Brian Mancuso <brianm@itg.net> wrote: > I recently became interested in satellites and astrodynamics > after learning about GPS. Could anybody recommend a good > introductory book on orbital mechanics? I recommend Bate, Mueller and White's "Fundamentals of Astrodynamics." It's a bit dated but for a basic text it's very good. Best of all it's a Dover paperback and it's cheap (under $10). If you don't like the book then you haven't lost much. ISBN 0-486-60061-0. To understand the book it helps to brush up on vector math. > I've heard of something called the SPG4 algorithm. My impression > is that SPG4 is more accurate then other methods. Is this true? SGP4 is the most accurate commonly available algorithm. > Do introductory texts discuss this algorithm, or would I have to > go to other sources for that? Is that algorithm difficult to > implement if you don't have a doctorate in astrodynamics? Texts don't discuss SGP4 as far as I know, but then I'm not an expert. Since the SGP4 source code is publicly available at celestrak.com you don't need a PhD. The code in the Spacetrack document can be confusing because you have to understand how the various Fortran 'drivers' interact with the SGP4 engine. Have fun with your project! ______________________________________________ Jim Varney Member, Sacramento Valley Astronomical Society www.calweb.com/~svas/index.html