Re: Net sources of astrodynamics

From: Tony Beresford (
Date: Wed May 17 2000 - 22:12:56 PDT

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    At 15:42 17/05/00 , wrote:
    >Are such formulas like the above on the web somewhere?
    The drag equation is simple fluid dynamics Jonathon,
    but you will find it and other material in BOOKS
    on Astrodynamics. The cheapest book i know on
    the matter is Fundamentals of Astrodynamics
    by Bate,Mueller and White. The nicest is P.R. Escobal's
    Methods of Astrodynamics. 
    >Also, can anyone refer me to some reference where I can make satellite
    >predictions with nothing more than paper, a pencil, and a TLE data set
    >(no computer being used)?
    This is possible but extremely tedious, as it amounts to turning
    yourself into a computer. With a scientific calculator (for the Trig
    functions) you could probably do 1 or 2 predictions per hour less if
    you used a book of mathematical tables. The early chapters of any book on
    celestial mechanics or astrodynamics will show you what steps are required
    to go from orbital elements to satellite position. Escobal even discusses
    an algorithm to decide satellite rise & Set. You might find the discussion
    given by TS Kelso, on his website archive ( of articles
    he has written for magazines about using TLEs. 
    The graphical methods of predicting satellites, illustrated in King-hele's
    book on observing Earth satellites, and used in the late 50s and early 60s
    by those of use observing then, assumes that lists of equatorial
    crossing times or orbit apex times were available. 
    These had to be calculated with a computer at a central location.
    The original TLEs were a minor part of NORAD output,
    the rest of the information being lists of equatorial crossing times
    and longitudes, and a table giving offsets in time and longitude
    for other latitudes. In my own case, I looked for suitable positions
    by eye, calculated longitude, latitude by hand, solved the
    spherical triangle by hand using mathematical tables to give
    distance and azimuth, and used a graphical device to convert
    great circle distance & height to elevation angle. This process
    took me 20 minutes pre prediction. A computer is so much quicker
    Tony Beresford
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