Observations and updated USA 129 elements

From: Ted Molczan (molczan@home.com)
Date: Thu May 10 2001 - 07:35:11 PDT

  • Next message: Ted Molczan: "RE: Observations and updated USA 129 elements"

    New observations have been provided by Daniel Deak, Bram Dorreman, Russell
    Eberst, Rainer Kracht, Walter Nissen, and myself. Here are updated elements:
    
    USA 129         15.0  3.0  0.0  5.1 v
    1 24680U 96072A   01130.10151620  .00018103  00000-0  25625-3 0    04
    2 24680  97.8172 192.9047 0483405 355.5269   4.1740 14.81198472    08
    
    WRMS residuals are about 0.03 degrees.
    
    The inclination now appears to have been unaffected by the manoeuvre; perigee
    height still appears to have increased; however, some of the points have higher
    than usual residuals, so further observations may change the picture.
    
    The pre and post-maneouvre orbits now appear to strongly coincide with the
    perigee-crossing of 2001 May 08 at about 16:23 UTC, indicating that that was
    the time of the manoeuvre. This is about 12 h later than my initial estimate,
    which was based on a few early post-manoeuvre observations.
    
    96072A's maneouvre may have been sufficient to delay the need for the major
    re-boost until at least the next equator crossing of 96072A's perigee, on 2001
    July 02. At typical rates of decay, the mean motion of either KeyHole is
    unlikely to exceed that maximum observed pre-maneouvre value of about 14.85
    rev/d, before that date.
    
    The sun is unpredictable, so the satellites' operators could decide to
    manoeuvre on or about 2001 May 18, when USA 116's perigee next crosses the
    equator. My guess is that the decision would also depend on whether or not USA
    116's required orbital changes require that its maneouvre take place at
    perigee. There are so many imponderables involved, that all we can do is to be
    aware of past behaviour, to help us to anticipate when manoeuvres are most
    likely to occur.
    
    Finally, here are my observations:
    
    96 072A 2701 F 010510 023650.980  0.1   1038.305   2601.455   2.0  S
    96 072A 2701 F 010510 023809.700  0.1   0542.577   6333.026   1.0  S
    
    Ted Molczan
    
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