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Space telescopes are vastly superior to ground ones. There is no competition, imo the decreasing cost of launching will enable incredible telescopes in the futu

Space telescopes are vastly superior to ground ones. There is no competition, imo the decreasing cost of launching will enable incredible telescopes in the future.

simion314 6y ago
If you have same size yes but the issue in space you can send only smaller telescopes, this ones are inferior on some dimensions versus the big ones we have on high mountains on deserts but sure a small telescope in space is better then a same size on the ground. 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/
DiogenesKynikos 6y ago
That's a bit like saying that forks are superior to knives. They're good at different things. 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.
- marcus_holmes 6y ago
  disclaimer: I know almost nothing about telescopes. 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)?
  - Gibbon1 6y ago
    Multiple mirror telescopes are a thing. They can be used to gather more light or increase the angular resolution. See European Southern Observatory's very large telescope.
  - zajio1am 6y ago
    AFAIK you can do that with radiotelescopes, but cannot easily with optical telescopes. That is because optical sensors lose phase information of incoming signal. 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.
    - DiogenesKynikos 6y ago
      That's correct. For optical telescopes, you have to physically combine the signals in real time to do interferometry. The VLT can do optical interferometry, and can create baselines as long as 200 meters (reaching nearly 100x the resolution that the Hubble Space Telescope achieves).[1] If you just combine the images from different telescopes, without doing interferometry, you only get one of the benefits of a larger telescope (you can see fainter objects), but you don't get all the benefits (e.g., higher resolution). 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/interferometry/ https://www.eso.org/public/teles-instr/technology/interferom... 2. https://www.aanda.org/articles/aa/full/2007/05/aa4519-05/aa4519-05.html https://www.aanda.org/articles/aa/full/2007/05/aa4519-05/aa4... 3. https://eventhorizontelescope.org/press-release-april-10-2019-astronomers-capture-first-image-black-hole https://eventhorizontelescope.org/press-release-april-10-201...
kergonath 6y ago
It’s funny how many people who know nothing about telescopes have been saying that recently...

Space telescopes are vastly superior to ground ones. There is no competition, imo the decreasing cost of launching will enable incredible telescopes in the future.

simion314 6y ago

If you have same size yes but the issue in space you can send only smaller telescopes, this ones are inferior on some dimensions versus the big ones we have on high mountains on deserts but sure a small telescope in space is better then a same size on the ground. 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/

DiogenesKynikos 6y ago

That's a bit like saying that forks are superior to knives. They're good at different things. 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.

marcus_holmes 6y ago
disclaimer: I know almost nothing about telescopes. 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)?
- Gibbon1 6y ago
  Multiple mirror telescopes are a thing. They can be used to gather more light or increase the angular resolution. See European Southern Observatory's very large telescope.
- zajio1am 6y ago
  AFAIK you can do that with radiotelescopes, but cannot easily with optical telescopes. That is because optical sensors lose phase information of incoming signal. 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.
  - DiogenesKynikos 6y ago
    That's correct. For optical telescopes, you have to physically combine the signals in real time to do interferometry. The VLT can do optical interferometry, and can create baselines as long as 200 meters (reaching nearly 100x the resolution that the Hubble Space Telescope achieves).[1] If you just combine the images from different telescopes, without doing interferometry, you only get one of the benefits of a larger telescope (you can see fainter objects), but you don't get all the benefits (e.g., higher resolution). 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/interferometry/ https://www.eso.org/public/teles-instr/technology/interferom... 2. https://www.aanda.org/articles/aa/full/2007/05/aa4519-05/aa4519-05.html https://www.aanda.org/articles/aa/full/2007/05/aa4519-05/aa4... 3. https://eventhorizontelescope.org/press-release-april-10-2019-astronomers-capture-first-image-black-hole https://eventhorizontelescope.org/press-release-april-10-201...

kergonath 6y ago

It’s funny how many people who know nothing about telescopes have been saying that recently...