Re: OT: Was this the Project Kevin Fetter Referred to?

From: Brian Weeden (
Date: Fri Dec 07 2012 - 15:42:28 UTC

  • Next message: Gavin Eadie: "Re: OT: Was this the Project Kevin Fetter Referred to?"

    A purist might argue that there is no strict cutoff of where the atmosphere ends and there are likely a few atoms of various gases at GEO and therefore there is some drag at GEO. But it has zero meaningful impact on GEO objects.
    There are significant perturbations affecting GEO objects, including gravitational pull of the Sun and Moon and solar radiation pressure.
    An important difference is that for the most part these perturbations do not remove significant energy from the orbit and thus don't lead to it eventually re-entering.  Instead they change and shape the orbit (eg, gravitational pull of the Moon increases inclination of GEO objects).
    I don't think these forces are what cause Molniya-type objects to decay.  They decay because they have a perigee that is low enough to experience drag effects and that removes energy from the orbit and causes it to eventually re-enter.
    Sent from my iPhone
    On Dec 7, 2012, at 10:20, Björn Gimle <> wrote:
    > And what about the much larger gravitational perturbations from Moon,Sun,
    > planets - and asteroids passing by/lingering ?
    > Most of them are long-periodic, but for the Molniya-type orbits they often
    > force the perigee down so the drag increases (too much).
    > /Björn
    > 2012/12/7 Jonathan W <>
    >> The author of the article below posits that geostationary satellites will
    >> remain in their orbits indefinitely - until they are removed, or the Sun
    >> becomes a red giant some 5 billion years from now, since there is
    >> absolutely no atmospheric drag at the altitude of 22,300 miles.  But is
    >> that really true?  Is there ABSOLUTELY *NO* atmospheric drag at that
    >> altitude?  Even if there is barely measurable drag when measured over a
    >> period of a few decades, the orbits wouldn't actually be permanent, when
    >> considering timescales in the billions of years.
    >> Jonathan
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