RE: STS 107 debris

From: Ted Molczan (molczan@rogers.com)
Date: Thu Apr 10 2003 - 11:50:29 EDT

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    Edward S Light asked:
    
    > Given the newly-released TLE for object 27713 = 03-003B, "STS 
    > 107 debris", and the actual STS-107 TLEs, could anyone, e.g. 
    > using COLA and/or its kin, determine when the two objects 
    > were coincident?
    
    Short answer: Not in this case. Long answer:
    
    Based on comments from CAIB (Columbia Accident Investigation Board) members,
    the object was detected on 2003 Jan 17 by Eglin AFB, on the pass that
    culminated at 15:44 UTC. The same sources believe that the object came loose
    about an hour earlier, during one of the few attitude manoeuvres made by
    Columbia that day.
    
    Here is a Columbia elset appropriate for this analysis:
    
    1 27647U 03003A   03017.58333333  .00054755  65718-5  11934-3 0    95
    2 27647  39.0149 223.0048 0012360 355.7135 358.5111 15.97626761   143
    
    The one that debris elset issued so far:
    
    1 27713U 03003B   03018.89361124  .04158089  28060-1  63330-2 0    15
    2 27713  39.0177 214.2209 0013015   7.8234 352.0943 16.06862990    17
    
    suggests that the separation occurred a little after 17:30 UTC - nearly 2
    hours after the first detection by Eglin, and about 3 hours after it is
    thought to have separated. I attribute this difference to the uncertainty in
    the rate of decay and/or limitations of the SGP4 model.
    
    The rate of decay was very high, and the epoch of the debris elset is more
    than one day after it separated, so even small uncertainties in the rate of
    decay will have a large effect on propagated position. 
    
    Increasing the B* term by less than 2 percent to 0.64500e-2, is sufficient to
    place the time of separation about an hour before the Eglin pass, as expected.
    I doubt that the B* term is more accurate than 2 percent, especially when
    propagating over one day.
    
    Ted Molczan
    
    
    
    
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