Ted Molczan wrote: > The period of variation of brightness of 99028C / 25746 has decreased > steadily > ever since it was launched, from about 150 s in 1999 June, to about 89 s > in 2005 > Aug: > > http://satobs.org/seesat_ref/99028C_period_of_var/99028C_period_of_var.jpg > > This plot is based largely on PPAS (Photometric Periods of Artificial > Satellites) reports, excluding observations that were obviously indicative > guesses. > > Its decreasing optical period tends to support the consensus that the > object is > not the payload (99028A / 25744), and most likely debris or a decoy. The > strongest evidence is its low area to mass ratio, as evidenced by the > significant SRP (solar radiation pressure) orbit perturbation discovered > in > 2002. > > That the object rotates at all is further evidence that it is not a > high-resolution imager, since those normally are three-axis stabilized. > Even if > rotation was desired, it would be maintained within a fairly narrow range, > unlike the dramatic change we have observed. > > My guess is that 99028C's slow spin-up may be due to SRP. A similar > example may > be Midas 6 (63014A / 574), which spun-up for more than 30 years, as shown > Fig. > 12 on this page: > > http://www.satobs.org/tumble/expresfpm.html > > It will be interesting to see how 99028C's period of variation continues > to > evolve. This might be a reason to make it a more important PPAS object. So a priority 2 object from now on. Also time to change its ID from 1999-028A to 1999-028C (in PROGRAM.ROB). Thanks for your alert (or what do you call such a message?) (PPAS or BWGS) Bram ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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