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Communications thru P5-A



It might be pertinent to the discussion to see what NASA used going to Mars
in 1965.  I checked my copy of NASA SP-130  (p. 11) "A Review of the Mariner
IV Results".  NASA used a 10 watt transmitter on board the spacecraft
"broadcasting continuously at 2300 megacycles".  Antenna was a "high gain
elliptical 4 foot antenna" (p.4).  Spacecraft was 3 axis stabilized with its
antenna pointed towards earth.

To establish a reliable data transfer the data rate was initially set at 33
1/2 bits per second, but before arriving at Mars the rate was slowed to 8
1/3 bits per second.  (BITS...not Kilobits or Megabits!)  At the receive
end, LARGE (!) antennas were used.

I'm not an engineer, but I'm having trouble seeing how the P5 thing is
really going to work.  If anyone asked, I'd rather see the resources go
toward building another "AO-13", a "Fuji" in just a little higher orbit, or
a truly operational "AO-40" with the correct orbit and working transponders.
One of those would get me excited!

Grant Zehr AA9LC

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