That needs some citations. The James Webb Telescope's mirror is 6.5m in diameter. It took decades and billions of dollars of overruns and a prayer to launch and work correctly. There is no hope of most hardware repairs.
That mirror size pails in comparison to what can be accomplished via ground based observatories for much, much cheaper.
And the available modes of operation are completely different between space and ground. For example, space observatories are using decades old instrumentation techniques, hardware, and software. And that's just for starters.
We cannot do astronomy via space exclusively.
For me personally, I never wanted to see something like Starlink with my bare eyes, and I have several times. It's beyond annoying to me that a company has been able to unilaterally pollute the Earth's sky.
> That needs some citations. The James Webb Telescope's mirror is 6.5m in diameter. It took decades and billions of dollars of overruns and a prayer to launch and work correctly. There is no hope of most hardware repairs.
Because it had to get launched folded up, because the launch vehicles were so space- and mass-constrained. The unfolding mechanism was enormously complicated and added to much of the cost.
Now we can send up bigger, heavier objects for much less money. The 6.5m mirror fits comfortably inside Starship's cargo bay, unfolded. JWST is a one-off clockwork masterpiece; future space telescopes will come off an assembly line. There will be thousands in orbit, pointed at every part of the heavens simultaneously.
The 39-meter primary mirror has 798 1.4-meter segments, each individually adjustable. The scaffolding required to hold all the segments is "significant" and must be assembled in orbit. We would stick this out next to the James Webb at L2, which means we would need the ability to travel to L2 to construct this mythical orbital extremely large telescope.
With our current technology, we can build ELT on Earth for a fraction of the cost of putting it in orbit.
For one thing, before this decade is out we will have the lift capacity to get an ELT-worth of mass to L2. And the lack of need to correct for atmospheric distortion would simplify the design considerably.
But it's beside the point. Such a singular mega-telescope would no longer be the only way to do astronomy in space. A world of radically lower launch costs gives more possibilities. We could have a fleet of thousands of independent small/medium sized space telescopes. That way, we wouldn't have to carefully ration imaging time between competing astronomy projects anymore. High quality data would become cheap and abundant, procured on-demand.
It doesn't simplify the design; it increases its complexity. All the problems of telescopes on Earth become significantly more problematic in space: temperature, flexure, warping, backlash, pointing models, optical alignment, and collimation are some of the issues.
Electronics, sensors, and consumables fail or run out, which means you need to be able to get there to fix things. Then, as research projects change, you need to change instruments.
Yes, one could have thousands of 1-5 m telescopes. A terrestrial scope is about an order of magnitude cheaper than an orbiting telescope. So, the big question is who will pay to replace the thousands of scopes in that size range that are already operating on Earth.
Rationing will still needed (Research projects always exceed the number of available scopes). High-quality data, will not be as cheap or abundant as you think it might be. With the number of scopes we are talking about and the sensors that astronomers use, we can expect hundreds or thousands of petabytes a second of data. How will we get that data down from orbit?
This is just one project. Could you imagine a thousand of these astronomical fire hoses running at the same time in orbit?
The next issue is where these telescopes should be placed. The more we learn about running telescopes in orbit, the more we realize that they need to be placed very far from Earth to increase the observable sky and the length of time one can study a chunk of it. As I said above, consumables need to be replaced, sensors need to be changed for the observing program, boils down to how you are going to get a repair crew out to wherever the telescopes are.
> Electronics, sensors, and consumables fail or run out, which means you need to be able to get there to fix things. Then, as research projects change, you need to change instruments.
So launch another. Launch capacity is getting cheap... let's use it.
Consider that 1% of SpaceX's annual launch capacity is enough to put one Hubble in orbit every year. Instead of sending astronauts to fix the fucked-up mirror, you just launch one with a not-broken mirror.
We as a planet don't even build that many ground-based telescopes with a 2.5m+ mirror each year. Think about how astronomy would change if you could just take every telescope we build today and put it in space.
This scope is not built for space travel. This model for space telescopes from NASA put a price tag on all the major components for building and operating a single space telescope is counted in billions. https://ntrs.nasa.gov/api/citations/20110015780/downloads/20...
A couple of things not covered in other comments are the costs of mission control and end-of-life deorbiting. It is far cheaper to rent a car, drive to an observatory, mount your evolving experiment on scope, and debug it on-site than to put the same experiment in orbit. Terrestrial telescope mission control is ad hoc and usually in a heated/air-conditioned shack on the mountaintop.
> 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.
It is not impossible. But you would have to design the telescope to be a rocketship complete with motors, fuel tanks, and all that other fun stuff. That would significantly increase the telescope's complexity to withstand the force and vibration of a rocket engine. Theoretically, one could use ion drives, but the engineering challenges of creating ion drives capable of moving a few hundred tons of telescope are significant.
It is much simpler to build the telescope equivalent of IKEA flatpack furniture and assemble it on-site than it is to build it and then move it.
Doesn't matter. The point is that, thanks to reusable boosters, launching satellite constellations, and other recent developments, space is becoming much cheaper - so if you can't fit 8 JWSTs in one Starship, just launch the rest on another, and it'll still come out cheaper than the original JWST.
Ultimately it becomes so cheap we'll be able to put workers up there to assemble and maintain the telescopes, just like on Earth. We might see telescopes in telescope farms near a small station for the workers. It might even be possible to send workers out to the Sun-Earth L2 point to maintain telescopes there.
mate I can't give you a citation for something that hasn't happened yet. it's a reasonable extrapolation of current trends. don't give me this "citation needed" whining.
If the promises made for new launch systems like SpaceX' Starship (and maybe even, one day, in some unknown future, Bezos' Blue Origin manages to launch something larger than a phallic pond hopper?) it should become radically less expensive to launch larger telescopes into orbit and/or to e.g. the moon.
That "should" needs a lot of backing up, and I don't understand why we need to singlehandedly rely on the same company creating the issues to apparently solve them with wishful thinking.
> I don't understand why we need to singlehandedly rely on the same company creating the issues to apparently solve them with wishful thinking.
It is because you did not start your own re-usable space vehicle company. Bezos did but thus far he seems to treat it as a billionaire's toy, throwing a few fellow class members just over the Kármán line. There's a few others making attempts to actually get to space - Rocket Labs etc. - but mostly it comes down to Musk's creation which opened the door to radically lower costs, i.e. without them the usual suspects would have had no reason to keep on pushing 70's technology at whatever price they manage to extract from the governments and the market.
The future of astronomy is both on the ground and in space.
There are so many things that you can only conceivably do from the ground. You can build vastly larger telescopes on the ground, you can install far heavier instruments (like cameras and spectrographs) on them, you can upgrade and repair components much more easily. You can build massive arrays of radio telescopes. You get the point.
There are some things you can only do from space, or that are better in space, but saying that everything will be done in space is like saying we only need laptops and don't need datacenters. You need both.
Yes, though I guess it depends on what you mean by lots: https://en.wikipedia.org/wiki/List_of_largest_optical_reflec.... Critically the 30+m monsters under construction have only recently become feasible on the Earh let alone in space, and much smaller instruments still provide significant value today.
There’s a much longer list of large radio based telescopes which have minimal advantages in space to the point where we haven’t launched any, and they are also negatively impacted by constellations. Also, several types of observations don’t really benefit from being in space. If you want to track killer asteroids space doesn’t provide much advantage even if you could get there for 100$/kg.
IMO the issue here isn’t satellites, it’s that they can harm multi billion dollar investments at zero cost to themselves. If you’re very clearly causing 10’s of millions in damages you really should be compensating the people affected.
> There’s a much longer list of large radio based telescopes which have minimal advantages in space to the point where we haven’t launched any
What if they could be put behind the Moon, completely shielding them from Earth RF emissions? It's been a cost-prohibitive idea now, but might not be for much longer.
The largest filled-aperture radio telescope in the world has a 500-meter diameter, and reportedly only cost $180 million. For comparison, the International Space Station costs $3 billion per year just to operate. Doing stuff in space is expensive.
For large (>10m) telescopes, it doesn't matter much, because no one is building rockets with big enough fairings. Even if the cost of launching to LEO was $0, in-orbit unfolding/assembly is a bottomless hole of engineering complexity that you cannot avoid. Again, see JWST/ISS.
I count 13 on wikipedia's list of the largest telescopes. There are 3 more currently under construction. The evocatively named "Extremely Large Telescope" is estimated to cost about $1 billion USD. Who knows how much it will actually cost, but for comparison, that's about $400 million less (adjusted for inflation) than the budgeted cost of the Webb telescope, which is about 1/6 the planned size (and therefore 1/36 the light collecting capability).
edit: italicized above. The Webb ended up costing $10 billion, so the savings could be even larger
But the point is that Webb was vastly over-engineered because we needed to get value out of every ounce of mass at the very high costs of legacy launch providers, and even more compromised because of Ariane 5’s tiny fairing.
You could build Webb for vastly, vastly less money if it launched on Starship, not just per unit of mass; volume is at much less of a premium in the new regime.
You can’t quite fit ELT pre-constructed into a single Starship, it’s true. But it’s built out of segmented mirrors. It doesn’t have to arrive on station in one piece.
If the satellites don't disrupt it, light pollution will anyway, or best case, it will be disrupted by atmospheric pollution.
There's no lack of clear skies in space.