Observations may show that Phobos-Grunt keeps orientation to Sun

From: satrack@libero.it
Date: Sat Dec 10 2011 - 19:23:16 UTC

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    Yesterday I received information (from a non official source) on the attitude 
    control suggesting
    that PhG might be designed to control only one axis in Earth orbit. I don't 
    know 
    if this is true so please take these results with caution: 
    
    One-axis attitude control could explain the changes in brightness that have 
    been observed 
    because the satellite is free of "tumbling" even if it is pointing towards the 
    Sun, therefore, 
    I decided to analyze accurately the reported flares. 
    
    I assumed that the attitude control is still operative and PhG maintains its 
    longitudinal axis 
    pointed towards the Sun but also that it can rotate along this axis. I also 
    supposed that one 
    of the solar panels has not deployed completely but it is stuck in a mid 
    position from which 
    it can cast flares to Earth. I have studied all the reported flares and for 
    each of them I oriented 
    PhG towards the Sun and I calculated the surface angle that satisfies the 
    observation. 
    
    The results seem very interesting: five of nine recently reported flares would 
    be generated by 
    the same surface, which is tilted of 55 +- 1 degree from the satellite axis 
    (satellite-Sun direction). 
    If these assumptions and calculations are correct, this might show that PhG is 
    still keeping itself 
    oriented towards the Sun (at least sometimes) with errors of about +- 1 degree 
    and that one of the 
    solar panels is stuck at 55 degrees from its expected position. Unfortunately 
    more flare data 
    should be used to validate these results. 
    
    On my web page I reported a table with the values and data that I used to 
    compute these angles. 
    I invite all of you to verify them.
    
    www.satflare.com/track.php?q=phobos
    
    Best Regards,
    Simone
    
    
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