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Space Science

Putting An Observatory On The Moon's 'Dark' Side 314

Posted by timothy
from the harsh-mistress-good-vantage dept.
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."
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Putting An Observatory On The Moon's 'Dark' Side

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  • Earth? (Score:1, Interesting)

    by Anonymous Coward
    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
    • A good point...

      They might have to put some kind of repeater on the surface of the moon or perhaps in orbit around the moon. This would be a pretty simple procedure, but would likely add significantly to the probably huge cost of any project like this.
  • The name... (Score:4, Funny)

    by vandelais (164490) on Saturday January 05, 2002 @09:37PM (#2792422)
    Instead of say, the Hubble, they should call it "The Floyd"
    • Re:The name... (Score:4, Insightful)

      by kzinti (9651) on Saturday January 05, 2002 @09:58PM (#2792501) Homepage Journal
      ``There is no dark side of the moon really... as a matter of fact, it's all dark.'' - Pink Floyd, Dark Side of the Moon
      • Damnit, you beat me to it. -)
      • Re:The name... (Score:2, Interesting)

        by freaq (466117)
        a more complete snippet:

        "There is no dark side of the moon really...as a matter of fact, it's all dark from time to time."
        --pink floyd, _dark_side_of_the_moon_

        gotta love parametric equalizers - just don't let your kids choke back a marley before playing with them. the results are...irritating, i've been told, enough to put you off your favourite albums.

        calling it floyd station would be hilarious on two counts. recall where the monolith was found in clarke's _2001_, and who got called out to see it...
  • gravity (Score:1, Funny)

    by Anonymous Coward
    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.
  • by brassman (112558) on Saturday January 05, 2002 @09:40PM (#2792431) Homepage
    ... the far side would be the dark side as far as you're concerned. The amount of radio crap we're spewing makes the work those guys are doing even more amazing, and sticking a robot observatory on the far side of a stable platform like Luna could produce some really cool results.

    Remember, the money isn't spent in space -- it's spent right here on earth in order to get into space.

    • by Waffle Iron (339739) on Saturday January 05, 2002 @11:31PM (#2792737)
      I'm not so sure if the moon is the ideal low-noise environment. I seem to recall reading somewhere that just last year they discovered some kind of huge black slab buried on the moon. It was supposedly making very powerful transmissions towards Jupiter or something. That sounds like a big source of potential interference.
    • L4 and L5. Put the communications satellite in the L4 or L5 Earth-moon Lagrange point [nasa.gov]. 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.

    • 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.
  • by CTho9305 (264265) on Saturday January 05, 2002 @09:42PM (#2792436) Homepage
    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.
    • I imagine you'd locate the radio telescope as close to the deliniation between 'blocked radio' and 'not blocked radio' and run a cable/fibre to a remote radio transceiver.

      Another option would be a series of small radio repeaters that get to a high power antennae eventually.

      Another, option is to have a moon orbit satellite system that relays the signals back, yes it negates the point of having a telescope on the moon a little, but in that situation you get to control what areas of the radio spectrum the satellites occupy, and don't have the same problem of interferance from random sources as with earth's orbital junkyard.

      You may think the satellite solution is cheaper, but its probably not - if you're building a telescope complex on the moon anyway, building a second building a few hundred miles away + solar array for the cable repeaters and transceiver. Isn't much more work in relation to the telescope. Plus satellite orbits need replacement satellites every few years or fuel to maintain the orbit, a ground radio link base would be far cheaper to operate in the long term.

    • 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.
    • This is a highly difficult undertaking. Communication is the one and only reason to do such a thing. In effect, it would take at least a base station (as oppossed to a second satellite) on the moon's pole to make this work. This would be enough to filter out the radio transmission and only send/receive those that need to communicate with the bird.

      First of all the bird would have to be placed a considerable distance from the moon to conteract not only its gravity, but also the Earth's. It is, in effect, in geosychronous orbit about the moon AND in orbit about the Earth as well.

      The physics of this might not be as difficult as some think. It may involve something as simple as putting around Earth in the same orbit as the moon, only at a much greater distance to account for the moon's gravitational effects as well.

      With this said, I highly doubt this will happen untill we can figure out a legitimate way of keeping low-maintenance satellites in orbit indefinately. I would much rather see any money going to this project be spent on researching some way to convert electricity (particularly solar energy) into direct thrust so no chemical fuel is needed to adjust satellite positions.
  • 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.
    • Re:Question... (Score:4, Informative)

      by sbeitzel (33479) on Saturday January 05, 2002 @09:52PM (#2792475) Homepage Journal
      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.
    • by aka-ed (459608)

      Dear Jared.Slashdot,
      I was quite interested to read your recent post to the Slashdot Message Board Community, concerning the difficulties of communicating with a radio telescope placed on the far side of the moon. You indicate that we could only communicate with it "half of the time." Which half do you mean? The half of the time when the moon is in between the earth and the radio-telescope? Or do you mean the other half of the time, when the exact same situation exists?

      • Which half do you mean? The half of the time when the moon is in between the earth and the radio-telescope? Or do you mean the other half of the time, when the exact same situation exists?

        Perhaps he means the half of the time when the earth is between the moon and the ground station. Not that this is a problem, just need a few more relay points.
    • Blockquoth the poster:

      it's much more difficult to repair

      Since we don't repair GEO satellites anyway, who cares if the Moon base is hypothetically harder to service?
    • It's better because it puts the mass of the moon in between itself and all the radio noise of earth. Also, the reason it's called the "dark side of the moon" is that it ALWAYS faces away from earth. That's the whole reason for putting it there. That does make communicating with it more dificult though, it would need either relay sattelites orbiting the moon, or a relay station on the side facing us connected by cable.
  • by Yakman (22964) on Saturday January 05, 2002 @09:44PM (#2792444) Homepage Journal
    How would the observatory communicate with the Earth though, since the "dark side" means it never actually faces the earth? They'd have to have a satellite orbiting the moon, recieving data while on the dark side and sending it back while on the "light" side.

    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!

    • It is impossible for it to get less than 0 Kelvin. Even in open space the temperature is around 2 Kelvin. Kelvin is an absolute scale, it starts at zero, there is nothing lower.
    • Rate me redundant as I posted this before...but why is everybody having difficulty with this? How hard can it be to drop a couple of compact relays on the lunar surface?

    • 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.

      ..so one of these dark side sats would be the "master" and one would be the "pupil" then?

      :)
  • 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...
  • by ch-chuck (9622) on Saturday January 05, 2002 @09:52PM (#2792473) Homepage
    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!?!?"
    • (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.
  • "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...
  • New Scientist (Score:5, Informative)

    by DeadBugs (546475) on Saturday January 05, 2002 @09:56PM (#2792485) Homepage
    New Scientist [newscientist.com] has more info including a graphic of how the moon shields raido waves
  • do they need to put a couple sattelites around the moon to bounce the info back to earth?
  • I believe the correct term is "Far Side" ie: the side that'salways turned away from the earth and is therefore (far)thest away.
    • Re:Dark Side? (Score:3, Informative)

      by kimihia (84738)

      "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).

  • Have they agreed to us putting it there? You do know that is where their base are. Hidden from our view.

    ahrm.
  • do real astronomers call it the 'dark side,'...

    Of course they don't. That would be foolish and un-"real astronomer"-like. They call it the 'far side' [gla.ac.uk]. :) Really though, what is it called? I doubt it is called the 'dark side', or the 'far side', although I may be wrong.

    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
    • ...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.
  • by pagercam2 (533686) on Saturday January 05, 2002 @11:29PM (#2792734)
    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.
    • While NASA could go to the moon in 1969, they don't have a single rocket to do the same now

      Oh? Never heard of the Shuttle? Of the Titan III? Of the Atlas-V? (Not to mention that this will likely be an international effort, which brings in Proton, Ariane V, the H series...)

      There are other rockets and other ways than One Big Noisy Booster. (Which had a really lousy payload capacity and was too expensive to use for earth orbital assembly.)
    • While it's true we don't have anything that can lift what the Saturn-V could lift now, that's mainly because there's been no market for such massive launches in the last few decades. This proposal could open that market, but even without such heavy lifters the mission is quite doable. The way you do it is in-orbit assembly of the mission from smaller components - the Shuttle can lift about 1/4 of a Saturn-V, and Boeing's Delta-IV can lift a similar amount; there are several active proposals for a lunar return using a total of 4-5 launches to get the components and crew up there, and involving the construction of re-usable components - a lunar transfer vehicle for example which would act like the Apollo command module in a way, except never actually return to Earth but keep shuttling back and forth. And of course a permanent lunar base that could be developed and built upon heading toward long-term habitation.

      Most of the costs in the Shuttle are sunk costs anyway, so the more missions that can be done with the Shuttle, the marginal costs per mission are actually not that big. That's not the way NASA and government accountants like to allocate costs though, which is part of NASA's problems with ISS... (and the recent directive to cut back even further in annual launches - while still paying the salaries of all those mission and support people...)

      Anyway, before we do anything again with people we'll likely have a number of robotic lunar missions first. In fact a private one is coming up soon, and you can help it out and send along a personal memento (words or image) for just $20-30 or so: TransOrbital's TrailBlazer [transorbital.net] mission.
  • by elrick_the_brave (160509) on Saturday January 05, 2002 @11:43PM (#2792759)
    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!
  • The Idea (Score:3, Insightful)

    by hubble29 (548626) on Sunday January 06, 2002 @12:32AM (#2792842)
    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.
    • Re:The Idea (Score:2, Informative)

      by mghiggins (61851)
      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

      How did this get modded up to 5, Insightful?? This is totally ridiculous. a) the moon has a tiny gravitational field compared to the Earth, b) the area of the moon is tiny compared to that of the Earth - it's not going to stop an appreciable amount of meteors. The reason the Earth isn't cratered is because there aren't that many meteors anymore (compared to 3B years ago), and because water/plant life smoothes out impact craters in a relatively short period of time.

      I think someone's watched Armageddon a few too many times.

      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.

      Kind of like radio telescopes on the Earth, you mean? How could anyone do any radio astronomy on the Earth with that annoying Sun there??

      I suspect we could live with this.
      • The earth is incredibly cratered, its just the the crators are covered with water, and vegatation.
        I watched a show on TLC or DISC, that showed what the earth would look like if you took away the water and vegetation. pretty scary actually.
    • by apsmith (17989) on Sunday January 06, 2002 @09:23AM (#2793649) Homepage
      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...
  • 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.
  • 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.
    • I believe there would be problems maintaining a spacecraft in orbit around the Moon. Lunar orbits are usually unstable. The Moon has a lumpy gravitational field due to the presence of mascons (mass concentrations). This was evident during NASA's Apollo missions when the orbital decays of the LEMs (lunar excursion module) left in orbit around the Moon were observed. See NASA Technical Paper 3394 [nasa.gov] for a study of the problem.
  • 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

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