short "half-life" orbital elements

From: Ed Cannon (
Date: Sat Apr 14 2007 - 16:36:34 EDT

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    Here is something I would like:  a list of (unclassified)
    objects whose orbital elements have a short "half-life".  
    That is, a list that includes objects with high drag, or 
    which are subject to significant maneuvers, or which are 
    for some other possible reason(s) unstable or unreliable 
    over more than a day or two or three.
    For most objects in orbit, the orbits are quite stable 
    over week or two or even three, and I sure do not need 
    nor want to download those from Spacetrack every single 
    day.  I would much prefer to download only a selected 
    list of elements that I really need to get every day and 
    the full catalog only every week or so, more or less.
    Not being an orbital analyst, I don't have the skill or 
    the software to rapidly and reliably and make up such a 
    list myself.  What I have been doing for a very long 
    time, when I have had the time, is running predictions, 
    finding those with the highest uncertainties, compiling 
    a nightly list that way, and then querying Spacetrack 
    for those objects, and then running predictions with the 
    updated elements.  Obviously, it would be a lot easier 
    for me if there were a ready-made list of such objects.  
    (There used to be one along those lines, more or less,
    called "highdrag.tle".)
    I would like the list to be given in the five-digit 
    catalog numbers, so that I can submit it directly to 
    Spacetrack "as is".
    I understand that making up such a list is a matter of
    some work for some person or persons, and so really this 
    is a "wish list" type of thing more than a request.
    I mentioned "(unclassified)" above because, of course,
    all of our elements for classified objects come from
    people like Mike McCants and Ted Molczan who are willing 
    to spend the time and effort to observe them and/or take 
    observations from other people (too numerous to mention
    at the moment), analyze them, and produce elements that 
    they freely distribute to everyone.  
    I don't know how many people know that besides providing 
    elements of two to three hundred classified objects now, 
    Mike frequently observes and does his own positional 
    measurements for dozens if not scores of classified 
    objects, as well as serving as a clearing-house for the 
    hundreds of positional observations taken by other people 
    for classified objects.  It's a lot of work which Mike 
    has shared freely with us for years.  I know that Ted 
    does similar work as well as administering this list, and 
    so I guess this is a way that I want to say thank you to 
    them and to all of the positional observers as well, since 
    I'm not one.
    Recently information on something like 140 additional 
    classified objects in near-geosynchronous orbits has been 
    added, and I hope that everyone understands how much
    additional work that means for Mike and the others who are
    observing and analyzing the data on those objects.
    Clear, dark nights to all --
    Ed Cannon - Austin, Texas, USA
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