Peter Guelzow, DB2OS, reports that Victor Kudielka, OE1VKW did an analysis some weeks ago and was the first to discover some odd changes in the Mean Motion of AO-40.
It appears that the eccentricity may have changed, but it is also influenced by other effects and can not be used alone to evaluate possible changes in AO-40 s orbit. Viktor has some expanded diagrams of mean motion and eccentricity, as well as for the heights of peri- and apogee and their velocities on his home page:
Viktor noted, I am unable to judge which points are just imprecise measurements and what are the influences of data smoothing or other manipulations. The only big enough effect is the change in mean motion Peter continues, If you look carefully on the data, you will see that the orbit change already happened *before* the sudden battery event. We can only speculate, that it is the battery. It could be indeed also some remaining fuel? Peter added. The thrust phase is also much longer than the battery event, not only a few hours or days. Perhaps,could be smoothing/manipulation of the NORAD data too. There is room for a lot of speculation.
Peter concluded, Assuming the S/C mass to be 400kg, than this change is due to an impulse of 40 kg m/s or equal to 5 minutes of hot Arcjet firing.I have no idea if the battery is capable to do this. Indeed, if it is shortened it will get glowing hot and vent everything.
[ANS thanks Peter, DB2OS for the above information]