Re: newbie sees flare

From: Bjoern Gimle (b_gimle@algonet.se)
Date: Wed Aug 09 2000 - 04:06:56 PDT

  • Next message: Rainer Kracht: "UNK000807"

    >
    > As I'm new in this I can't know if what I say has any "added value" or
    > you have seen it a thousand times, but yesterday 8 august at 20:28 UT I
    .....
    >
    > Perhaps I saw a flare from Seasat-1. żDo you think that's possible? Is
    > there any flare-prediction program out there which predicts flares from
    > non-iridiums? I suppose these are most likely pretty dumb questions, so
    > please forgive me.
    >
    Not dumb at all - as a matter of fact I think this is a subject not
    covered sufficiently in FAQ.
    
    Bart de Pontieu did an impressive project on 'regular' flashers, using
    the subtle changes in flash periods due to synodic effects, and the
    rare occasions of phase shift when the rotation axis is nearly aligned
    with your observing direction.
    
    Rob Matson computed Superbird A, using the observations that there are
    two surfaces, nearly aligned, and the phase shift when the two flashes
    are bright, and equal in brightness, determine a sharp direction.
    
    New flashers can tumble with different periods along several axes, but
    the energy is gradually transferred to one axis, with a slow
    precession. If the object has flat surfaces, the SIDERIAL directions
    (or times + reliable elset) of exceptional flares can be used to
    determine the axis and orientation of the flashing surface(s).
    
    I have written such a model in Excel, which I intend to transform into
    an executable program, if there is sufficient interest in reporting
    these flash positions.
    
    I used it successfully on ETS-6, which appears to have three good
    surfaces (only two sufficiently observed), and possibly on some
    more satellites with too few observations.
    
    If the observations are spread over a large part of the sky, little
    more than three positions per surface are needed, with a precision
    of a few degrees.
    
    But operational satellites may have their surfaces oriented on
    command, like the Hubble (and KHs ?). Iridiums can be viewed as
    rotating once per orbit, but their solar panels are controlled
    in three different ways (one fixed) depending on Sun's "declination"
    above the orbit plane.
    
    
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