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From: bgarwood@cisunx.UUCP (Robert  Garwood)
Newsgroups: sci.space,sci.crypt
Subject: Re: Satellites and diffraction limits
Summary: Seems reasonable to me
Message-ID: <6239@cisunx.UUCP>
Date: 15 Jan 88 19:49:46 GMT
References: <22587@ucbvax.BERKELEY.EDU>
Reply-To: bgarwood@unix.cis.pittsburgh.edu.UUCP (Robert  Garwood)
Organization: Univ. of Pittsburgh, Comp & Info Sys
Lines: 17
Distribution:na

In article <22587@ucbvax.BERKELEY.EDU> tedrick@ernie.Berkeley.EDU.UUCP (Tom Tedrick) writes:
>Here is an extract from "The Puzzle Palace" (James Bamford)
>
>page 259: " ... the Code 467 satellite, better known as Big Bird
>... first launched on June 15, 1971 ... built around an extraordinary,
>superhigh resolution camera capable of distinguishing objects eight
>inches across from a height of ninety miles ... "

Lets see, 8 inches from 90 miles corresponds to an angular size of
0.3 arc seconds.  This is only a factor of 3 or so smaller than the best
seeing of ground based astronomical telescopes and a factor of 4 to
5 larger than the diffration limit of a 2-m telescope at optical 
wavelengths.  Seems reasonable to me. 

Bob Garwood
Dept of Physics and Astronomy
Univ. of Pittsburgh