8 ms·

Since the JWST design started, there's been a revolution in the "easiness" of launches. I wonder if a future evolution of space telescopes will be some kind of

Since the JWST design started, there's been a revolution in the "easiness" of launches. I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one. Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie. And rather than have a fearsomely complex integrated sunshield, you could have a similar swarm of simpler satellites that provide a large cool area at L2, and then the observers just need to handle their own heat. I suppose this could be described as microservices...in spaaaaace. Draw what parallels you will from that!

OrvalWintermute 5y ago
> Since the JWST design started, there's been a revolution in the "easiness" of launches. Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs. > I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one. With space recovery and repair mission capabilities like https://nexis.gsfc.nasa.gov/osam-1.html https://nexis.gsfc.nasa.gov/osam-1.html growing, a single large asset could be easier to repair than constant refresh. Anyways, small satellites = small sensors. There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now. > Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie. Keeping a swarm of space assets ideally situated over time, with proper attitudes and control is a non-trivial problem. Look at Magnetospheric Multiscale Mission, that is considered a hard problem. Software solutions don't always translate to hardware.
- mikepurvis 5y ago
  "Hubble has been operating for ~30 years now." Right, and the GPS constellation has been active for almost thirty years too. I think the GP is probably right that it would be great if the risk associated with a single mega launch/deployment could be spread over a fleet, but ultimately it does no good if you can't use that configuration to get the observations you want, hence the question. It has less to do with it being a "software solution" and more just whether it would actually practically work. To their point, though, lots of ground-based radio telescopes are now also arrays of many dishes [1], so it's not at all hard to imagine that a similar configuration could be of value in space. [1]: https://public.nrao.edu/telescopes/vla/ https://public.nrao.edu/telescopes/vla/
  - adhesive_wombat 5y ago
    The fearsome requirements imposed by optical interferometry are a real killer here: the JWST mirror segments can be controlled with 10nm precision for a reason. Radio is a billion times easier (at least in naive terms): wavelengths in the kilometers rather than hundreds of nanometers
    - mikepurvis 5y ago
      Ah, that is a helpful distinction. I had been thinking that JWST was for radio observations, but it's the opposite of course; JWST is for making high energy observations of things like gamma rays.
      - bashinator 5y ago
        On the contrary, JWST is mostly focused on the near infrared. Good for seeing through dust and for capturing highly red-shifted faraway objects.
- adhesive_wombat 5y ago
  Well of course its not going to be simple, and I doubt it would even be possible for the JWST successor, which I assume are already being sketched out, but its an interesting idea to think about. Satellite swarms are a very active area of research, along with cheap launches enabling cheap hardware based on substantially COTS electronics, which means 10 "unreliable" things, of which 9 may fail may be cheaper than 1 gold-plated one that will definitely not fail. And yes, they have small elements, that's the whole point. A small element is disproportionately easier to produce than a bigger one. The point of The Swarm would be to offset the small area individually small elements with a large number of them. ALMA does this, and they even pick the dishes up with giant forklifts and move them around to reconfigure the array. Optical interferometric arrays are very hard and only recently even possible, so it's unlikely you could do it in space "soon" (even LISA is still a long way out, and that's been planned since I was at school). I obviously don't have a handle on if the added noise from positioning errors outweighs the literally astronomical baseline advantage. And yes, Hubble might have lasted 30 years, but JWST has about 10 years life, and then it's dead and will fall away from L2 unless they can get a refuel/regas mission launched (it does have the ports for it) to it in time. Of course any number of practical issues can torpedo such a thing from the phase space of feasible implementations, but they're still fun to think about.
- snewman 5y ago
  > Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs. This is exactly the point: launch costs are coming down, and there is widespread anticipation that they will start to plummet as the next generation of launchers comes online. If/when Starship (a) becomes available + (b) has any significant competition, launch costs could plummet by an incredible factor.
- bigiain 5y ago
  > There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now. Is there anything other than manoeuvring/orbit-correction propellant that puts an upper limit of t5he James Webbs projected life? (At least until micro meteors trash too much of the optics?) Is it possible a resupply mission capability could effectivel7y extend its useful life indefinitely? (Did they even bother putting a fuel filler on it?)
  - OrvalWintermute 5y ago
    Resupply is definitely a possibility. Though resupply missions are not yet going out to those orbits, it is completely conceivable that they will in time. For the price of a $100M mission they'll be able to recoup or fix more expensive ones. I normally hear about batteries, reaction wheels, and fuel limiting life, but I think that would relate most to orbit, propulsion type, etc. IDK about a fuel filler.
  - Rebelgecko 5y ago
    There's a lot of miscellaneous things that can break on a spacecraft Reaction wheels (which use momentum to help you point the vehicle) are a semi common failire. There's usually some redundancy built in, but if enough of them wear out you'll lose stability and pointing accuracy. Even radiation-hardened electronics will wear out over time. If you look at unprocessed images from the Hubble, there's a shitload of pixels that have been fried in the cameras (the effect kind of look like stuck pixels in a computer monitor)
dylan604 5y ago
>in spaaaaace in recognition of getting old(er), i wonder how many youngins even know there's a reference to be caught here.
- csdvrx 5y ago
  Would you care enlightening about the reference? On duckduckgo I only found some references to The Muppets, a Springer article and a streaming playlist on archive.org
  - johnny22 5y ago
    i've never played the game, but i think it's from portal 2
    - throwamon 5y ago
      I've never played it either, but I actually know the reference thanks to this video[1] (which in turn comes from the once-viral Keyboard Cat[2]). [1]: https://www.youtube.com/watch?v=c7C_1QfhpMQ https://www.youtube.com/watch?v=c7C_1QfhpMQ [2]: https://www.youtube.com/watch?v=J---aiyznGQ https://www.youtube.com/watch?v=J---aiyznGQ
      - dylan604 5y ago
        Ahhh, sorry. Thanks for playing. We've got some lovely parting gifts for you... https://www.youtube.com/watch?v=EmI77ZBeJrQ https://www.youtube.com/watch?v=EmI77ZBeJrQ
    - scrollaway 5y ago
      I believe GGP was referencing the far older Muppet Show bit of Pigs in Spaaaaace :)
      - dylan604 5y ago
        Ding ding ding. Now, let's take a look at the prizes...
peterburkimsher 5y ago
Yes, small satellites are simpler and cheaper. Larger systems are complicated and expensive. But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics. At what point do we want to accept the financial tradeoffs involved? Humans and the economy also benefit from the large projects, and the management structures also teach efficiency to more people who can go on to create other exciting new sensors. We could start with a small satellite like Sputnik, and make them grow. Eventually it will reach a point of stability with the neighbouring environment. That could be much larger than we expect. "That's no moon, it's a spaceship!"
- pilsetnieks 5y ago
  > But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics. I'm going to go and assume that you used the strong force and gravity as metaphors here.
- adhesive_wombat 5y ago
  One advantage of L2 is that it's a point of gravitational metastability when entropy inevitably hits, your satellite will slowly fall away from the point, and either depart for a long, initially slow, fall back to something rocky, or spiral out from the Earth-Moon system into interplanetary space. An L2 swarm isn't bound together by gravity, it actually has to maintain active control to stay there, so it's a "self cleaning" area.
samwillis 5y ago
The other thing to bear in mind is the size of up coming launch vehicles. SpaceX Starship will be 9m and Blue Origin’s New Glen is expected to be 7m in diameter. Both of those could take a telescope the size of James Webb with much lest or no “unfolding” required. Annother option with some of these cheaper launch vehicles is to build the telescope into the upper stage, using it as a bus/platform. So for example you could convert a Starship upper stage into a telescope, using its full 9m diameter for a mirror. Fully assembled on the ground before launch.
- jjoonathan 5y ago
  Now that the folding trick has been proven and loaded into institutional memory, I'd rather use it, e.g. LUVOIR-A at 15m in diameter, planned for the 8.4m fairing on SLS but suitable for the 9m fairing on Starship.
  - adhesive_wombat 5y ago
    I do love me a scientific megaproject, but I still do wonder if a glorious $24 billion (and that's before the overruns) monolith is the most effective thing in terms of science per dollar, especially if it also has a limited lifespan due to consumables. That's fabulously expensive: you could have four LHCs, have enough change to replace Arecibo with 10 FASTs and then maybe a aircraft supercarrier on top just for funsies. It feels like JWST again: it's so expensive that it cannot be allowed to fail, so it's engineered to near perfection, but that costs so much that it has to be engineered even more to be sure, and so on until it's 1900% over budget, a decade late and muscling other science out of funding. But, also dayum it's a piece of art.
    - OrvalWintermute 5y ago
      > I do love me a scientific megaproject, but I still do wonder if a glorious $24 billion (and that's before the overruns) monolith is the most effective thing in terms of science per dollar, especially if it also has a limited lifespan due to consumables. The 2nd mission with which I got involved, an Air Force Captain explained to me that continual trend was to massively underbudget a mission, and then make it whole through cost overruns. Of course, my work was all about increasing the security capabilities of the constellation, which likely added in the tens, to hundreds of millions in cost to the system. > It feels like JWST again: it's so expensive that it cannot be allowed to fail, so it's engineered to near perfection, but that costs so much that it has to be engineered even more to be sure, and so on until it's 1900% over budget, a decade late and muscling other science out of funding. Launch costs are dropping and the space body of knowledge is changing rapidly System Engineering tools are in their infancy, so rework or changing requirements are pricey. I expect this will really the cost of missions over time, since it directly relates to labor costs. Simultaneously, the space operator mentality of "extreme availability at all costs" is meeting the hard reality of "space is now an offensive and defensive cyber domain". We're building too many one-offs and too few constellations, both the birds, and the sensors. If you want lower cost we need to get past unit volume of one.
semaphoreP 5y ago
Astronomer here, we are thinking about doing interferometers in space[1,2], but it won't be a catch-all for everything. One reason is that the instrumentation is equally as important as the telescope optics itself, and it's non-trivial to have your swarm of satellites both collect light, but also do science experiments with the light. One thing we are thinking of is to fly more proto-typing missions to get the technology readiness of various components to mature stages before assembling it all together for the real thing (I would say we did not do this as well for JWST). [1]: https://www.life-space-mission.com/ https://www.life-space-mission.com/ [2]: https://lisa.nasa.gov/ https://lisa.nasa.gov/
- ajuc 5y ago
  Is there any sense in using internet providing sattelites for astronomy? Like if starlink published it's noise data from all sattelites in realtime could it be used as one huge radiotelescope?
  - semaphoreP 5y ago
    Probably pretty difficult to find too many compelling cases. The bands starlink transmits in are designated communication bands, so interference from other satellites is going to be so high that it will drown out any signals. There are astronomers working on removing this foreground, but it's really difficult! It's actually becoming quite a problem in radio astronomy with the amount of the electromagnetic spectrum that is quiet enough for science.
stackedinserter 5y ago
"Satellites are livestock, not pets"!
marcyb5st 5y ago
Instead I believe JWST will be the last telescope with reflective optics we will launch. The new thing will most likely be based on diffraction based optics (Aragoscope). It is much easier to launch in space a disc of some light and bendy material of some lightweight material than a set of hyperdelicate and precise mirrors. According to the simulations performed in [1], an aragoscope of 1km would be able to directly image objects the size of Jupiter's moons (so basically exoplanets even on the small side) 23 light-years away. EDIT: Took the time to scavenge the numbers: JWST has 0.1 arcseconds angular resolution, a 100m aragoscope would have a 1 milli-arcsecond angular resoulution, a 1km aragoscope 0.1 milli-arcsecond which translates to be able to alpha centauri in a 70x70 pixels patch (and so see its sunspots) or as I mentioned above exoplanets on the smaller scale at 23 light years away (Europa is 1560 km in diameter). [1] https://www.nasa.gov/sites/default/files/atoms/files/2014_phase_i_webster_cash_the_aragoscope.pdf https://www.nasa.gov/sites/default/files/atoms/files/2014_ph...

OrvalWintermute 5y ago

> Since the JWST design started, there's been a revolution in the "easiness" of launches. Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs. > I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one. With space recovery and repair mission capabilities like https://nexis.gsfc.nasa.gov/osam-1.html https://nexis.gsfc.nasa.gov/osam-1.html growing, a single large asset could be easier to repair than constant refresh. Anyways, small satellites = small sensors. There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now. > Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie. Keeping a swarm of space assets ideally situated over time, with proper attitudes and control is a non-trivial problem. Look at Magnetospheric Multiscale Mission, that is considered a hard problem. Software solutions don't always translate to hardware.

mikepurvis 5y ago
"Hubble has been operating for ~30 years now." Right, and the GPS constellation has been active for almost thirty years too. I think the GP is probably right that it would be great if the risk associated with a single mega launch/deployment could be spread over a fleet, but ultimately it does no good if you can't use that configuration to get the observations you want, hence the question. It has less to do with it being a "software solution" and more just whether it would actually practically work. To their point, though, lots of ground-based radio telescopes are now also arrays of many dishes [1], so it's not at all hard to imagine that a similar configuration could be of value in space. [1]: https://public.nrao.edu/telescopes/vla/ https://public.nrao.edu/telescopes/vla/
- adhesive_wombat 5y ago
  The fearsome requirements imposed by optical interferometry are a real killer here: the JWST mirror segments can be controlled with 10nm precision for a reason. Radio is a billion times easier (at least in naive terms): wavelengths in the kilometers rather than hundreds of nanometers
  - mikepurvis 5y ago
    Ah, that is a helpful distinction. I had been thinking that JWST was for radio observations, but it's the opposite of course; JWST is for making high energy observations of things like gamma rays.
    - bashinator 5y ago
      On the contrary, JWST is mostly focused on the near infrared. Good for seeing through dust and for capturing highly red-shifted faraway objects.
adhesive_wombat 5y ago
Well of course its not going to be simple, and I doubt it would even be possible for the JWST successor, which I assume are already being sketched out, but its an interesting idea to think about. Satellite swarms are a very active area of research, along with cheap launches enabling cheap hardware based on substantially COTS electronics, which means 10 "unreliable" things, of which 9 may fail may be cheaper than 1 gold-plated one that will definitely not fail. And yes, they have small elements, that's the whole point. A small element is disproportionately easier to produce than a bigger one. The point of The Swarm would be to offset the small area individually small elements with a large number of them. ALMA does this, and they even pick the dishes up with giant forklifts and move them around to reconfigure the array. Optical interferometric arrays are very hard and only recently even possible, so it's unlikely you could do it in space "soon" (even LISA is still a long way out, and that's been planned since I was at school). I obviously don't have a handle on if the added noise from positioning errors outweighs the literally astronomical baseline advantage. And yes, Hubble might have lasted 30 years, but JWST has about 10 years life, and then it's dead and will fall away from L2 unless they can get a refuel/regas mission launched (it does have the ports for it) to it in time. Of course any number of practical issues can torpedo such a thing from the phase space of feasible implementations, but they're still fun to think about.
snewman 5y ago
> Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs. This is exactly the point: launch costs are coming down, and there is widespread anticipation that they will start to plummet as the next generation of launchers comes online. If/when Starship (a) becomes available + (b) has any significant competition, launch costs could plummet by an incredible factor.
bigiain 5y ago
> There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now. Is there anything other than manoeuvring/orbit-correction propellant that puts an upper limit of t5he James Webbs projected life? (At least until micro meteors trash too much of the optics?) Is it possible a resupply mission capability could effectivel7y extend its useful life indefinitely? (Did they even bother putting a fuel filler on it?)
- OrvalWintermute 5y ago
  Resupply is definitely a possibility. Though resupply missions are not yet going out to those orbits, it is completely conceivable that they will in time. For the price of a $100M mission they'll be able to recoup or fix more expensive ones. I normally hear about batteries, reaction wheels, and fuel limiting life, but I think that would relate most to orbit, propulsion type, etc. IDK about a fuel filler.
- Rebelgecko 5y ago
  There's a lot of miscellaneous things that can break on a spacecraft Reaction wheels (which use momentum to help you point the vehicle) are a semi common failire. There's usually some redundancy built in, but if enough of them wear out you'll lose stability and pointing accuracy. Even radiation-hardened electronics will wear out over time. If you look at unprocessed images from the Hubble, there's a shitload of pixels that have been fried in the cameras (the effect kind of look like stuck pixels in a computer monitor)

dylan604 5y ago

>in spaaaaace in recognition of getting old(er), i wonder how many youngins even know there's a reference to be caught here.

csdvrx 5y ago
Would you care enlightening about the reference? On duckduckgo I only found some references to The Muppets, a Springer article and a streaming playlist on archive.org
- johnny22 5y ago
  i've never played the game, but i think it's from portal 2
  - throwamon 5y ago
    I've never played it either, but I actually know the reference thanks to this video[1] (which in turn comes from the once-viral Keyboard Cat[2]). [1]: https://www.youtube.com/watch?v=c7C_1QfhpMQ https://www.youtube.com/watch?v=c7C_1QfhpMQ [2]: https://www.youtube.com/watch?v=J---aiyznGQ https://www.youtube.com/watch?v=J---aiyznGQ
    - dylan604 5y ago
      Ahhh, sorry. Thanks for playing. We've got some lovely parting gifts for you... https://www.youtube.com/watch?v=EmI77ZBeJrQ https://www.youtube.com/watch?v=EmI77ZBeJrQ
  - scrollaway 5y ago
    I believe GGP was referencing the far older Muppet Show bit of Pigs in Spaaaaace :)
    - dylan604 5y ago
      Ding ding ding. Now, let's take a look at the prizes...

peterburkimsher 5y ago

Yes, small satellites are simpler and cheaper. Larger systems are complicated and expensive. But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics. At what point do we want to accept the financial tradeoffs involved? Humans and the economy also benefit from the large projects, and the management structures also teach efficiency to more people who can go on to create other exciting new sensors. We could start with a small satellite like Sputnik, and make them grow. Eventually it will reach a point of stability with the neighbouring environment. That could be much larger than we expect. "That's no moon, it's a spaceship!"

pilsetnieks 5y ago
> But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics. I'm going to go and assume that you used the strong force and gravity as metaphors here.
adhesive_wombat 5y ago
One advantage of L2 is that it's a point of gravitational metastability when entropy inevitably hits, your satellite will slowly fall away from the point, and either depart for a long, initially slow, fall back to something rocky, or spiral out from the Earth-Moon system into interplanetary space. An L2 swarm isn't bound together by gravity, it actually has to maintain active control to stay there, so it's a "self cleaning" area.

samwillis 5y ago

The other thing to bear in mind is the size of up coming launch vehicles. SpaceX Starship will be 9m and Blue Origin’s New Glen is expected to be 7m in diameter. Both of those could take a telescope the size of James Webb with much lest or no “unfolding” required. Annother option with some of these cheaper launch vehicles is to build the telescope into the upper stage, using it as a bus/platform. So for example you could convert a Starship upper stage into a telescope, using its full 9m diameter for a mirror. Fully assembled on the ground before launch.

jjoonathan 5y ago
Now that the folding trick has been proven and loaded into institutional memory, I'd rather use it, e.g. LUVOIR-A at 15m in diameter, planned for the 8.4m fairing on SLS but suitable for the 9m fairing on Starship.
- adhesive_wombat 5y ago
  I do love me a scientific megaproject, but I still do wonder if a glorious $24 billion (and that's before the overruns) monolith is the most effective thing in terms of science per dollar, especially if it also has a limited lifespan due to consumables. That's fabulously expensive: you could have four LHCs, have enough change to replace Arecibo with 10 FASTs and then maybe a aircraft supercarrier on top just for funsies. It feels like JWST again: it's so expensive that it cannot be allowed to fail, so it's engineered to near perfection, but that costs so much that it has to be engineered even more to be sure, and so on until it's 1900% over budget, a decade late and muscling other science out of funding. But, also dayum it's a piece of art.
  - OrvalWintermute 5y ago
    > I do love me a scientific megaproject, but I still do wonder if a glorious $24 billion (and that's before the overruns) monolith is the most effective thing in terms of science per dollar, especially if it also has a limited lifespan due to consumables. The 2nd mission with which I got involved, an Air Force Captain explained to me that continual trend was to massively underbudget a mission, and then make it whole through cost overruns. Of course, my work was all about increasing the security capabilities of the constellation, which likely added in the tens, to hundreds of millions in cost to the system. > It feels like JWST again: it's so expensive that it cannot be allowed to fail, so it's engineered to near perfection, but that costs so much that it has to be engineered even more to be sure, and so on until it's 1900% over budget, a decade late and muscling other science out of funding. Launch costs are dropping and the space body of knowledge is changing rapidly System Engineering tools are in their infancy, so rework or changing requirements are pricey. I expect this will really the cost of missions over time, since it directly relates to labor costs. Simultaneously, the space operator mentality of "extreme availability at all costs" is meeting the hard reality of "space is now an offensive and defensive cyber domain". We're building too many one-offs and too few constellations, both the birds, and the sensors. If you want lower cost we need to get past unit volume of one.

semaphoreP 5y ago

Astronomer here, we are thinking about doing interferometers in space[1,2], but it won't be a catch-all for everything. One reason is that the instrumentation is equally as important as the telescope optics itself, and it's non-trivial to have your swarm of satellites both collect light, but also do science experiments with the light. One thing we are thinking of is to fly more proto-typing missions to get the technology readiness of various components to mature stages before assembling it all together for the real thing (I would say we did not do this as well for JWST). [1]: https://www.life-space-mission.com/ https://www.life-space-mission.com/ [2]: https://lisa.nasa.gov/ https://lisa.nasa.gov/

ajuc 5y ago
Is there any sense in using internet providing sattelites for astronomy? Like if starlink published it's noise data from all sattelites in realtime could it be used as one huge radiotelescope?
- semaphoreP 5y ago
  Probably pretty difficult to find too many compelling cases. The bands starlink transmits in are designated communication bands, so interference from other satellites is going to be so high that it will drown out any signals. There are astronomers working on removing this foreground, but it's really difficult! It's actually becoming quite a problem in radio astronomy with the amount of the electromagnetic spectrum that is quiet enough for science.

stackedinserter 5y ago

"Satellites are livestock, not pets"!

marcyb5st 5y ago

Instead I believe JWST will be the last telescope with reflective optics we will launch. The new thing will most likely be based on diffraction based optics (Aragoscope). It is much easier to launch in space a disc of some light and bendy material of some lightweight material than a set of hyperdelicate and precise mirrors. According to the simulations performed in [1], an aragoscope of 1km would be able to directly image objects the size of Jupiter's moons (so basically exoplanets even on the small side) 23 light-years away. EDIT: Took the time to scavenge the numbers: JWST has 0.1 arcseconds angular resolution, a 100m aragoscope would have a 1 milli-arcsecond angular resoulution, a 1km aragoscope 0.1 milli-arcsecond which translates to be able to alpha centauri in a 70x70 pixels patch (and so see its sunspots) or as I mentioned above exoplanets on the smaller scale at 23 light years away (Europa is 1560 km in diameter). [1] https://www.nasa.gov/sites/default/files/atoms/files/2014_phase_i_webster_cash_the_aragoscope.pdf https://www.nasa.gov/sites/default/files/atoms/files/2014_ph...