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From: dietz@SLB-DOLL.CSNET (Paul Dietz)
Newsgroups: net.space
Subject: Re: Phase conjugation
Message-ID: <8601241437.AA04546@s1-b.arpa>
Date: Fri, 24-Jan-86 08:12:16 EST
Article-I.D.: s1-b.8601241437.AA04546
Posted: Fri Jan 24 08:12:16 1986
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n

>Why won't the phase conjugation technique work in reverse to build a
>large earth based telescope that removes the effects of atmospheric
>turbulence?  One would need a laser in the field of view (on a
>satellite, say) to determine the distortion during the trip down through
>the atmosphere, then apply the correction for that distortion to all
>incoming light to produce an undistorted image.  If it works, it sounds
>like it could make the Space Telescope obsolete.

I'm not sure if phase conjugation is what you want, but it doesn't
seem impossible to use a laser beam to determine what the
atmosphere is doing, then correct the image by computer.  You might
have some problems if the atmosphere causes different wavelength light
to travel along different paths.  There's already a technique, called
speckle interferometry, that stacks short snapshots of a star into
one image with resolution better than normally allowed by atmospheric
distortion.

I don't think it would make the space telescope obsolete; the ST can
also be used to see infrared and ultraviolet light in wavelengths where
atmospheric absorption and interference is important.