Re: BSTAR value

From: Moritz Heger (
Date: Tue Apr 20 2004 - 10:59:26 EDT

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    An amplitude of +/-10% due to the moon in the drag value is unlikely for
    LEO. More likely it would be noticed as a change in node orientation.
    The change is sinus-like, so I do not believe it is the result of
    orientation changes of the ISS between two modes of operation.
    BSTAR includes the atmosphere density at the mean height of a satellite at
    the epoch of the TLE. To be more exactly, it contains a factor that
    resembles the relation of the real atmospheric density at the epoch
    (measured through the acceleration of the satellite) and the fourth degree
    polynom used to model the atmospheric density in SGP4 (see my paper So atmosphere density has an
    influence on the BSTAR value.
    Most likely it seems to me now that the change of the perigee being in
    sunlight, the line of nodes lying in line or perpendicular to the sun, or
    similar effects have an influence on BSTAR, which could explain the
    variation. This is where I will look further.
    Thank you to all who made suggestions!
        Moritz Heger
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