USA 193 elements from observations

From: Ted Molczan (molczanseesat@rogers.com)
Date: Fri Jan 12 2007 - 22:42:57 EST

  • Next message: Greg Roberts: "Optical 12 Jan 2007"

    USA 193          5.0  2.5  0.0  3.9 v
    1 29651U 06057A   07011.04195112  .00018515  00000-0  14770-3 0    08
    2 29651  58.5008   3.5021 0008679 100.9351 259.2711 15.70574448    03
    Arc 2007 Jan 03.49 - 11.05, WRMS residuals = 0.041 deg
    
    It appears that for this orbit, SGP4 works best with arcs no longer than about 8
    days. When I try longer arcs, e.g. 10 days, points near the middle of arc that
    had earlier proven accurate, suddenly do not fit. I can force a fit by excluding
    those points, but then the elements seem slightly off - despite reasonable
    residuals
    
    This may be due to the combination of an apparently frozen orbit (argument of
    perigee seems to hang around near 90 deg) and moderately high rate decay. SGP4
    expects the argument of perigee to precess, so when it does not, something has
    to give.
    
    These are tentative conclusions, subject to verification through additional
    tracking.
    
    Ted Molczan
    
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