Mean motion in old elements

From: Mike Waterman (Mike.Waterman@marconi.com)
Date: Tue May 08 2001 - 02:36:39 PDT

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    OIG orbit elements include "mean motion" in revs/day.
    This is normally revs measured from perigee to perigee, but in
     some old elements the data does not fit this definition.
    
    Example from 
    http://hea-www.harvard.edu/QEDT/jcm/space/elements/disk1/00400/S00424
    
    1 00424U          63349.11300369 -.00000170           00000-0 0   203
    2 00424  80.4713  91.6706 0017354 275.3552  84.4470 13.66095625 60302
    at/Z60S
    1 00424U          63365.60122080  .00000345           00000-0 0   211
    2 00424  80.4875  75.5042 0027501 194.8387 165.0807 13.66091969 62557
    at/Z60S
    1 00424U          64020.60696148  .00000344           00000-0 0   221
    2 00424  80.4875  55.8521 0027434 143.5005 216.6867 13.65348028 65285
    at/Z60S
    1 00424U          64020.60696172  .00000345           00000-0 0   229
    2 00424  80.4875  55.8521 0027434 143.5005 216.6867 13.66105769 65289
    at/Z60S
    1 00424U          64041.49202226  .00000060           00000-0 0   237
    2 00424  80.4734  35.3073 0030027 114.1196 246.1947 13.66098609 68133
    at/Z60S
    1 00424U          64071.17068313  .00000000           00000-0 0   247
    2 00424  80.4748   6.1623 0030690  59.9480 300.3560 13.66101054 72186
    at/Z60S
    1 00424U          64110.37564562  .00000443           00000-0 0   252
    2 00424  80.4721 327.6648 0022611 313.1602  46.6510 13.65339186 77537
    
    The epochs clearly show that the mean motion is about 13.653 as seen
    on 64020.60696148 and 64110.37564562 (and all later elements).
    
    The mean motions near 13.661 are clearly wrong.
    A similar problem occurs in some other old satellites.
    
    Can anyone explain what the 13.661 is?
    (if not I will investigate)
    
    Mike Waterman      mike.waterman@marconi.com
    
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