Roger Roerick asked:
Could the Hubble space telescope see the footprints made by the Apollo astronauts on the moon’s surface?
Dave - Well, Hubble is an incredible telescope but looking up it’s resolution — I reckon it has a resolution of 0.05 arcseconds, that means it can distinguish two objects which are 0.000013 degrees apart, any closer together than that and they sort of merge into one object. Now –
Chris - In practical terms what does that mean?
Dave - That means if something – the distance of the moon away from us, Hubble is essentially near the earth its very level, but –
Chris - So about a quarter of a million miles to the moon?
Dave - About 384,000 kilometres—that means you can see something 9 to 10 metres across on the moon, so probably not.
Chris - That would be a very big footprint – Bigfoot literally. Okay, thank you Dave!
Roger Röhrig asked the Naked Scientists:
"Hubble's keen vision (0.085 arc seconds.)"
The Chandrayaan-1 lunar orbiter is, apparently, able to resolve objects of 5 to 10m. Fine enough to see a landing site but no footprints. lyner, Wed, 13th May 2009
But this OSSP unit requires another component to be meaningful. It needs to be OSSP per some distance value. Vern, Thu, 14th May 2009
1 OSSP Per 26 miles 385 yards to keep with the same system Fortran, Thu, 14th May 2009
There is no hope that Hubble's resolution could be increased a hundredfold, assuming everything is made perfectly the resolution is determined by the size of the mirror and the frequency of the light it is operating at, Hubble is already at that limit. syhprum, Thu, 14th May 2009
I am not sure I understand "500 feet at 250,000 miles" and why this is okay for seeing footprints.
Once the Lunar reconaissance orbiter is in place the conspiracy theorists will need to step everything up a notch. But will they admit they were wrong? No, it will just involve a further layer of conspiracy.
The Mars orbiter,s have been able to identify the rover landing sites. syhprum, Fri, 15th May 2009
So the field of view is 500 feet - will a footprint 1/500th the size of that field be visible? Isn't that asking a lot? Isn't that like looking at a photo of a family holiday on the beach and then being able to see a single grain of sand in one corner of the photo? Sounds like a tall order to me.
I just read the NASA link posted by Fortran. As I suspected it says:
Hello all, great replies so far for the resolution question,
ya...We can see the foot steps raghavendra, Sat, 16th May 2009
The danger to the cameras of direct sunlight has precluded Hubble from ever viewing Mercury syhprum, Tue, 19th May 2009
Just stumbled on a gret post on "Bad Astronomy":
Taking a photo of the moon (the bright bits) is just the equivalent exposure to an object on Earth, in full Sunlight: 1/125second at f8 or thereabouts. The f number of the Hubble is not particularly low - dunno what it is exactly but it will have a fairly long focal length for its diameter. lyner, Wed, 20th May 2009
So the answer to the original question is "only if it were a lot closer to the moon or if the astronuats had really big feet." Bored chemist, Thu, 21st May 2009
"The FOC (faint object camera)offers three different focal ratios: f/48, f/96, and f/288 on a standard television picture format. The f/48 image measures 22 X 22 arc-seconds and yields resolution (pixel size) of 0.043 arc-seconds. The f/96 mode provides an image of 11 X 11 arc-seconds on each side and a resolution of 0.022 arc-seconds. The f/288 field of view is 3.6 X 3.6 arc- seconds square, with resolution down to 0.0072 arc-seconds"