[geocentrism] Geosynchronous/Geostationary satellites
- From: "Neil Robertson" <nroberts@xxxxxxxxxxxxxxxxxx>
- To: <geocentrism@xxxxxxxxxxxxx>
- Date: Sat, 23 Oct 2004 16:56:48 +1000
Hi Gary,
I noticed that you were still having troubles with the details of these
satelites and although others have provided some details about the matter
there are aspects of the orbits that can more fully explain their varied
behaviour and perhaps make the whole thing clearer to you.
The terms geostationary and geosynchronous are usually used interchangeably
to describe certain satellites and loosely this is true however the way I
see it that is not strictly true. A geostationary satellite is certainly
geosynchronous however a geosynchronous satellite is not necessarily
geostationary. Some examples would be the best way to get the info across:-
If a satellite orbits the earth in 24 hours in sync with the rotation of the
earth, orbits over the equator and with no inclination, and its orbit is
circular, it will appear to a person on the earths surface to remain fixed
in the sky. The classic geostationary satellite.
Now take a satellite with the same orbital parameters except that its orbit
is inclined at some angle to the earths equator. During its 24 hour orbit it
will sometimes be above the equator and at times below the equator. To a
person on earth the satellite will appear to move up and down vertically in
the sky over a 24 hour period. The larger the orbits inclination the larger
that up and down motion will be.
Now take a satellite with the same orbital parameters as the original
satellite but this time make its orbit elliptical instead of circular. The
satellite will still orbit the earth in 24 hours but due to the elliptical
nature of the orbit its speed will vary over the orbital period. Sometimes
it will be orbiting faster than the earths rotational speed and sometimes
slower. These speeds will of course even out and the satellite will still
complete the orbit in 24 hours. To a person on the earths surface the
satellite will appear to move horizontally back and forth in the sky over 24
hours.
Now take the original satellite but this time make its orbit inclined like
the second satellite and make its orbit elliptical like the third example.
In this case a person on the earths surface will see the satellite move back
and forth as well as up and down in a 24 hour period. The satellite will
appear in fact to transcribe a figure 8 in the sky. The larger the
inclination and elliptical nature of the satellites orbit the larger the
figure 8.
Obviously if the elliptical nature and inclination of a satellites orbit is
slight there will be a corresponding slight motion of the satellite in the
sky and to all intents and purposes it will be geostationary. That is why as
I understand it that the geostationary and geosynchronous terms are used
interchangeably.
I hope my examples have cleared the matter up for you.
Neil
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