Subject: IW Mailing List iw/960221
Date: Tue, 20 Feb 96 15:06:49 EST
From: "Mark S. Perry" 
Subject: Strano Network
Careful, careful, quick analysis based on first looks are often leads to 
incorrect conclusions.  Take another look at the original Zapatista article:

   The "Zapatista" experience has put again under discussion the concept of 
   internationalism as a way to solidarize with organizations, guerrilla 
   movement of marxist style whose main goal is the conquest of the power. Now, 
   after the falldown of the Berlin's wall and of the realist socialismm, the 
   concept of solidarity has a new mean.  The first ones to understand this are 
   the "Zapatistas" by the issue of their first announcement outlining the 
   differences existing between them and the "Sandinista" and "Salvador"'s 
   fronts.  As a concequence, the Zapatistas take in more consideration the 
   several antagonist movements fighting against the capitalist model all over 
   the world rather than a powerful party.
Note in particular the reference to "internationalism" and "movement(s) of 
marxist style".
Date: Wed, 21 Feb 1996 06:34:18 -0800
From: Bruce Sterling 
Subject: from Open Media Research Institute, Inc (c) 1996

This clipping from the most recent edition of Open Media Research
Institute's invaluable "Daily Digest" describes these Bosnian
Serbs as a "news agency," but I think they might be better described
as "information warfare guerillas."  

has seen better days, although it probably never was a fancy place in
the romantic ski resort surrounding Pale. Hidden in the woods aside a
small and icy path stretching down and uphill again, no one would expect
a highly efficient propaganda news agency. "We have a thousand
journalists in the Republika Srpska hidden in places nobody knows. They
[NATO] were never able to track them," SRNA's Director Brane llic said
sometime later
The two small rooms full of technical equipment are overcrowded. Of
altogether 111 agency journalists, 59 work and sleep in Pension
Bellevue, and most of them are refugees from Sarajevo. "This is an
incredible, enthusiastic group," says llic. "We live and work together
under very special circumstances. The government provides our food at
the Hotel Panorama. These people are young, devoted, and ready to work
and improvise 24 hours a day, to counteract the misinformation of the
At the beginning," says llic, "we were just five to six people. We had
to leave our entire infrastructure behind under Muslim control in
Sarajevo and to start completely anew. But already on 7 April, three
days after the beginning of the war, we founded SRNA." Now the agency
has 25 correspondents throughout the Republika Srpska, six in Serbia
proper, and 21 foreign correspondents from Athens to Sydney. "It is
important to reach our emigrants." His voice heightens: "Immediately
after the war started, the Muslims hired PR agencies and cooperated with
all international networks to stage their media war. They got all kinds
of money and know-how helping them to demonize Serbs. However, nobody
supported us. All during the war we never had any cooperation with any
international agency. Muslims and Croats simply provided the agencies
with the information which they simply took. They never rechecked the
sources, simply spreading that information around the world. We never
did that." llic offers Japanese whisky, then continues: "Both sides were
engaged in a media war. But thanks to the much better technical
equipment and higher funds the other side had, we had no chance to
compete. All we could put against it was our professional dignity and
objective information. And we only defended our people from the Muslims
and Croats attacks, not to leave shame on us. Otherwise our people would
not have believed in us."
While doing this job SRNA has expanded rather well. The Pale authorities
equipped their mouthpiece with its first computers, and whatever else
was needed was provided by Serbian media colleagues and emigrant
friends. Though "handicapped due to the blockade," the agency managed to
reach the world by sending its messages via satellite to Belgrade, from
where they were sent on. Meanwhile, notwithstanding all technical
difficulties after the NATO bombing of the transmitters in September,
SRNA managed to get its word out. "The bombing was a catastrophy," says
Ilic. We had nothing left, all news had to be delivered via amateur
radio operators in Belgrade. Nevertheless we managed to give out 40 to
50 news items daily, even though Muslim radio amateurs tried to
interfere and were permanently insulting us over the radio. At first we
were scared using radio at all because it would lead NATO right to us.
But then it became clear that they knew exactly where we were. There
were many foreign media crews here, so we dared."
"If there were no blockade", complains llic, "many more requests would
reach us. We ourselves replace our lack of contacts with the world
through monitoring, but the world receives much too little from us."
SRNA monitors all receivable broadcasters via satellite, from CNN to
RFE/RL's South Slavic Service. Does this feeling of an unfortunate lack
of contact include the missing contacts to the agencies of the other
entities? Would Serbia wish an exchange with Onasa, the independent news
agency in Sarajevo? A long pause follows. Ilic quotes history, but is
interrupted. Does the director of SRNA wish such an exchange? "Well", he
finally answers. "it would be interesting on purely professional
grounds, just to see how the oppressor puts things, and of course just
for information. Not to make use any of it." Another pause, then, in a
more conciliatory tone, llic says: "First both sides have to be taught
to live next to one another. Then they have to learn to respect each
other. Only later, very slowly, can we start doing things together. To
rush us can lead to an incident which would make the whole process
Anyway, being a state agency, no such thing could be agreed upon without
the approval of Pale's minister of information. It does not seem that
llic expects such approval. Half an hour later the interlocutors talk to
Minister Dragan Bozanic. It takes him two seconds to approve. A first, a
tentative media link may be established. Nonetheless, no fax lines
between the two entities are working and the three daily outlets of both
agencies will have to be delivered by hand, brought over probably with
IFOR's daily shuttle between Sarajevo and Pale. Still, at least in Pale,
the news will be read as "information only" and not be provided to the
public. At any rate, it is a beginning. -- Yvonne Badal

For information on all other OMRI publications, look at our World Wide
Web page at
Date: Wed, 21 Feb 1996 17:17:28 -0500
From: (John W. Cobb)
Subject: Diffraction limited optics (Re: iw/960126)

[Moderator's Note: If only every posting to this list could be this well
done.  Great job John - and thanks!]

I apologize for taking so long to get back on track with this thread. At
the later part of January (before my life got really busy, there was a
short discussion about the absolute minimum resolution of a spy satellite.
The moderator claimed there was no "fundamental limit" above twice the
wavelength of light used for observation while I had posted some
information about diffraction limiting and turbulent refraction. The exact
references are the 1/25 and 1/26 mailing lists. Below I will quote a part
of the discussion and amplify on it here now with reference to a few
freshman-level physics texts.

>Subject: Re: IW Mailing List iw/960125 - satellite imaging resolution
>The theoretical basis is called diffraction limited optics.  The
>resolution depends not only on the wavelength of light, but on the
>distance and the size of the collector (space antenna).  Smaller
>wavelength or larger collectors or shorter distances all lead to higher
>resolution.  The theoretical diffraction limit is almost always the
>limiting factor for satelite observations (at least to my knowledge)
>except for obscuring cloud problems.
>Another limit is turbulent atmospheric motion.  This is what causes
>stars to twinkle.  Well from a satellites view, it also causes
>streetlights to twinkle and dance about a bit.  This is the reason that
>the Hubble ST gets such good resolution.  For telescopes the collectors
>(main mirrors) are huge so the limit is actually twinkle and not
>Now both of these problems can be skirted with some very ingenious

Let me give a few introductory Physics texts as good references that are
very physically motivated.

- "Waves" by Frank S. Crawford, Jr. (3rd book in the Berkely series)
(McGraw-Hill, New York, 1968) Sec. 9.5 pp. 473-477)

-"Introduction to Physics for Scientists and Engineers" by Frederick J.
Bueche 3rd. Ed. (McGraw-Hill, New York, 1980) sec. 32.2 pp.683-685 (in
general look at ch.31-32)

I think the basic problem is that people usually have a well
internalized notion of geometrical (ray) optics because thjey can draw
and visualize lines very well.  However, one must remember that light is
a wave phenomenon and that the geometrical approximation only works on
scales larger than some limit.  In this case the limit is the
diffraction limit, NOT the wavelength.  Imagine a slit in a piece of
cardboard that is lite from behind by sunlight.  How does one analyze
what is going on here? Well, the name of the game in resolution is to
measure the slit's size.  So how should we analyze this problem to
determine what we can and cannot see.  One easy way (the easiest I know
of) to think about this is to consider that each point on the slit is
actually a small light of its own.  Since the slit is backlit by the
same radiation source, the far away sun, then each of these lights at
the slit are also phase correlated meaning that the up and down of the
electromagnetic fields in the light are coordinated between points. 
suppose the wavelength of the light is given by "lambda" Now consider a
2 dimensional geometry with the Sun at x=-infinity, y=0, the slit at x=0
and y is between -d/2 and + d/2.  Now look downfield at x=L where there
is an imaging screen and try to gues what is seen.  At y=0 the light
from the slit has just gone straight through to the right and the
signalt from all of the "little lights" at x=0 just adds up to give a
bright spot.  This is sometimes called the central peak.  Now look at
y=L * lambda/ b.  The light at the bottom of the slit will have to
travel lambda further than the light that came from the top of the slit. 
Since the light sources are phase correlated, this means that the light
from the top of the slit will cancel the light at the bottom of the
slit.  A similar cancellation occurs all along the slit [Remember from
your Trig course: sin(theta) = -sin(2*pi - theta) ?]. 

A good illustration of this is given in Beuche on p. 662. Consequently the
screen will be dark at y=  L * lambda/b. This is diffraction. Notice that
if one just drew rays one would think that this point on the screen would
be bright, but it is not. This is a fundamental manifestation of the wave
nature of light. This can be seen better if one looks at their shadow on a
bright day. there is a dark inner shadow (umbra) and a lighter (pernumbra).
In the umbra there is no direct light from the sun, but in the penumbra
some light from som parts of the sun are getting there, although most of
the light is blocked. This is because ilght is literally "bending around
your body." In this example the way to tthink about it is that your body is
now a series of small lights, but the lights are phased exaclty 180 degrees
out of phase with the sun so your "body lights" and the sun's lights are
cancelling in most of your shadow. However, when we move from directly
behind you to some point displaced a small amount, the distance these
different lights from different parts of your body have to travel change
and thus is is not completely dark. Now in actuality your body is not
covered with "little lights" 180 degrees out of phase, but a vey similar
effect is occurring. This is the molecular level description of light
reflection and/or absorption. Light wiggles the electrons which means in
turn that they are emitting a light wave 180 degrees out of phase. However,
"emiting 180 degress out of phase" is the same thing as damping - check the

The point is that light is not a ray, but that it diverges via diffraction.
The good rule to memorize is the formula for angular dispersion of a beam
in the far field case (i.e. viewing distance >> resolution). Then:

sin (theta) = lambda/b.

where: theta=divergence angle
       lambda = light wavelength
       b = limit of resolution.

Now consider an antenna in orbit of diameter D with an altitude, or
distance from the object of L.

This means: sin(theta) = D/L

This igves the final result of:

b = lambda * L / D

Assuming the idealized case of no atmospheric turbulence problem or no
clouds, etc. There are also correction factors like 1.22 for circular
apertrues, etc. so any answers I give here should be taken to indicate that
order of magnitude and to indicate scaling relationships.

So what does this imply? So suppose we have an observation sattelite at 500
Km (~310 Miles) with a collector antenna diameter of 3m (10 feet). Viewing
in visible light (wavelength: 5000 Angstroms = 5 microns)

Then the resolving power is:

b = 5E-6 * 5E+5 / 3 = 80 cm or about 3 feet.

Now these were just numbers picked out of the air. If one wants to get
better resolution, what do you do?

1) Build a bigger collector antenna
2) fly your satellite lower
3) employ image enhancement devices.
    this works by noting that the usual image convolution formula is
sin(theta)/theta type function. Actually, given a particular antenna
geometry and expected viewing pattern more specialized filters can be used.
These are the optical analogs of improving signal to noise ratios. These
can work miracles, but they will peter out fairly quickly. So you can get
small factors of improvement, but soon you will bump up against the fact
that information in the viewspace is limited and the image is rich with

Flying at say 100 miles instead of 300 will push the resolution down to 1 foot.
(second science trivia quiz of the day: What is the minimum altitude of
viewing for a spy satellite? - this is an interesting question in and of

[Moderator's Note: Goesynchronous orbit is 35,786 km and at 4,190 km we
have only a 3 hour orbital period.  As you get closer you also run into
a lot other problems like large gravity well effects, atmospheric
effects, more fuel utilization to maintain positioning and altitude, and
less time over target to take pictures and correlate signals.  You can
use eliptical orbits to get closer at perigee, but of course at apogee,
we are far further away.  ELIPSAT runs at a 426km perigee.  The Russian
MOLNYA has a perigee distance of about 548 km.  IRIDIUM and other
similar satelites orbit at about 1000km, while SPOT which is used for
observation orbits at 830km.  (see Satellite Communications Systems -
1993 - Maral and Bousquet - Wiley and Sons) The shuttle runs at about
240km and drops off satellites on its way.  At about 160km you start to
hit the atmosphere and lose momentum quickly - 160km is near the bottom
for satellites if you want them to run for a year or more - but
technically, anything over 90km is called outer space.  For a few days
you could run at 90km, but you eat satellites quickly and they are quite
expensive.  Under that, you start to run spy planes that can get shot
down and unmanned drones (which do really well and cost a lot less but
are no longer satellites and thus beyond the present topic).  Special
thanks to Steve Salgaller ( for much of this
last part.]

... Increasing the antenna size to 10m would decrease b to 4 inches,
but adding a realistic aperture correction factor of 1.22 would increase
this back to ~5 inches. Add some image enhancement and maybe you are
getting close to reading my pocket watch from space -- but then again maybe

[Reading a pocket watch gets really hard - that's 1/10 inch or less. 
Maybe 1/2 inch is possible, but the image enhacement stuf quickly
reaches deminishing returns, and even a 10m antenna for optical
frequencies is quite large.  The Hubble only has 92 inches or so of
diameter (under 3 meters).  Realistically, let's say 3 meter lense,
160km orbit, factor of 5 for image enhancement, 1.22 correction factor
or about 5E-6 * 1.6E+5 / 3 = .25m/5 *1.22 = .061m or about 2.2 inches -
a bit bigger than the size of a golf ball.]

The other thing to think about is using another wavelength. IR or microwave
is longer wavelength, so the problem there is worse. To increase resolution
one must go to shorter wavelengths, but these are shielded by the

Also note that when we get to say 1 foot for a 100 mile satellite, our
angular resolution is down to 2.0e-6 radians, or about 1/2 of a arc-second
which is again pushing technology on the problem of atmospheric turbulence,
so such sophisticated imaging systems will also need some sort of phase
conjugation system.

So now we have a satellite with a huge coolector, electronic image
enhancement and very high-speed sophisticated phase-conjugation feedback
mirror actuators (or electronic correction) No wonder so much money is
spent on black programs for satellite observation. It is not an easy game.