Apollo

Why can't we see the Apollo lunar landers from Earth ?

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• published: 29 Dec 2016
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When you look up at a full moon, just remember that somewhere on the lunar face, the remains of Apollo 11, 12, 14, 15, 16 and 17 along with 8 unmanned Russian Luna missions and 5 pre-Apollo unmanned American surveyor missions are all still there….. silently looking back….. unless of course you’re a NASA non-believer. so… why can’t we see these from the earth, why can’t we train our best telescopes on to the moon’s surface and see them there exactly where we left them the best part of 50 years ago. Well, there a bit of a problem…. and that is that the moon is 384,000 kilometres or 238,000 miles away and the landers and all the other things left behind are just few meters across. To give you an Idea how difficult a problems that it is….. it’s like looking for an object the size of a coin from 1000 miles away or the equivalent from New York to Florida…. so you going to need a pretty serious telescope. One telescope that springs to mind is the Hubble space telescope, after all if it can see galaxy’s billons of light years away then it should be able to see the Apollo landers easily…. shouldn’t it ?? Well, as with many things to do with space it’s not that simple. Yes, the Hubble space telescope was indeed designed to look at very faint objects at astronomical distances but those objects are clusters of galaxy’s trillions of millions across, it was not designed the take high resolution images of small objects at fairly close ranges in astronomical terms like to the moon. The problem is down to the resolution of the images that the telescope can produce and that is limited by the laws of physics. The resolution determines the size the smallest Picture Element is or pixel in the image. The higher the resolution more of the fine detail in an image can be seen. In a telescope, the bigger the mirror, the more the magnification, so the closer the object will appear but at the very large magnifications the image is also affected by the wavelength of the light itself. The shorter the wavelength like ultraviolet light, the finer the detail that can be captured and the resolution increases but in visible light as we go from blue through green to red, the wavelength increases and the resolution is decreased. The Hubble has a mirror which is 2.4 meters in diameter, that was the largest that could fit in to the Space Shuttle when it was placed in to orbit. This gives it a single pixel resolution in ultra violet light of about 43 meters across on the moon’s surface, anything smaller than 43 meters across will just be hidden in a single dot which cannot be resolved any further, in fact we need really 2 pixels or more to make out anything at all. In visible light, it’s even worse and the size of area covered by a single pixel increasing to 90 meters. The only way we are going to see objects a few meters across on the lunar surface is to either increase the size of the mirror or get closer to the object you looking at. Back on earth, the current largest optical telescope in the world is GTC on the canary islands with a mirror diameter of 10.4 meters. This increase’s the resolution so that the smallest area covered by one pixel would be 20 meters across in visible light, still too big to see the apollo lander which is just over 4 meters across. In fact to see the Apollo landers from earth you need a telescope with a mirror size 10 times that of the GTC or about 100 meters across and that does not yet exist. Even then a 100 meter telescope would only give you a 2 meter resolution coverage, so the lander would be 2 pixels in visible light and 4 pixels in ultra violet light, still not enough to discern any real detail. This is the reason why we have been unable to the see any on the vehicles on the moon from earth and although in theory it is possible to use a group of telescopes in an array to get a higher resolution, no one has yet don’t it because telescope time is in very high demand and very limited and looking for objects that we know exist is not a high priority just to disprove the none believers. What we need is to put a camera in orbit around the moon, just like the spy satellites and the ones which give us satellite mapping services like google earth for example. In 2009 that’s exactly what happened, when the Lunar Reconnaissance Orbiter or LRO was launched to photograph and survey the moon from a distance of between 12 and 100 miles above its surface. Even with a much smaller camera lens, at its closest passes, it has a resolution of just 0.5 meters or 18 inches per pixel, so now all of the Apollo sites with the lunar landers and rovers as well as the Russian sites can be seen for the first time since they landed. GTC footage ©2015 Gianluca Lombardi/GTC Title: Adam Are You Free? Author: P C III Source: www.pipechoir.com Nightingale sounds from Gerry Gutteridge flic.kr/ps/Mk2zU License: Creative Commons Attribution 4.0