# User talk:Owlmaster08

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## Geosynchronous orbit

Greetings Owlmaster and welcome to Wikipedia!

Can you put the relevant portion of the reference you added to this article onto the Talk page? The problem I can see here is that a single "altitude" figure would only be correct for a circular orbit (such as a Geostationary orbit), and an elliptical orbit could be geosynchronous but have a continuously varying altitude. I'm not an expert on this and I haven't tried the math, so I'd be interested to see your derivation.

Happy editing :) Franamax (talk) 08:38, 6 February 2008 (UTC)

Thanks. I changed the text to "average altitude". I'd thought about the semi-major thing and it seemed a little strange - how could the elliptical orbit fit inside the circular orbit and still have the same period? - so I'm glad you've clarified. On a side note, any chance you could put the mathematical derivation of the orbit into the article? Along the lines of what is in Geostationary orbit, just to enhance this one for the technically minded. Franamax (talk) 09:07, 6 February 2008 (UTC)
I added a formula. I'm not quite sure what you wanted. If you clarify I could add more. --Owlmaster08 (talk) 09:32, 6 February 2008 (UTC)
The formula you added is a good one. Add whatever else you think is interesting, if someone doesn't like it, they'll just take it out again.
I'm now questioning my change to "average altitude" though. If I understand that formula correctly, then for a zero-eccentricity orbit, wouldn't 35,780 km be the maximum altitude? If that's true, then what's the right way to qualify "altitude"? "Maximum altitude" won't work in the case where eccentricity is non-zero. So then do we come back to using "semi-major axis"? Franamax (talk) 19:35, 6 February 2008 (UTC)
The a in the formula is semi-major axis, not altitude. Altitude is not necessarily directly related to the semi-major axis. Altitude is simply the distance from the satellite to the surface of the Earth. Altitude plus the radius of the Earth (6,378 km) is equal to the radius vector of the satellite. As a satellite orbits the altitude will change for non circular orbits, as well as the magnitude of the r vector. The semi-major axis does not change as the satellite orbits. It is an orbital element and is not based upon the true anomaly (current position) of the satellite. If the orbit is really eccentric, then giving an average altitude is usually pretty worthless, for example, Molniya satellites. If you want to use the semi-major axis instead of the altitude, which is actually the more common value, then you would use the number 42,158 km, which is the altitude plus the radius of the Earth. Altitudes are nice because they are practical in the real world. You can find the distance from yourself (on the surface of the Earth), to a satellite pretty easily. The bad thing about altitudes is that most of the equations use the semi-major axis or radius vector instead. Physics operates based upon a radius from the center of the Earth, so you have to add this 6,378 km into the altitude. --Owlmaster08 (talk) 21:38, 6 February 2008 (UTC)
Forgot this: I moved your post to Talk:Geosynchronous orbit down to the bottom, usual practice is to add the newest to the bottom on talk pages. Cheers! Franamax (talk) 09:09, 6 February 2008 (UTC)
Yeah, I'm new at wikipedia (obviously). I was just doing some homework and caught the error about the semi-major axis. Thanks for helping me out w/ proper wiki etiquette. --Owlmaster08 (talk) 09:14, 6 February 2008 (UTC)
Well you've made your first edits as a registered user now, you might just get hooked like the rest of us :) There are lots of projects you can join, lots of people willing to help you and lots of things to improve. Have fun! Franamax (talk) 09:21, 6 February 2008 (UTC)