TJM obs of 2003 Apr 25 UTC; IGS 1A and IB elements

From: Ted Molczan (molczan@rogers.com)
Date: Fri Apr 25 2003 - 11:27:11 EDT

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    As expected, IGS 1B manoeuvred; it was about 1.5 min early. IGS 1A may also
    have manoeuvred.
    
    27698 03 009A   2701 G 20030425024201430 17 25 1839689+630849 28 S
    
    27698 03 009A   2701 G 20030425024253360 17 25 2123439+650140 37 S
    
    27699 03 009B   2701 G 20030425033913900 17 25 0414778+482867 28 S
    
    Site 2701: 43.68764 N, 79.39243 W, 230 m
    
    I derived the following from observations by Bjoern Gimle, Mike Waterman and
    myself, received to this moment:
    
    Arc 2003 Apr 23 - 25 UTC:
    
    IGS 1A           0.0  0.0  0.0  5.6 v
    1 27698U 03009A   03115.10353359  .00008866  00000-0  35165-3 0    07
    2 27698  97.4064 187.1418 0008435 152.9921 207.1758 15.25381256    01
    
    WRMS residuals = 0.2 deg
    
    Arc 2003 Apr 25 - 25 UTC:
    
    IGS 1B           0.0  0.0  0.0  3.1 v
    1 70000U          03115.15224421  .00010000  00000-0  39700-3 0    04
    2 70000  97.4104 187.1102 0003000 119.3753 294.0848 15.25380000    05
    
    WRMS residuals = 0.015 deg
    
    I am reasonably confident of IGS 1A's mean motion, but I cannot exclude the
    possibility that it made a small downward manoeuvre prior to my observation.
    
    The IGS 1B search elements are based on the assumption that its mean motion
    was the same as that of IGS 1A. I propagated the pre-manoeuvre elements to the
    time of my observation, then adjusted the mean anomaly for best fit.
    
    Regardless of the accuracy of the above mean motions, we can reasonably assume
    that both objects are destined to have operational values of about 15.26 +/-
    0.002 rev/d (required for exact 61:4 resonance); therefore, it would be
    prudent to expect them to be at least 30 s early tonight.
    
    Ted Molczan
    
    
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