Fw: NSA good guys

[tpb-crypto at laposte.net]

> Message du 19/04/14 21:49
> De : "jim bell" 

> From: Troy Benjegerdes 
> To: jim bell  
> 
> > [I didn't get a bounce off of CP the first time]
> >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.
> 
> I sure find that difficult to imagine!  Particularly because the assemblage would presumably be flying at about 500 kilometers altitude, and would therefore be buffeted by extremely-small-but-significant orbital winds.  In addition, the amount of information that would have to be interchanged (phase and amplitude, in TWO dimensions!) of an entire field of view would be phenomenal.  
> What I suspect the US military would really like to see is a spy satellite at geosync altitude (22,000 miles) with an apparent aperture of perhaps 150 meters, so that it has roughly the same resolution on the ground as existing fast-orbital spy satellites.  (orbital period circa 90 minutes or so). 
>              Jim Bell

Balloons, that's what the military uses for high resolution imagery. And they are so good to stay aloft that not even with a .50 machine gun you would be able to down it. The only way to do that is to fly a drone nearby carrying some pounds of dynamite and fire it off.