# Why no telescopes on the moon?

• Stargazing
Gerinski
We are placing everyday more telescopes in satellites in orbit. Would't it be convenient to have some permanent telescopes placed on the moon's surface? I guess if we don't do that it's because that would be much more expensive than launching satellites? Are there no plans to place telescopes on the moon and why?

Staff Emeritus
2022 Award
I guess if we don't do that it's because that would be much more expensive than launching satellites?

Partly, yes. Satellites in orbit don't require heavy and expensive hardware that's required to land it on the Moon's surface. In addition, a telescope in orbit can be turned to point in nearly any direction at any time, whereas a telescope on the Moon is limited to whatever area of the sky is currently in view.

james gander, harshith_cs, Ryan_m_b and 1 other person
Staff Emeritus
If you Google this, you will find many objections. There are two immediate questions, though - 1) what question can be answered better by a lunar telescope than the alternatives, and 2) how will you get the images back to earth, given that the moon is between the telescope and the planet,

james gander
ViperSRT3g
Now this has raised the question of why such a telescope couldn't be positioned on the lunar poles to allow for observations, communications, and power? It wouldn't be ideal, but it would allow for a very large telescope.

Homework Helper
Gold Member
how will you get the images back to earth, given that the moon is between the telescope and the planet,

Er, no it doesn't have to be. And we could take astronomical selfies with it.

Staff Emeritus
You want to put it on the near side?

Homework Helper
Gold Member

newjerseyrunner
The moon isn't ideal either, it has a very thin "atmosphere" of dust. The Apollo astronauts noticed a haze on the moon which turned out to be dust help in position by electro-static forces.

Gerinski
But indeed a moon telescope could be much larger than one in orbit. Having rotation so it can be pointed to any direction (except the sky area blocked by the moon itself of course) doesn't seem a big problem either, and the moon / Earth rotation would allow for observing (I guess) any point in space. I don't know how much the dust could be a problem though.

newjerseyrunner
A single telescope you may be right, but not for a telescope array. An array of small telescopes is much more powerful than one large one, and the further you put them away from each other they better.

rootone
What could we observe from the surface of the Moon that we could not observe from other Earth orbiting scopes?

Staff Emeritus
2022 Award
But indeed a moon telescope could be much larger than one in orbit.

How so?

ulianjay
Gold Member
What could we observe from the surface of the Moon that we could not observe from other Earth orbiting scopes?

Exactly, nothing, and having scopes based on the moon adds an even bigger headache for maintenance issues
I can't see any point in moon based observatories unless there is already established significant manned moonbase

Dave

Gold Member
A moon teledcope would be fabulous if we had a moon base, that is the bigger question in my mind - why do we not have a moon base on the drawing board? That is the logical first step for space exploration.

Gerinski
How so?
I have read that a moon telescope's mirror could be largely made out from lunar dust, so the payload to take from Earth would be rather limited. This article says that with this method a 50 meter telescope could be built on the moon, far larger than anything in orbit.

http://www.technologyreview.com/news/410253/a-moon-based-telescope/

Mentor
I have read that a moon telescope's mirror could be largely made out from lunar dust, so the payload to take from Earth would be rather limited. This article says that with this method a 50 meter telescope could be built on the moon, far larger than anything in orbit.

http://www.technologyreview.com/news/410253/a-moon-based-telescope/
That doesn't make any sense: You wouldn't have to carry the mirror to the moon...just an entire manufacturing plant for making mirrors, which, necessarily, would be larger than the mirrors it is making.

Staff Emeritus
Gold Member
I can think of one type of telescope that could benefit by being placed on the far side of the Moon, a radio telescope. The distance and intervening bulk of the Moon would shield it from Earth based electromagnetic interference. Whether or not this benefit would be worth it is another question.

Mentor
That doesn't make any sense: You wouldn't have to carry the mirror to the moon...just an entire manufacturing plant for making mirrors, which, necessarily, would be larger than the mirrors it is making.
You would make the primary mirror segmented. A small plant that makes many mirrors. I think it would still need more material than the primary mirror, but the comparison is not as obvious as it might look like.

newjerseyrunner
I have read that a moon telescope's mirror could be largely made out from lunar dust, so the payload to take from Earth would be rather limited. This article says that with this method a 50 meter telescope could be built on the moon, far larger than anything in orbit.

http://www.technologyreview.com/news/410253/a-moon-based-telescope/
50m is nice, but an array of smaller telescopes put far apart in orbit can have an effective apature way beyond 50m.

What could we observe from the surface of the Moon that we could not observe from other Earth orbiting scopes?
Not all telescopes orbit earth, we have several at the L points and several orbiting the sun.

A moon teledcope would be fabulous if we had a moon base, that is the bigger question in my mind - why do we not have a moon base on the drawing board? That is the logical first step for space exploration.
Money. Both Russian and China have plans for a base in the later part of the 2020s, but they're still way too expensive.

Dr_Zinj
My apologies for the brevity of my post. This is off the cuff without all the links to references that a more scholarly reply would have.

Drakkith is correct. And there are a couple of other factors as well.

Space telescopes in orbit around the Earth are closer than the Moon, so control signals don't take as long to get there. Remember the delays between asking a question of the astronauts on the Moon and receiving their reply?

It costs somewhat less to put a satellite telescope in orbit than it does to take it to the moon; much less land it as Drakkith mentions.

If you intend to perform periodic maintenance and upgrades on your telescope, it's much cheaper and faster to get to it in Earth orbit than on the Moon.
The Moon has a limited amount of surface area which limits the practical size of of a telescope, even if you build an array. You can theoretically build a much larger free floating array in orbit than you can on the surface of the Earth or the Moon.

In orbit, there's no gravity to distort the shape of your lens. While the Moon has only about 1/6th the gravity of the Earth, that would still limit the size of the reflective lens you can use; although that might be surmountable by placing actuators behind the lens to bend it into whatever curvature you needed. A lens 6 times larger than the Mount Palomar one would definitely flex, even if the backing was a glass honeycomb; although I don't know how brittle it would be in those temperatures (probably very.)

All of this applies to optical telescopes. Now there might be a good reason to place a radio telescope on the far side of the Moon as the bulk of the Moon should shield the telescope from most Earth radio transmissions.

Mentor
You would make the primary mirror segmented.
The article is poorly written, but I'm pretty sure the intent was for a single-piece mirror.

rootone
We would have to establish a permanent base on the Moon first.
That is huge and expensive challenge and there would need to be a big economic reason for doing it.
Telescopes might get on the 'things-to-do ' list eventually.

Jon Richfield
The idea of putting a telescope of any sort whatever on the moon strikes me as nutty, for reasons largely already discussed in this conversation. As for building a large, high-quality telescope of moon dust on the moon... least said soonest mended. Let me know when we have achieved such a feat on Earth, never mind the moon. And let me know when we have achieved even a shaving mirror on the moon, let alone the equipment to direct it for astronomic purposes...! And if it is NOT high quality, it would be even nuttier, given what such a project would cost.
IMO if we had more scientists and fewer politicians in charge, we would decades ago have had many observatories in Earth orbit and many more around various other bodies in the solar system all the way out to Eris at least, but one of the first would have been a number of types in the lunar L2 point shielded from Earth noise, and a few in the L2 points of planets such as Venus and Mercury to shield them from solar noise.
Getting data back to Earth? Nothing special; where the orbit is small, park relay comms satellites at the L4 & L5 points. They always would have at least some channel open to Earth or to other relay satellites at various strategic locations in the solar system. Being largely specialised for comms, those satellites could do a good job of it, though they also could have secondary observation functions.
In special cases one could orbit three to six orbiting comms satellites around the bodies whose Lagrange points harboured observatories. There always would be at least one or more in view of the observatories and each would regularly be out of sight of the observatories and accordingly be able to signal Earth with minimal noise for the observatories.

sk1105
Gold Member
I fail to see any great dfifficulty in placing a large telescope on a moon base. It need not be monolithic so manageable sized modules could be manufactured on Earth and shipped to a moon base without inordinate difficulty or expense. A moon base would require supplies from Earth indefinately before it could hope to become self sufficient, so, transport of telescope modules to the moon would not pose undue logistical complexity. A moon base would offer inumerable other advantages so it would make perfect sense to add an observatory to the host of other facilities required for a permanent moon base.

Jon Richfield
I fail to see any great dfifficulty in placing a large telescope on a moon base. It need not be monolithic so manageable sized modules could be manufactured on Earth and shipped to a moon base without inordinate difficulty or expense. A moon base would require supplies from Earth indefinately before it could hope to become self sufficient, so, transport of telescope modules to the moon would not pose undue logistical complexity. A moon base would offer inumerable other advantages so it would make perfect sense to add an observatory to the host of other facilities required for a permanent moon base.

Nice to find you so positive. Now all we need to know in the light of the current progress and cost in building the space station, when you think it would be realistic for us to expect a viable moon base (by which I mean something slightly more usable than our moon landers' exuvia.)
I'll refrain from asking what scale you might envisage for "inordinate difficulty or expense" or why a permanent moon base might be dependent on a competitive astronomic observatory, in particular one to rival far cheaper and less demanding units in lunar L2 orbit, let alone dirt cheap eyes in Earth orbit. We could manage such space units, even including comms relays for the L2 project, at a tiny fraction of the price and hazard, a century before we could get a single moon base off the ground, if you would excuse the expression. And that is without waiting till the moon base project even got round thinking of scientific instruments.
Nor does it take into account the superior quality and versatility of space-based observatories, whether manned or not. For the foreseeable future moon bases are for flag planting, not function.

15characters
Gold Member
A permanent moon base would offer ready access to Helium 3 - a fusion fuel candidate. This is sufficiently attractive to draw interest from several countries, notably China and India, to develop their own plans for a moon base. Even NASA has below the radar plans with this end in mind. While H3 fusion remains an unproven technology, a ready supply of H3 could rapidly alter that situation. Access to an unlimited energy supply would shift the economic balance in favor of a moon base. Once the economic justification for a moon base exists, all the other pieces will fall into place. Even space based astronomical platforms would become far more attractive to launch from the moon.

tom aaron
A permanent moon base would offer ready access to Helium 3 - a fusion fuel candidate. This is sufficiently attractive to draw interest from several countries, notably China and India, to develop their own plans for a moon base. Even NASA has below the radar plans with this end in mind. While H3 fusion remains an unproven technology, a ready supply of H3 could rapidly alter that situation. Access to an unlimited energy supply would shift the economic balance in favor of a moon base. Once the economic justification for a moon base exists, all the other pieces will fall into place. Even space based astronomical platforms would become far more attractive to launch from the moon.

The Space Shuttle averaged 1.6 billion dollars a mission. Energy was less than a thousandth of the cost of each flight. Energy is the least of issues. The ISS has topped a hundred billion. The Spacecraft for a Moon mission was scrapped once development costs hit 'x ' billion with more 'x billion over budget needed. The insane James Webb Telescope cost...no need to say anything!..it isn't even a proven project.

A permanent Moon base just isn't going to happen for decades...perhaps much longer. Let alone the tens of billions needed to build a telescope for the moon, get it there and then the bezillions in infrastructure to keep it functional.

And all this money to accomplish what exactly? Earth based and space based telescopes is 'all there is going to be' this century.

Jon Richfield
Jon Richfield
A permanent moon base would offer ready access to Helium 3 - a fusion fuel candidate. This is sufficiently attractive to draw interest from several countries, notably China and India, to develop their own plans for a moon base. Even NASA has below the radar plans with this end in mind. While H3 fusion remains an unproven technology, a ready supply of H3 could rapidly alter that situation. Access to an unlimited energy supply would shift the economic balance in favor of a moon base. Once the economic justification for a moon base exists, all the other pieces will fall into place. Even space based astronomical platforms would become far more attractive to launch from the moon.
The He3 proposal is such a ridiculous idea that I suspect it to be satirically intended. It is unrealistic and vandalistic. It is about as sensible as scavenging cellulose from abraded wallpaper in public buildings instead of growing it by the ton. I have no problem with the value of He3 whether its fusion would prove to be practical or not, but to mine the moon for it on any more than a trivial scale would be insane.
Asiatic plans for moon bases are of no interest till they make moves to annex it and tow it home. If they are publicising any such plans it is to distract the US or each other into wasting resources on keeping up with the Joneses (or Changs, Patels, or Ivanovs or whichever it might be). Either that or some idiot left the door open and politicians or similar simple minded black-noise sources blew in. Heaven help anyone who listens. If NASA has any sense (JUST conceivably) they will concentrate on practical objectives and leave Mars and Lunar colonies for the suckers.
We have huge scope for space projects for goodness sake, why waste our substance on kids' cock-measuring contests? And what do you mean by "ready access"; grubbing and toasting the surface of the moon for material that we could far better, faster, more cheaply and on a larger scale get elsewhere?
If you are sufficiently interested in the topic of He-3 collection, I have dealt with it on line, but PF is apparently too retentive for me to give you an URL. Maybe however I am permitted to suggest that if you paste 'Full Duplex "Jon Richfield" Collection Helium-3' into a suitable online search engine it will point out a site where I explain where to get more of the stuff than the moon offers whether we establish a base there first or not. If not, then can you suggest how I am to inform you where to look?
As for launching space based astronomical platforms from the moon, don't you think you are overlooking something?

15characters
Staff Emeritus
Heloum-3 costs about $1M per kilo. Moon rocks, in 2010 dollars, cost$300M per kilo. So even if Helium-3 did not need to be mined and extracted, the economics are such that it would have to be 300x cheaper. Furthermore, there have been ~20 fatalities in ~300 manned spaceflights. I am not sure the public will be willing to tolerate that level of loss of life.

Getting back to the telescope, the idea that you want a moonbase to run a telescope and if you're going to have a moonbase, might as well put a telescope on it, seems circular to me. The first question that NASA will ask is "We have a list of science drivers from the last decadal survey. Which ones can be answered by a lunar telescope? Which ones can be answered better by a lunar telescope? Including cost." People have mentioned the JWST. I might point out that this is the most anti-science device ever created by mankind. It has killed dozens of other missions because of cost overruns, and it's still sitting on the ground. A moonbase will be at least two orders of magnitude more expensive.

Jon Richfield
Mentor
Moon rocks, in 2010 dollars, cost $300M per kilo. Based on 0 missions that were optimized for payload per dollar. The Apollo missions sent 50 tons to moon, the ascent stage of Apollo 17 had a dry mass of 2400 kg. You would not send humans for every transfer vehicle, so most of this mass could be replaced by He-3. The ascent stage was jettisoned in the actual Apollo missions, but we don't need the much heavier command module here. This is a very conservative estimate, as you save (literally) tons of other payload in an unmanned mission. Let's scale all those numbers down by a factor of 2. That would allow a total mission cost of about 1.2 billion for 1200 kg, if the He-3 market is large enough. The Falcon Heavy rocket is planned to deliver 50 tons to a low Earth orbit with ~$2000/kg, or 100 millions per launch. With ion drives and sufficient time, about half that mass should be able to reach the moon (the Apollo missions had 40% with conventional rockets), which matches the previous Apollo-like mission. For every mission that returns He-3, we can launch about 10 additional missions for helium collection infrastructure.
I have no idea how much infrastructure He-3 collection on the moon needs, but all other parts are well within reach of current technology and costs.

Staff Emeritus
Based on 0 missions that were optimized for payload per dollar.

True, and if the costs mismatched by a factor of 2, I'd be much more positive. But these are the only numbers we have now based on experience, and we need to improve by many orders of magnitude. It may yet come to pass, but it is hardly present technology.

Mentor
True, and if the costs mismatched by a factor of 2, I'd be much more positive. But these are the only numbers we have now based on experience, and we need to improve by many orders of magnitude. It may yet come to pass, but it is hardly present technology.
This is like calling Chris Hadfields music video "the most expensive music video ever made" by assigning the full ISS costs to it. The resulting cost estimate is not helpful in any way for estimating costs of a commercial mission.

Staff Emeritus
. The resulting cost estimate is not helpful in any way for estimating costs of a commercial mission.

I keep hearing the line from The Big Bang Theory. "For what it cost them to make that movie, they could have made an actual Hulk."

Let's take the price of Constellation - even though it doesn't exist. Let's assume that instead of the 3 lunar missions, you get 10 (maybe by dropping some ISS missions). Let's assume you can bring back, I dunno, 3x what Apollo did per mission. (Already suspect because 3He takes up more space per kilo than rocks, especially with cryogenics) You still miss breakeven by a factor of 75. You want to argue that maybe SpaceX will do better someday, fine. But we're still talking about the future.

The other issue is that the industrial use today of Helium-3 is tens of millions of dollars - call it a round \$100M. I think we can all agree that you can't do a moonshot for that. You can barely get to LEO for that. So any mission is going to bring back years or decades worth of 3He. One might argue, yes, but when we use the stuff for fusion, we'll need more, but I would counter that we don't have a fusion reactor yet. Again, we're talking about future technologies that don't exist.

mheslep
Staff Emeritus