Re: Phobos-Grunt Orientation and Flare Prediction

From: Paul Salanitri (
Date: Mon Dec 19 2011 - 22:06:33 UTC

  • Next message: Tony Beresford: "resent Satobs December 19 @ 8597"

    Drag profile perhaps turning?  We'll see in the next
    few days.
    If it swings back to about B* 0.00018 : re-entry will be about 8 January
    If it remains at its current value about 0.00014 : re-entry will be about
    15 January
    Paul S
    On Saturday, December 17, 2011, Paul Salanitri <>
    > 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:
    > Also, here is a visibility guide for the next 24hrs and the solar flux graph
    > Paul Salanitri
    > On 17/12/2011, at 6:59, "" <> wrote:
    >> These days I have been investigating the orientation of Phobos-Grunt
    >> 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
    >> 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
    >> any drift.
    >> It is reasonable to think that Phobos-Grunt actively orient its axis
    >> 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
    >> angles,
    >> several 3D representations and a crossed eye stereographic picture of
    >> Grunt
    >> orientation during an observed flare.
    >> Best Regards,
    >> Simone
    >> _______________________________________________
    >> Seesat-l mailing list
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