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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."
Instead of say, the Hubble, they should call it "The Floyd"
Game: Player 'Donald J Trump' now has AI skill level 'experimental'.
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
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!
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); }
A satellite in geostationary orbit still receives a lot of radio noise from Earth. That's sort of the point of GEO, after all. On the far side of the moon, though, there's this big hunk of radio absorbing rock between the antenna and Earth, which would allow the 'scope to pick up much fainter signals.
Oh, go on, check out my job.
New Scientist has more info including a graphic of how the moon shields raido waves
http://www.kubuntu.org/
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
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
Why not? you just spent ~$60 (15B) to bailout the airlines, and you didn't even notice did you.
- Adam L. Beberg - The Cosm Project - http://www.mithral.com/
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
The last time I checked, the moon rotated.
Correct. Once per orbit.
If i am incorrect about this, please Xplain why.
Look at it this way -- when was the last time you looked up at the Moon and saw the far side?
-- Alastair
"Far Side" sounds like something by Gary Larson. :-)
Yes, "Far Side" is a more correct term for the side of the moon furtherest from Earth. It most certaintly isn't dark - where does the other light from the Sun when there is only a "quarter moon" in the sky? And surely the "Dark Side" would be light during a lunar eclipse. :-)
The moon's orbit around its axis is the same length as its orbit around the Earth, so the same side of the moon is always facing the Earth. When you look up there at the moon, that's the same part of the Moon you always see. That's why sticking an observatory on it means they'll always be able to point out into space, but they'll still have trouble when the sun shines on them (during a "New Moon" from our perspective) and blots out its vision of the stars with interference (which I assume would be lessen by the lack of an atmosphere to scatter waves).
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.
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.
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.
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
I'm going to contribute to the rampant correction of misconceptions here. (have to do my part)
THERE IS NO PERMANENT DARK SIDE OF THE MOON
There are permanent near and far sides to the moon, as viewed from Earth. The same side of the Moon is always pointed toward the Earth. The "dark" side of the Moon is whichever side of the Moon is pointed away from the Sun at the time.
The fact that the Moon does not rotate relative to the Earth is the whole point of putting a radio observatory on the far side of the Moon. Astronomers want the Moon between their radio telescopes and the radio noise of human civilization so they can observe in peace.
Other posters have explained how one could communicate with such a facility, given that it's on the far side of the Moon, so I'm not going to go into that.
But then again, I could be wrong.
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.
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.
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!
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.
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
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