Re: Converting TLE to state vector ?

From: Tony Beresford (starman@camtech.net.au)
Date: Wed May 10 2000 - 23:57:18 PDT

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    At 15:55 10/05/00 , Ed Cannon wrote:
    >Below are a couple of online sites.  The first one 
    >purports to do the conversion in either direction, from
    >state vector to TLE or vice versa.
    >
    >"The applet below allows conversions between orbit 
    >elements and state vectors.":
    >http://alpha.fesg.tu-muenchen.de/dieter/java/TLOrbit.html
    >
    >"Transform from orbital elements to state vector"
    >http://www.geocities.com/SiliconValley/2902/ele2vec.htm
    >
    Ed, I think both of these sites just use the two-body formulation
    of the conversion. If one used them to go ftom state vector to elements,
    one will get the osculating elements, not mean elements
    like the SPG4, SPD4 element sets in TLEs. 
    This means these sites are OK for solar system calculations,
    but not of much practical use for earth satellite prediction,
    but may be useful for satellite orbit design studies.
    
    Thus there use  is not the same as converting TLE's to
    position and velocity, which i understand the query was about.
    To go from TLE's to state vector one should follow the formulae given
    in the spacetrack documentation, or copy the code from a publicly
    available source code, like TS Kelso's example programme, TRAKSTAR.
    Tony Beresford
    
    
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