Re: strange Iridium 48 elset

From: Alan Pickup (alan@wingar.demon.co.uk)
Date: Wed Jun 21 2000 - 12:55:37 PDT

  • Next message: Alan Pickup: "Decay watch: 2000 Jun 21"

    Tristan Cools mentions the following strange elset, found in my elset
    files available via my satEvo WWW page...
    
    >Iridium 48 tum   4.0  1.8  0.0  6.0 d   13       29716 x 29265 km
    >1 25107U 97082D   00168.87002011  .00039028  00000-0  13497-2 0  6316
    >2 25107  86.3837 304.7888 0062845 195.7471 164.1831  1.27814685340080
    
    The log of my automatic elset collection operation shows I received the
    following from OIG at 07:03 UTC on June 18:
    IRIDIUM 48
    1 25107U 97082D   00168.87002011  .00039028  00000-0  13497-2 0  6316
    2 25107  86.3837 304.7888 0062845 195.7471 164.1831 1.278146851340081
    My elset extraction/sorting operation failed to recognise this as a
    badly formatted elset - the mean motion has its decimal-point (period)
    in the wrong column. Instead, my software propagated it as it appears in
    Tristan's message.
    
    The correct elset for this epoch should probably have been received
    as...
    IRIDIUM 48
    1 25107U 97082D   00168.87002011 +.00039028 +00000-0 +13497-2 0 06394
    2 25107 086.3837 304.7888 0062845 195.7471 164.1831 15.27814685134008
    ...though this has a different elset number (639 vs 631, near the end of
    line 1).
    
    Somehow, OIG (?) dropped the "5" of the 15 of the mean motion on line 2
    and appended an extra "1" as the checksum digit after the left-shifted
    "8" of the original checksum. In fact, the checksum for the mean-motion-
    mangled line should have been "0", as it appeared in the elset I
    published. The line-zero data was added by my software using the
    eccentricity and mangled mean motion - which is why the orbit's height
    is so daft.
    
    
    Alan
    -- 
     Alan Pickup | COSPAR 2707:  55d53m48.7s N  3d11m51.2s W   156m asl
     Edinburgh   | Tel: +44 (0)131 477 9144     Fax: +44 (0)870 0520750
     Scotland    | SatEvo page:   http://www.wingar.demon.co.uk/satevo/
    
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