Re: Fobos-Grunt: analysis of orbit evolution

From: Bill Bard (
Date: Tue Nov 22 2011 - 14:45:55 UTC

  • Next message: "Re: Fobos-Grunt: analysis of orbit evolution"

    How about some aerodynamic lifting during perigee as a result of a fixed orientation then?
    On Nov 22, 2011, at 9:41 AM, "George Roberts" <> 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
    > _______________________________________________
    > Seesat-l mailing list
    Seesat-l mailing list

    This archive was generated by hypermail 2b29 : Tue Nov 22 2011 - 14:46:54 UTC