a lot less to build (~$200m versus $4.7billion) & costs less to operate per year ($15m versus $100m) than Hubble. So based on cost alone, ground telescopes will be around for a while yet. There are generally no do overs in space when something goes wrong (hello Hitomi X-Ray telescope), so new technology and techniques will continue to be honed on the ground too, before being tried in space (Hubble is a happy exception to the no do overs rule). There's a lot of unique & exciting things that can be done with telescopes in space (eg you could set up some truly huge interferometry arrays) though, so it's likely that more and more of the flagship scale observatories will become space based in the coming decades.

[YNM]

On 7/28/2019 at 1:44 AM, Mitchz95 said:

does this mean ground-based telescopes, like the controversial one planned in Mauna Kea, obsolete in the near-term?

The two existing 10m telescopes can achieve resolutions higher than Hubble through lucky imaging, without the fuss of trying to make something you can't service afterwards.

So the answer is no. Regardless of how reusable your rocket is, creating a 30-m diameter mirror in space is still a larger PITA than making one on the ground - yeah you don't have to counter gravity, and you don't have to be worried about the ground moving about or the air blew you off, but you also don't require stationkeeping, and space manufacturing and assembly is still in it's earliest stage. If those last two were to change, then we might really see things shifting; but even then they'd have less proven experience than doing them on the ground.

A much more promising view would be on the increased availability of wavelengths that simply doesn't reach the ground - gamma rays, x rays, UV, Infrared, Microwave and such.

Edited July 29, 2019 by YNM