[Server-sky] Wildblue satellite internet in Ohio

[Keith Lofstrom]

My wife and I spent Sunday and Monday visiting friends on their
farm in rural Ohio.  They are on the electrical grid, but miles
from broadband internet.

They connect to the internet through the Wildblue internet service,
provided by ViaSat-1 .  Here is a map of the transponder coverage:
http://www.northlc.com/_images/beam_priority_map.png

As you can see, they share a single 2Gbps transponder with every
other Wildblue customer in Ohio.  I measured the ping time at
750 milliseconds - that is two 250 ms trips up and back, plus
queuing time for the network.  This could get a lot worse if
Wildblue becomes oversubscribed;  for now, they limit the 
number of customers and cap bandwidth.

During our stay, there were a few hours of torrential rain;  when
the clouds are thick, the Ka-band signal is attenuated too much
to use.  Even if the signal power was much higher, reflections
and dispersion in the clouds smear out the bits and limit bandwidth.

On Viasat-1 itself, 65 transponder feedhorns are bolted in place
to reflect off a large complex-shaped dish and focus on fixed
400km wide spots on the ground.  The satellite must maintain
very accurate position and orientation so that the transponders
stay aimed at the right customers.  If the satellite rotates by
a tenth of a degree at geosynchronous, the spots move 70km
east-west, or 100km north-south.  That is 1° in latitude or
longitude, about 30% of the spot size.

Once the satellite is in orbit, it is impossible to move
transponders in response to unforseen demand changes.  And if a
transponder fails, everyone in the associated service area loses
service permanently, or until a replacement satellite takes over.

Imagine what we can do with much more signal power, and with
rapidly steerable spot sizes as small as a township, not as
big as a state or a small country.

Keith
-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993