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>It will likely affect some earthbound astronomy significantly, but much (most?) of the most important work in modern astronomy is satellite based. I'm not an

>It will likely affect some earthbound astronomy significantly, but much (most?) of the most important work in modern astronomy is satellite based. I'm not an astronomer but I'm not convinced that that's the case. The number of space telescopes pales in comparison to the number of terrestrial observatories. Moreover, advances like adaptive optics have done a lot to close the gap between ground and space capabilities (for optical telescopes). Even once you've invested in expensive tech like adaptove optics, a telescope in space still costs an order of magnitude more than one on the ground (thats being really conservative. JWST has already cost ~10x more than the most expensive ground telescope ever, and the thing hasn't even launched yet) There were a few space based radio telescopes in the past, but I don't think there are any now. Imagine building something like the Arecibo Observatory[1] or VLA[2] in space. And speaking of the VLA, some of the techniques for getting high quality results (e.g. interferometry without physically conjoining the receivers) are difficult if not impossible to do in space. [1]: https://en.wikipedia.org/wiki/Arecibo_Observatory https://en.wikipedia.org/wiki/Arecibo_Observatory [2]: 27 of these guys, which are able to move around precisely on rails to generate constructive interference with the different waves they're receiving: https://public.nrao.edu/wp-content/uploads/2016/04/vla_panorama_med-1.jpg https://public.nrao.edu/wp-content/uploads/2016/04/vla_panor...

shadowgovt 7y ago
Can adaptive optics be applied to filter out objects like Starlink satellites?
- toomuchtodo 7y ago
  You can filter them out computationally without adaptive optics with enough frames captured.
  - HorstG 7y ago
    Modern astronomy works at the edges of whats possible, a single frame might take hours. Needing multiple frames would mean multiple days per observation. It would mean no longer seeing faint and distant objects, limiting us to younger, closer and frankly far more boring objects. It would make observing variability impossible for certain timescales. You need old distant objects for cosmology, observing the structure if the universe, big bang and stuff. You need variability for finding exoplanets, measuring distance and observing transitions such as supernovae. Oh, and then a huge part is taking spectra, which means bouncing the light directly off a grating. Filtering transients is hard to impossible there. You need spectra for relative motion, magnetic fields, composition of matter and radiation and of course temperature. Needing such filters would set astronomy back a few decades
    - toomuchtodo 7y ago
      Astronomy will need to catch up or pay for a resource they’ve been getting for free (unobstructed sky). Or start lifting more advanced platforms to orbits (whether that’s Earth or Lagrange points).
      - HorstG 7y ago
        Well then, we should also have Elon pay rent for use of space...
        toomuchtodo 7y ago
        I think it’s hard to argue it belongs to you if you can’t get there. If you can’t defend it or control it, you can’t stake a claim to it. https://en.wikipedia.org/wiki/Extraterrestrial_real_estate https://en.wikipedia.org/wiki/Extraterrestrial_real_estate
        HorstG 7y ago
        Defense would actually be quite easy. Just undesirable. There are working antisat weapons in the major powers' arsenals. However, they would produce nasty debris clouds. And then there is also the vulnerability of the lauch site and control center...
        gpderetta 7y ago
        And it is probably significantly cheaper to take down a sat than putting it up. So it would be a losing battle.
        shadowgovt 7y ago
        Not in general. A kinetic striker would require as much energy to reach the satellite as the satellite used to get there. Something fancier, like a targeted laser, to my knowledge doesn't exist with anything like the wattage needed to punch through atmo and still have effective kill on anything that far out (assuming you could solve the targeting problem to resolve the beam that tightly in the first place).
  - SiempreViernes 7y ago
    No, they are too bright and will saturate the detector with even very short exposures. Best you can do is just discard the affected area, at worst you have to discard several exposures because the saturation effected the readout electronics.
  - jsweojtj 7y ago
    Hey you're back! I asked you previously "That might work for imaging, but what's your fix for spectroscopy?" here: https://news.ycombinator.com/item?id=21577081 https://news.ycombinator.com/item?id=21577081 You replied "Optical, RF, or Xray?" Then I said, "Let's start with optical." but then you disappeared! So, what's your solution for long-slit optical spectroscopy?
    - toomuchtodo 7y ago
      Hey! I'm still waiting to hear back from the astronomer I paid to do the research. I still intend to report back with their DOI from the resulting paper. I recognize when I've exceeded my domain knowledge and need an expert. To be clear, I think we're well in the realm of academic discussion; no one is stopping any global constellation due to astronomy concerns. As I've said many times in this thread and elsewhere, I think it's a growth opportunity for the astronomy community to move towards space based observation platforms, and with the plummeting cost of lift (ie SpaceX Falcon and Starship) I don't think that's an unreasonable position to hold.
- Rebelgecko 7y ago
  Don't think so. Adaptive optics works by changing the physical shape of the mirror. If you measure the atmosphere continuously and bend the mirror the right way, you can remove atmospheric distortion from the image. If anything, AO just gets you sharper images of the starlink satellites (or significantly worse ones if a satellite flies in front of the guidestar that you're using as a reference point to measure atmospheric distortions).
ogre_codes 7y ago
> I'm not an astronomer but I'm not convinced that that's the case. I'm not entirely certain what the balance is here. I don't think my post made it clear that I'm not certain how big the effect would be, only that there is a tradeoff here which is hard to quantify. I do know there is a lot of significant astronomy done by space telescope and that the importance of space astronomy is only growing. Seems to me the answer is that those who benefit from the new satellite constellations (SpaceX, etc) should finance additional investment in astronomy to mitigate the effects.
- cptskippy 7y ago
  What about amateur astronomy? Are we now saying that only those with the means to afford space telescopes or expensive software can participate?
  - ogre_codes 7y ago
    Are you an amateur astronomer or just trying to be the devil's advocate? I'd be curious to know what the impact is on impactful amateur astronomy (as opposed to backyard hobbyists who are just engaged for personal pleasure). I know some amateurs use images created by public telescopes, I'm not sure how much meaningful work is done by amateurs using backyard equipment anymore. Not being dismissive, genuinely curious.
    - Rebelgecko 7y ago
      In recent news, the only confirmed interstellar comet in our solar system was found by a dude who worked at an observatory (not as an astronomer) and decided to build own telescope for fun in his spare time. It's one of only two known interstellar visitors we've had, and because he found it early enough the pros were able to make very detailed observations. A decent number of asteroids and comets are still found by backyard astronomers.
    - cbanek 7y ago
      Variable star observing is actually a place where amateurs really help, since it's about observation time, and not necessarily some hugely powerful telescope. And the more powerful a telescope is, the more people want to use it to point at all sorts of things, which makes it kind of expensive to use those telescopes for variable star observations which take a lot of time. "Since professional astronomers do not have the time or the resources to monitor every variable star, astronomy is one of the few sciences where amateurs can make genuine contributions to scientific research." [0] [0] https://en.wikipedia.org/wiki/American_Association_of_Variable_Star_Observers https://en.wikipedia.org/wiki/American_Association_of_Variab...
nwallin 7y ago
Arecibo and VLA aren't affected by starlink at all. Those are radio telescopes. They don't even need to wait until nighttime to observe. It's only an optical/ir problem.
- manicdee 7y ago
  Starlink uses radio to communicate with the ground. A common complaint from radio astronomers is new radio satellite operators promising to not interfere with radio astronomy and then making no effort to follow through in that promise.

shadowgovt 7y ago

Can adaptive optics be applied to filter out objects like Starlink satellites?

toomuchtodo 7y ago
You can filter them out computationally without adaptive optics with enough frames captured.
- HorstG 7y ago
  Modern astronomy works at the edges of whats possible, a single frame might take hours. Needing multiple frames would mean multiple days per observation. It would mean no longer seeing faint and distant objects, limiting us to younger, closer and frankly far more boring objects. It would make observing variability impossible for certain timescales. You need old distant objects for cosmology, observing the structure if the universe, big bang and stuff. You need variability for finding exoplanets, measuring distance and observing transitions such as supernovae. Oh, and then a huge part is taking spectra, which means bouncing the light directly off a grating. Filtering transients is hard to impossible there. You need spectra for relative motion, magnetic fields, composition of matter and radiation and of course temperature. Needing such filters would set astronomy back a few decades
  - toomuchtodo 7y ago
    Astronomy will need to catch up or pay for a resource they’ve been getting for free (unobstructed sky). Or start lifting more advanced platforms to orbits (whether that’s Earth or Lagrange points).
    - HorstG 7y ago
      Well then, we should also have Elon pay rent for use of space...
      - toomuchtodo 7y ago
        I think it’s hard to argue it belongs to you if you can’t get there. If you can’t defend it or control it, you can’t stake a claim to it. https://en.wikipedia.org/wiki/Extraterrestrial_real_estate https://en.wikipedia.org/wiki/Extraterrestrial_real_estate
        HorstG 7y ago
        Defense would actually be quite easy. Just undesirable. There are working antisat weapons in the major powers' arsenals. However, they would produce nasty debris clouds. And then there is also the vulnerability of the lauch site and control center...
        gpderetta 7y ago
        And it is probably significantly cheaper to take down a sat than putting it up. So it would be a losing battle.
        shadowgovt 7y ago
        Not in general. A kinetic striker would require as much energy to reach the satellite as the satellite used to get there. Something fancier, like a targeted laser, to my knowledge doesn't exist with anything like the wattage needed to punch through atmo and still have effective kill on anything that far out (assuming you could solve the targeting problem to resolve the beam that tightly in the first place).
- SiempreViernes 7y ago
  No, they are too bright and will saturate the detector with even very short exposures. Best you can do is just discard the affected area, at worst you have to discard several exposures because the saturation effected the readout electronics.
- jsweojtj 7y ago
  Hey you're back! I asked you previously "That might work for imaging, but what's your fix for spectroscopy?" here: https://news.ycombinator.com/item?id=21577081 https://news.ycombinator.com/item?id=21577081 You replied "Optical, RF, or Xray?" Then I said, "Let's start with optical." but then you disappeared! So, what's your solution for long-slit optical spectroscopy?
  - toomuchtodo 7y ago
    Hey! I'm still waiting to hear back from the astronomer I paid to do the research. I still intend to report back with their DOI from the resulting paper. I recognize when I've exceeded my domain knowledge and need an expert. To be clear, I think we're well in the realm of academic discussion; no one is stopping any global constellation due to astronomy concerns. As I've said many times in this thread and elsewhere, I think it's a growth opportunity for the astronomy community to move towards space based observation platforms, and with the plummeting cost of lift (ie SpaceX Falcon and Starship) I don't think that's an unreasonable position to hold.
Rebelgecko 7y ago
Don't think so. Adaptive optics works by changing the physical shape of the mirror. If you measure the atmosphere continuously and bend the mirror the right way, you can remove atmospheric distortion from the image. If anything, AO just gets you sharper images of the starlink satellites (or significantly worse ones if a satellite flies in front of the guidestar that you're using as a reference point to measure atmospheric distortions).

ogre_codes 7y ago

> I'm not an astronomer but I'm not convinced that that's the case. I'm not entirely certain what the balance is here. I don't think my post made it clear that I'm not certain how big the effect would be, only that there is a tradeoff here which is hard to quantify. I do know there is a lot of significant astronomy done by space telescope and that the importance of space astronomy is only growing. Seems to me the answer is that those who benefit from the new satellite constellations (SpaceX, etc) should finance additional investment in astronomy to mitigate the effects.

cptskippy 7y ago
What about amateur astronomy? Are we now saying that only those with the means to afford space telescopes or expensive software can participate?
- ogre_codes 7y ago
  Are you an amateur astronomer or just trying to be the devil's advocate? I'd be curious to know what the impact is on impactful amateur astronomy (as opposed to backyard hobbyists who are just engaged for personal pleasure). I know some amateurs use images created by public telescopes, I'm not sure how much meaningful work is done by amateurs using backyard equipment anymore. Not being dismissive, genuinely curious.
  - Rebelgecko 7y ago
    In recent news, the only confirmed interstellar comet in our solar system was found by a dude who worked at an observatory (not as an astronomer) and decided to build own telescope for fun in his spare time. It's one of only two known interstellar visitors we've had, and because he found it early enough the pros were able to make very detailed observations. A decent number of asteroids and comets are still found by backyard astronomers.
  - cbanek 7y ago
    Variable star observing is actually a place where amateurs really help, since it's about observation time, and not necessarily some hugely powerful telescope. And the more powerful a telescope is, the more people want to use it to point at all sorts of things, which makes it kind of expensive to use those telescopes for variable star observations which take a lot of time. "Since professional astronomers do not have the time or the resources to monitor every variable star, astronomy is one of the few sciences where amateurs can make genuine contributions to scientific research." [0] [0] https://en.wikipedia.org/wiki/American_Association_of_Variable_Star_Observers https://en.wikipedia.org/wiki/American_Association_of_Variab...

nwallin 7y ago

Arecibo and VLA aren't affected by starlink at all. Those are radio telescopes. They don't even need to wait until nighttime to observe. It's only an optical/ir problem.

manicdee 7y ago
Starlink uses radio to communicate with the ground. A common complaint from radio astronomers is new radio satellite operators promising to not interfere with radio astronomy and then making no effort to follow through in that promise.