Apollo Moon flags still standing, images show | Hacker News Reader

Apollo Moon flags still standing, images show

bbc.co.uk

75 pointscskau34 comments

I always wondered what kind of telescope one would need to look at the stuff we left on the moon (flag, cars, what was left of the rocket, ...). Anybody know or tried that? Is equipment like that even accessible to a regular joe like me?

Not possible because of optical resolutions. If you web search that question you'll get more details.

https://www.google.com/search?q=can+I+use+a+telescope+to+see...

Here are some responses:

http://answers.yahoo.com/question/index?qid=20100906195045AA...

http://stupendous.rit.edu/richmond/answers/lunar_lander.html

http://curious.astro.cornell.edu/question.php?number=134/

http://blogs.discovermagazine.com/badastronomy/2008/08/12/mo...

I was sure you could use the Hubble at least. Shows how much I know about this stuff :) Thanks for the links, they are quite informative.

Actually, I remember reading somewhere that the Hubble was in fact pointed at the Lunar landing sites at one point, but that even its resolution was too low to produce any conclusive images of the landing sites.

We just need to get the NRO to let us borrow one of their satellites :)

Well, not with a direct telescope, but optical interferometry could achieve the milli-arcsecond resolution needed.

http://en.wikipedia.org/wiki/Astronomical_interferometer

I'm not sure if there exists a telescope that has the resolution, but it's within current technology.

And to point out that not only do you need an Aperture that you can't currently get, you need to air to stop moving so that you can look through it. The heat in the atmosphere causes the gas molecules to bounce around and they tend to refract light so you end up with foggy vision.

Its also why you can't get a clear image of the ISS (which is in low earth orbit) or even geostationary satellites. This is something governments have taken advantage of. Once you launch a satellite its hard to 'view' it without actually being in space.

This should answer your question: http://www.telescopes.com/telescopes/canyouseeobjectsleftbeh...

tldr: you would need a 200 meter telescope to see the flag, or a 75 meter 'scope to see the lunar rover. The largest earth bound 'scope is 10meters. The Hubble scope is 2.4m

Also goes in to the 'rippling flag' question that someone asked in a different comment below.

It's not the same, but several Apollo missions left behind retroreflectors, tri-corner reflectors like in car taillights, which can bounce back laser probes:

http://science.nasa.gov/science-news/science-at-nasa/2004/21...

They are used to get precise earth-moon distances.

Simple rule of thumb:

The resolving power of a telescope is a function of aperture (diameter of primary lens or mirror). A telescope with an aperture of 100 mm (4") has a resolving power of 1 arcsec. Then 200 mm of aperture buy you 0.5 arcsec, and so on.

What is the minimum size of detail to distinguish those objects? Let's say 10 cm - kind of blurry, but intelligible.

What's the distance to them, from a telescope in low orbit? It's approximately the semi-major axis of the orbit of the Moon - 384,000 km.

arctan ( 10 cm / 384000 km ) = 2.6 * 10^-10 radian = 5.4 * 10^-5 arcsec

The aperture you need to get that kind of resolving power is:

100 mm / (5.4 * 10^-5) = 1800 m

You'd need a telescope with 1.8 km of aperture to see the Moon lander with 10 cm linear resolution. Scale down the aperture if you're content with less resolution, the function is linear.

Please note this is for a scope in vacuum, above the atmosphere. Air turbulence will reduce its resolving power dramatically, requiring some kind of adaptive optics to dynamically counteract the blur, which typically is not 100% efficient.

If going back to the moon to examine the condition of the flags is the excuse we need to go back, then I'm all for it! I just hope they do some real science while they are there.

If we ever plan to have an extended presence in space then examining artifacts left on the moon would be very informative. We left a lot of machinery up there, exposed to the vagaries of space for 40 years. There's a lot to be learned from the state of that equipment.

This reminds me of a passage from Arthur C. Clark's Imperial Earth, set in 2276, in which a retrospective video on the first flight to the moon segues to a shot showing Tranquility Base at the (then) present time, complete with fallen flag and space tourists waving to cameras in the background.

There's an ongoing preservationist debate over whether or not to re-plant the flag or leave it where it is.

Other than UV bleaching and depolymerization of plastics (including the nylon the flag is made from), and slow micrometeorite ablation, these relics should stand for billions of years.

I would love to visit these sites someday in person.

Based on the lighting from the rest of the image, shouldn't the flag shadow be longer and falling the other direction??

Looking at the illumination of the craters it looks like the Sun is on the right hand side of the picture in the BBC article (craters are dark on the right hand side, light on the left hand side). The shadow of the flag appears on the left hand side of the flag itself so it looks correct to me.

I wasn't seeing craters but mounds which, of course, is improbable for lunar geology. (Strangely, even after this revelation, my mind still processes the lighting as falling on objects the rise above the surface...)

Why does the flag look rippley in the picture at the top? Had he just planted it?

(hope you're not trolling)

It's rigid, but made to look like it's in a breeze.

http://en.wikipedia.org/wiki/Lunar_Flag_Assembly

I know, it does sound like I am but I'm genuinely curious.

This might help you - http://www.badastronomy.com/bad/tv/foxapollo.html

I can see how a bar would hold it stretched out, but what is giving the appearance of motion? And making the bottom corner look somewhat lifted up?

Given that there is no air resistance on the Moon, any residual motion when it was planted would remain for some time. If the astronaut started it flapping when he planted it in the ground and adjusted the arm, it would probably flap for quite a while.

It looks to me like it's still crumbled and creased from being packed up tightly.

Maybe with 1/6 gravity the creases stay folded up more than they would on Earth?

This page, linked off the above mentioned Wikipedia article, is actually a pretty interesting read on the engineering challenge of shipping a flag to the Moon in such a manner that people in space suits could unpack it and set it up.

http://www.jsc.nasa.gov/history/flag/flag.htm

The first U.S. flag on the moon was deployed by Neil Armstrong and Edwin "Buzz" Aldrin during their historic EVA on 20 July 1969 (at 4 days, 14 hours and 9 minutes mission-elapsed time). The flag was seen worldwide on live television (Fig. 6). At their technical crew debriefing, Armstrong and Aldrin reported few problems with the deployment. They had trouble extending the horizontal telescoping rod and could not pull it all the way out. This gave the flag a bit of a "ripple effect," and later crews intentionally left the rod partially retracted.

The first answer to this (idiotic) question is the correct one: http://physics.stackexchange.com/questions/12051/if-there-is...

http://www.hq.nasa.gov/alsj/alsj-usflag.html

"Armstrong and Aldrin reported few problems with the deployment. They had trouble extending the horizontal telescoping rod and could not pull it all the way out. This gave the flag a bit of a "ripple effect," and later crews intentionally left the rod partially retracted."

Little known fact, astronauts are trolls.

Fact: The whole manned mission to the moon was just to troll the USSR.

The flag is fabric and was packed very tightly into a small container. The extender bar stretches it out, but does not eliminate the creases and wrinkles from being packed so tightly. On Earth, fabric tends to relax over time as it is pulled downward by gravity and absorbs water vapor from the air. Not much of either on the moon.

For those interested, here are some of the underlying posts on the LROC site itself...

1. http://lroc.sese.asu.edu/news/index.php?/archives/620-Questi...

2. http://lroc.sese.asu.edu/news/index.php?/archives/619-A-New-...

We have a huge amount of interesting images.

1. One half of my brain thinks: Why shouldn't they?

2. Other half thinks: Amazing!

Until they're crushed by an impact, or the material somehow erodes by solar wind, they'll probably be there for a long time.

Many huts in the Antarctic from the earliest days of exploration are still standing despite being considerably older and those conditions are far harsher than on the moon.

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