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Putting An Observatory On The Moon's 'Dark' Side
wytcld writes: "CNN reports astronomers are pushing for a radio telescope on the 'dark side of the moon' (do real astronomers call it the 'dark side,' when it gets plenty of light?). The proposal by Yuki David Takahashi is amazing mostly because a guy just starting work on his Master's is managing major press for it. Still, a nice dream."
I see an issue: talking to it - the moon is in the way.
but, maybe if earth's radio broadcasts interfere with radio telescopes in someway, this would avoid that
Instead of say, the Hubble, they should call it "The Floyd"
Game: Player 'Donald J Trump' now has AI skill level 'experimental'.
This will be very interesting since we only see the same side of the moon due to gravity. More interesting would be an observatory headed for a black hole...I'd volunteer.
Remember, the money isn't spent in space -- it's spent right here on earth in order to get into space.
"Ain't no right way to do a wrong thing."
The article says this is good because the moon would shield the telescope from your satellite TV and internet access interfering.
Of course, it doesn't mention how exactly they plan on communicating with it! Sure, radio from the earth / reflected off the earth doesn't interfere, but important signals are also blocked.
My server
If you had read the article, you would see that the advantages are that the moon would shield the telescope from garbage radio transmissions from Earth and that we would be able to detect emmissions that our atmosphere blocks. Also it would be built ON the moon not orbiting around it.
What good is a used up world, and how could it be worth having? --Sting
Why would this be better than a satelite in a geo-stationary orbit around earth? if it is fixed on the moon, we can only communicate with it half of the time, and it's much more difficult to repair when it innevitably dysfunctions.
Alternatively have 2 geostationary sats such that the observatory can transmit to one, and that one transmits to another one it can "see" which has line of sight to earth.
I'm sure there's a simpler solution, but i'm no space communications guru :)
The temperature is as low as 80K in polar regions (reduced thermal noise in detectors). - 40K inside permanently shadowed craters (coldest place in the Solar System!)
Heh, with temperatures like that they could REALLY overclock the PCs running these observatories!
This is a great idea if I can just get everyone in the country to pitch in 100 bucks (~25 billion) to do it... I think I pay enough taxes without paying for someone elses toys...
What if you put a Satelite in a polar orbit on the moon, it could store data on one side, and transmit it on the other side as it goes around. Might be a little slow but it would work. Or maybe a network of a few Satelites would work better, depending on how much money you want to spend.
In particular, scientists involved in the Search for Extraterrestrial Intelligence (SETI) project like the prospects of a lunar listening post. A major nuisance they face as they eavesdrop on the universe is the constant interference of radio emissions from Earth.
I'm sure it's a major nuisance to the Aliens too: "How can we continue with our search for intelligent life with all this crap coming from those idiots on Earth!?!?"
try { do() || do_not(); } catch (JediException err) { yoda(err); }
"It's like we've always worn red sunglasses. When we take them off, we'll discover red flowers, red apples, red ladybugs, red flames."
Does anyone else think that part of this project has to do with research into "pharmaceuticals" in addition to the astronomy research? Sounds kind of "spacey" to me...
It's only software!
New Scientist has more info including a graphic of how the moon shields raido waves
http://www.kubuntu.org/
do they need to put a couple sattelites around the moon to bounce the info back to earth?
slashdot: where everyone yells sarcastic metaphors to themselves to understand the issue
I believe the correct term is "Far Side" ie: the side that'salways turned away from the earth and is therefore (far)thest away.
You're using her as bait, Master!
Have they agreed to us putting it there? You do know that is where their base are. Hidden from our view.
ahrm.
Did you really think that was witty when you typed it?
--
Some weasel took the cork out of my lunch.
They're not talking about putting it in orbit around the moon, they want to put it ON the moon. Also, off the top of my head without doing any math, I'd guess that a "lunosynchronous" orbit would be impossible, I think the orbital radius would be the same as the distance to the earth...
Bzzzt. But thanks for playing. The Moon rotates at exactly the same rate as it revolves. Thus it always presents the same face to the Earth. That face might be lit (full moon) or might be dark (new moon), but it is the same always. That's why the Soviet pictures (Luna 3 -- see here for one telling) were such a big deal, as they were the first time any human had seen the "dark" (better, far) side.
The Moon is "tidally locked" to the Earth. Tidal forces have adjusted its rotation so that it presents the same face, due to the equality of rotation rates and revolution rates. So something on the Far Side would indeed be shielded from Earth-based transmissions.
The Mongrel Dogs Who Teach
Think small, be small.
-- Slashdot: When Public Access TV Says "No"
Doesn't anybody watch Fox?
In order to put install a radio telescope on the moon, we have to put a man there first!
Nope, you've got it backwards. The same side of the moon always faces toward the earth. The phases of the moon are caused by the fact that the sun illuminates different portions of the moon as the moon revolves around the earth. A new moon occurs when the far side of the moon (aka the "dark" side of the moon) is facing the sun.
My only political goal is to see to it that no political party achieves its goals.
It does rotate, but it's in sync with its revolution around Earth. 29 day rotational period; 29 day revolution (rounded for the sake of simplicity). So in the end, because of the tidal effect from earth, we only see 58% of the total surface area of the moon. The other 42% we never see due to this syncing of rotation and revolution.
Karma whorin' since 1999
The moon rotates around the earth and its own axis in such a way that only one side is ever facing us. There is a bit of a "wobble" due to slight orbital differences so that we see a few degrees of the "dark" side now and then, but on the whole we never see the "other" side of the moon directly. It's not really dark either, the sun hits it too, it was just called that because it was an unknown during early space exploration (because we couldn't see it).
What you're referring to as a new moon occurs when the Earth is in between the sun and the moon (ie. the opposite of an lunar eclipse on earth)
-Legion
The phrase "dark side of the moon" is misleading here. "Far side of the moon" would be better. The new moon does not come from the moons's rotation, but from its revolution around the earth every 28 days.
I survived the Dick Cheney Presidency 7 to 9 AM 7-21-07
do real astronomers call it the 'dark side,'...
:) Really though, what is it called? I doubt it is called the 'dark side', or the 'far side', although I may be wrong.
Of course they don't. That would be foolish and un-"real astronomer"-like. They call it the 'far side'.
If this proposal does go through though, and NASA begins research and development, hopefully it will reignite interest in the moon. We shouldn't dirty up the moon, but we should definately learn more about it.
~thebabelfish
"I don't trust goats," --To Catch a Spy
Hmmm... Can you pass over a $100 dollar check to me, you wouldn't believe what I can accomplish if I only didn't have to work and pay for everyone elses cockeyed ideas...
Actually while you are at it, pay for my wife and kid too.
Thank you for your support
The dark side of the moon does face the earth half the time. Have you ever heard of a new moon?
Bzzzt. But thanks for playing. The Moon rotates at exactly the same rate as it revolves. Thus it always presents the same face to the Earth. That face might be lit (full moon) or might be dark (new moon), but it is the same always.
Uh, I think you lose the semantic battle, even though you don't state anything factually incorrect. Sometimes the "dark side" of the moon is the facing the earth. It is just that the "dark side" of the moon isn't always the same landscape. Sometimes the Sea of Tranquillity is on the dark side, sometimes it's on the light side, but it's always on the side facing Earth.
Of course, back to the relevance of the original post, as far as radio noise goes, the side on the far side from the Earth is the dark side.
-Rob
I guess it would have to be too high and therefore unstable for a the moon, a 28 day "day" would place any object to high to be at all stable wouldn't it?
I believe the prefered term is "near side" for the side that faces Earth, and "far side" for the one away.
The siderial month, the true period of the revolution of the mon around the earth is 27 days, 7 hours, 43 minutes and the period of axial rotation of the moon is 27 days, 7 hours, 43 minutes.
Thus the same side of the moon is always facing the earth.
Actually, since the moon 'woobles' a bit (libration) we can actually see about 59% of the moons surface, and 41% remains permanently hidden from view from the earth's surface.
Hence the terms 'far side' and 'dark side' of the moon.
Steve M
prolly less than the paint on a B2 bomber
* Carthago Delenda Est *
long cable from far side station to near side, transmit back from there.
or antennae at line of site around to near side.
I'm not sure there's a moon stationary orbit that's stable enough not to need fuel to correct the orbit. there is a huge gravity well that gets in the way.
More interesting would be an observatory headed for a black hole...I'd volunteer.
Yep a sure winner.
Steve M
They use only Metric or only US formulations... otherwise there could be trouble...
Why not put it on the Dark Side of the Sun?
A feeling of having made the same mistake before: Deja Foobar
L1 is between Earth and Moon, L2 is on the other side. Those positions are neutral, but unstable; however satellites can been kept in "halo" orbits around such unstable points for a long time with only relatively small fuel expenditure to keep them in the right position.
L1 and L2 are about 60,000 km above the lunar surface, if I recall correctly, so somewhat further away than geo-synchronous orbits from Earth, but they would serve a similar purpose for lunar communications. L2 is the most logical for communicating with a far side observatory; laying several thousand km of cable that has to withstand 400 degree temperature swings could get rather expensive.
Energy: time to change the picture.
Unfortunately your post is situated between two notable posts of the scholar and poet "Klerck", at least in the view im in, and you're using the Anonymous Coward ID, therefore im afraid very few will notice your post, as they would be distracted by the awesome and stunning magnitude of his thought process.
:P
The space shuttle can only reach a maximum altitude of 600 miles. This is with no additional weight and isnt even close to the clarke/GEO orbit, at 22,500 FT. Anything higher that the shuttle carries has to be launched by the Inertial Upper Stage (IUS) mechanism you often see satellites spinning out of. The external tank and SRB's, at 154 FT and 116 FT respectively, are dwarfed by the 373 FT tall SaturnV stack that was used to get the spacecraft far enough out that the S4-B could begin its translunar injection. The space shuttle's current EFT cannot be refueled.
In short, you'd have to dust off the Saturn-V diagrams. Since the government would be paying more than likely, this step alone could cost millions.
Of course, we would want/need to revise a little. Computer weight, increased efficency in fuel, etc.. Chalk up a couple extra hundred mill..
Providing you successfully launch materials into space and onto the surface of the moon. You still need to get assembly teams up - and staff. You could use the same launch system.. But you'd need a completely different capsule design.
Apollo designs just wouldnt cut it. For one, you need seating for more than 3. Granted the space savings of the computer (which was only 1 SQ FT in the original apollo.. dont ask me about that one.) could assist marginally.. a soft cockpit also.. but this theoretical new launch system would likely have the power to launch human weight simply, if its hauling tons and tons of building materials to the moon.
You can see where this is going, and i would love to continue this discussion, unfortunately, my computer is cursed and won't stay up for more than a few minutes at a time. I've had to write this post in notepad.
Don't get me wrong. I'm 150% for space exploration. I think the visions of humanity have become severly limited - the age of wonder has gone the way of Camelot. I'd be on the first moonshot, if i could. I guess they need sysadmins on the moon. I just don't think the US, especially under the republicans, is going to do the space thing much. Remember - Republican translates into "Warmonger, rich oil tycoon" in politiceese - Very little room in dubya's brain for science. Its not christian, anyway. The world still rests atop a stack of giant tortoises. err, wait.. thats hindu.
And before anyone decides to begin a diatribe on the instability of windows, its not windows - its my computer itself. 1)
Linux locks, too, 2) The computer HANGS, the OS doesn't crash.
Anyone remember that episode of the Tick where some supervillian halfway puts his name on the moon with a giant laser? And then this half of his name stays on the face of the moon, besmirching its image for the remainder of the series? The far side of the Moon offers innumerable possibilities for settlement which does not alter Luna's earthly appearance. It seems like putting probes/telescopes/colonies on the far side would be much more admissible to the gazing public, in addition to allowing for wonderful views of the outer universe, to the attendant eyes. Of course, this would eliminate views of the earth from lunar installations, but our orbitting satellites see this planet well enough as it is, I think.
Aren't you dead?
Ammendment to above comment: The shuttle's highest launch to date was the HST launch to my opinion, which was in the 300-400 MI LEO.
Correction: I'm stupidtired.
Change:
22,500 FT
to
22,500 MI in reference to the clarke orbit.
Anybody remember the old Robert McElwaine Usenet postings?
Those astronomers better be careful; the Soviets have their PARTICLE BEAM support bases on the far side of the moon...
May I make it clear [after several classes in astronomy] that we are in TIDAL LOCK with the moon. We always see the same side of the moon because of that. No Rotation. Thats why we call one side the dark side of the moon. Its always facing away from the earth. OF COURSE, this doesn't mean it doesn't get sunlight, it just means that it doesn't recieve any of the Solar Spectrum that we either reflect or transmit. [Radio Waves are part of the Solar Spectrum.]
So why is it good to have a Radio Telescope on the Moon? The Dark side for that matter? A clearer image of the skies, is my immediate thought. I'm sure there are far more reasons then this one, but they're all too complicated for me to speculate on.
The only problem is, that while an observator on the far/darkside of the moon has a lot of benifits, we can't get there. While NASA could go to the moon in 1969, they don't have a single rocket to do the same now and radio telescopes are huge, less gravity will help, but you still need a huge capture area to hear signals from 100/1000/10000 lightyears away. The moon missions only required the transport of 3 people and life suport (and dune buggy), but the requirements of an serious observatory would be much greater requirements. The article doesn't mention if there is expected to be a support staff or if this would be purely robitic. There is a further problem in that they want it place it on the far/dark side of the moon, to avoid radio interference, (if this was built an optical telescope seems like a simple addition), so how do you get the information back to earth, the cabling required to get the signals back to the near/(bright?) side of the moon would be huge, or maybe you orbit a sattilite for relay purposes, but in anycase this is still a huge undertaking. Don't get me wrong I'd love to see this but this would cost Billions and Billions (said with carl sagan voice) and take 20-30 years, and as the US gov has canned SETI and they were make to look like fools in Contact I can't see them too keen on this.
For half of each month, the darkness of
the nights on Earth is moderated by the
sun-illuminated moon hanging overhead.
For the moon, it's the same thing, except
that it does not rotate with respect
to the earth, other than the single rotation
that matches its revolution.
So the side of the moon on the Earth's side
is illuminated every fortnightly lunar night by earthlight, so it is never
truly dark, and the occulted side is
never illuminated by earthlight at night, so it is much darker.
And earthlight is, as one would expect, significantly brighter than any full
moon would appear here.
Imagine orbiting over the far side during
a lunar night, with only stars and planets
lighting up the soil. Any man-made light
would probably be easily visible.
This would be good material for a
sci-fi/horror flick!
Actually, when the Earth is between the Sun and Moon, we get a full Moon (lunar eclipses always happen during the full moon). Conversely, during the new moon, the moon is between the Earth and Sun (Solar eclipses always occur during a new moon)
There are no tiger attacks in my area and it's all because this rock I'm holding keeps the tigers away.
Although this appears to be a neat idea. I can't help but get shivers every time I see someone want to put something up there. I guess I like the relatively unspoiled view (no I don't have a telescope) that we have. The Earth is not so lonely and we have thousands of satellites kicking around in orbit.
Wouldn't it make more sense to push for Mars? It's further away from the sun (1.52 AU as opposed to the moon 1 AU), has relatively little atmosphere (mind you there are the dust storms but we're talking radio here), and is the next likely place we humans could go for off-planet colonization. It would be a great precursor to humans coming over... and with an established communication network because of this and possibly other missions, it could encourage private industry to help fund exploration. I would imagine the cost could be the biggest factor that would prevent Mars from being the candidate... damn.. I love our mostly pristine Moon!
(1st sig) If this were a snappy sig, you'd be reading it right now. (2nd sig) I'm a karma whore. >Insert FUD here
Ricardo Montalban said, "In space it is very cold". I heard him say it in Star Trek so it is true.
Will the cooler temperature in space allow me to overclock my CPUs, thereby increasing the overall speed of my beowulf cluster?
I imagine it will.
Then I can get even more framerates when I play my favoraite Linus game, DOOM.
Wouldn't this thing get pelted pretty bad by meteors?
"Two candidate spots on the moon include Daedalus and Saha, each a formidable crater dozens of miles in diameter."
Now, if I remember my astronomy, the moon has little atmosphere so even the little meteors make it to the moon's surface, causing pretty big damage. A big crater isn't going to provide too much protection is it?
Great idea for an optical scope but have you ever seen the size of the Arecibo dish in Puerto Rico? They would be looking at building a dish perhaps as big as a few kilometres across.
---
I didn't want to leave this space blank.
Good idea except for a couple of significant problems. Number 1 is the meteor problem, during the 2 wks in which the moon leads the earth through space, the combined gravational forces of the moon and earth significantly increase the probability of a meteor striking the telescope system if it where built on the far side. Take a look at some of the photos NASA has from the far side, the near side is silky smooth compared to the far side. The moon acts as a meteor shield for the earth,this plus our atmosphere are the main reasons why the earth's surface isn't cratered like the moons surface. The second major problem is that over half the time the telescope would be pointed at or at least exposed to the sun which in it self is a significant source of rfi. If you had the logitical problems covered you still would be hard pressed to have this very expensive instrument usable more then 1 wk. out of 4 wks. If anyone is actually serious about this concept, it would be much more feasible to place a radio telescope device with massive rfi shielding from the earth's noise out in deep space.The idea of a radio telescope on the moon's far side is not new and neither are the practicalities. The cheap and dirty solution is to ask everyone to turn off the power for a few hours. I hope this guy is not trying for a degree in astrophysics, he hasn't done his home work if he is.
Hu, most of your post I can not follow.
... hu hom ... 108,000,000 feet?
... the moon is way: 1,152,000,000 feet.
...
But you are right according the height of a Shuttle, about 600 miles is far higher than I asumed(knew).
However a GSO is far higher than you say, its not 22,000 feet. Its about 36,000 kilometers!!! Thats about 6000 times higher, there are even planes flying at 22,000 feet(and higher).
36.0000 kilometers are
As you seem to like feet
Well, why can't you at least measure in yards? He he
Regards,
angel'o'sphere
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
I know I shouldn't feed the trolls - but they're so damn cute sometimes. :) So hear goes:
It is cold in space.
Unfortunately, vacuum is an excellent insulator. It's very difficult to dissipate heat in space.
Ever see pictures of the shuttle in orbit with it's doors closed? No - the reason is that the insides of the doors contain giant radiators just to dissipate the heat generated by the people and equipment. They MUST keep them open at all times to dump waste heat.
Well that would be a good idea except the article states that the telescope would be on the lunar surface, not in orbit. However the idea of having relay satellites in L4 or 5 is interesting. If the telescope were near the terminator relaying the info to L4 would be easy and the actual satellite could be very cheap.
Live in hope. Die in despair.
I can hear the Floyd sequel now!
I hope the band I'm in is not playing different tunes.....
Of course the moon rotates. How do you think we see the same side of it all the time? Because it rotates at the same rate at which it orbits the earth. Do some research. It took me 5 seconds to find this on googleh tm
http://newton.dep.anl.gov/askasci/env99/env093.
Just to add a little something to the dark/far side threads in this discussion...
;)
Did you know that the period of the Moon's orbit which causes the same side to appear facing Earth was once used as a proof of God's existance ? The thinking was that, given the probability that this 'coincidence' would occur, that only a divine creator could have set it in motion.
We know now that with one moon and the Earth's tidal forces that it was in fact inevitable that the period would fall into this pattern.
This of course proves that the divine creator does not play dice with the universe
"Whoever would overthrow the liberty of a nation must begin by subduing the freeness of speech."--Benjamin Franklin
Thanks for the explanation. I was quizzing a bit over the correct name of the eclipse.(Solar? Lunar?)
I see you also understand why the moon appears dark. :-)
Cheers.
...that damn bright object in the sky that is blacking out all the good things too look at. Thanks to it there is one good day a month, compounded by clouds appearing 85% of the time leaving one good month for observing.
That month being the said coldest day of the year, usually somewhere in the low single digits, then the wind helps it to double digit negatives.
As a rock-in-roll Physicist once said, No matter where you go, there you are.
L4 and L5. Put the communications satellite in the L4 or L5 Earth-moon Lagrange point. These are the stable points. While they won't "view" the exact center of the far side disk, if the observatory is built, say, 45 degrees back from that center, a satellite can view it from L4 or L5. The observatory would still be blocked from Earth noise by a huge mass of the moon, but it would be able to see L4 or L5 (which one depending on which way it was positioned) just above the horizon all the time. And with 3 or 4 active links to it on the Earth, continuous contact could be maintained. While a satellite there would actually be in order around a virtual point, it could be a small orbit, allowing for a fixed antenna at the observatory, and potentially very high bandwidth continuous communications.
now we need to go OSS in diesel cars
Imagining a satellite around a moon around a planet around a sun is a little out there.
Tough to imagine, eh? How about visualizing something closer to home--an electron in your wristwatch's second hand.
It's orbiting the nucleus of an iron atom,
which every 60 seconds circles the axis of your wristwatch,
which every 24 hours circles the axis of the Earth,
which every 365.242 days orbits the Sun,
which every 200 million years orbits the center of the Galaxy,
which every 150 billion years or so orbits the center of the Local Group,
which every few trillion years orbits the center of the Virgo supercluster.
I suppose those last two are somewhat optimistic predictions, especially considering that I have no first-hand knowledge of your wristwatch.
The advantages are plain too... you get an orbit of 28 days, and it passes over points of the earth roughly once a day (quite a slow orbit)
But the most important aspect would be observations during a lunar eclipse.
Not to mention the fact that transmitting data back to earth would be easier.
Most of the similar proposals I have seen includes an optic fibre link past the horizon to a relay station in view of the Earth. A satellite link would not be ideal, since the radio communication would mess up the observations. Anyway, the satellite solution would probably not be any cheaper than a cable, because:
The observatory would be in a permanently shadowed crater near a pole, not in the "middle" of the far side, so it's not like they would need a cable a thousand miles long. This would give access to stable temperatures to preserve the construction materials for a long time, as well as permanently illuminated solar panels on the crater rim.
So the near side of the moon will be close to the site, and the cable will be short. With todays technology and resources the cable is of course more expensive than a satellite, but if the problems of actually putting the observatory there are solved, then the additional cost for the cable would be quite reasonable.
Some people have pointed out that sending data back to earth would be costly, since transmission from the Dark Side is tricky.
But what about deploying a relay satelite orbiting around the moon? As another post sugested, this is possible. (Although the life expectancy may only be about 20 years...)
I'm not an astrophysisist. Don't shoot the idiot.
;)
ME.
A syncronus orbit on the moon would have a additive one direction pull on the satelite steadly pulling it out of position. Check the path of the orbit of anything placed in a stationary orbit over anyplace on the moon except directly between the moon and earth, or directly over the far side of the moon. A handy spot "beside" the moon where the earth and farside of the moon can communicate in a stationary orbit will not stay put for long.
The accelerating force is in one direction for a very long period of time. Earth satelites do not have this problem as the lunar gravity pulls for a relatively short period of time in one direction and shifts in the other direction for the same period of time as the moon orbits. The satelites wobble a little just like the ocean tides come and go. A moon satelite will get pulled and keep going... it won't wobble just a little. It will move until it reached the other side (East to West) and then it will come back (West to East). True it will take years to get a cycle complete, but the thing will not stay stationary.
The truth shall set you free!
The ban would leave the skies clear for a relatively cheap geosynchronous sattelite to take a snapshot of the 30MHz band - and even though the protection wouldn't be perfect, it probably would be much better than what we have now. Keep in mind the radio transmission ban would only have to be enforced over half the Earth at once, and it could be at night, when hardly anyone would notice anyways. Put the ban on the countries that are asleep when they're facing the direction you want to look, and time things right so that the majority of the radio ban is over a major ocean, and there wouldn't be any real hardship.
Uh, I don't think so or we're talking about some other Clementine probes...
"The Clementine Lunar Image Browser (CLIB) is available. Version 1.5 allows access to over 170,000 Clementine images and includes a new interface that allows the user to zoom in to any location on the moon. The full version, due in 1995, will serve all 1.8 million images as well as their associated data."
Two points:
- While antennas for microwave astronomy could, of course, resemble the familiar parabolic dishes found on earth (although other types are possible), their size would be limited less by design problems caused by the effects of gravitational stress (as they are on Earth) than by material shipment and construction costs. However, antennas for the lower frequencies of radio astronomy, e.g., 1-10 MHz, could be markedly different from those found on earth. Since, for equivalent performance, the dimensions of an antenna are proportional to the radio wavelength being received, a 1 MHz (300 m wavelength) antenna, for example, requires a million (a thousand squared) times the physical area as the equivalent antenna at 1 GHz (30 cm wavelength). Thus, land costs are the largest problem on earth for low frequency antennas (along with other impracticalities). This problem is effectively eliminated on the moon, freeing the antenna engineer to study other possibilities.
Also note that, while the 1 MHz antenna is larger than the 1 GHz antenna, the tolerance on the placement of its physical components is looser by the same proportion: While a very fine mesh reflector for the 1 GHz antenna must have wires, say, every 3 cm or so, +/- 1 cm, the equivalent specification on the 1 MHz antenna would be wires every 30 m +/- 10 m. This may be significantly easier to build by robotic devices. (For practical reasons one probably wouldn't use a reflector-type antenna at 1 MHz, but the principle holds regardless of the antenna type.)
- There is a second, equally important problem to doing low-frequency (30 MHz) radio astronomy on Earth, besides the man-made interference. It's the ionosphere. The same refractive layer(s) in the atmosphere that enable worldwide shortwave communication also shield the surface of Earth from external radio sources; signals that do reach the surface are greatly attenuated, and have significant phase and angular (i.e., apparent location) distortion. Since the moon has only a trivial (most would say substantially nonexistent) atmosphere, the ion density in it is much, much lower; this leads to refraction of radio signals only at much lower frequencies, something on the order of 100 kHz or less, IIRC.
The main site doesn't say a word about cost, and it casually postulates robotic construction, which is not a currently deployed technology even on Earth. It seems to be ivory-tower science. The CNN and New Scientist pieces just say "billions."
Is there any reason to think that this thing could actually be built for a reasonable cost? Has anyone even tried to come up with a real estimate? Bear in mind how low the estimates have been for our most recent space construction. Off the top of my head I wouldn't be surprised to see a real cost in the hundreds of billions, between dozens of Saturn V launches and the development of entirely new technologies like lunar robotic construction.
Tim
However, if your computer was located on a planet, you could use the ground to conduct heat away from it. (Though the thin atmosphere might help, I'd want to stay indoors - and keep my computer away from the dust...) Heck, imagine overclocking on Pluto. ;-)
Uh... this is very wrong, but not obviously so I suppose the moderators can be forgiven. The reason for the cratering difference between the near and far sides of the Moon is ENTIRELY due to the fact that the near side is a slightly younger surface than the far side. You know all those dark "mare" areas you see on the near side? There are essentially none on the far side; what those are are lava flows dating back generally 3+ billion years, filling large basins created by giant impacts that mostly date back 3.9 billion years or more. Those mare lava flows covered over all the old craters, giving a somewhat smoother surface (by the way, if you look through a telescope at the Moon any time, near the terminator, you wouldn't ever again call it "silky smooth", anywhere).
In any case, the Moon does NOT act as a meteor shield for the Earth, in any significant way: the Moon's mass is only a little over 1% of that of Earth, it's cross-sectional area around 10%, and the Earth-Moon distance is so relatively huge that the chance of anything destined to hit the Moon also coming in a direction that it would have hit the Earth if the Moon wasn't there is somewhere around the 0.1% level - i.e. 99.9% of the meteors that hit the Moon wouldn't have gone anywhere near Earth anyway; and generally the Earth will receive about 10 times as many meteor hits as the Moon does, so the Moon shields a miniscule 0.01% or so of the ones that do hit.
Ok, so much for that theory. What about the rest of the post? Half the time the telescope would be unusable? That's sort of typical of telescopes actually - have you ever tried looking at the stars in daytime? In any case, one of the proposals mentioned was actually a polar observatory, in one of the craters that never receives any sunlight in the amazingly deep south pole basin. These are also shielded from Earth, and would be close to ideal 100% of the time - except they can only look south relative to our orbit around the sun, so somewhat over half the sky would be missing...
So it would be much more feasible to "place a radio telescope device with massive rfi shielding from the earth's noise out in deep space"? First consider the proposed size of these telescopes is huge - several km across! How do you propose to launch such a huge structure (the most massive parts of a lunar telescope would be constructed from in situ materials, and thus not require any launch from Earth)? How do you propose to launch the immensely more massive shielding? We're talking billions of tons here, when it costs $10,000 to launch a pound in the US these days?! Why is it that any time someone talks about the Moon these days it's a ridiculous proposal, but then the same people come up with immensely more hare-brained and expensive schemes!!!
"ask everyone to turn off the power for a few hours"!? I'm sure a few hours a year of telescope time (and remember they're dedicating some sort of Arecibo or bigger-size telescope to this) will really satisfy the astronomers... and what sort of totalitarian political system do you think the world would need to actually get a request like that followed?
Oh well, just had to respond to the +5 on the post...
Energy: time to change the picture.
Essentially correct, but there's another thing: the interference from the sun is no great issue, astronomers also observe during daytime. Not only that, but the frequency you're observing on may not even have significant interference from the sun at all.
Then there's the issue of not actually seeing all of the sky at once (radio telescopes have [a few] lobes in which they're most sensitive) so the sun may not bother you much at all even if it _is_ radiating at your observing frequency!
Overall, radio telescopes can almost always be usefully employed, unlike optical ones.
Personally I'd want to place an optical telescope in one of those polar regions, preferably in a crater that doesn't get much sunlight. That'd be really useful (good seeing and stable soil).
(I've studied astronomy at Leiden University for 7 years although I got sidetracked by sysadminning so I didn't graduate.)
--
(snort) We've only had 50-75 years of punching out crap (and hell, maybe aliens *like* I Love Lucy). That's hardly enough time for electromagnetic radiation to annoy aliens. By the time they notice us, if anyone does, we'll probably have converted almost entirely to cable or some other futuristic entertainment deployment technology.
Even though the cable would not stretch half-way around the moon it would still be long enough for potential problems to arise.
What if the cable breaks somewhere? It would be a major undertaking just to fix it (think of cable failures under the oceans for comparison).
The satellite option has some real problems (where to put it, radio-noise) but I think this danger with a cable option is more serious.
Die dulci fruere. Have a nice day.
I was half-asleep when writing that - I corrected the post as soon as i had seen the error.
If you take "dark" to mean "not visible", how is "dark side of the moon" any different than Stallman's use of "free" in "free software" or that something is a "black box" (you can't see into it and figure out how it works) that isn't really "black"?
If you ask Dark Sith of the Moon, you might be able to lent his reciever ;)
Carbon based humanoid in training.
Can anyone speculate how easy it would be to sustain a stable orbit around the moon for long periods of time?
There are 5 lagrange points in a two-body system such as earth-moon. The L2 point behind the moon is unstable, but a very small amount of station-keeping thrust every now and then would keep a relay satellite there.
The moon obscures L2 from earth. But you could do a second bounce off a satellite at L4 or L5. Those are 1/6th of the way around the orbit behind and ahead of the moon and are stable second order - a satellite drifts off the potential peak but then ends up in a stable orbit around it.
See an explanation here
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Timothy: (do real astronomers call it the 'dark side,' when it gets plenty of light?)
...
brassman: If you're a RADIO astronomer, yes...the far side would be the dark side as far as you're concerned. The amount of radio crap we're spewing
Also: The far side doesn't get light or solar radio noise reflected from the earth, while the near side sees the earth illuminated (at the nearest point: first quarter (half-lit) through full to last quarter) any time the sun is down.
Put two observatories a bit over the horizon from Earth on opposite sides and you get nearly continuous observation of the half-sky opposite the sun without interference from either the sun or the earth.
Don't put one EXACTLY opposite the earth: There's a diffuse "hot spot" of signal that diffracted around the moon there - diffuse because the moon isn't a sphere smooth down to radio or light wavelengths.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
It does rather blow one's mind that Richard Stenger, paid by CNN for "Sci-Tech" reporting, would look at a bunch of proposals and papers referring to the FAR side of the moon, and still write "DARK side."
/. readers know what they are actually talking about building. It's like a bunch of Pathfinders with radio antennas on them, plus a control module. The big "dish" is done with baseline interferometry, like the VLA in New Mexico.
Anyway, CNN may not be very good at commenting on this stuff, but Slashdot isn't either. These postings are weird! (That one about the meteors is so embarrassing that I was hoping I could meta-moderate it, but all I got was junk about Quake parties...)
You should read the proposal. I'm not sure
We absolutely have the tech to get these things up there, red herrings about the Saturn V notwithstanding. This is a run of the mill planetary probe... with a lot more trips, but each one only takes a few days or weeks, depending on the boost method used.
One thing we don't have is a TDRS-type relay satellite to communicate with the farside. We could park one at the Lagrangian libration zones L-4 or L-5 - diagram here - depending on which crater was chosen, or we could low-orbit a fleet of them and play relay games.
A farside radio observatory is a reasonable proposal and the researchers discussing it have already thought through most of the casual objections raised here, so I hope it's given further study.
of course the FAR side is always pointing away... but when there's a new moon, the DARK side is pointing towards us. Get it? It's humor. ha ha. ha.
So they are considering building a large radio telescope on The Dark Side of The Moon?
Where you can't even Breathe so the astronomers would suffer from brain Damage
It will obviously cost lots of Money
And take a long Time
and it wouldn't work during an Eclipse
According the Buzz Adrian's "The Return", (a work a fiction, but I'm pretty sure he got the science right) the moon has a stable "Halo" orbit, which is an orbit about a gravitational balance point just beyond the moon opposite Earth (I don't know if this a Langerain point or not). Its properties are such that you can orbit it, just as if it were any other mass. Thus you could orbit this point with full view of the dark side of the moon, and broadcast back to earth from a point that appears to just circle the horizon of the moon. So only one satellite is needed. In fact you could just put the radar antenna at the center of the point and have reasonable shielding I'm without having to enter the moon's gravity well.
As for weight, this thing could be made of aluminum foil; thinner than kitchen variety, since almost all the weight of Radar Dishes on earth are to resist weather and wind, of which there are none on the moon. In fact you wouldn't have to have a perfect dish, just take square chunks of foil (of whatever is the ideal metal), and plant them along a crater wall. The pattern can be sparse, but has it fills up; the signal will of course get better. Something not much more sophisticated than Sojourner could haul the plates into place. Wouldn't matter if it takes a long time (astronomers are nothing if not patient), wouldn't need advanced robotics, the moon is close enough that these is just over 1 second delay time round trip for light, so remote control is good enough to control the construction robots.
Now we have something like Arecibo, with a spherical antenna array. The receiver would have to be suspended over the crater, and elevated. This would be the hardest part, but of course 1/6 g makes it much more doable, plus, once again, it doesn't have to battle the elements, so it doesn't have to be over engineered.
This project needn't be massively expensive due to weight of materials needed. It needn't be massively expensive if NASA could adopt a build-it/design-it as you go along philosophy (with the exception of the receiver portion). Unlike like smaller-faster-cheaper, this would be, "figure it out as we go along". Here is a project, where the ground controllers would really feel like they are part of the action. Lessons learned here would come in handy for doing other more ambitious construction projects in the future. Other projects to date have not had the luxury of experimentation, and had to rely on over engineering and expenses to ensure success.
Letter To Iran
If these are stable points for a satellite, are they not also going to be stable points where all sorts of crap can accumulate?
Would it make collisions any more likely?
In short, you'd have to dust off the Saturn-V diagrams.
I like reading the sci.space.* newsgroups on USENET. Henry Spencer has discussed the idea of building more Saturn V rockets.
The problem is that blueprints only take you so far; there is a lot of know-how that was distributed among the various contractors who built the various pieces. All that know-how is irretrieveably lost. No one ever wrote down the special heat-treating process that made this part here strong enough, no one ever wrote down the custom jig used to machine that part there, etc.
So you really cannot build a Saturn V now. You would be starting all over from a design. And, says Henry Spencer, there is no reason to start all over from the Saturn V design; you would do just as well, or better, to start with a fresh design that made modern assumptions (like modern computers).
By the way, for similar reasons, you really cannot build a Space Shuttle orbiter now either. We already have as many orbiters as we will ever have; let's just hope no more of them explode.
If we ever do want to build a heavy-lift launcher, the correct way to do it is to announce that the US government will pay $X dollars per each heavy payload launched into space, and will commit to launching Y payloads. Then stand back and let the market work. NASA, as presently constructed, cannot pull off projects like building a new heavy-lift vehicle, at least not without spending an insane amount of money and running far over schedule.
steveha
lf(1): it's like ls(1) but sorts filenames by extension, tersely
I am afraid your base data is wrong about the moon. The moon's diameter is approx 27% yielding a cross sectional area 6% of the earth's and it's mass is 10% of the earth's mass. The fact remains that during the rotational period when the moon leads the earth that the farside IS exposed to a greater probability of impact without the benefit of any significant atmosphere and that the earth is not shielding the moon at this point. Comet debris would seem to be th biggest hazard, we aren't talking big particles but at the given velocities, their impact energies could be considerable. Astronomers do visually see impacts at the moons terminator, these are rare but still are frequent enough that many amateur astronomers do invest time waiting for a visible impact event. If the probabability for damage to a receiver is negligble from meteors in space than why do we take precautions with our orbital satellites? The combined gravitional forces acting on a meteor that is in the orbital path will have an increased velocity and potential for increased impact and damage to any structure that is built on the moon's farside. I also am assuming that we would want more than a 10 yr. design life out of this project. I also was assuming that if serious SETI research where going to be done and we were going to invest this much money into a project such as this, that a very wide frequency spectrum would be employed, thus you would want to shield it from the sun's noise. Also I was assuming since you were desiring to construct an extemely sensitive detector that you would want to protect it from proton and electron radiation which could be significant in the case of a solar flare. If you where to construct this antenna system out of insitu materials than wouldn't you have a dish that is not steerable except for limited steering allowed by phase arrays? At least Arecibo can do a 360 deg.scan once every 24 hrs instead of this projects 4 wk. scan period. A radio telescope's antenna does not have to be massive to work. All you need is a radio reflective material that has a surface continuity that is greater than 1/4 wavelength of the signal's wavelength. In a zero G environment very thin films are excellent candidates for an antenna structure. For rfi shielding the same parameters apply, you don't necessarily need a large mass in the way, I was using massive in the effective sense i.e. extemely effective. Most earth based optical telescopes are usable more than 25% of the time (more than 6hrs./day) and are maintainable. I think one of the critera for site selection is that they need observable skies greater than 80% of the time. If the real problem is earth based rfi than why don't we invest a fraction of a moon far side based project into active rfi suppression technology? Look what active optics have done for earth based visual telescopes.
Put one relay satellite in orbit around the moon. It will not be in synchronous orbit for reasons already discussed. The satellite will be over the telescope on the far side part of the time, then on the earth-facing side. Assuming a real-time conversation with a telescope is unnecessary, the satellite can simply store transmissions until in position to relay.
Think email, not telephone.
Robin
With respect to radio waves, calling the far side of the moon the "dark side" is not so inaccurate.
Actually the mass of a satellite is irrelevant in regards to its orbital radius.
Actually, you can orbit the Moon. If you stay in a low enough orbit (less than a few 1000 km's) the
gravitational perturbation due to the Earth is small. HOWEVER, there is another source of gravitational
perturbation that will cause orbits to change in a few months: large concetrations of dense rock called
"mascons" (for "mass concentrations") formed from early lava flows. These have a large enough effect that
e.g. satellites left in lunar orbit during the Apollo program decayed and impacted the Moon within a year, as
I recall.
Human genome = 3 billion base pairs = 6 GBit. Windows + Office = 20 Gbit. Which is more impressive?
If they built 2 observatories, each just over the horizon wrt earth, but on opposite sides of the moon, then you get a 'virtual' receiver the size of the moon. Plus then they just need to build stations just on the earth side of the moon, to transmit the data back.
Then all we need to work out is a practical method for adjusting the azimuth and elevation of the moon, to aim the antennae.
MrCreosote Meow!Thump!Meow!Thump!Meow!Thump! "You're right! There isn't enough room to swing a cat in here!"
The dark side of the moon is the one neves faces Earth, so placing there a radio telescope prevents any "False Alarm" by receiving a local radio signal, also that radio telscope will require less mainteinance, (there's no wind, erosion, rats, moisture,...) and could be self powered, recharging batteries during the time it faces the sun for use later on. Also a crater can be used (as a lake was used in Arrecibo) to build tha main dish of the antenna. If it is on the dark side of the moon it can't broadcast the results back, but placing three or four satelites to work as rally points of data.
They are stable, but wide. The stability is not that stuff falls inward, but that objects would orbit around the point. But, yes, there is a risk that crap can accumulate there. But astronomers have looked and found nothing more than some dust in the Earth-Moon L4/5 points. The Sun-Jupiter and Sun-Saturn L4/5 points do have some big rocks in there.
now we need to go OSS in diesel cars
FarScope!
(David Bowman, EVA near HUGE Monolithic Win-PC in orbit around Jupiter) "My God - its full of Malware!"
They obviously would have to name the observatory "Floyd" in honor of Pink Floyd's "Dark Side of the Moon" and Dr. Floyd from 2001 moon base fame.
It is by the juice of the coffee bean that thoughts acquire speed, the teeth acquire stains. The stains become a warning
"Actually, there is no dark side to the moon. As a matter of fact, it is all dark" - Nick Mason, I believe, from the album.
Just think - if we hadn't been cursed with this weird coincidence (rotation period == orbital period) our scientists and philosophers might have cottoned on to the laws of orbital motion and the sphericity (?) of the Moon and Earth millennia ago.
It's not a weird coincidence. Because the Moon is so big and so close (relative to most planet/moon relations), tidal forces will affect it's rotational period until it is in sync with the orbital period. To not be tidelocked, the Moon would have to be so far away that it's unlikely that the rotation would be visible to the naked eye...
No. You go back to the original lunar mission plans (earth orbit assembly), from back before political considerations turned it into "Get two guys there the fastest way possible. And make this the first exploratory voyage in history with zero fatalities."
Keep in mind that electronics we have now is immensely better than it was during the Apollo missions. You can do things with robots that they were scared to try with or without live crews in 1968. The following plan takes a decade of development work, but none of the pieces are too big, and there will be other applications for the technology created:
You use the shuttle to haul pieces of the mission ships into orbit. You don't actually need a space station, just an area where the shuttles bring the pieces and shuttle crews bolt them together. I think one shuttle brings up an orbital transfer robot "tug", the next one brings up a load of communication satellites. The tug has some very efficient low-thrust drive. The tug first takes the comsats out and drops them off in lunar orbit, so we have the needed com relays to the far side.
The tug returns, and meets one to three more shuttles with a disposable robot lunar lander, payload, and fuel. After the pieces are bolted together, the tug takes the lander out to lunar orbit, drops it, and returns for the next piece. The lander lands (of course). Subsequent landers home in on the first piece.
You better have two tugs, and you will need some spares of the landers and telescope sections, because some units will malfunction. But eventually all the pieces of the scope are landed on the moon, and you now know the transportation there is trustworthy. So now you send your man-rated lander out on one tug, with the second one following just in case. The crew lands, bolts things together, and comes home.
Alternately, send out some robot cranes, robot wrenches, etc., and have the final assembly done by robots. It will be slow and rather expensive, but maybe cheaper than sending men. And when you get done, you know how to make robots to tackle the biggest jobs...
So the dark side of the moon is actually the bottom
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The world's largest steerable radio telescope measures only 110 x 100 meters.
And, it can be used during the daytime. The optical wavelengths given off by the sun don't interfere with radio astronomy. The sun does give off RF interference, but you have to point the telescope almost directly at the sun to encounter a problem.
You wouldn't have to launch billions of tons from Earth. Techniques for processing lunar materials into structural building components have been tested for decades.
That that is is that that that that is not is not.
You wouldn't assemble a lunar radio telescope in orbit, and then attempt to land it on the moon. You would assemble it on the lunar surface.
That that is is that that that that is not is not.
1. The lunar radio telescope could be operated, and perhaps even constructed, remotely. No need for a staff of humans to reside there.
2. I'm a Republican, and I'm not a warmonger, and I don't have anything to do with the oil business, and I'm a pro-space activist. Please spare us your hack political comments.
That that is is that that that that is not is not.
How?
That that is is that that that that is not is not.