Number of Objects in Orbit

From: Gerhard HOLTKAMP (
Date: Sun Jul 13 2008 - 17:35:24 UTC

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    The latest issue of Orbital Debris Quaterly News (Volume 12, issue 3, July 
    2008) mentions in an abstract that approximately 17,000 objects are currently 
    tracked in orbit by the U.S. Space Surveilance Network (USSSN) while the 
    Satellite Box Score on the final page shows the number of cataloged (by 
    USSSN) objects as 12,851 (as of 25-JUN-08). Why are there over 4000 objects 
    tracked but not cataloged? Are those objects which cannot be correlated with 
    a particular launch?
    At the same time the publicly available TLE list by Spacetrack contained 
    11,556 unclassified objects while our own classfd.tle stands at about 223 
    objects. This makes it 1072 cataloged objects (over 8% of the total) for 
    which the general public does not have any orbit information. I assume the 
    majority of those objects will probably be small debris pieces which are 
    difficult to track consistently with our visual observations.
    Gerhard HOLTKAMP
    Darmstadt, Germany
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