The case for building a SETI observatory on the moon

https://www.supercluster.com/editorial/the-case-for-building-a-seti-observatory-on-the-moon

by pseudolus • 6 years ago

166 76 6 years ago

hanniabu• 6 years ago

Makes more sense now than ever with the advent of starlink.

DennisP• 6 years ago

Yes, and in a positive way. Starlink plays a big part in funding Starship/Superheavy, and giving it an initial customer to get launch volume up. That's what will allow the much lower space transportation costs, cited by an astronomer in the article as making this observatory feasible.

_Microft2• 6 years ago

I have seen lots of complaints from astronomers about Starlink interfering with optical observations but cannot remember hearing about radioastronomy being affected.

On the other hand - if it is up there, it sure can reflect radiosignals from Earth back again.

Has anyone heard about Starlink and the radioastronomy community?

gammarator• 6 years ago

The impact of these constellations on radio astronomy is arguably worse, not least because it’s harder for the average person to see the impact.

https://www.thespacereview.com/article/3702/1

(They don’t just reflect radio waves, they broadcast them!)

Mr_lavos• 6 years ago

Yes please.

koheripbal3• 6 years ago

Why does it need to be physically ON any planetary body? What are the advantages of having it on the moon rather than free floating in a moon-like orbit? ...or for that matter a more distant eccentric orbit?

koheripbal3• 6 years ago

I should have read the article... the answer is shielding. even in lunar orbit, it's better than orbiting the Earth for brief periods.

pueblito• 6 years ago

One advantage would be a foothold on a strategically valuable location

whimsicalism4• 6 years ago

Democracies are far too short-sighted for this to be an actual reason. Also, this is just a paper published in a journal.

jvanderbot5• 6 years ago

Size also. It's easy to spool dish wires out on the ground on the moon, hard to spool them out and keep them where you want in orbit.

a1369209993• 6 years ago

hard to spool them out and keep them where you want in orbit.

Well, it's easy if you rotate the whole thing and use centrifugal force, but that has other problems.

Rebelgecko2• 6 years ago

Thermal management is easier when you can physically touch other objects, easier to know where you are, easier to maintain pointing accuracy, etc

jcims• 6 years ago

For large aperture radio-telescopes like Arecibo or VLBA one advantage would be that you can use gravity and the structural reinforcement of the surface to maintain precise formation and location of your reflectors.

One of these days we'll perfect fine stationkeeping and be able to fly large clusters of scopes/reflectors/etc and surface-based scopes will likely become less attractive.

tgflynn3• 6 years ago

I'm fed up with titles like this that suggest that an entire scientific community, or at least some body with a legitimate claim to representing the interests of that community, wants something when all that is really happening is that some particular group of scientists has submitted a proposal.

Here's the first line of the article:

On Monday, a group of researchers sponsored by Breakthrough Listen, the world’s largest program, submitted a paper to National Academy of Sciences’ Planetary Science and Astrobiology Decadal Survey that makes the case for establishing a SETI radio observatory on the farside of the moon.

Note that this line is also incorrect due to a missing word. Breakthrough Listen may be the world's largest SETI program, but it is certainly not the world's largest program, whatever that would even mean.

So this is some particular group of SETI specialists, which I highly doubt represents the interests of the astronomical community at large (I would guess that only a small fraction of astronomers even work on SETI).

Don't get me wrong, I'm not criticizing the project itself, just the misleading title of the article and the general decline in journalistic standards.

arbuge• 6 years ago

I think these concerns would be addressed by adding a single word to the title. "Some", at the beginning.

tgflynn3• 6 years ago

I think a more accurate title would be something like:

SETI Project Proposes Building an Observatory on the Moon

JoeAltmaier• 6 years ago

Not worth the emotional investment. Of course "some" is assumed. And isn't it more correct to talk about who wrote the paper, than which organization published it?

tgflynn3• 6 years ago

Of course "some" is assumed.

That's not how it initially parses for me, and I think for most people.

As for the emotional investment, for this one case certainly not, but this same pattern keeps coming up time and time again, not to mention the constant barrage of other nonsensical statements the media constantly exposes us to. I think this incessant stream of micro-aggressions against logic and common sense ends up having a significant impact on our well-being and at a larger scale may even be contributing to extremism, conspiracy theories and the growing absence of any semblance of truth from the ambient political discourse.

And isn't it more correct to talk about who wrote the paper, than which organization published it?

I'm not sure what you mean by that.

dmos62• 6 years ago

Hacker News readers are fed up with inaccurate generalizations.

dredmorbius4• 6 years ago

Fair point. It's a bait-and-switch, motte-and-bailey equivocation tactic: on casual reading, the bailey is that "all astronomers‘, or a majority, or some authoritative generally representational body speaking authoritatively, is making a claim. The motte is that those making the claim are astronomers.

https://rationalwiki.org/wiki/Motte_and_bailey

The harm is greater in that we're used to headlines referencing, say, public opinion (majority or at least plurality of a population), organisations (official spokesperson as opposed to some arbitrary worker or whistleblower), etc.

It's a cheap shot. All the more so because it seeks to borrow from the greater reputation and fame of the larger group, admitting by deed the obscurity of the actual group in question.

"SETI Group Wants to Build Radio Observatory on Moon" avoids all these problems here.

Addendum:

The article originally appeared with the title "The Case for Building a Seti Observatory on the Moon" here:

https://www.supercluster.com/editorial/the-case-for-building...

dredmorbius4• 6 years ago

Link and title have just been changed from https://www.smithsonianmag.com/science-nature/why-astronomer...

dang2• 6 years ago

The submitted title was "Astronomers Want to Build a SETI Observatory on the Moon" which came from the submitted URL (https://www.smithsonianmag.com/science-nature/why-astronomer...). I think you're reading it with the wrong quantifier: to me the claim is not "[all] astronomers want [etc.]" but "[some] astronomers want [etc.]", which is perfectly reasonable.

But it's fine to change a title when it's landing the wrong way with some readers, and it seemed like there was a better link in this case, so a mod changed both the URL and title.

jessriedel5• 6 years ago

This is the millionth article on lunar far-side telescopes I've seen that conveniently fails to explain why you'd want to place a radio telescope on the surface rather than just at the Earth-Moon L2 Lagrange point (i.e., the point on the far side of the Moon that orbits with the Moon around the Earth and keeps the Moon between itself and the Earth). I'm sick of not having this obvious question answered, so I dug into it.

Like the lunar surface, a telescope at L2 keeps the Moon permanently between itself and the Earth to block incoming radio waves. For a fixed telescope size, going down into the Moon's gravity well increases costs tremendously. And, although doing construction in a vacuum is never easy, it's a lot easier when you're in zero-g and you don't need a crane! Unlike the far-side surface, L2 has exposure to sunlight for power for ~90% of the time. (You would still need a relay satellite in a different lunar orbit for communications, of course, just like the far-side surface.)

As far as I can tell from browsing the article

https://arxiv.org/abs/2009.12689

and the much more helpful analysis of the lunar radio environment that they cite

https://sci-hub.st/https://arc.aiaa.org/doi/pdf/10.2514/6.IA...

the only benefits to going to to the surface is (1) you get better shielding of the extremely low frequencies (≲ 1 kHz) which are long enough wavelength to diffract around the Earth, but don't think those are detectable unless you have a telescope that's many kilometers in size. (2) you avoid radio signals from satellites in geostationary orbits, but these should be very small since the transmitters are pointing toward the Earth.

Indeed, the faculty member who is advising the undergraduate intern lead author says

“The first SETI observations that are done from the lunar farside will be done from orbit, there’s no question about that,” says Andrew Siemion, the director of the Berkeley SETI Research Center and the second author on the paper. “I think eventually we absolutely want to do something on the surface because we want to build a very large aperture telescope, but even when we’re at that point I don’t think that would negate the utility of doing things from orbit as well.”

and I think he's downplaying how tremendously costly going to the surface would be for very little benefit.

EDIT: Note that the FARSIDE array on the surface they mention is much better justified, but it's not SETI, it's an array, the surface benefits from solar storm shielding, and it probably only makes sense because it piggybacks on high bandwidth connection for the NASA Lunar Gateway. More details here:

https://www.lpi.usra.edu/leag/white-papers-astronomy/FARSIDE...

https://twitter.com/di_goldene_pave/status/13123915724079554...

koheripbal3• 6 years ago

The article literally says that a satellite in orbit is likely the first step.

Also, the further you are from the moon - the worse the shielding.

jessriedel5• 6 years ago

First, the orbital option described in the article is not L2 but rather a low lunar orbit which spends only a small fraction of it's time in the lunar shadow.

Second, in my comment I literally quote the "first step" claim and explain why it's an extreme understatement, in particular because the shielding is not worse except for undetectable wavelengths and sources not actually pointed at the telescope. It's like saying we should we should build transparent houses so we get more vitamin D but of course as a first step we should go outside or take a multivitamin.

jvanderbot5• 6 years ago

From this study: https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

The sun is cited as a significant source of noise that can be shielded by the lunar body.

jessriedel5• 6 years ago

Yes, thanks! That's mentioned in my edit (although it should just be "solar wind" rather than "solar storm") and the twitter thread I link. Note that that's only a particular (though valuable) frequency range, and that it's still unclear to me whether it's cheaper to go down to the lunar surface rather than just build a 10 times larger telescope at L2.

TeMPOraL3• 6 years ago

And, although doing construction in a vacuum is never easy, it's a lot easier when you're in zero-g and you don't need a crane!

That's not exactly true just yet!

All our construction knowhow is based on thousands of years of building things on Earth's surface, under a constant 1G force pulling everything in a single direction, as well as a landmass to brace against. Every technique we have has these conditions baked in as assumptions; we exploit them all the time, without even thinking about it. Like, e.g. if you put some mortar on a brick, and then a brick on top of that, you're relying on gravity to supply the pressure that makes the two bricks strongly bound.

Meanwhile - AFAIK - we have zero experience in constructing anything in 0G, beyond assembling some large prefabs. The closest we come to microgravity construction is whatever it is that underwater welders do, but that's still not the same.

With this in mind, it may be that for now, building installations on Moon's surface will be easier than constructing them in space.

jessriedel5• 6 years ago

I think your overall point is wrong, but it would be a large discusssion. So I'll just concentrate on this: a telescope on the moon or at L2 will, in fact, be large pre-fab. Indeed, we have zero experience building anything in a vacuum in gravity, but we have decades of experience assembling pre-fab structures in zero gravity vacuum. That's what will be easiest.

manfredo2• 6 years ago

Meanwhile - AFAIK - we have zero experience in constructing anything in 0G, beyond assembling some large prefabs.

Weren't the ISS and Mir constructed in zero G? Well, in free fall but that's still zero gravity in effect.

ArtWomb• 6 years ago

There's a NASA funded lunar colony simulation game for MS-DOS circa 1991. You begin with $10K ;)

Playable on archive via DOSBox:

https://archive.org/details/msdos_Moonbase_1990

thepete2• 6 years ago

It runs in the browser? Archive.org is awesome :)

sp332• 6 years ago

Yes, and they not only take the time to tweak each game's emulation settings to make sure it works, but they have the attention of the emulator devs too. IA just rolled out an update today! https://mobile.twitter.com/textfiles/status/1312464355812753...

Rebelgecko2• 6 years ago

There's also 2010's Moonbase: Alpha[1], which became notorious due to how it applied text-to-speech on in-game chat messages [2][3]

1: https://store.steampowered.com/app/39000/Moonbase_Alpha/

2: https://youtu.be/Hv6RbEOlqRo

3: https://youtu.be/CNPKXfb3rws

tdeck• 6 years ago

I tried for about 45 minutes to play this game (and lunar command) and couldn't figure it out. Is there any guide somewhere online? Specifically my habitat capacity never seemed to increase despite building and wiring/connecting/piping up habitats.

cure• 6 years ago

A manual would be handy, I agree...

For the habitats, you need to hook up power and thermal pipes. As long as you connect the habitats together through the white tubes, they only need one hookup with electric/thermal for the entire site.

It seems to take ~ a month in game time for the increased habitat capacity to show up in the 'Population...' menu.

raverbashing• 6 years ago

I think we need at least some 50yrs of physics to understand how to even begin tapping into the cosmic internet

As with fusion and processing power, some things are faster if you wait for the advancements instead of building it with today's technology.

poma88• 6 years ago

I will change fields to use tha data and find life out there!! :-)

feralimal• 6 years ago

Good idea! 1972 was so long ago...

jvanderbot5• 6 years ago

Y'all might be interested in a robotically assembled km-scale antenna on the farside.

https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

sneak• 6 years ago

That's super cool, and I hope that they do this.

It's also astounding that it's legal for NASA to embed that much crazy 3p tracker javascript into that webpage, considering that they're publicly funded.

ieatmyownpoop• 6 years ago

Ah yes. The death star.

jagged-chisel• 6 years ago

But it’s a moon, not a space station.

skadamou• 6 years ago

That's no moon

dang2• 6 years ago

Trollish usernames aren't allowed on HN because they effectively troll every thread they post to. I've banned the account, and would be happy to rename and unban it if you want to pick a more neutral username. Best to email hn@ycombinator.com if that's the case.

https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme...

wazoox• 6 years ago

It should be made in the form of a black monolith, I guess. Just for the kick.

aurizon• 6 years ago

A number of smaller dishes can be made that will robotically unfurl. With the ability to drop a number of them on a flat maria. They will be made with as large as possible self levelling/rotating ability. They can be each driven with their own solar array and will have optical data links so they can work as a large array. They will need an optically linked set of orbiters - which is doable, that can report sequentially. This is a fairly complex task, but once the design is settled and works well, it can be tested and then it can be replicated and an array gradually built with successor dishes. The dishes can be improved as flaws emerge. Being mainly made of aluminum, with vaccuum/dust proof bearings with solar shades it will need to tolerate the temperature range. I think this is a good idea as the other side of the moon is indeed a quiet zone. The lunar lagrange point is also a good place, however the lagrange point will be a hard place for a number of dishes to be sited apart while maintaining precision array positioning.

7373737373• 6 years ago

A while ago I read an article about which properties signals might have that could indicate that they originated from intelligent life, something about having "acceleration", higher order derivatives, that are usually not generated by natural events. Does anyone know how this is called?

screye• 6 years ago

Space brothers did it first

tambourine_man2• 6 years ago

Any observatory for that matter. I keep dreaming of humongous mirrors, easily accessible, with no clouds or atmosphere to get in the way. Or, you know, moon. Imagine what we would discover.

I fell like we neglect the moon to a embarrassing degree. It’s right there (cosmologically speaking), it’s got water, plenty of sun light (24/7 even, on the pole), building materials… what are we waiting for?

Already__Taken• 6 years ago

it builds up static change and rains hyper abrasive Lunar dust into things I think I've read for one.

jvanderbot5• 6 years ago

A ~100m telescope could be assembled in orbit from segmented mirrors and a few falcon heavy lifts. It could image exo continents.

https://science.nasa.gov/technology/technology-highlights/in...

Bias alert: I briefly worked on in space assembly and firmly believe it is the future of space travel, exploration, and exploitation.

tambourine_man2• 6 years ago

I imagine it would be a lot easier to assemble on something you can stand on and mine from, right?

Only an amateur here, but I see James Webb many years and billions overdue and wonder if it wouldn’t be easier, cheaper, faster on ground.

credit_guy• 6 years ago

SETI is complete and utter non-sense.

If you don't know why, here's a riddle for you: you are the first space colonist who reaches our closest star, Proxima Centauri. How do you send a message back, such as "We arrived" , plus maybe a photo of a planet you intend to colonize? Piece of cake, you say. Point your parabolic antenna back towards Earth and beam the message. Voyager is doing just that, but from closer to home. Only 20 light-hours away from Earth. Voyager is using a transmitter of about 20 W and an antenna of about 2 meters in diameter. You are about 2000 times farther away. Since radio waves lose power with the square of the distance, you have a problem 4 million times harder to solve than Voyager. Actually, your problem is much, much harder than this: your friends on Earth pointing their antennas towards you are blinded by the star that practically touches your spaceship. You are separated from that star by an angle measured in seconds of arc. You need to shout very loud to be heard over the tremendous noise made by your fiery neighbor. But you can do that, you presumably have a portable nuclear reactor with you and can use gigawatts to solve this essential problem.

But now, imagine you are an alien chatting merrily over radio waves with a friend in the same planetary system around Proxima Centauri. If you don't take a humongous antenna, point it in the absolute exact direction of Earth, and use a few Gigawatts of power to beam a message, how are we, Terrans, supposed to hear you? How is SETI supposed to discover aliens who are not purposely beaming waves straight at us?

nine_k• 6 years ago

I bet you can build an antenna on / near Earth large enough to pick up the Voyager's signal at 4 light years. I don't think that a star emits much radio waves at the same frequently range you choose for your radio transmission, and especially has the same modulation side bands.

That said, MW-class radio transmittets are not heavy, their cooling systems are. You also don't need to transmit continuously, you can send bursts as long as your thermal budget allows. For energy, you have unlimited sunlight.

centimeter• 6 years ago

4 million times harder

I don't think you really understand the problem domain. There are 3 main independent parameters you can tweak to improve maximum transmission range: transmit power (100,000x more power has been done commercially), antenna size (we now have a dish antenna over 250x larger), and you can increase the transmission frequency to substantially improve collimation by many orders of magnitude (e.g. use a laser instead of sub-GHz).

your friends on Earth pointing their antennas towards you are blinded by the star that practically touches your spaceship

A star puts out a lot of power, but it's spread pretty evenly across a blackbody spectrum. You can certainly overpower it within a very narrow frequency range. Your bandwidth/power ratio might be quite abysmal compared to wifi, but it's workable.

How is SETI supposed to discover aliens who are not purposely beaming waves straight at us

I think the idea is that perhaps they would be beaming waves straight at various stars. This is something I can easily imagine humans doing in the near future.

dehrmann• 6 years ago

Could the sun be used as a gravity lens for radio waves? I know people are thinking about doing it for building a telescope, so I assume longer wavelengths work, too.

speakeron• 6 years ago

The assumption of SETI has been that an advanced civilization is broadcasting a narrow-band (in the 'water hole' and possibly modulated) omni-directional signal using a large amount of energy. We can see stars across the galaxy (and, indeed, in other galaxies), so by using some large fraction of a star's energy this should be possible.

We're not far from having the telescope technology that enables us to spectrally sample the atmospheres of extrasolar planets to detect gases that are associated with life (as we know it) and even of technological civilizations (e.g. chlorofluorocarbons). This is a form of SETI too. Using such technology, an alien civilization could beam signals to selected planets that show such signs and save the energy of broadcasting omnidirectionally.

The purpose of SETI is not necessarily to confirm such possibilities (my opinion is that civilizations like us are really rare at this stage of the Universe's evolution - maybe less than one per galaxy). But at least to rule them out.

daniel-cussen• 6 years ago

Easy, just communicate in basically Morse code, but with nuclear detonations.

There's probably a better way, but that sets a lower bound.

sytelus• 6 years ago

One of the problems that no one talks about: how do you protect against meteor strikes on moon? On Earth mountains form slowly over thousands of years but on moon they appear instantly when something strikes the surface. It’s like waiting for bullet coming from sky all the time.

The case for building a SETI observatory on the moon

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