Re: Number of Objects in Orbit

From: Brian Weeden (
Date: Sun Jul 13 2008 - 18:04:49 UTC

  • Next message: Brian Weeden: "Re: Number of Objects in Orbit"

    The main reason is identification and a secondary is the ability to
    maintain the orbit.  To be placed in the catalog, an object must be
    tied to a specific launch event.  That's where the International
    designator comes from.  Those few thousand objects (17000 - total
    cataloged) are the ones that are tracked fairly reliably but haven't
    been tied to a launch.  Might have been a piece of a piece from
    something to broke up decades ago, or possibly something that was lost
    for several years.  The unit that maintains the catalog tends to take
    association of an object with a launch very seriously because it
    implies ownership by a State and perhaps liability if something were
    to happen involving that object.  And yes, some of those objects are
    the very small pieces of debris and/or ones with very erratic
    perturbations for which it is hard to maintain a good element set.
    On Sun, Jul 13, 2008 at 1:35 PM, Gerhard HOLTKAMP
    <> wrote:
    > 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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