9 ms·

Not since the advent of modern adaptive optics[1]. Ground-based telescopes now outperform space telescopes in the visible spectrum[2]. For as long as the cost p

Not since the advent of modern adaptive optics[1]. Ground-based telescopes now outperform space telescopes in the visible spectrum[2]. For as long as the cost per kilo to orbit is higher than the cost per kilo to the Atacama desert, ground-based astronomy is going to be superior. The other great advantage of ground-based telescopes is that _they're easy to fix and improve_. The iteration loop is that you walk into the dome and you fiddle with things. You don't need multiple years of planning to polish a mirror. There's an excellent Twitter thread on this issue here[3]. [1] https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics [2] https://astronomynow.com/2018/07/19/adaptive-optics-tomography-provides-hubble-class-images/ https://astronomynow.com/2018/07/19/adaptive-optics-tomograp... [3] https://twitter.com/cynosurae/status/1196567663977230336 https://twitter.com/cynosurae/status/1196567663977230336

semiotagonal 7y ago
Perhaps a deal could be worked out where the satellite companies also have to launch Atacama-scale telescopes, where Musk et al have to pay for the difference in cost between Atacama and orbit.
- Rebelgecko 7y ago
  Telescopes are pretty big. It would take 5-10 Falcon 9 launches to put something with that mass into orbit (although in space you could probably have a lighter mechanism for orienting el/az). The telescope's mirror is also too big to physically fit into the F9's fairing. Once you get it there, you need to assemble it and keep it running. Maintenance is a real doozy— building a telescope on Earth is expensive. Building a telescope in space is even harder, since it won't be regularly serviced and you have to overengineer it. A typical space telescope still costs an order of magnitude more than a recordbreakingly expensive earth-based one.
  - DennisP 7y ago
    Yes but the point of Starlink is to fund Starship, which is a lot bigger than Falcon 9. Its fairing is 9 meters in diameter[0], large enough for all but the top six land-based telescopes.[1] Its payload is 100+ tonnes, five times larger than Falcon 9's. Starship is also a lot cheaper per kilogram of payload; at scale, as low as $20/kg. Cheap launch also makes your satellites cheaper to build, since it's less of a disaster if you have to replace them. Musk has already floated the idea of building a second-generation Starship with an 18-meter fairing.[2] [0] https://www.spacex.com/starship https://www.spacex.com/starship [1] https://en.wikipedia.org/wiki/List_of_largest_optical_reflecting_telescopes https://en.wikipedia.org/wiki/List_of_largest_optical_reflec... [2] https://www.teslarati.com/spacex-elon-musk-starship-the-next-generation/ https://www.teslarati.com/spacex-elon-musk-starship-the-next...
    - Rebelgecko 7y ago
      Even if it becomes physically possible to launch them at some point in the future, I should have mentioned that launch costs are only a relatively small part of the cost of space based telescopes. As launch prices continue to go down, this will be more and more true in the future. For the upcoming JWST, the launch is only costing around 1-2% of the overall price. It will be a similar number for WFIRST if that gets built on budget. The expensive part is engineering a device that can assemble itself in outer space, and continue to run 24/7 for decades without regular maintainence.
      - DennisP 7y ago
        You don't need much orbital assembly if you can launch something with a 9-meter or 18-meter diameter. And again, cheaper launch cost also makes space hardware cheaper; you can afford to make it heavier, and you can afford to replace it if necessary.
      - avmich 7y ago
        This is outdated model regarding space telescopes. With radically cheaper launches, it's becoming quite possible - not now, but somewhat soon - to actually service telescopes, with conditions superior to those under which the Hubble was serviced by Shuttle teams. With radically cheaper launches, it's not necessary to ensure the 'scope runs 24/7 for decades without regular maintenance. It can even be replaced regularly; including by bringing it to Earth, servicing it and sending back. Launch prices are going to drop, but so is the necessity to be extremely reliable for the space equipment, for the same two reasons: 1) it's comparatively easy to get to it for a service and 2) it's comparatively easy to just send a replacement if needed. With space manufacturing advancements still ahead of us - we didn't really experimented with making telescopes in orbit - it's not clear if space telescopes won't outperform terran ones. Space telescopes are going to have advantages like "atmosphere doesn't block part of the spectrum" and "there is no need to make a big structure capable withstanding 1g gravity". It's still crucially important to be able to do terran-based astronomy, and that's a problem, but there is no doubt that the astronomy revolution which started with Hubble still has major advancements to have in the near future.
strainer 7y ago
Adaptive optics should be able to adapt to any number of satellites traveling, quite predictably and diminutively through their frame of capture.
- willis936 7y ago
  Signal to noise ratio is the limiting factor in these observations. Decrease the signal and suddenly whole sets of galaxies fall below the noise floor.
  - strainer 7y ago
    I have not seen any information that light from these satellites could scatter and brighten the night sky a significant amount. This article just shows their paths are visible on a sensitive image, but the paths themselves amount to tiny fraction of the image. There is no claim they added significantly to the overall exposure. With their being bright planets and stars already present in the sky, I don't expect they could.
- colanderman 7y ago
  That is not remotely what "adaptive optics" means. Word arguments like that degrade the quality of debate.
  - ISL 7y ago
    In case the commenter isn't aware, adaptive optics compensate for the shimmer of the atmosphere, not the presence of light-scattering objects between the telescope and a dim object part-way across the universe.
    - strainer 7y ago
      Relevant light scattering occurs in the atmosphere between the satellite and the telescope. It also occurs between every other light source, across the universe, and the telescope. Thats why the satellites contribution to light scattering is tiny. Even in the morning where one might catch the sun - the sky is already lightened. Hard or soft optical adaptations to remove atmospheric distortions are far more demanding than processing required to remove low magnitude satellite trails, which is already developed and required on occasion.

semiotagonal 7y ago

Perhaps a deal could be worked out where the satellite companies also have to launch Atacama-scale telescopes, where Musk et al have to pay for the difference in cost between Atacama and orbit.

Rebelgecko 7y ago
Telescopes are pretty big. It would take 5-10 Falcon 9 launches to put something with that mass into orbit (although in space you could probably have a lighter mechanism for orienting el/az). The telescope's mirror is also too big to physically fit into the F9's fairing. Once you get it there, you need to assemble it and keep it running. Maintenance is a real doozy— building a telescope on Earth is expensive. Building a telescope in space is even harder, since it won't be regularly serviced and you have to overengineer it. A typical space telescope still costs an order of magnitude more than a recordbreakingly expensive earth-based one.
- DennisP 7y ago
  Yes but the point of Starlink is to fund Starship, which is a lot bigger than Falcon 9. Its fairing is 9 meters in diameter[0], large enough for all but the top six land-based telescopes.[1] Its payload is 100+ tonnes, five times larger than Falcon 9's. Starship is also a lot cheaper per kilogram of payload; at scale, as low as $20/kg. Cheap launch also makes your satellites cheaper to build, since it's less of a disaster if you have to replace them. Musk has already floated the idea of building a second-generation Starship with an 18-meter fairing.[2] [0] https://www.spacex.com/starship https://www.spacex.com/starship [1] https://en.wikipedia.org/wiki/List_of_largest_optical_reflecting_telescopes https://en.wikipedia.org/wiki/List_of_largest_optical_reflec... [2] https://www.teslarati.com/spacex-elon-musk-starship-the-next-generation/ https://www.teslarati.com/spacex-elon-musk-starship-the-next...
  - Rebelgecko 7y ago
    Even if it becomes physically possible to launch them at some point in the future, I should have mentioned that launch costs are only a relatively small part of the cost of space based telescopes. As launch prices continue to go down, this will be more and more true in the future. For the upcoming JWST, the launch is only costing around 1-2% of the overall price. It will be a similar number for WFIRST if that gets built on budget. The expensive part is engineering a device that can assemble itself in outer space, and continue to run 24/7 for decades without regular maintainence.
    - DennisP 7y ago
      You don't need much orbital assembly if you can launch something with a 9-meter or 18-meter diameter. And again, cheaper launch cost also makes space hardware cheaper; you can afford to make it heavier, and you can afford to replace it if necessary.
    - avmich 7y ago
      This is outdated model regarding space telescopes. With radically cheaper launches, it's becoming quite possible - not now, but somewhat soon - to actually service telescopes, with conditions superior to those under which the Hubble was serviced by Shuttle teams. With radically cheaper launches, it's not necessary to ensure the 'scope runs 24/7 for decades without regular maintenance. It can even be replaced regularly; including by bringing it to Earth, servicing it and sending back. Launch prices are going to drop, but so is the necessity to be extremely reliable for the space equipment, for the same two reasons: 1) it's comparatively easy to get to it for a service and 2) it's comparatively easy to just send a replacement if needed. With space manufacturing advancements still ahead of us - we didn't really experimented with making telescopes in orbit - it's not clear if space telescopes won't outperform terran ones. Space telescopes are going to have advantages like "atmosphere doesn't block part of the spectrum" and "there is no need to make a big structure capable withstanding 1g gravity". It's still crucially important to be able to do terran-based astronomy, and that's a problem, but there is no doubt that the astronomy revolution which started with Hubble still has major advancements to have in the near future.

strainer 7y ago

Adaptive optics should be able to adapt to any number of satellites traveling, quite predictably and diminutively through their frame of capture.

willis936 7y ago
Signal to noise ratio is the limiting factor in these observations. Decrease the signal and suddenly whole sets of galaxies fall below the noise floor.
- strainer 7y ago
  I have not seen any information that light from these satellites could scatter and brighten the night sky a significant amount. This article just shows their paths are visible on a sensitive image, but the paths themselves amount to tiny fraction of the image. There is no claim they added significantly to the overall exposure. With their being bright planets and stars already present in the sky, I don't expect they could.
colanderman 7y ago
That is not remotely what "adaptive optics" means. Word arguments like that degrade the quality of debate.
- ISL 7y ago
  In case the commenter isn't aware, adaptive optics compensate for the shimmer of the atmosphere, not the presence of light-scattering objects between the telescope and a dim object part-way across the universe.
  - strainer 7y ago
    Relevant light scattering occurs in the atmosphere between the satellite and the telescope. It also occurs between every other light source, across the universe, and the telescope. Thats why the satellites contribution to light scattering is tiny. Even in the morning where one might catch the sun - the sky is already lightened. Hard or soft optical adaptations to remove atmospheric distortions are far more demanding than processing required to remove low magnitude satellite trails, which is already developed and required on occasion.