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> Since the JWST design started, there's been a revolution in the "easiness" of launches. Producing novel observation platforms is going to be expensive regar

> 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)

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)