Comment by LeifCarrotson | Hacker News Reader

Comment by LeifCarrotson | Hacker News Reader

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It's fascinating to me that the telescope costs so much more than the launch.

A high-quality 24" or 1-meter university-grade observatory telescope can be had for well under $1 million. If you multiply that by a factor of 100 to mount it on a satellite, you're still at 'just' $0.1 billion and can buy a whole Ariane-5 launch just like the JWST to put it at your desired orbit for $0.15B, for a total of $0.25B (a Falcon Heavy runs about half the cost for a launch). You could launch 30 of those (hopefully improving your factor-of-100 cost increase to something more manageable) for less than what the JWST will cost.

I get that JWST is a 6.5 meter telescope, not a piddly backyard 24" device, but why do we have to launch the best single scope possible?

There are only 7 visible-light space telescopes listed at https://en.wikipedia.org/wiki/List_of_space_telescopes#Visib.... I wish there were 70 or 700, with live Internet feeds.

JWST is being built to do things that are truly impossible on Earth. It is an infrared telescope that will image things that cannot be seen through Earth's atmosphere.

JWST is not the first IR telescope (Spitzer Space telescope, retiring this month comes to mind, 0.85 m diameter primary), but its size will allow both improved resolution (diffraction limit falls like 1/diameter) and improved collection efficiency (grows like diameter^2). Without constellation-flying and interferometric telescopes (see Keck Observatory), one cannot get either one from an array of small telescopes.

There are a lot of scientists grumpy about JWST because of its huge budget, but as long as JWST works, the view it gives of our universe will be spectacular. At this point, I think everyone really wants JWST to work, as so much has been sacrificed to make it possible.

Your $1 million university telescope probably wouldn't work long in space without maintenance, the ability to regulate temps, and rad-hard electronics.

See https://doi.org/10.1117/1.2031216 for the scaling of cost with size. It is very much not linear. Rather if you double the diameter the cost goes up by about a factor of 3.5 (closer to the area that went up by 4).

The university grade telescope, not sure what the entails, but I'm guessing it isn't hardened for radiation exposure and heat cycles seen in space. You can't use some off the shelf product unfortunately.

Making things survive in space is hard. Working functionally for the lifespan of the telescope is really hard. There's not a lot you can do once it's up there.

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