[time-nuts] Sun Outage

Brooke Clarke brooke at pacific.net
Thu Oct 9 18:23:27 EDT 2014

Hi Bob:

The geostationary sats are in a 24 hour orbit.  The orbit is also in the plane of the Earth's equator.  Because of these 
two facts they appear stationary.
Also because of that twice a year near equinox the Sun will be directly behind the sat and the C/N goes to pot so no signal.

I have a mirror with masking tape reducing it's size to about 5/8" on a window sill that gets light at equinox and all 
through winter.  I've marked the ceiling so I can just look up to see if the Sun is anywhere near the satellite. 
http://www.prc68.com/I/Sundial.shtml#SSB  I can also tell when it's noon local time from this ceiling sundial.

The orbit time for GPS sats is 12.0 sidereal hours and the plane of their orbits is angled 55 degrees from the equator 
so the Sun at most can be behind only one sat and then not for long, so you will not see any solar blockage, unless you 
are in a single satellite time only mode of operation and even they it would be a science experiment to detect the 
effect of the Sun.

Have Fun,

Brooke Clarke

Bob Stewart wrote:
> Two days this week, there was a 3 or 4 minute outage on DirecTV as the sun aligned with the satellite and my dish.  So I was wondering what kind of effect this has on the GPS system and especially timing receivers.
> Bob - AE6RV
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