Re: BSTAR value

From: Ed Cannon (
Date: Tue Apr 20 2004 - 01:23:49 EDT

  • Next message: Mgr. CSc. Antonín Vítek: "Re: BSTAR value"

    >Looking closer on the BSTAR drag value of the ISS over time, 
    >I noticed that it is varying by around 10% with a period of 
    >about 20 days.
    What about where its perigee is -- at the equator versus 
    elsewhere, and is the perigee occurring in darkness or 
    daylight?  This yields four conditions:
    near equator in daylight (most drag)
    near equator in darkness
    away from equator in daylight
    away from equator in darkness (least drag)
    There's at least one other thing, the issue of the southern 
    hemisphere being "fatter" than the northern (pear-shaped 
    Earth), but I don't know if it could produce a noticeable 
    I'm neither equipped nor qualified to do the analysis, but 
    maybe the above might be involved in the 20-day variation.
    Ed Cannon - - Austin, Texas, USA
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