Presumably to the point where people who want to can subscribe to a Hubble-like satellite service and get all the space photos their hearts desire.
Also, we made a similar trade-off a long time ago - most people live in heavily light-polluted cities, because we value having street lighting more than being able to see the stars.
1. Space is a hostile place, and developing telescope that works there is much harder. 2. There are very real limits on size and weight of what can be put there right now, and rocket equation is ruthless. 3. Any type of maintenance or upgrades are basically impossible, compared to earth based. 4. Adaptive optics were such a huge breakthrough, that basically negated need for most of space based telescopes.
There's a feedback loop in space launches: they're expensive, therefore you launch less, so you need to add redundancies and spend more time ensuring the payload will work, which raises the development cost and increases mass, which makes launches less frequent and more expensive.
Conversely, reducing the cost of access to space means you can send more stuff that's less robust, which shortens development time and makes it less expensive, and of course makes technological progress faster.
Which translates to: suddenly space telescopes may be more affordable, and more of them will be launched.
Even with cheaper launches it's much harder to get that benefit in space--servicing missions are much more expensive than driving up a mountain...
We should be fair and acknowledge all the downsides, and if you disagree I would ask to waste a bit of effort and explain why we should ignore this costs on the public(maybe the costs are worth it in the long run but we should not ignore them)
Let me know if somehow I am wrong and for example Hubble is superior to all telescopes on the ground at the time it was launched. The best thing is to have it all, giant telescope arrays on the ground, telescopes in orbit, on the moon, on the other side of the sun/
Ground-based telescopes have a number of very significant advantages over space-based telescopes. You can build much larger and heavier telescopes and instruments on the ground. If you want to observe faint objects, you need more photons. To capture more photons, you need a larger primary mirror.
Space-based telescopes used to give higher resolution, but adaptive optics undo much of that advantage. In fact, because the diffraction limit is dependent on the size of the primary mirror, ground-based telescopes can achieve better resolution than space-based telescopes.
You can attach large, heavy instruments, such as massively multiplexed spectrometers, to ground-based telescopes. And you can switch instruments out and do periodic upgrades and maintenance.
Space-based telescopes have advantages in certain specific areas. They can observe wavelengths that Earth's atmosphere absorbs or emits at (such as the ultraviolet and infrared). They can achieve much better calibration, because there's no atmosphere to calibrate out. They can achieve high resolution across a wide field of view (adaptive optics negates the effects of the atmosphere in a small field of view). Sometimes you need these particular advantages, so space telescopes are critical. Often you don't, and ground-based telescopes are superior.
Isn't there a way of multiplexing lots of small telescopes together to gather more photons and effectively emulate a larger telescope in software?
If so, could you launch 1000 small telescopes into space and effectively have a (set of <1000) larger telescope(s)?
See European Southern Observatory's very large telescope.
There are telescopes formed from arrangement of smaller telescopes (like mentioned Very Large Telescope of European Southern Observatory), but these have to be connected optically (by a system of precise mirrors), not just digitally.
Interferometry is much easier with radio telescopes. You can record the waveform at each dish, and then digitally combine the signals afterwards (there is specialized "correlator" hardware that is purpose-built to do this very efficiently).[2] That means you can put receivers anywhere (on Earth or even in space), as long as you are able to synchronize the timestamps in the data well enough to digitally combine the signals afterwards. One of the major technical challenges faced by the Event Horizon Telescope, which imaged the black hole at the center of M87,[3] was synchronizing clocks at stations on opposite sides of the Earth. They had to physically bring atomic clocks from one location to another. After they took their observations, they flew hard drives with the recorded signals to a centralized location to do the correlation.
1. https://www.eso.org/public/teles-instr/technology/interferom...
2. https://www.aanda.org/articles/aa/full/2007/05/aa4519-05/aa4...
3. https://eventhorizontelescope.org/press-release-april-10-201...
The article on interferometry implied that this is "just" a matter of computational difficulty - the higher frequency means that more accuracy and computing power is needed to resolve an image. Is that right?
If so, surely this is a Moore's Law problem, solved by waiting a few years for the needed computing power to be cheap enough to use?
CCDs just count photons (incoming photons kick electrons into the conduction band, and you count electrons after each exposure). There are more advanced detectors that tell you the energy of the photons, but not their phase. If you can't measure the phase of individual photons, you can combine light from different telescopes directly, and let nature do the correlation for you. That's what optical interferometers do.
To me it seems like the moment we got a proper space telescope( Hubble) there was a ton of low-hanging fruit to discover at such a degree that so many years later we are still finding out new stuff. Compared to that Earth based telescopes seem to have to go through massive efforts to make headline discoveries( not that any other less discussed paper isn't important, it's just that... how would we know about e.g. the acceleration of the universe from an Earth based observatory?).
That's a function of how the media works. Ground-based telescopes are extremely important for astronomy, and I would even venture to say are involved in most major discoveries. Space telescopes are also extremely useful, but they're also much flashier than ground-based telescopes.
> how would we know about e.g. the acceleration of the universe from an Earth based observatory?
By observing type-Ia supernovae (SNe Ia), for example. Not only is it possible to do this with ground-based telescopes, but ground-based telescopes are the primary way it is done. Most of the SNe Ia observations that went into the discovery of the acceleration of cosmic expansion were done from the ground.
All of these things are coming, in subsequent revisions of hardware.
Everyone on HN should recognise the pattern - it's very much a launch of a minimum viable product.