IGS1A and IB elements

From: Ted Molczan (molczan@rogers.com)
Date: Sat Apr 26 2003 - 00:15:57 EDT

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    I derived the following from observations by Daniel Deak, Bjorn Gimle, and
    myself, received to this moment:
    
    Arc 2003 Apr 25 - 26 UTC:
    
    IGS 1A           0.0  0.0  0.0  5.6 v
    1 27698U 03009A   03116.08726228  .00010000  00000-0  39161-3 0    07
    2 27698  97.4064 188.1157 0008359 149.5421 210.6304 15.25806823    02
    
    WRMS residuals = 0.060 deg
    
    Daniel's obs confirmed my suspicion that IGS 1A had lowered its orbit prior to
    my obs earlier the same day. The above mean motion is consistent with my
    estimate that the design value is to be maintained near 15.26 +/- 0.002 rev/d.
    
    Arc 2003 Apr 25 - 25 UTC:
    
    IGS 1B           0.0  0.0  0.0  3.1 v
    1 27699U 03009B   03115.86408980  .00010000  00000-0  39600-3 0    03
    2 27699  97.4104 187.8152 0003000 116.8739 243.2806 15.25464819    00
    
    WRMS residuals = 0.051 deg
    
    At any time, IGS 1B can be expected to lower its orbit to match the mean
    motion of IGS 1A, at which time both will be in their operational orbits,
    their node crossing times separated by a fixed interval, with IGS 1B leading
    by about 38 minutes.
    
    In anticipation of IGS 1B's manoeuvre, it would be prudent to expect it to be
    early by about 30 s per day since the above epoch.
    
    Ted Molczan
    
    
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