Fw: NSA good guys

[Troy Benjegerdes]

On Sat, Apr 19, 2014 at 10:44:50AM -0700, jim bell wrote:
> [I didn't get a bounce off of CP the first time]
> 
> From: "dan at geer.org" <dan at geer.org>
> 
> |     It may be possible, in the not-so-distant-future, to record
> |     people in ultra high definition from a mile away, but the
> |     'technology'  can be rendered rather useless with somthing
> |     like...this
> | 
> |     http://ramitia.files.wordpress.com/2010/02/japan-face-masks.jpg
> | 
> 
> 
> >At this time, it is possible to do facial recognition at 500 meters,
> >iris recognition at 50 meters, and heartbeat recognition at 5 meters.
> >A newspaper open on a table can be read from orbit. 
> 
> I strongly doubt the part about reading the newspaper from orbit.  I don't doubt that the pattern of text and pictures on the  front page could be identified from orbit. ('Identifying the difference between Pravda and Izvestia'.)   An approximation I once heard is that a lens or mirror of about 4.5 inch in diameter can resolve an angle of one arc-second.  A mirror of the size of the Hubble Space Telescope (which I assume approximates that of the typical spy satellite today) is about 20x larger, so the resolution should be 20x better, or 1/20 arc-second.  That's 1/(57 degrees per radian)(3600arcseconds per degree)(20) = 1/4,100,000 radian.  From an altitude of 500 kilometers, that's about 1/8 of a meter, or 120 millimeter.  Maybe that's a pixel-pair, but it's far too large to resolve the text on a newspaper.  
> 
> The best prospect to improve on this resolution would be to use a 'multiple-mirror-telescope' technology.  Light-gathering capability isn't important in this application; high resolution is.  Making a spy-telescope out of a few different mirrors, held precisely many meters apart, could conceivable achieve resolutions substantially greater than this.
>         Jim Bell


Such a mirror array would at some point reflect enough light at odd angles to be visible with the 
naked eye.

I find it more likely that multiple-mirror-telescope tech would be implemented with a swarm of small
satellites and extremely precise location tracking and a lot of signal processing later on.