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Texas astronomers revive idea for 'Ultimately Large Telescope' on the moon
- csunbird 6y agoForgive me for my ignorance, since my knowledge of advanced physics and orbital mechanics are limited to KSP, can't we build something like this on orbit, thus saving a lot of headache from landing and constructing on the moon? A stable polar orbit is easier to get to and return from the moon.
- deleted 6y ago[deleted]
- Fumtumi 6y agoWe are already doing this with James Webb Space Telescope. That one will be further away from sun than earth and moon.
- NikolaeVarius 6y agoJWST is not being assembled in space
- Fumtumi 6y agoyeah my fault; I interpreted the question as 'hey sounds difficult to do that, can't we make it easier?' in sense of the person asking without knowing the JWST exists.
- rtkwe 6y agoThe core of it is a liquid mirror which is harder to do in space because to shape it into a parabola you need spin and a down which would require constant acceleration since it want's to look at a single point in space. Also long duration attitude holding is harder in space than it is on the ground. If we wanted to build something similar in space it's essentially a 5x larger James Webb Space Telescope which is having some trouble last I heard with it's folding mechanism so building one 5 times larger to fit into a faring is a big task.
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- abecedarius 6y agoOTOH in zero g a mirror needn't support its own weight. A shade would eliminate temperature fluctuation. Naively I'd expect it should be practical for a very large, very lightweight telescope mirror to be built in situ in space instead of trying to launch and unfold one built on Earth. I guess the big problem for that right now is that for humans to do the building, it'd have to be in low orbit, a less-than-ideal environment for a long-lived scientific instrument. (Just kibbitzing, am not a rocket scientist.)
- csunbird 6y agoI mean the construction can be done on low earth orbit, then the satellite telescope can do a transfer to a higher orbit. Again, forgive my ignorance :)
- rtkwe 6y agoWe've only built a tiny number of things in orbit and haven't yet built something that then gets sent off somewhere like a shipyard. It's all been stations that are then left basically where they [0] are so we don't really have the experience of how to do that yet. Also that takes a long time because it's just slow to move around in space. It does need to support it's own mass through during maneuvering and pointing operations as well so it can't be completely flimsy. Also you'd want to get further from the earth to avoid all that drag from a huge mirror in LEO. [0] Beyond periodic small orbit boosting burns
- abecedarius 6y agoPointing needn't be at all quick, as long as you're not trying to catch a gamma-ray burst in the act or the like. Agreed about the badness of LEO. Another problem: a very large mirror is a significant target for micrometeoroids. It'd need to be made able to keep going after losing little patches.
- Rebelgecko 6y agoNormally liquid mirror telescopes depend on having some amount of gravity to work correctly (the liquid needs to pool in a certain way). There's workarounds to do this in space but it gets really complicated. Other issues with space based telescopes: They need fuel + thrusters to go where you want them to be (or just to maintain their orbit!) Heat dissipation is a big problem. Being able to use the whole moon as a thermal flywheel could help out a lot. In space you can use things like cryocoolers to regulate temps, but they cause vibrations which can be problematic if you need your telescope to remain steady. If this requires refrigeration, you can put the vibrating parts far enough away from the telescope that they don't move it. Putting the thing in a crater probably helps regulate temps too (less direct sun) Humanity in general is better at building and maintaining things on solid ground. If you drop a bolt on the moon, you lean over and pick it up. If you drop a bolt in orbit, you have to worry about it damaging your spacecraft at the next conjunction.
- metalliqaz 6y agoIt's hard to imagine how this could be easier or cheaper than just launching another space telescope. I see from the article that it uses a spinning liquid mirror, so yes, that would require gravity to work, but how many extra launches would it take to get the telescope to the moon and also the lander equipment.
- helsinkiandrew 6y agoI assume (its a shame the article didn't go into this) that the telescope would basically be a big fabric structure and it and the liquid mirror can be easily transported and set up without humans. The magnification of the 100M mirror make up for the lack of being able to point it anywhere at a much reduced cost than a 'traditional' space telescope.
- mannykannot 6y agoThe thinking might be that if we are going to return to the moon, then the more we have in the way of useful projects to do there, the better. The JWST is not exactly going smoothly, and telescopes of that size will not be powerful enough to study the era of the first stars.
- mkoubaa 6y agoLaunch a mining and manufacturing unit and built it along with anything else we need on the moon
- metalliqaz 6y agoThat technology doesn't exist...
- m4rtink 6y agoUntil someone starts working on it, no technology usually exists.
- metalliqaz 6y ago
- Jyaif 6y agoHow would they keep the liquid from evaporating? Would they need to enclose it?
- janmo 6y agoIf the liquid is kept in the shadow it will be at a temperature of zero kelvin (-273 °C). I guess that at this temperature mercury won't evaporate.
- henearkr 6y agoThen on the contrary how do they keep it from freezing?
- NikolaeVarius 6y agoBy heating it
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- henearkr 6y agoIf the phase diagram permits it... They need to find a solid that does not just sublimates when heated in the void.
- kingbirdy 6y agoWon't it still boil due to the near-zero pressure?
- jandrese 6y agoDepends how cold you can keep it. Even if it doesn't boil it could sublimate away if not kept extremely cold.
- sp332 6y agoPermanently shaded regions don't get much below 25K, maybe up to 70K. http://lroc.sese.asu.edu/posts/979 http://lroc.sese.asu.edu/posts/979 Still good enough for mercury of course.
- janmo 6y agoThere is also the interesting idea of building a radio telescope on the moon. https://en.wikipedia.org/wiki/Lunar_Crater_Radio_Telescope https://en.wikipedia.org/wiki/Lunar_Crater_Radio_Telescope
- rozab 6y agoI think this might have been posted on HN recently. To me this is a far more appealing project. It could require very little payload weight, and it achieves something that is only really possible on the moon. I would like this to be the project that really drives future human presence on the lunar surface.
- dylan604 6y agoAccording other headlines, they are going to need to create a radio free zone on the moon as they are talking about installing a 4G network.
- NikolaeVarius 6y agoThey build on the far side to address this.
- sandworm101 6y agoBut why put it on the moon? Why not out in space? For the same launch costs we could fly a much larger structure in zero gravity.
- tracerbulletx 6y agoI'm not sure but the moon would probably create a radio shadow shielding it from radio waves originating from earth as well.
- eightails 6y agoCould we? I assumed the whole point was to use a crater as a ready-made, almost-parabolic dish, meaning that only the receiver and suspension wires would have to be sent over -- vastly reducing the required payload vs constructing an entire 1km diameter dish in space.
- _Microft 6y agoArxiv paper linked at the bottom of the article: https://arxiv.org/abs/2007.02946 https://arxiv.org/abs/2007.02946 For the sort of telescope which they propose to use, they reference: https://iopscience.iop.org/article/10.1086/588034 https://iopscience.iop.org/article/10.1086/588034
- mturk 6y agoThe article suggests they will be able to "unambiguously identify" Population III stars, which would be absolutely incredible.
- detritus 6y agoFor anyone else unfamiliar with the term, here's a link to an explanation: https://kipac.stanford.edu/highlights/population-iii-stars-universes-ultimate-reclusive-pop-stars https://kipac.stanford.edu/highlights/population-iii-stars-u... Particularly – "Astronomers grouped stars in the order they were observed, so Pop I stars are present-day stars, with Pop II stars being one generation older. Pop III stars are the hypothesized oldest stars in existence."
- DanielBMarkham 6y agoI have a space commercialization question. SpaceX is purportedly at some point going to be able to put 100 tons in LEO for around 100M. I'll roughly assume with a second launch full of fuel, a purchaser with the right gear could put close to 100 tons on the lunar surface for 200M or so, once they get the kinks out and the price down. So why not just pre-purchase 20 of these for your favorite lunar project, such as the ULT? If they bring prices down you get a cool lunar base. If they don't, you don't pay. That much payload delivered to the moon for $4B would be an incredible bargain, and it also serves to further incentivize SpaceX. I'm sure I have something about the economics wrong, but I don't know what. Seems to me like we should be very close to a lot of back-burner space projects getting off the drawing boards. What don't I understand?
- peterpost2 6y agoThe cost of rocket launches is not the largest part of creating a lunar base, designing and manufactoring all the landers, base, electronics, software etc. is the larger part of it. If I recall correctly, for the apollo program about 30% was for the launch vehicle.
- ethbr0 6y agoIt seems like this would be somewhat of an interrelated valuation. If launch costs decrease by an order of magnitude, reliability of payload can be relaxed, and therefore costs of payload engineering and manufacture decrease.
- m4rtink 6y agoIf mass reduction is no longer super critical, you can use heavier but cheaper materials that provide the needed strength. There could be other knock off effect of cheaper and more frequent space launch - you can send multiple versions and see which works the best, ship prototypes back for extensive evaluation, send robots or people to fix broken things. A lot of things are done differently if you have just a couple super expensive shots per decade & everything needs to work without external help at the first time.
- shireboy 6y agoWhy stop with one? Wouldn't a network of 3-4 spread across the dark side of the moon and networked together be even better?
- dharmab 6y agoYou only need one because the moon moves. You can take multiple measurements at different parts of the earth and moon orbit.
- VMG 6y agothere is no dark side of the moon (except for a pretty cool album)
- Out_of_Characte 6y agoThe moon is tidally locked to earth, that's what's called the 'dark side' of the moon from earth's perspective.
- AnIdiotOnTheNet 6y agoAs a matter of fact, it's all dark. But seriously, the "dark side" of the moon is the side we can never see from earth. It isn't literally dark so much as just unseen. Consider similar usages like "dark energy" or "a shot in the dark".
- pdabbadabba 6y agoIsn't it true that the far side is darker? The near side will be illuminated either by the sun directly or by light bouncing off the earth. The far side is also, of course, intermittently illuminated by the sun. But when it isn't, wouldn't it be much darker?
- inglor_cz 6y agoAlbedo of the rocks matters. Almost all the lunar maria, which are very dark, are on the near side. So, in those places, you get some extra light from the Earth, but less of it is going to be reflected from the ground towards your eyes. The far side is mostly highlands, with albedo twice as high.
- ilaksh 6y agoI think it would be a nice idea to have several more normal telescopes on the moon with an internet site that would allow you to rent time and operate them remotely somehow. And maybe one or two really big visible light ones. This would theoretically provide a superior level of clarity versus ground telescopes. And it would allow for viewing of the earth.
- m4rtink 6y agoThere is already one in place: https://www.newscientist.com/article/dn28323-china-has-had-a-telescope-on-the-moon-for-the-past-two-years/ https://www.newscientist.com/article/dn28323-china-has-had-a... https://en.wikipedia.org/wiki/Chang%27e_3#Lunar-based_ultraviolet_telescope_(LUT) https://en.wikipedia.org/wiki/Chang%27e_3#Lunar-based_ultrav... Quite a small one, but first of its kind. :)
- VMG 6y agoI hoped this would be about converting a meteorite crater into a mirror
- Out_of_Characte 6y agoIt might still be, creating a disk of 100m in diameter on the moon would need all the help you can get. There aren't exactly alot of bulldozers on the moon.
- BlueTemplar 6y agoYou could a bit like in Arecibo, and pick a properly-sized crater ?
- jvanderbot 6y agoOne sign that this is a good idea, is multiple different instantiations and simultaneous teams working on it. 1. NASA STMD study with robotic assembly: https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_I_Phase_II/lunar_crater_radio_telescope/ https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_... 2. Article on the basics + decadal survey paper: https://phys.org/news/2020-10-moon-seti.html https://phys.org/news/2020-10-moon-seti.html 3. Recent lecture on the "FARSIDE" mission concept at Caltech: https://kiss.caltech.edu/lectures/2020_Hallinan.html https://kiss.caltech.edu/lectures/2020_Hallinan.html "There is some urgency in establishing a lunar far-side radio-quiet reserve before we get the burgeoning problem we have in Earth orbit with optical interference from communications satellites. We are already concerned about the Chinese communications satellites—so this needs to be a global consensus now!" -- Dr. Pete Worden, the Chairman Breakthrough Prize Foundation and the former director of NASA's Ames Research Center
- rtkwe 6y agoThis is a different project entirely. All your links are for a radio observatory on the farside and this is a polar light telescope.
- hikerclimb 6y agoHopefully this doesn’t work
- jsnider3 6y agoI look forward to the Supremely Ultimate Large Telescope being built on Ceres.
- m4rtink 6y agoTo The MAX!
- NikolaeVarius 6y agoSolar system sized radio interferometry telescope please
- mnw21cam 6y ago> To study the first stars, it would stare at the same patch of sky continuously, to collect as much light from them as possible I hate to be the one to spoil the party, but the moon rotates. The main problem with a rotating liquid mirror is that you don't get to choose the axis of the parabola, and that axis rotates as the moon orbits the Earth. You may be able to get a decent view of stars drifting through the view, and with enough orbits you could build up a decent picture, but that's different from staring "at the same patch of sky continuously".
- rthomas6 6y agoSurely these career scientists have considered this problem that you came up with seconds after reading a press release about the idea.
- deliveryboyman 6y agoThe paper mentions this limitation. You really think a team of scientists would not recognize this?
- teraflop 6y agoAs others have pointed out, this was considered. Here is the relevant excerpt from the paper: > To avoid an articulating mount, the telescope would be placed at the lunar pole, constantly pointing at the zenith. [...] The limit on exposure time is then given by the precession of the moon, and is of the order of several days. This can only be extended by the addition of some active tracking facility, for example a moving prime focus platform.
- ant6n 6y agoSo is there Anything interesting to look at?
- uCantCauseUCant 6y agoMy biggest problem is with the outdated concept of optics used in telescopes today. There is usually a large mirror and lenses which should be redundant. A NN trained on the physics simulation of a wobbling droplet of e.g. mercury should be able to use this "predictable, deterministic" partial mirror, to glimps everything needed to see. If a ferro-fluid with electromagnetic actuators is used-the shape of the mirror could be even modified by the observer NN in realtime, to sharpen, or block parts of the mirror. If this would be acceptable to the astronomic community - we could mass produce Hubbles.
- moralsupply 6y agoThe major issue with a telescope in the moon would be the very fine sand in moon's surface that would cause mechanical failures
- evan_ 6y agoWould it? With no wind, the sand mostly stays on the ground. When it does get kicked up by something, it goes right back down since there's no atmosphere.
- NikolaeVarius 6y agoWhat. Things come down because of gravity, not because the pretense of an atmosphere. Presumably the stuff required to move stuff to make the scope will disturb at least some sand
- SlipperySlope 6y agoEarly moon mission demonstrated that rock and feather fell at the same speed. Ergo, ultra fine dust will fall to the moon's surface at the same rate as a boulder. Dust will stick with static electricity however much better on the moon - so your point has an even better justification.
- lstodd 6y agoThe point of lacking any atmosphere is that dust is not getting blown around. It just goes down.
- snowwrestler 6y agoUS astronauts found that static charge made the regolith stick to everything that came near it. Basically anything that moved across the surface got quickly coated. And because there is no weathering on the moon, the particles could be extremely small and sharp, which made it difficult to exclude or expel them. Apollo suits at the Smithsonian are still gray with embedded regolith. Conservators try to minimize flexing as the embedded sharp particles chew up the fabric fibers over time.
- api 6y agoI've thought for a long time that this would be a great science mission for a manned lunar landing or a series of them. This is probably something too complex and large to robotically assemble on the Moon, and a human mission could also use in-situ lunar resources (e.g. lunar concrete) to help build such a thing. You could build a massive telescope up there that would be able to outperform anything we currently have by many factors. Even better would be an array of them precisely positioned and bound together. I wonder how big you'd have to go to actually see exoplanets? Wow.
- remote_phone 6y agoThey missed such a good opportunity to call it the “Unearthly Large Telescope”!
- ChuckMcM 6y agoOr simply the BFT, but I expect it will be something "Lunar Telescope" or something "Lunar Observatory" (which implies people present as I recall)
- saucoidev 6y agomandatory xkcd: https://xkcd.com/1294/ https://xkcd.com/1294/
- autocorr 6y agoA common question seems to be: why not put such a telescope in Earth orbit? This is a spinning, liquid mirror telescope that uses centripetal acceleration to turn a pool of liquid mercury into a parabolic mirror. Orbit does not provide the gravity to continuously 'cast' the mirror into a parabola. The parabolic shape is necessary to focus light to a point. A few prototypes have been carried out on Earth, notably one by the University of British Columbia. The main advantage is that a 100m (one hundred meters!) aperture with near optical perfection can be transported in a compact reservoir in liquid form. There are other ideas for large optical telescopes in space like 'painting' part of a balloon with a reflective material. The disadvantages are that these produce spherical rather than parabolic surfaces and would require complex re-imaging optics (like Arecibo). The other is that to observe optical and near-ultraviolet light the surface must be very accurate with deviations less than 15 times the wavelength of the light (so in the 20 nanometer regime). The technology has not been demonstrated for this with a space balloon, but there are plans to use this scheme for far infrared or microwaves where the surface accuracy constraints are less severe.
- valuearb 6y agoThe cost of landing stuff on the moon is roughly 6 times more expensive than low earth orbit, so that has to be balanced out as well.
- 8bitsrule 6y agoNeedless to say, it will discover some details that can only be resolved with a Mega-Ultimately-Large Telescope.
- timka 6y agoI've been told that building such a telescope on Earth orbit is effectively the same but much easier to do.