Xref: utzoo sci.space:4145 sci.crypt:726
Checksum: 40921
Lines: 24
Path: utzoo!lsuc!sq!msb
From: msb@sq.uucp (Mark Brader)
Date: Tue, 12-Jan-88 18:08:15 EST
Message-ID: <1988Jan12.180815.685@sq.uucp>
Newsgroups: sci.space,sci.crypt
Subject: Re: satellites
References: <873@uop.edu> <2166@umd5.umd.edu> <4910@well.UUCP> <1952@netsys.UUCP> <2209@bloom-beacon.MIT.EDU>
Reply-To: msb@sq.UUCP (Mark Brader)
Organization: SoftQuad Inc., Toronto
Keywords: resolution

> A telescope at sea level, in perfect 
> weather, is typically limited to no better than 1" (that is a unit 
> of angle: 1 arc-second, not 1 inch).  At 200 km this is a linear 
> distance of 1 meter.  I would believe that looking down 
> from orbit would give a different result (though I don't know).  

Probably it would be considerably better, since the atmosphere is at
the right end of the light path.  However, diffraction is still a limit,
as you say.  They might not be using visible light; how many times the
frequency of violet light must you go to before viewing becomes impossible?

> I would be impressed if any intelligence agency could regularly scan
> a city at 4 inch resolution while also doing its other (presumably 
> more important) business.

This could have BEEN considered important business, or they could have
gotten lucky, or, as you say, they could have known where to look.

I'm not saying that people CAN be spotted by satellite, only that it's
not as easy to dismiss as one might think.

Mark Brader		"You wake me up early in the morning to tell me I am
Toronto			 right?  Please wait until I am wrong."
utzoo!sq!msb, msb@sq.com	-- John von Neumann, on being phoned at 10 am