Phobos-Grunt Orientation and Flare Prediction

From: Paul Salanitri (paul.salanitri@gmail.com)
Date: Fri Dec 16 2011 - 23:59:23 UTC

  • Next message: Brad Young: "BY C 121711"

    Hi Simone,
    
    Some further evidence of orientation is looming with the recent reducing
    drag figures (from the TLEs) and the orbital plane alignment approaching
    and now receding from almost perpendicular (beta angle up to about -74 deg).
    
    If the spacecraft is sun oriented along its longitudinal axis (to
    illuminate the solar panels) then the panels themselves will be oriented
    edge on to the atmospheric trajectory and possibly even 'edge on side on'
    both of which would be less than the 'random/average/arbitrary'
    presentation to the stream. This appears to be happening, although this
    will need to be separated from the reduced drag due to reduced solar flux.
    This should become apparent over the next several days as the spacecraft
    increases its beta angle away from perpendicular and presents more solar
    panel to the stream. If it eventually stops reducing drag and starts
    increasing, we will have a good clue to its orientation and stability (i.e.
    it is sun pointing AND we may even get a clue to its orientation around the
    longitudinal axis).
    
    Here is a B* drag curve from recent radar data: http://twitpic.com/7u0d5g
    
    Also, here is a visibility guide for the next 24hrs
    http://twitpic.com/7u6fd2 and the solar flux graph http://twitpic.com/7u6fd2
    
    Paul Salanitri
    
    
    On 17/12/2011, at 6:59, "satrack@libero.it" <satrack@libero.it> wrote:
    
    > These days I have been investigating the orientation of Phobos-Grunt
    analyzing
    > different possibilities for all the reported flares, however, the only
    > reasonable
    > explanation that correlates the reported times is that Phobos-Grunt keeps
    the
    > longitudinal axis actively oriented towards the Sun while it rotates along
    > this axis.
    >
    > I analyzed 12 flares (or marked brightness maxima). Excluding 2 of them,
    > which
    > give completely uncorrelated angles, the remaining 10 flares are
    generated by
    > 2 surfaces.
    >
    > The first surface generated 5 observed flares: all of them lead to a tilt
    > (angle between
    > the satellite axis and the surface normal) of 55 +- 1 degrees.
    >
    > The second surface generated the other 5 flares: all of them lead to a
    tilt of
    > 65 +- 2 degrees.
    >
    > Alexander Repnoj on December 7 observed both the surfaces during the same
    > pass,
    > reporting 2 of these 10 flares just 1 minute apart each other.
    >
    > I extracted also the flare data from Kevinís video and it perfectly leads
    to
    > the second
    > surface giving a tilt of 64.2 degrees.
    >
    > Despite observations cover a period of about 8 days, the angles do not
    show
    > any drift.
    > It is reasonable to think that Phobos-Grunt actively orient its axis
    direction
    > towards the Sun.
    >
    > These days new flares should be visible from these two surfaces so new
    > observations
    > could definitely show whether this model is correct or not.
    >
    > I can provide predictions, so, if you are willing to help with morning
    > observations, just
    > send me your coordinates.
    >
    > More details can be found at my web page. I included all the analyzed
    flare
    > angles,
    > several 3D representations and a crossed eye stereographic picture of
    Phobos-
    > Grunt
    > orientation during an observed flare.
    >
    > http://www.satflare.com/track.php?q=phobos
    >
    > Best Regards,
    > Simone
    >
    > _______________________________________________
    > Seesat-l mailing list
    > http://mailman.satobs.org/mailman/listinfo/seesat-l
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