Re: Fobos-Grunt: analysis of orbit evolution

From: Bill Bard (wbard@wb-web.org)
Date: Tue Nov 22 2011 - 14:45:55 UTC

  • Next message: rkresken@t-online.de: "Re: Fobos-Grunt: analysis of orbit evolution"

    How about some aerodynamic lifting during perigee as a result of a fixed orientation then?
    
    Bill
    
    On Nov 22, 2011, at 9:41 AM, "George Roberts" <gr@gr5.org> wrote:
    
    >> Is there a way to calculate kinetic energy of Phobos-Grunt vs time to see 
    >> if energy has
    >> been added to the system (thrusters, leak) or if it's just been 
    >> redistributed (circularization)?
    > 
    > The middle part of Ted's graph shows that the orbit is decaying overall.  In 
    > other words the orbit has less potential and less overall energy (but more 
    > kinetic - this is the nature of lower orbits).
    > 
    > However, even though it has decreasing energy mostly due to drag, it takes a 
    > significant amount of energy to change PG's orbit in the way it seems to 
    > have changed.  Energy other than drag.  More energy than expected from 
    > "solar wind".  This suggests thrusters or a leak.  The best way to explain 
    > the anomaly to me is that PG is maintaining an orientation such that it is 
    > always pointed to the same star as it orbits the earth and it is constantly 
    > thrusting towards that star.  This would explain the increase of one half of 
    > the orbit and excessive decrease of the other half.
    > 
    > - George Roberts
    > http://gr5.org
    > 
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