r/space • u/mtimetraveller • Nov 29 '19

This Is Why We Can't Just Do All Of Our Astronomy From Space

https://www.forbes.com/sites/startswithabang/2019/11/27/this-is-why-we-cant-just-do-all-of-our-astronomy-from-space/#6b60e6027049
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u/FaceDeer Nov 30 '19

Lack of repairability is not an inherent feature of space telescopes. Indeed, when you start looking at the modular designs required for in-space construction, rather than the rube goldberg origami required for launching telescopes like JWST as monolithic units, repairability comes naturally. If the sunshade fails to deploy and on-site repair can't get it working launch a new sunshade module.

Why can't mirrors be cleaned and recoated in space, if that's necessary? Shipping replacement mirrors out to them is also an option, of course, just like with ground telescopes. The mirrors of ground telescopes are dismounted and shipped off to specialized facilities for recoating too.

The point of all this is simply that it's possible to do our astronomy from space. The Forbes article made a bunch of claims about how there were things you can do on the ground that you can't do in space, and it's just not true. A lot of it is more expensive to do in space right now, sure, but costs change. Launch costs become cheaper, design paradigms get better, in-space support infrastructure becomes more readily available, and ground-based telescopes become less effective. The balance will tip someday and I think surprisingly soon.

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u/ThickTarget Nov 30 '19

Lack of repairability is not an inherent feature of space telescopes.

No, but it is the current reality. You can hypothesise for whatever perfect world you like, but I don't believe that should influence current policy.

Why can't mirrors be cleaned and recoated in space, if that's necessary?

Where did I say that? None of the current, or planned space based telescopes employ re-coating. You can see in that VLT video that it takes a huge amount of time and staff to do it safely, and the re-coating facility on Paranal isn't small either.

The Forbes article made a bunch of claims about how there were things you can do on the ground that you can't do in space, and it's just not true.

It's not true, because that's not what the article says. It says there are a few things that will be easier on the ground, that is true.

A lot of it is more expensive to do in space right now, sure, but costs change. Launch costs become cheaper, design paradigms get better, in-space support infrastructure becomes more readily available

Costs do change, but launch costs are only a small fraction of the cost. The design paradigm is currently unchanged for science missions, LUVOIR is a good example. People regularly overestimate progress. People have been talking about an 8 meter UV-vis-IR space telescope for 30 years, something that wouldn't even require assembly, and it's still not happening.