Orbital surveillance satellites now exceed 1 inch resolution.

On Apr 24, 3:30 am, Pat Flannery wrote:
Orval Fairbairn wrote:

It would take one HELL of a focal length!

Think of that hypothetical gizmo... you could pull it off looking at the
Moon, or another atmosphere-free body.
But peering down though sixty miles of turbulent atmosphere?
It would make more sense to use radar.


Looking down is not the same as looking
up, Pat. It's not a mirror image (ugh :-( ).
Looking up through the atmosphere puts
atmospheric refraction errors at the beginning
of the optical path; looking down through the
atmospheres puts refraction errors at the
end of the optical path. Like looking at
your hand at a distance from a frosted
glass--or in contact with the glass.
I'm not sure how much of that sixty-mile
path you mention is really significant.

There are probably physical limitations.
However, I suspect that launch cost
llmitations may still be more important.
Hurrah for low-cost space access :-)

Len

Pat

Len wrote:

On Apr 24, 3:30 am, Pat Flannery wrote:
Orval Fairbairn wrote:

It would take one HELL of a focal length!

Think of that hypothetical gizmo... you could pull it off looking at the
Moon, or another atmosphere-free body.
But peering down though sixty miles of turbulent atmosphere?
It would make more sense to use radar.


Looking down is not the same as looking
up, Pat. It's not a mirror image (ugh :-( ).
Looking up through the atmosphere puts
atmospheric refraction errors at the beginning
of the optical path; looking down through the
atmospheres puts refraction errors at the
end of the optical path. Like looking at
your hand at a distance from a frosted
glass--or in contact with the glass.
I'm not sure how much of that sixty-mile
path you mention is really significant.

There are probably physical limitations.
However, I suspect that launch cost
llmitations may still be more important.
Hurrah for low-cost space access :-)


A very long optical base of multiple satellites reduces the need for large
mirrors. Collecting vast amounts of light doesn't yield a better picture
for something bright and up close. A bunch of small mirrors with an
extremely large base (or base lengths) would allow you to read what he is
reading, over his shoulder so to speak. Probably correct for the first 60
miles of frosted glass too.

In article t, Craig Fink writes:
Len wrote:

On Apr 24, 3:30 am, Pat Flannery wrote:
Orval Fairbairn wrote:

It would take one HELL of a focal length!

Think of that hypothetical gizmo... you could pull it off looking at the
Moon, or another atmosphere-free body.
But peering down though sixty miles of turbulent atmosphere?
It would make more sense to use radar.


Looking down is not the same as looking
up, Pat. It's not a mirror image (ugh :-( ).
Looking up through the atmosphere puts
atmospheric refraction errors at the beginning
of the optical path; looking down through the
atmospheres puts refraction errors at the
end of the optical path. Like looking at
your hand at a distance from a frosted
glass--or in contact with the glass.
I'm not sure how much of that sixty-mile
path you mention is really significant.

There are probably physical limitations.
However, I suspect that launch cost
llmitations may still be more important.
Hurrah for low-cost space access :-)


A very long optical base of multiple satellites reduces the need for large
mirrors.

Only if you can combine the amplitudes (as opposed to the intensities)
of the images, else there is no improvement on resolution.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

In article ,
wrote:
Only if you can combine the amplitudes (as opposed to the intensities)
of the images, else there is no improvement on resolution.


perhaps you meant: combine both the amplitude and phase information
from each detector, rather than just the intensities

or...