[PLUG-TALK] DBS eclipse

[Russell Senior]

>>>>> "Russell" == Russell Senior <russell at personaltelco.net> writes:

>>>>> "Denis" == Denis Heidtmann <denis.heidtmann at gmail.com> writes:
Denis> I wonder.  In the absence of scattering due to atmosphere, how
Denis> can there be much light in the direction of the sun?  In the
Denis> direction of the earth is a different story, but I would doubt
Denis> the collectors are pointing toward the earth.  I expect the
Denis> question is how long would a satellite be in full shadow in the
Denis> case when it is in the path of a moon shadow.  -Denis

Russell> According to my calculations, a geosynchronous satellite is
Russell> (around the time of the equinox) regularly eclipsed by the
Russell> earth for durations of about 30 minutes (using physical
Russell> parameters from wikipedia, counting only the umbral period,
Russell> ignoring the penumbral periods).  So, they must have
Russell> batteries sufficient to survive outages at least that long.

D'oh!  I was working with just the half-angle.  Doubling my
approximation makes it about 66 minutes, pretty close to Keith's
number and also the one cited here:

  http://www.intelsat.com/resources/tech-talk/eclipse-seasons.asp


-- 
Russell Senior, President
russell at personaltelco.net