SatEvo predicts now reentry on the last week of the year, about two weeks earlier than predictions with the previous TLEs. Updated figures: http://www.satflare.com/track.php?q=phobos Regards, Simone >----Messaggio originale---- >Da: paul.salanitri@gmail.com >Data: 30-nov-2011 6.02 >A: "Ted Molczan"<ssl3molcz@rogers.com> >Cc: "<seesat-l@satobs.org>"<seesat-l@satobs.org> >Ogg: Re: Fobos-Grunt: no manoeuvring evident in TLEs after 2011 Nov 20 UTC > >There has been a small anomalous change, not the orbit increase desired, but something has happened. We'll stay tuned.... > >Paul S > > > >On 29/11/2011, at 23:07, "Ted Molczan" <ssl3molcz@rogers.com> wrote: > >> Manoeuvring was last clearly evident in the USSTRATCOM TLE of epoch 11324.94169617. It appeared to have ended by the >> epoch 11325.19110916 TLE, and appeared not to have resumed as of the epoch 11333.12745729 TLE (2011 Nov 29 03:04 UTC). >> >> Orbit evolution for the latest 5-day period (11328.24537235 - 11333.12745729): >> >> http://satobs.org/seesat_ref/phsrm/Fobos-Grunt_orbit_evolution_v9.pdf >> >> Assuming solar activity remains near the low end of normal, STOAG propagates the orbit to decay on 2012 Jan 16. >> Uncertainty +/- 10 days, based on the rule of thumb of 20% of time remaining until predicted decay. >> >> I have been watching some recent small variations between the TLEs and theory, that are too small for me to attribute to >> manoeuvring, but perhaps worth noting. For example, the unusually high rate of precession of the argument of perigee was >> one of the manifestations of the manoeuvres. The theoretical rate, per the SGP4 model was about 4.05 deg/d, but during >> the manoeuvres it averaged ~5.21 deg/d, as shown on the following plot: >> >> http://satobs.org/seesat_ref/phsrm/Fobos-Grunt_precession_arg_of_perigee_v1. pdf >> >> The red triangles are derived from the TLEs, calculated as the mean rate of precession between pairs of TLEs about 2 >> days apart. Shorter intervals yielded similar, but more scattered (noisy) results. This clear evidence of manoeuvres >> ended late on Nov 20 or early Nov 21 UTC, and was fully reflected in the 2- day average by Nov 23 UTC. For the next few >> days, the 2-day mean rate of precession was nearly identical to the theoretical rate, but then it began to rise on Nov >> 26, reached a peak of 4.39 deg/d the following decay, then declined, and returned to nearly the theoretical rate as of >> the latest TLE. The effect appears to have been real, but I suspect it was more likely due to a gradual correction of >> the elements than a manoeuvre. During this period, the rate of orbital decay decreased slightly, and the rate of >> decrease of the perigee distance was slightly less than predicted by STOAG for the same mean rate of decay, but these >> effects appear to be normal variations. >> >> Ted Molczan >> >> >> _______________________________________________ >> Seesat-l mailing list >> http://mailman.satobs.org/mailman/listinfo/seesat-l >_______________________________________________ >Seesat-l mailing list >http://mailman.satobs.org/mailman/listinfo/seesat-l > _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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