Re: (SNES) Earth as a 10,000- Mile Aperture Objective Lens

["Les Coleman" <les11@cox.net>]

Ernie,

I love it!! There would be all sorts of technical details (such as each wavelength having
its own focal length and a circle of confusion that would be huge) but still and all
theoretically managable. As far as I know the refraction program and the percentage of the
atmosphere programs both work correctly, but you are the first person to try to use them in
such a complex manner.

However the refraction program is written with the assumption that we are at the bottom of
the pool of air, not out in space where the air dives into the atmosphere and then leaves
again. So it quite likely isn't what you need. However, the problem of atmospheric
distortrion and extinction was a major deal to NASA. I'll bet that they have what you need
somewhere.

I see that I have inverted above and below in the Atmosphere Density. I've just fixed it.
(Just have to put the percentages in the other slot). It seems to behave just about
correctly. Every time you rise 5.9 km roughly 50% of the remaining air is left from the
previous step. The exact number depends on the temperature.

Les

> Our atmosphere should act as a gigantic lens approximately 10,000 miles in
> diameter with a  focal length of about 458,00 miles (f/46). (Talk about
> aperture fever!) Of course, the Earth itself would be an 8,000 mile central
> obstruction, but this still leaves PLENTY of clear aperture. The cloudy and
> most turbulent atmospheric conditions are in our troposphere, which extends
> only up to about seven miles above the earth's surface. A space probe with
> adaptive optics in earth orbit at the earth's atmosphere's focal length
> could provide some truly spectacular views! For example, extra solar planets
> might be easily seen directly by using the Earth's body as an "occulting
> disk."
>
> I realize I'm over-simplifying the situation in this brief posting, as the
> Earth's atmosphere is not perfectly spherical (that would introduce
> spherical aberration anyway), varies in size and shape with solar activity,
> would have chromatic aberration, etc.; but I'm surprised no space probe
> equipped with the proper aberration correcting and adaptive optics has been
> used to test this concept as an aside to its primary mission.
>
>
> I tried to use the FDO Website's Utility Tools on refraction and amount of
> atmosphere above/below a given altitude to firm up the feasibility of such a
> concept, but couldn't make its answers gel; is the atmosphere above/below
> function working properly? Appreciate any feedback on using our atmosphere
> as a lens.
>
> Ernie
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