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Astrokiwi t1_jb995xe wrote

Maybe just barely!

The maximum possible resolution you can physically get depends on the size of the telescope. The next generation of ground-based optical telescopes will have mirrors around 30m in size. At the distance of the Moon, these could have a resolution of about 5 or 10 metres, if they have perfect optics. So you might be able to make out the lander as a fuzzy blob at the limit of resolution, but won't be able to see any astronauts, and definitely not any footprints. You'd really want something like a 200m telescope if you wanted down to 1 metre resolution.

Interferometry isn't the best thing to help here. While you can combine light from multiple telescopes separated by some distance to increase their resolution, this is really tricky to do with visible wavelengths, and you're limited to a small number of telescopes on the same site. What you end up with isn't quite an image as you don't have enough combinations of baselines between telescopes to get the full visual information. At lower wavelengths (e.g. radio) it becomes easier to do interferometry affordably with a large number of telescopes (possibly even spread over the world!), but longer wavelengths also inherently have a lower resolution, and you're often dealing with a much dimmer image - the Sun emits a lot of visible light, so most things in the solar system are brightest in the visible ranges.

Overall, to photograph the Moon (and many other solar system objects) you get much better resolution by sending a small telescope to orbit the Moon than building a big one on Earth.


mdw t1_jb9p080 wrote

You don't mention that there will be issues with atmospheric seeing. To realize the potential of the telescope you'll need adaptive optics and I am not sure if the usual wavefront sensors will work well with a target like Moon.


Astrokiwi t1_jb9pbou wrote

Yeah, this is assuming totally ideal circumstances with perfect optics.


mfb- t1_jb9yclg wrote

Starship HLS is pretty white while the surface of the Moon is pretty dark. Landing near the pole will also mean it's at a nice angle relative to our line of sight. So maybe it's an elongated blob.


ChrisGnam t1_jbd8sc9 wrote

> get much better resolution by sending a small telescope to orbit the Moon ...

Just to comment on this part, we already have such a probe! We at NASA Goddard operate tbe Lunar Reconnaissance Orbiter (LRO) which has two a Narrow Angle Camera's (LROC NAC-L and NAC-R), each have a focal length of ~700mm and so are effectively mini telescopes.

Infact, with these camera's we've been able to photograph the old Apollo landing sites

If anyone is interested in diving further, all the imagery taken by the LRO is available to the public and can be explored using the LROC QuickMaps tool. If you zoom in you'll see the actual mosaic of NAC images. You may be wondering why each segment of the image looks really long, and this is because NAC is a push-broom sensor rather than a framing one. A framing sensor (like in most camera's today) is a rectangular grid of pixels where each pixel on the sensor is sampled once and corresponds to one pixel in the final image. A push-broom sensor is a single line of pixels, which each pixel represents a column of the final image. It is sampled at a regular interval, and each time it's sampled, that forms a new row of the image. So as you fly over a surface, you construct the image one row at a time. It maps the surface kinda like you're pushing a broom over the surface, hence the name.


draenogie t1_jba6qfk wrote

What about image stacking with many photos? I see that technique getting amazing resolution of galaxies.


Astrokiwi t1_jba953w wrote

That is useful for reducing the noise and increasing the exposure time, but doesn't actually increase the resolution.


mfb- t1_jbce8if wrote

Lucky imaging should still be useful if the adaptive optics doesn't work perfectly.


bkinstle t1_jbaapys wrote

Would it be better with a space telescope like Hubble?


mfb- t1_jbcdq2r wrote

No. It doesn't have the atmosphere to worry about, but the mirror size is too small (2.4 m vs. 30 m for upcoming telescopes) and resolution scales inversely with that size. At best it could detect a brighter featureless blob.


IllstudyYOU t1_jbal69m wrote

What if they write " Hi Mom " On the moon dust with their foot prints in big letters?


zekromNLR t1_jbj740f wrote

There is also the problem of atmospheric seeing, which uncorrected limits the resolution to about 1 km at the distance of the Moon with excellent seeing conditions.


steelcryo t1_jb9nso4 wrote

The other comments have already answered the question, but I'm going to add in a bit of context that's really obvious, but rarely thought about and that is that the moon is massive.

We often think of the moon as quite small, because we see it in the sky all the time and it looks small. Then we get these really high resolution pictures of it, normally something you can't do at great distances. Which further increases the perception that the moon is quite small.

Truth is, the moon is huge. Compared to the Earth, it's small, but as a physical entity, it's pretty big. Now I'm saying all this to give some comparison to the main question.

This is the Tycho crater. It's not the biggest crater on the moon, but it is one of the most visually distinct in that you can easily see the edges of it. That crater looks fairly small, but is actually 83km in diameter. So if that's how small something 83km across looks, it puts into scale just how tiny something as small as a rocket/lander would be.

Yes, telescopes can magnify much more than that picture, but it gives a good sense of the scale of what you are actually trying to look at.


extropia t1_jb9r3q7 wrote

That's a great example! Without any obvious Earth-like features like coastlines and clouds to compare it to, it's easy to look at the crater and think you could walk across it in a day.


Mr__Teal t1_jbb7wvi wrote

It's 83km, you could walk that in a day at least on Earth. Might be easier to do an easy run on the moon rather than walk, but outside needing a support crew to resupply you with air you could probably do it on the moon as well.


clonked t1_jbbwclz wrote

If you managed to do a constant pace of 15 minute miles, walking non-stop, it would take nearly 13 hours to walk ~51 miles (83 km). That is technically achievable, but not by a majority of people.


zxyzyxz t1_jbcw5kz wrote

How does the lower gravity factor into it? Does it make it easier to walk across? What would the effort feel like as opposed to walking that far on Earth?


clonked t1_jbd22vy wrote

The lower gravity can actually make you walk slower, because there is less ground tension from the lower gravity. Overall it would be a considerably harder task on the moon, their gravity is ~16% of what earth's is.


Wild_Sun_1223 t1_jbc0bez wrote

Yes, since a Earth day is 86.4 ks, then you can do it at a walking pace of 83 / 86.4 ~ 1 m/s, which is slower than average (1.4 m/s). But in practice you'll wanna sleep, so maybe two Earth days is better than one. Note that regarding oxygen, bottles could be laid out in advance similar to an Everest climb on Earth, and there could be a half-way camper for sleeping.


_Jam_Solo_ t1_jbbvelw wrote

I find 83km is less than I was expecting. That's not very far at all. It's like a 45min drive.


Tidorith t1_jbcf8gb wrote

Linear distances are small, areas are large. It's easy to drive across an 83km crater, but imagine trying to paint the whole thing.

Volumes are even larger still.


andrewmaixner t1_jb9rqlv wrote

And for those who benefit from geographic comparison, the moon is almost as wide as the continental United States, or 2/3 as wide as China.


formerlyanonymous_ t1_jb9tqbf wrote

Huh, I'd definitely thought bigger. Thanks.


coren77 t1_jb9xyaf wrote

Me too.... so I looked it up just to get a grasp on difference! From a purely diameter related measurement, the moon is ~2100 miles, while the earth is around 8000 miles in diameter. The US is around 2700 miles across depending on how you measure. However in actual square miles, the moon is MUCH more massive (sphere, yay!) than any one country on earth; the moon is around 14.6million square miles, wile the entire continent of asia is around 17.2million sq miles (largest country on earth, Russia, is "only" 6.6 million miles).

The More You Know!


Legitimate_Bat3240 t1_jbamjqk wrote

Surface area of the moon is a few million less sq miles than the total surface area of Asia.


andrewmaixner t1_jban7wi wrote

Yes. My super-basic comparison is based on diameter or width (not surface area), Asia is != China, and the moon is spherical not mostly-flat. This is "X river is Y football fields long" quality of comparison ;)


aecarol1 t1_jba5q5u wrote

There is no telescope on Earth today that could resolve the lander. Even telescopes planned over the next few decades, with perfect skies, probably can't do much better than a couple of pixels. The can't effectively can't do anything other than say "something" is there. But they can't produce a "photo" of the lander you would recognize.

But the astronauts will lay down retroreflector panels, just like the Apollo astronauts did. Any decent size university has the equipment to flash a laser at that part of the moon and see a few photons reflected. This is done all the time to establish the distance between the Earth and the Moon, as well as to study the wobble of the moon.

Before they go, the place that they will land will not reflect laser pulses, but after they lay out the panel, it will.

tl;dr it will not be possible to photograph the landers from Earth, but it's easy to shoot large lasers at the moon and observe the photons come back only from places where astronauts or other man-made objects have landed. This is because they carefully place retroreflector panels.


LordHivemindofCeres t1_jb9bftf wrote

As u/astrokiwi mentioned, the maximum resolution achievable by modern or near-future groundbased optical telescopes comes down to about 5-10m. Depending on the lander used this would be anywhere between 1 and 5 pixels of lander visible in the image. The Lunar Gateway might be a different story however, as it will be large enough that such a telescope might be able to discern some of its structure.