Re: SV: Consideration of a OIG/GSFC SSR policy change

From: Vladimir Agapov (avm@kiam1.rssi.ru)
Date: Mon Apr 17 2000 - 08:34:59 PDT

  • Next message: Mike McCants: "Re: 99057C debris plot"

    > I assume that the date of the first 2xxxx elset for a debris object
    can be
    > accuretely enough "interpolated" from known launches.
    > But the object may have a month or more of pre-history as an 8yyyy
    object,
    > and the analysts at USSPACECOM who give it a catalog no. and an
    > international ID must have a pretty good idea when the separation from
    the
    > parent occurred.
    >
    > This date would be much more valuable to have in the listing.
    
    The question of assigning of the proper "date of the birth" to each
    tracking
    object is not so simple. Especially, if we're talking about  an
    _official source_
    like the OIG. What they could be do for us?  I assume, the OIG is
    receiving
    official notes (in an electronic form) from the Space Command containing
    
    info on the newly cataloged objects (i.e. objects with the catalog
    number and
    ID assigned). So, the only date which the OIG can provide as an official
    
    is the date of cataloging (of course, if the message contains such
    date).
    As for "true date", it should be noted that it's knowledge is strictly
    depends of
    which type of the tracking object we're studying. All cataloged
    near-Earth
    objects can be divided into the three major groups:
    
    1) payloads (including active and non-funcioning spacecrafts as well as
    passive payloads like calibration spheres)
    2) spent rocket bodies (including upper stages)
    3) fragments, which in turn could be divided into operational debris,
    fragmentation
    debris and "degradation" (or surface deterioration) debris. Also, debris
    can
    appear as a result of collision (remember CERISE).
    
    Usually, there're no problems to identify objects of the first two
    groups with
    the specific launch. But for some classes of high orbits it can be
    difficult
    task too.
    As for fragments, three groups gives us very different info on
    the date of object "creation". We can more or less accurate to say when
    the fragmentation debris were created based on fragmenation studies.
    And in this case it doesn't matter whether the ID and permanent catalog
    number
    were assigned to the object right after  an explosion or after some
    months tracking
    as an "analyst" 8X,XXX sat. For example, we can say (as the first
    estimation)
    that all fragments related to the 94-029B explosion on June 1996 were
    created
    the same date independently when they were put into the permanent part
    of the
    U.S. SpaceCom catalog. Unfortunately, for high elliptical orbits our
    knowledge
    of fragmentations is very pure due to lack of measurement sensors. Due
    to this
    dates of some fragmentations are known as accurately as "the first
    decade" of
    "the first half of the month", but I assume it is still enough info for
    us to give the
    first estimation when the object was "born". More complex case is
    several
    fragmentations of the same parent body (for example, som EORSATs). But
    we can solve the problem giving each such fragmentations objects the
    date
    of the earliest fragmentation event in a row as the "object creation
    date".
    
    Operational debris (in case of their relatively large sizes to be
    tracked by
    radars) usually (in 1990ths) are associating with the specific launch
    right after their
    discovering and we can use the method of seraching the parent object
    trying
    to propagate orbit back. The latest examples are 26146/99067D and
    26147/99067E. These two operational debris of the DMSP F15 had
    separated from the main craft last December (or early January, I haven't
    time
    to analize this yet) but were officially cataloged just the last week.
    Of course,
    in such cases only the spacecraft operator could give us most correct
    info on
    operational debris separation but I assume will not give it. Of course,
    Al2O3
    particles created during solid rocket engines burns can be assumed as
    operational
    debris too but fortunately for us they are not tracking since in other
    case we were
    doomed to infinite search of the parent body :-)
    
    The latest gorup is fragments of so called "anomalous events". Usually
    these
    are small pieces of debris with low relative separation velocity. Some
    of
    such objects, for example, are associated with old Transit navigation
    spacecrafts. Most anomalous fragments "productive" parent satellite was
    COBE. The only way to find the date of anomalous event (and the parent
    object) is an orbit propagation both for the fragment and parent
    candidates.
    
    So, we can establish own research project on the assigning to the each
    orbiting (at least currently) object the date since it's existing as an
    separate
    one. I can prepare such info for the fragmentations objects. Who will
    maintain the catalog with these dates added? Mike, Ted?
    
    As for OIG, I assume we can propose them just to give us only the date
    of an official cataloging that would be useful too.
    
    Best regards,
    Vladimir Agapov.
    
    
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