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Comment by MengerSponge | Hacker News Reader

Until we get a space elevator, our most sensitive optical telescopes will be terrestrial. Space is hard, and modern telescopes have enormous optical elements.

Look at these absolute units: https://en.wikipedia.org/wiki/List_of_largest_optical_reflec...

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The situation isn't quite so bad as requiring a space elevator, since we can apparently use interferometry to combine the power of several smaller telescopes. However as I understand it, we lack the capability to do this on satellites at present and there are unique challenges to address.

From what I see there, the largest mirror is 30m. JWST has a 6.5m mirror. Assuming that 6.5m is the largest that can be launched at once (which is probably not true, and will be less so when Starship is operational), it would take 25 launches to get a 30m diameter meter built. 25 launches from SpaceX costs $1.5 billion, which is in the budgetary realm of space telescopes. So I don't think it's as far fetched as you think.

Yes, the famously operational JWST. The telescope that should be used as a benchmark for how to implement an orbital system on time, under budget, and if I may be so bold: easily. /s

  1) You're talking about replacing existing capabilities.
  2) It's easy to spend someone else's money.

Those terrestrial telescopes are paid for, built, and running. Finding funding for them was really hard the first time around, and do you think constellation operators will spring for the replacement costs?

I'm not saying it's technically impossible to replace all of our terrestrial telescopes because some people want to make a lot of money from the commons of our night sky, but $1.5 billion is just for the launches. It doesn't include design, fabrication, assembly, testing, or contingencies.

The idea of assembling large space telescopes is very exciting, although there are obviously many engineering challenges to solve. What that doesn't yet address is large, ground based radio telescopes. Consider the square kilometer array, which will have one million square meters of observing surface. How many launches would it take to get something comparable into orbit? Oddly, the bandwidth requirements (about one terabyte/second) for the SKA might be the hardest thing to meet in space.

JWST is the cutting edge of space telescopes, hasn't actually been successfully deployed and now you're suggesting building and launching 25+ of them and then assembling them in orbit.. Right now the only things 'built' in space are all handled by astronauts on the ISS assembling things by hand which adds on the conservative end a staggering amount of cost to the budget. Add on to that that now you have a much harder job of building any new experiments to run on this monster space telescope which is a fairly common thing for ground observatories. We're many steps away from being able to move the best ground observatories into space and get equivalent data out of them.

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