RE: Total confusion about SZ-4 elsets?

From: Ted Molczan (molczan@rogers.com)
Date: Tue Dec 31 2002 - 12:18:58 EST

  • Next message: Alan Pickup: "Re: Total confusion about SZ-4 elsets?"

    Responding to Sven Grahn's comment on the possibility:
    
    "that we do not have any element sets for the real Shenzhou-4 
    spacecraft in its initial orbit (before the manoeuvre)! Am I right?"
    
    Looking at the ground track, it appears that there could not have been
    any U.S. radar tracking of the objects prior to the payload's manoeuvre
    to the 340 km circular orbit. 
    
    In my earlier message, I speculated that payload and rocket IDs had 
    been incorrect in the initial elements:
    
    1 27630U 02061A   02363.99130504 -.00002620  82868-5 -20368-5 0    19
    2 27630  42.4085 338.1747 0100490 131.4080 229.5479 16.03477566    55
    
    1 27631U 02061B   02363.99063452 -.00002648  83756-5 -15794-5 0    11
    2 27631  42.4166 338.1817 0096007 122.0244 238.9998 16.07463202    45
    
    I now believe that both were of the rocket, and that the first one is
    more accurate than the other. It shows the correct transfer orbit:
    207 x 341 km. Except for the rate of decay, it agrees very closely with 
    this later elset of the rocket, which was miss-tagged as the payload:
    
    1 27630U 02061A   02364.38854632  .00779380  82659-5  57683-3 0    50
    2 27630  42.4073 335.6309 0099754 134.9968   2.7393 16.04294545   119
    
    The circularization burn occurred near apogee on 2002 Dec 29 at about
    23:35 UTC. This is the first fully reliable elset I have after the burn,
    miss-tagged as a third piece:
    
    1 27634U 02061C   02364.52326389  .00036453  00000-0  20245-3 0    37
    2 27634  42.4084 334.8952 0004789 166.1818 340.4082 15.78784343    44
    
    The first two elsets (above) have epochs about 12 min after the burn,
    which correspond to their ascending nodes, near 117 deg W. I suspect that
    the first radar observations were made sometime over the next 15 min,
    as the objects approached and passed over the Gulf of Mexico and Central
    Florida, the payload about 20 s behind the rocket.
    
    It is odd that they managed to generate a reasonable elset for the rocket
    (though miss-tagged), but were way off on the payload, ending up with 
    elements very similar to that of the rocket. Whatever the cause, that 
    probably set the stage for the three grossly incorrect rocket elsets
    that followed over the next several hours.
    
    So, if the payload's insertion orbit is required, the best available
    elset is this one of the rocket, miss-tagged as the payload:
    
    1 27630U 02061A   02364.38854632  .00779380  82659-5  57683-3 0    50
    2 27630  42.4073 335.6309 0099754 134.9968   2.7393 16.04294545   119
    
    Ted Molczan
    
    
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