USA 125 recovered by Greg Roberts

From: Ted Molczan (molczan@rogers.com)
Date: Sun Nov 10 2002 - 09:00:44 EST

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    Greg Roberts has recovered an object that is believed to be USA 125. He will post his observations in the near future.
    
    An observer who prefers not to be identified provided an approximate search orbit based upon a very short arc:
    
    1 71001U          02233.27083333  .00000000  00000-0  00000-0 0    01
    2 71001  63.5900 202.0000 7143000 271.4000 116.5300  2.00630000    04
    
    Greg took excellent advantage of his southern hemisphere location and his computer-controlled CCD camera to recover the object on
    2002 Nov 06 UTC. 
    
    Knowing that the predicted time would be unreliable, Greg programmed his camera to stare at the orbital plane for a long period of
    time around the predicted time of the pass. This requires that the pointing system compensate for Earth's rotation, to keep the
    orbital plane centred within the field of view. 
    
    Greg found the object running about 68 min late relative to the 77 day old search elements, and he obtained 11 accurate points.
    Using those points I obtained the following orbit:
    
    1 23945U 96038A   02310.86007639  .00000000  00000-0  00000-0 0    07
    2 23945  63.6507 193.7140 6920287 271.4039 348.2961  2.00665000    09
    
    WRMS error = 0.011 deg
    
    I manually set the mean motion, and allowed Elcor to adjust the other elements. I chose the mean motion that resulted in
    approximately the same ephemeris as the search elements on their epoch date.
    
    On 2002 Nov 09 UTC, Greg found the object trailing the above elements by about 8 s, and he obtained 7 more points. Using the 06 Nov
    and 09 Nov points, I obtained the following elements:
    
    USA 125          0.0  0.0  0.0  5.7 v
    1 23945U 96038A   02313.88997685  .00000000  00000-0  00000-0 0    01
    2 23945  63.6190 193.3656 6917012 271.2979  17.0173  2.00658750    08
    
    WRMS error = 0.01 deg
    
    The standard magnitude is based on Greg's observations.
    
    Users of software that employs the SDP4 "deep space" model, please note that the above elements were fit to SGP4; therefore,
    accuracy will be somewhat degraded using SDP4, even though it is superior for this type of orbit. The discrepancy is small within
    the observational arc - 2 or 3 s of time. I do not know how that will propagate over time.
    
    Finally, the identification as USA 125 may change after further tracking / analysis.
    
    Ted Molczan
    
    
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