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    Re: FOGs
    From: George Huxtable
    Date: 2008 Jan 30, 23:34 -0000

    Lu Abel wrote-
    | I am tremendously enjoying this discussion.  And thanks, Frank, for the
    | pointer to NASA's Gravity B experiment.   Its technology is truly
    | mind-boggling.
    George adds-
    Me too. I hope the thread will continue, and perhaps expand.
    However, the link to the Gravity B experiment came from Paul Hirose, not
    Frank. And it leads to a further question-
    That article, http://einstein.stanford.edu/sitemap.html  , was written in
    the future tense, describing a proposed experiment which was intended to
    launch in 2003, and last for two years. So by now it should have
    been-and-gone. Can anyone tell us whether it actually happened, an if so,
    what the results were?
    Just as Lu describes, there's a combination of technologues in that
    experiment that is indeed mind-boggling. The bit that tickles me best is the
    notion of floating the spinning ball within the spherical cavity, by
    accelerating the spacecraft about, with puffs of gas, to keep it
    centralised. That certainly puts the egg-and-spoon race in the shade.
    Knowing little about the optical  versions of these gyros, I had asked- "...
    isn't it the case that there is effectively zero long-term drift in the
    orientation sensing of these devices; quite different from the behaviour of
    their mechanical predecessors?"
    And Frank responded-
    "No, they drift for many little reasons."
    I would like to know a bit more than that, if anyone can tell me. What,
    roughly is the current limit on the long-term drift of a ring laser gyro,
    suitably "dithered"? And how does it differ from that of a fibre-optic gyro?
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    To post to this group, send email to NavList@fer3.com
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