Xref: utzoo sci.space:4162 sci.crypt:732
Path: utzoo!utgpu!water!watmath!clyde!rutgers!mcnc!gatech!udel!princeton!phoenix!pupthy2!lgy
From: lgy@pupthy2.PRINCETON.EDU (Larry Yaffe)
Newsgroups: sci.space,sci.crypt
Subject: Re: satellites
Keywords: resolution
Message-ID: <1457@phoenix.Princeton.EDU>
Date: 13 Jan 88 04:46:22 GMT
References: <873@uop.edu> <2166@umd5.umd.edu> <4910@well.UUCP> <1952@netsys.UUCP> <2209@bloom-beacon.MIT.EDU> <2604@calmasd.GE.COM>
Sender: news@phoenix.Princeton.EDU
Reply-To: lgy@pupthy2.PRINCETON.EDU (Larry Yaffe)
Organization: Physics Dept, Princeton Univ
Lines: 33

In article <2604@calmasd.GE.COM> jnp@calmasd.GE.COM (John Pantone) writes:
>> [[ Quoted comments about limits on image resolution omitted. ]]
>
>Except sattelites don't use cameras - in that sense of the word.  They use
>CCD's and all sorts of bizarre imaging equipment - but they DON'T take
>pictures - I don't think that the same limitations apply (although they no
>doubt have other limitations).
>
>John M. Pantone @ GE/Calma R&D, 9805 Scranton Rd., San Diego, CA 92121
>...{ucbvax|decvax}!sdcsvax!calmasd!jnp   jnp@calmasd.GE.COM   GEnie: J.PANTONE

    The fact that CCD sensors are used in place of film is completely
irrelevant to the issue of diffraction-based resolution limits.
Diffraction by the primary mirror of the imaging system limits
the best acheivable focusing of the incoming light irrespective
of what sort of sensor is used to record the picture.

    On a marginally related note - an earlier posting (sorry, no reference),
implied that spy satellite mirrors are no larger than the primary mirror
of the Hubble Space Telescope.  I doubt that this is true (but not by
enough to change the improbability of recognition of Waite from orbit!).
The size of the space telescope mirror was far more strongly influenced
by economic realities than by technical limits.  Supposedly, when the bids
for the fabrication of the space telescope mirror were solicited,
the lowest bids came not from traditional optical companies like Corning,
but from defense companies like Lockheed.  Seems that they already had
lots of experience...

------------------------------------------------------------------------
Laurence G. Yaffe
Department of Physics			lgy@pupthy.princeton.edu
Princeton University			...!princeton!pupthy!lgy
PO Box 708, Princeton NJ 08544		609-452-4371 or -4400