Re: [amsat-bb] AO40 velocity

[Margaret Leber <maggie@xxxxxxxxxxxx>]

Bob V Johnson wrote:

> I was asked how fast "those things" go.  I took a guess and probably was
> fairly correct.  That got me thinking how fast really is it.  Given the
> MA, at that part of the orbit is there a formula that would yield the
> velocity at that point?  

Oh, dear.

Whle W4SM and N4HY have given good answers, am I being my usual pedantic 
  self to point out that "what is the velocity of AO-40" is not a very 
meaningful question without selecting a frame of reference?

Stacy chose an LEO in circular orbit at AO-40's perigee altitude to 
generate an answer, and I'm thinking that vis-viva gives an answer 
relative to the center-of-mass of the primary (which in this case is the 
Earth), and that's what one would use in dealing with stuff like "escape 
velocity".

Robert's probably right that this is closest to what your friend  was 
asking, even though nobody is actually at the center of mass of the 
Earth. Reminds me of George Carlin mocking broadcast weather reports 
that give the temperature at the airport because "I don't know *anybody* 
who lives at the airport, man". :-)

Of course, neither of those answers is the "range rate" that you'd use 
to calculate Doppler...

  73 de Maggie K3XS

-- 
-----/___.   _)   Margaret Stephanie Leber    / "The art of progress  /
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