Lunar based Observatory
TBerk
- Barely any atmospheric interference.
- 'Dark Side' of the Moon will have less Earthshine to deal with.
- Lesser gravity allows for different construction and perhaps larger
optical elements.
- Lunar material could be used for building stuffs, given a decent
smelter.
We could collect the images 'locally' and beam them back to Earth via
laser (or microwave or whatever).
There could even be a superbig Lunar version of the Arecibo Radio
Telescope (if you saw the movie 'Contact'...) that was built in Puerto
Rico.
Just blue-sky daydreaming, but sketching out some brainstorms might
lead somewhere, someday.
berk
Davoud
> Seems like a good idea off the top of my head. Lets see:
>
> - Barely any atmospheric interference.
Check.
> - 'Dark Side' of the Moon will have less Earthshine to deal with.
?? But still sunshine. Well suited for radio astronomy, however.
> - Lesser gravity allows for different construction and perhaps larger
> optical elements.
Check.
> - Lunar material could be used for building stuffs, given a decent
> smelter.
Bzzzzzzt! Wrong answer. That answer calls for hundreds or possibly
thousand of humans and dozens of factories and millions of tons of
support for those humans. That's the SF way. Cost: incalculably large.
Relatively simple robots do the work with materials prefabricated on
the Earth.
> We could collect the images 'locally' and beam them back to Earth via
> laser (or microwave or whatever).
Check. We do have some considerable experience sending imagery across
long distances. I vote for radio so that we can get our images on
cloudy days as well as sunny :-)
> There could even be a superbig Lunar version of the Arecibo Radio
> Telescope (if you saw the movie 'Contact'...) that was built in Puerto
> Rico.
Do you mean the one they're getting ready to shut down for lack of
funding? That doesn't bode well for spending a trillion $ or so to
build observatories on the Moon, does it?
> Just blue-sky daydreaming, but sketching out some brainstorms might
> lead somewhere, someday.
Someday. Maybe.
Davoud
--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.
usenet *at* davidillig dawt cawm
Chris L Peterson
wrote:
>Seems like a good idea off the top of my head. Lets see:
A radio telescope on the lunar farside would seem to make a lot of
sense. I can't see that the Moon really provides any advantages for
optical telescopes that can't be realized much cheaper from a
space-based platform, though. For that matter, it probably doesn't
provide such a huge advantage over Earth-based optical telescopes, which
can be made arbitrarily large fairly easily, can be maintained and
upgraded easily, and are increasingly able to cancel most of the effects
of the atmosphere (the highest resolution images today come from
ground-based telescopes, not the HST.)
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
Thomas Womack
>TBerk wrote:
>> There could even be a superbig Lunar version of the Arecibo Radio
>> Telescope (if you saw the movie 'Contact'...) that was built in Puerto
>> Rico.
>
>Do you mean the one they're getting ready to shut down for lack of
>funding? That doesn't bode well for spending a trillion $ or so to
>build observatories on the Moon, does it?
There is an Arecibo successor being built in central China at the
moment, in a natural depression of the same sort of shape as the
Arecibo one; called the Five Hundred Metre Spherical Telescope.
Perhaps it too will be shut down for lack of funding in another fifty
years.
Tom
_
> TBerk wrote:
>
>> - 'Dark Side' of the Moon will have less Earthshine to deal with.
The "dark" side gets more light than the side that faces us.
palsing
wrote:
> The "dark" side gets more light than the side that faces us.
OK, I'll bite.
This is not intuitive to me. Perhaps you could provide a little
explanation.
\Paul
Chris L Peterson
wrote:
>> The "dark" side gets more light than the side that faces us.
>
>OK, I'll bite.
>
>This is not intuitive to me. Perhaps you could provide a little
>explanation.
It's not such an easy analysis. The near side is occasionally in the
Earth's shadow, which would bring down the overall average amount of
light for that side. But the far side never sees Earthshine, which would
reduce its total light.
Realistically, both effects are going to be negligible compared with the
total light received from the Sun, I would think.
Sam Wormley
A spinning orb in the sunlight has a side (other than the poles)
that gets more light? Care to explain?
Martin Brown
> On Sat, 21 Nov 2009 23:48:32 -0800 (PST), TBerk <bayar...@yahoo.com>
> wrote:
>
>> Seems like a good idea off the top of my head. Lets see:
>
> A radio telescope on the lunar farside would seem to make a lot of
> sense.
Only a very large one working at frequencies where the Earth is radio
bright at due to artificial emissions. There are enough gaps in the
radio spectrum window for most astrophysics to be done from the ground.
Although whenever a new spectral gap opens even for an instant
astronomers will have a look in it to see if there are any new
discoveries to be had. This is occurring in the switchover to DTV as
some analogue frequencies are freed up and unoccupied for a while. eg
http://www.popsci.com/science/article/2009-11/digital-tv-switch-boon-astronomers
> I can't see that the Moon really provides any advantages for
> optical telescopes that can't be realized much cheaper from a
> space-based platform, though. For that matter, it probably doesn't
> provide such a huge advantage over Earth-based optical telescopes, which
There is an advantage to space based scopes in that they can use
wavelengths that are not available on the ground.
> can be made arbitrarily large fairly easily, can be maintained and
> upgraded easily, and are increasingly able to cancel most of the effects
> of the atmosphere (the highest resolution images today come from
> ground-based telescopes, not the HST.)
Increasingly light grasp for spectroscopy is more important than
resolution as such. So big scopes will always be in demand.
Regards,
Martin Brown
Thomas Womack
Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
>Increasingly light grasp for spectroscopy is more important than
>resolution as such. So big scopes will always be in demand.
A lot depends on the source; if you're hunting planets, a light-bucket
is perfect and you can spend all your money on the spectrometer. But
there's also interesting science to be had in very crowded fields (the
Galactic centre most obviously), where you might want to get distinct
spectra for each of a hundred stars at the core of omega Centauri to
see what the dynamics are like, and for that you need resolution and
spectral grasp.
There are some interesting recent arxiv papers doing dynamics on M31's
satellites by using multi-object spectrographs on a sample of several
hundred red giants.
(out of curiosity, who here reads arxiv astro-ph? A lot of it is some
way over my head, and some of the applied-relativity is miles over my
head, but I can pretty well understand the exoplanet papers now; I
suppose it's my main amateur astronomic activity, I have no car and my
neighbours recently put in bright security lights)
Tom
_
Lunar eclipses; though Peterson's (valid) point means that more strictly
speaking the dark side gets more SUNlight.
Sam Wormley
Somehow, I can't help but think you learned something
new (under the sun)! Maybe not--Far Side not Dark Side!
<smiling>
-Sam
Quadibloc
> I can't see that the Moon really provides any advantages for
> optical telescopes that can't be realized much cheaper from a
> space-based platform, though.
There is one advantage nobody mentioned so far. When you point the
telescope somewhere, all you have to do is point the telescope. You
don't have to spin up big flywheels, and eventually use up propellant
to keep things in balance.
Having the ground under one's feet is a convenience.
John Savard
Chris L Peterson
wrote:
>There is one advantage nobody mentioned so far. When you point the
>telescope somewhere, all you have to do is point the telescope. You
>don't have to spin up big flywheels, and eventually use up propellant
>to keep things in balance.
>
>Having the ground under one's feet is a convenience.
I'd say having the ground under one's feet is a huge inconvenience when
it comes to telescopes. On the ground, a huge part of the telescope is a
complex and expensive mounting and pointing system. In space, a flywheel
and propellant system is comparatively simple. Sure, you need
propellant, although there are systems that can last as long as the
instrument is designed for.
All you have to do with any system is just "point the telescope". That's
a LOT easier with a space-based platform.
Bill Owen
However, it's a whole lot easier to fix hardware when it's on the
ground. Reaction wheels eventually fail (Cassini is keeping a close eye
on theirs, and even Hubble has had its replaced), and of course
thrusters eventually run out of fuel.
But you don't have flexure in space, and you don't have seeing to
contend with. Nor atmospheric absorption at UV and most IR wavelengths.
But you also can't launch huge light buckets, at least not yet, and
we've got adaptive optics.
I have to conclude that both ground- and spaced-based scopes have their
place.
As for lunar -- the original topic of this thread -- it seems to me that
you'd have all the problems of space, *and* most of the problems of
ground, plus others (moon dust anyone?), and the only real benefits
would be a longer tracking time and lack of atmosphere.
-- Bill Owen
Martin Brown
It is also a huge inconvenience in that to keep the optical figure good
at all elevations requires very complex engineering. Radiotelescope
dishes do it with a design that stays parabolic but changes focal length
with altitude. This doesn't hurt interferometry.
Optical wavelengths and finer require very rigid supports and or clever
active compensation for the changing direction of gravity as the scope
tracks. It is a huge advantage for a big scope to be weightless.
Regards,
Martin Brown
Thomas Womack
Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
> Optical wavelengths and finer require very rigid supports and or clever
> active compensation for the changing direction of gravity as the scope
> tracks. It is a huge advantage for a big scope to be weightless.
I was going to post something of that form, but I was concerned that
the advantage only appeared if you were able to build the scope in
weightlessness; any scope that you build in the Lockheed Martin or
Bell Aerospace clean-room has to be able to hold together in 1G for
years as you build it (indeed, to hold together for a few minutes at
6G as the Ariane goes up), and I suspect the documentation for the
testing gets an awful lot lighter if the scope is able to focus
correctly in a 1G environment at at least one orientation, and lighter
still if you manage more than one.
JWST has active optics (little motors behind the mirror segments) and
the task of getting the mirror segments phased seems quite a difficult
one; I suspect any large space scope really wants to have active
optics, partly so that you can test it with gravity correction and
partly so that you can afford to make the mirror light and floppy to
get a bigger mirror to fit in the very finite payload allowance.
Tom
Chris L Peterson
<two...@chiark.greenend.org.uk> wrote:
>JWST has active optics (little motors behind the mirror segments) and
>the task of getting the mirror segments phased seems quite a difficult
>one; I suspect any large space scope really wants to have active
>optics, partly so that you can test it with gravity correction and
>partly so that you can afford to make the mirror light and floppy to
>get a bigger mirror to fit in the very finite payload allowance.
You still avoid dealing with a mount that outmasses the telescope
itself. And designing a scope that operates in a microgravity
environment has got to be simpler than one that operates at one (or
one-sixth) G, even if it has higher storage and transport requirements.
Chris L Peterson
>I have to conclude that both ground- and spaced-based scopes have their
>place.
>
>As for lunar -- the original topic of this thread -- it seems to me that
>you'd have all the problems of space, *and* most of the problems of
>ground, plus others (moon dust anyone?), and the only real benefits
>would be a longer tracking time and lack of atmosphere.
Agreed. Pretty much what I said in my initial post <g>.
I.N. Galidakis
[snip]
> You still avoid dealing with a mount that outmasses the telescope
> itself. And designing a scope that operates in a microgravity
> environment has got to be simpler than one that operates at one (or
> one-sixth) G, even if it has higher storage and transport requirements.
Chris, do you or anyone know how space telescopes are guided when taking
deep-space photographs?
Controlling accuracy with an equatorial mount for very long photos seems to be a
challenge to amateurs. So, suppose the Hubble needs to take a 1-2 hour worth of
photons of a DSO.
What is the procedure for moving, centering and then keeping it on target
without the ground as a reference point?
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
--
Ioannis
Chris L Peterson
<morp...@olympus.mons> wrote:
>What is the procedure for moving, centering and then keeping it on target
>without the ground as a reference point?
Actually, the HST uses the same reference that ground-based telescopes
do: guide stars. The telescope is positioned by rotating about its CG
using reaction wheels- flywheels on motors. That's a pretty simple
system. To manage the reaction wheels (you don't want them to get up to
their maximum speed, or you lose control) magnetic torquers are used.
These operate against the Earth's magnetic field, and can provide a low
but continuous torque to offset the reaction wheels. Again, a simple
system. It works as long as the mechanics last and the system has
electricity. There is no dependence on chemical propulsion.
I don't mean to trivialize the system- certainly there is a complex
control system to manage the feedback from gyroscopes and the star
tracker, and to drive the reaction wheels and magnetic torquers. And the
mechanical and electronic redundancy is sophisticated. But these systems
nevertheless represent very mature, safe technology, which is relatively
easy and inexpensive to implement (as much as anything space-based can
be easy or inexpensive <g>).
_________________________________________________
Martin Brown
> In article <Q5iPm.36778$ky1....@newsfe14.iad>,
> Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
>
>> Optical wavelengths and finer require very rigid supports and or clever
>> active compensation for the changing direction of gravity as the scope
>> tracks. It is a huge advantage for a big scope to be weightless.
>
> I was going to post something of that form, but I was concerned that
> the advantage only appeared if you were able to build the scope in
> weightlessness; any scope that you build in the Lockheed Martin or
> Bell Aerospace clean-room has to be able to hold together in 1G for
> years as you build it (indeed, to hold together for a few minutes at
> 6G as the Ariane goes up), and I suspect the documentation for the
> testing gets an awful lot lighter if the scope is able to focus
> correctly in a 1G environment at at least one orientation, and lighter
> still if you manage more than one.
ISTR that most big space telescope mirror designs will only behave as
correctly figured on Earth when pointing vertically upwards on
appropriate support structures (and not on the flight structures). There
is a big conflict between minimum weight and optimum rigidity. Part of
what caught out the HST was that there was no possibility for a full
system imaging test on the ground. Which was doubly ironic as the
defects in the primary mirror as manufactured would easily have been seen.
>
> JWST has active optics (little motors behind the mirror segments) and
> the task of getting the mirror segments phased seems quite a difficult
> one; I suspect any large space scope really wants to have active
> optics, partly so that you can test it with gravity correction and
> partly so that you can afford to make the mirror light and floppy to
> get a bigger mirror to fit in the very finite payload allowance.
Given that some of the more exciting experiments are now looking for
planets near stars then being able to put a deep null on the stars
location by tweaking the mirrors phase contributions becomes useful.
http://planetquest.jpl.nasa.gov/TPF-I/stateOfTheArt.cfm
Regards,
Martin Brown
William Hamblen
<morp...@olympus.mons> wrote:
>What is the procedure for moving, centering and then keeping it on target
>without the ground as a reference point?
Spacecraft have used stars for orientation for decades. The HST Guide
Star Catalog was created for pointing the Space Telescope. The Hubble
uses gyroscope-like electrically powered reaction wheels to point the
telescope. They use conservation of angular momentum to skew the
telescope and maintain position once on target. The telescope's
frame of reference is the telescope itself.
Terrestrial observatories also are oriented to the stars rather than
the ground. The ground just supports the telescopes.
Bud
BradGuth
Fine and dandy for rad-hard robotics. However, why would the
extremely electrostatic charged moon offer any less radiation than our
GSO of <2e3 Sv/year while shielded by 5/16" aluminum?
~ BG
Mike Collins
>
> - Show quoted text -
Brad
Why don't you discuss the evidence now available showing how
wrong you are on the moon landings
http://www.skyandtelescope.com/community/skyblog/newsblog/70099067.html
BradGuth
wrote:
We still need to know; How did they do it?
How did unfiltered Kodak film have dynamic range superior to the best
digital cameras?
Where did all the lunar sodium go?
Where did the gamma and X-ray radiation go?
Where did all the raw UV fluorescence go?
How did NASA/Apollo manage to always hide Venus?
Where did all of that dark and electrostatic charged dust go?
Where's a working prototype fly-by-rocket lander of that era?
Why the extensive image sharing delay from our LRO team?
Where's the other 99.9% of our LRO science?
Space that's between Earth and our moon is not cold, so why did A-13
nearly freeze to death?
I have a few more questions, but since you can't answer these, so what
the difference?
~ BG
Mike Collins
Al those questions have been answered many times but you choose to
disbelieve the answers.
What you are doing is the equivalent of saying a bumblebee can't fly
because someone, many years ago used poor science to "prove" it
impossible. What they were really doing was proving the inadequacy of
their science since bumblebees can be observed to fly.
The images show that tracks were left on the Apollo 11 and other
landing sites. How were they made? By Neil Armstrong and Buzz Aldrin
of course.
But these images show that you are wrong.