[amsat-bb] Re: Mystery Spacecraft Identified.

Joe nss at mwt.net
Fri Jun 14 06:04:27 PDT 2013

Thanks Steve.

Yes this was a learning thing for me.  I knew all about the 
Geosynchronous I thought. But i guess my thinking was actually 
Geostationary. Even after 30+ years playing with these birds I never 
thought of a Geo sync that moved he he he.

The Original Rolling Ball Clock
Idle Tyme
On 6/13/2013 8:26 PM, Stephen Melachrinos wrote:
> Joe -
> You used two different terms here, and there's a distinction that 
> helps with the explanation.
> A "geosynchronous" satellite is one whose orbital period is one 
> sidereal day. This makes its orbit track (on the earth's surface) 
> repeat day after day. A "geostationary" satellite is a special case of 
> geosynchronous that is truly stationary with respect to the earth. 
> This means that not only is its orbital period one sidereal day, but 
> its inclination and eccentricity are zero. (This requires regular 
> orbit adjustments, typically referred to as north-south stationkeeping 
> and east-west stationkeeping.) From your description ("a good amount 
> of vertical drift"), Terrestar is geosynchronous but not geostationary.
> Unfortunately it's not always obvious which is meant when we describe 
> a satellite with the shorthand term "Geo." Furthermore, some 
> satellites start out as geostationary and end up becoming simply 
> geosynchronous when the owner decides to (or has to) skip the 
> stationkeeping maneuvers (e.g., to save fuel).
> Steve
> W3HF
> On 06/13/13, Joe<nss at mwt.net> wrote:
> <snip> It's a Geosynchronous communications
> satellite.
> <snip>And thats where we also got messed up, the Geo bird is more or less
> Stationary in the sky. It has a pretty good amount of vertical drift
> tho. it's orbital period makes it Geo Stationary. but it has a pretty
> high inclination so it drifts up and down in declination some.

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