[time-nuts] Speaking of Costas loops (WAAS)
David J Taylor
david-taylor at blueyonder.co.uk
Thu Jul 11 15:17:22 EDT 2013
If you look at the pictures here
http://www.orbital.com/NewsInfo/Publications/Galaxy_Fact.pdf
the satellite on the right has things sticking out the bottom, in the
back corner, that are missing on the others and that look a lot like
the antennas on GPS satellites. The WAAS satellite is also 350 pounds
heavier than the other two even though the C-band payload is identical
on all three, so it seems like there could be a fair amount of extra
stuff added for WAAS support.
Dennis Ferguson
_______________________________________________
Thanks, Dennis. The antennas don't surprise me, as they would need to
produce a near-whole-disk coverage at a similar ground received power level
to the GPS satellites. That extra weight /does/ sound a lot if it were
"just" a simple transponder for earth produced information. Here in Europe
was have three EGNOS sources (all on other satellites, I believe), and I
don't believe they play any part in actual position fixing, but they do
provide extra information enabling the fix to be refined.
Cheers,
David
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Email: david-taylor at blueyonder.co.uk
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