Silly question....

What is the smallest object that the HST could resolve on the surface of the
moon? Would it be possible to see the remains of the lunar landers at the
Apollo landing sites?

ROB

To my best knowledge: no. Furthermore I suspect that the moon would emit
too much light for Hubble, "burning" the instruments on board - but I
will stand corrected if I am wrong :-)


--
observer

Bernhard Rems
Editor - 'The Astronomers' (http://theastronomers.com)

On Wed, 21 Sep 2005 05:15:21 -0500, observer
wrote:


To my best knowledge: no. Furthermore I suspect that the moon would emit
too much light for Hubble, "burning" the instruments on board - but I
will stand corrected if I am wrong :-)

Hubble has imaged the Moon in the past without any 'burning'.
--
Pete
http://www.digitalsky.org.uk

observer wrote:
To my best knowledge: no. Furthermore I suspect that the moon would emit
too much light for Hubble, "burning" the instruments on board - but I
will stand corrected if I am wrong :-)



This topic is raised here often.
Hubble can image the moon, (eg
http://hubblesite.org/newscenter/new...eases/1999/14/ )

Hubble does not have the aperture to image the lunar landers, Hubble can
resolve a little less than 0.05 arcseconds or about 90 meters at the
moon. To resolve the LM descent stage which is about 10 meters across,
you'd need better than 10 meters of resolution, perhaps 3 meters which
means a telescope about 30 times larger than the HST in orbit around the
Earth to resolve the largest equipment left on the moon. (and that's
from orbit, without AO)

Steve

As I said, I stand corrected :-). Thanks for the clarification.


--
observer

Bernhard Rems
Editor - 'The Astronomers' (http://theastronomers.com)

"Robert Flint" wrote in message
...
What is the smallest object that the HST could resolve on the surface of
the moon? Would it be possible to see the remains of the lunar landers
at the Apollo landing sites?

ROB
No.
In fact Earth based scopes have more resolution than the Hubble anyway
(remember that for planetary imaging, you can use short exposures, and
hence 'obviate' a lot of the atmospheric problems). Potentially, a current
large scope could just about resolve the shadow cast by a base lander in
the right circumstances. However the objects themselves are much too
small. For an object about 3m across on the Moon, you would need a scope
aperture in the order of about 70m, to start to resolve it.

Best Wishes

Robert Flint wrote:
What is the smallest object that the HST could resolve on the surface of the
moon? Would it be possible to see the remains of the lunar landers at the
Apollo landing sites?

ROB

Hi Rob,

The Wide Field camera on the Hubble Space Telescope (HST) has a
resolution of 0.1 arcseconds per pixel at F12.9, and the Planetary
Camera has a resolution of 0.043 arcseconds per pixel at F/30.

The angular diameter of the Moon (assuming it is circular) is roughly
1860 arcseconds with a physical diameter of roughly 3430 km. So dividing
the latter by the former we can now calculate that each arcsecond on the
lunar surface corresponds to 1844 m.

Therefore, under optimum conditions the Wide Field camera has a Lunar
spatial resolution of 184 m per pixel, and sing the Planetary Camera has
a Lunar spatial resolution of 79 m per pixel.

The Lunar Module (LM) used for the Apollo missions (and critically the
component left behind on the surface of the Moon) has a diameter of 4.27
m. Therefore the LM will fill 1/18 of a pixel using the Planetary Camera.

You might be interested in the Astronomy Picture of the Day from 28th
June 2002 (http://antwrp.gsfc.nasa.gov/apod/ap020628.html). The image on
this website shows an actual image of the landing site of a LM at
Taurus-Littrow.

Hope that helps!
John
http://physics.open.ac.uk/~jdtanner

"John D. Tanner" wrote in message
...
Robert Flint wrote:
What is the smallest object that the HST could resolve on the surface
of the moon? Would it be possible to see the remains of the lunar
landers at the Apollo landing sites?

ROB

Hi Rob,

The Wide Field camera on the Hubble Space Telescope (HST) has a
resolution of 0.1 arcseconds per pixel at F12.9, and the Planetary
Camera has a resolution of 0.043 arcseconds per pixel at F/30.

The angular diameter of the Moon (assuming it is circular) is roughly
1860 arcseconds with a physical diameter of roughly 3430 km. So dividing
the latter by the former we can now calculate that each arcsecond on the
lunar surface corresponds to 1844 m.

Therefore, under optimum conditions the Wide Field camera has a Lunar
spatial resolution of 184 m per pixel, and sing the Planetary Camera has
a Lunar spatial resolution of 79 m per pixel.

The Lunar Module (LM) used for the Apollo missions (and critically the
component left behind on the surface of the Moon) has a diameter of 4.27
m. Therefore the LM will fill 1/18 of a pixel using the Planetary
Camera.

You might be interested in the Astronomy Picture of the Day from 28th
June 2002 (http://antwrp.gsfc.nasa.gov/apod/ap020628.html). The image on
this website shows an actual image of the landing site of a LM at
Taurus-Littrow.

Hope that helps!
John
http://physics.open.ac.uk/~jdtanner
You are making the assumption though, that the optics can resolve to the
pixel level. This is not actually the case. the resolution of the
planetary camera, was selected to just about meet the critical sampling
criteria of two pixels across the highest frequency component resolvable
by the optics.

Best Wishes

snip

You are making the assumption though, that the optics can resolve to the
pixel level. This is not actually the case. the resolution of the
planetary camera, was selected to just about meet the critical sampling
criteria of two pixels across the highest frequency component resolvable
by the optics.

Not quite sure what you mean by that I'm afraid Roger. I've just checked
the WFPC2 handbook
(http://www.stsci.edu/instruments/wfp...t3.html#440477)
and the quoted pixel scale is ~100 milli-arcseconds (Wide Field) and ~46
milli-arcseconds (Planetary). Email and Newsgroups are such a pain to
get over what you are trying to say :-)

I feel that the value of 79pix/m for the Moon is still reasonable
considering the assumptions made and that NASA back me up at the
Astropix website that I quoted :-)

All the best,
John
http://physics.open.ac.uk/~jdtanner

SNIP

I feel that the value of 79pix/m for the Moon is still reasonable
considering the assumptions made and that NASA back me up at the
Astropix website that I quoted :-)

So can it see the double decker bus?

Steve