SDP4 problem

From: Ted Molczan (molczan@rogers.com)
Date: Fri Dec 26 2003 - 16:53:51 EST

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    Mike McCants has alerted me to a large prediction error in ObsReduce, which
    includes my implementation of SDP4. The error occurs in another of my programs
    that includes the same version of SDP4.
    
    When I compare my SDP4-generated ephemeris of 02048C against Greg Roberts'
    observations, I find that my predictions are late by nearly 4.5 minutes. SGP and
    SGP4 predictions agree closely with the observations.
    
    My implementation of SDP4 includes the corrections discussed on SeeSat-L in
    1997, but perhaps I introduced an error of my own somewhere.
    
    Before I do a lot of work debugging, I want to be certain that the problem is
    unique to my software, so I would appreciate knowing how other programs that
    include SDP4 fare.
    
    Judging by the appearance of 02048C elsets, they look like they could be
    translations from one orbital model to another. For all we know, SGP4 may have
    been used, not SDP4.
    
    I have appended the elset I used, and Greg's observations.
    
    Thank you,
    Ted Molczan
    
    
    1 27542U 02048C   03355.83333333  .00000000  00000-0  00000-0 0  1564
    2 27542  69.6631  68.7344 8843894 310.2100   0.7376  0.36887561    69
    
                                                     R.A.   Dec
                           YYYYMMDDHHMMSSsss       HHMMSSs DDMMSS
    27542 02 048C   0433 G 20031221200340500 17 15 0512499+121424 39 S+075 05
    27542 02 048C   0433 G 20031221200355200 17 15 0512514+121751 39 S+075 05
    27542 02 048C   0433 G 20031221200415900 17 15 0514533+141930 39 S+075 05
    27542 02 048C   0433 G 20031221200429600 17 15 0515492+150645 39 S+075 05
    27542 02 048C   0433 G 20031221200452100 17 15 0517056+162106 39 S+075 05
    27542 02 048C   0433 G 20031221200528300 17 15 0519144+181402 39 S+075 05
    27542 02 048C   0433 G 20031221200543300 17 15 0520057+185918 39 S+075 05
    27542 02 048C   0433 G 20031221200556700 17 15 0520507+193803 39 S+075 05
    27542 02 048C   0433 G 20031221200647100 17 15 0523345+215615 39 S+075 05
    27542 02 048C   0433 G 20031221200715600 17 15 0525040+230949 39 S+075 05
    
    Site 0433 : Longitude 18.51294 deg East, Latitude  33.94058 deg S, Elevation 10
    metres
    
    
    
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