
Extremely Large Telescope - bryanrasmussen
https://projectescape.eu/science-projects/extremely-large-telescope
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martythemaniak
The Hubble has a launch mass of 10000kg and has a mirror with a 2.4m diameter
and 4.525 m^2 collecting area. The ELT has a diameter of 39.3m area of 978
m^2, that is 216 Hubbles.

The target cost of getting stuff to LEO using Starship/SuperHeavy is $2m per
100000kg, or $200k per Hubble. It would only cost $43 million to launch the
light-gathering equivalent to the ELT. Now, $20/kg to LEO is very optimistic,
but even at 5-10x that rate, a more believable $100-200/kg, that would still
make the launch possible for 200-400m, which is roughly the cost of a Delta
Heavy launch. Scaling this up, a 100m telescope (The OWL) would be 1,735.69
Hubbles and cost $350m to launch at the optimistic price, but still less than
$3.5B at the believable price.

Basically, if Starship is successful it could have a dramatic effect on
astronomy. 216 Hubbles may sound a bit insane, but mass producing them would
drive the cost for each down considerably. Without the atmosphere, you don't
need the fancy laser-actuator correction mechanism, and you certainly don't
need to fight local activists for one of very few locations worldwide where
you can plausibly put these things (AFAIK, there are only 3 such locations
worldwide - Canary Islands, Cerro Amazones and Hawaii). Not only that, but if
you had a constellation of Hubbles, they could be spread out and use
interferometry to construct a telescope larger than the Earth (this is the
technique that Event Horizon Telescope used).

So the question is, is it possible to design a standardized, flatpack hubble-
sized mirror+cam sattelite and pull it off for the price of a regular
telescope? At ~1.2Eur for the ELT, that would imply $45m per "hubble". Seems
doable.

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__tg__
Not sure about the Starship numbers but if its is $2m per Hubble mass, then
launching 200 hubbles would be $800m, not $43m. This however is not about
sending bricks into orbit. The ELT mirrors are segmented and need precise
alignment with each other to micron precision. Deploying a segmented mirror in
orbit has still not been done (the James Webb Telescope launches in 2021); the
engineering involved adds orders of magnitudes of complexity over a single-
piece primary mirror such as Hubble has. Add to this maintenance costs: a
mirror the size of ELT in orbit needs a huge maintenance program behind it to
work at all. The lifetime cost for such a mirror would be in tens of billions,
if not hundreds. This is why such large telescopes keep getting built on
Earth.

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dylan604
> the James Webb Telescope launches in 2021

The JWT has been re-scheduled many times with the latest attempt scheduled for
2021. I'm sure that'll get pushed, yet again.

~~~
sandworm101
Manditory XKCD: [https://xkcd.com/2014/](https://xkcd.com/2014/)

I still think that 2026 remains a reasonable estimate.

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bawana
Why bother with Leo? Jus build one on the moon (along w a moon base) The
interferometry would be awesome when coordinated w a telescope in the atacama.
And no worries about maintaining a spacecraft, no shuttle missions, no
astronaut exposure to radiation. Compare the rate limiting factors of working
on the ISS versus doing the same thing in the Atacama. Having a safe,
protected environment with gravity allows a much more human friendly working
situation. Space is for transiting, not living in. We need to be on planets.

~~~
BurningFrog
"Just build a moon base" might be overly optimistic :)

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rbanffy
To say nothing about radiation shielding on the Lunar surface.

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nordsieck
> To say nothing about radiation shielding on the Lunar surface.

Compared to space, radiation shielding on the moon is trivial - humans belong
underground except for short stints on the surface.

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nabla9
ESO had plans for Overwhelmingly Large Telescope (OWL) but they did not get
enough funding so they had to settle for ELT.

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Ididntdothis
I wonder how the successor to the OWL would be named. “Insanely large
telescope”?

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api
BFT, which stands for Big FXXking Telescope?

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frabert
That's the Nvidia branding for it

~~~
saagarjha
[https://en.wikipedia.org/wiki/Starship_development_history#B...](https://en.wikipedia.org/wiki/Starship_development_history#Big_Falcon_Rocket)

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bouvin
The excellent Omega Tau science podcast recently did an in-depth episode on
the not inconsiderable complications of the ELT’s five mirror lightpath and
its control: [http://omegataupodcast.net/150-5-controlling-the-
elt/](http://omegataupodcast.net/150-5-controlling-the-elt/)

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tigershark
I wonder why they decided to make it so dark... f/17.48 is really really dark.
Actually reading Wikipedia numbers it seems even darker at f/18.91. The focal
length is impressive at 3/4 km, so probably they wanted to privilege the
angular resolution going toward the diffraction limit.

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peter_d_sherman
"It will be able to correct for image distortions caused by the turbulence in
the Earth atmosphere, providing diffraction-limited images that are 16 times
sharper than those from the Hubble Space Telescope."

I would love to learn about this technology, in depth, because my own
knowledge in this area is close to zero.

Can anyone point me to any web pages, books, articles, courses, explainer
videos, anything in this field... Also, what is the correct terminology around
this subject area?

This technology seems to exist at some confluence of the science of optics and
the computer discipline of image correction... but maybe there's a better
name, a better set of terminology for it... well, any and all comments about
this area would be welcome!

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nfg
[https://en.m.wikipedia.org/wiki/Adaptive_optics](https://en.m.wikipedia.org/wiki/Adaptive_optics)

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autokad
personally, hearing this makes me happy, can't wait till it's built.

Has anyone heard of terrascopes? (telescopes using celestial bodies)

[https://www.youtube.com/watch?v=jgOTZe07eHA](https://www.youtube.com/watch?v=jgOTZe07eHA)

if it is workable, it sounds fantastical but probably not something I'd see in
my lifetime either way

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dang
Related from 2015:
[https://news.ycombinator.com/item?id=9185815](https://news.ycombinator.com/item?id=9185815)

2012:
[https://news.ycombinator.com/item?id=4096294](https://news.ycombinator.com/item?id=4096294)

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blackrock
Instead of building it on the ground, testing it, then launching it, where you
are limited by maximum payload size.

I wonder if it is now easier to launch the raw components, and manufacture it
in space. There are some engineering challenges of course, but it might be a
worthy industrial exercise.

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google234123
It seems to me that the ESA is getting better value for money than NASA. They
seem to have more projects completed or on the way than NASA. Is it just the
fact that NASA is focused on a maned space missions that takes away from more
general science projects?

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fsh
The ELT is built by the ESO (European Southern Observatory), not ESA.

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rbanffy
Every article like this should have a simulated photo of a small object in the
solar system compared to other telescopes.

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adamtj
How close will this be to being able to resolve starspots on something other
than our sun?

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tigershark
I didn’t run the numbers but I would say very very far.

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torpfactory
[https://xkcd.com/1294/](https://xkcd.com/1294/)

