RE: "Old" observation

From: Matson, Robert (
Date: Tue Mar 01 2005 - 12:52:40 EST

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    Greetings Dr. Efimov,
    > Recently I had encountered with a problem of identification of observed
    > maybe-satellite. It was quite bright, and observers decide it was UFO.
    > I know that there are several online resourses (like Heavens-Above), but
    > they (those I know) deal only with the current (or near-current) dates.
    > However, the problem is that the observation was made SEVERAL
    > YEARS AGO. Maybe, anybody could advice me why I could identify
    > satellite in this case?
    As long as you have osculating orbital elements reasonably close to
    the date of the observation (within a few weeks is probably fine), then
    you can use one of a number of satellite propagation tools to check
    for candidates.  Fortunately, your satellite was bright, so it would
    certainly have been in Mike McCants' mccants.tle file or Ted
    Molczan's molczan.tle file at the time.
    If the date of the observation was sometime from 1992 to August of 2000,
    you can find appropriate orbital elements using the following link:
    For example, if the date of the observation was May 24, 1997, you
    would click on "cs-1997", and then click on the link for cs970522.z
    (corresponding to an epoch around May 22, 1997).
    If you are unfamiliar with .Z files, these are gzip encoded.  The command
    for unzipping the example file above would be:
    gzip -ad cs970522.z
    This will uncompress the archive into an ascii text file named
    "cs970522" (i.e. no extension).  You may want to rename it so that
    it has a recognizable extension like .TLE.
    > So, one should determine, which objects were quite bright at
    > this date, and obtain data for them. And then calculate its position
    > at the sky. A lot of work.  What is the best way to do it?
    With SkyMap, you would just set your location, set the date and time to
    match the approximate date/time of the observation, and then do an
    All-File search for all bright satellites making passes within, say, 15
    minutes of the observation.  (You might need a longer search duration
    if you don't have a good recollection of the exact time of the pass.)
    If you know what part of the sky the satellite passed through, that's
    even better, since it is likely that more than one bright satellite will
    have made a pass at the approximate time of your observation.  Finding
    the satellite that matches the time, location and direction of your
    unidentified object will give you high confidence that you've correctly
    identified it.
    > I am deliberately not provide you with exact date, because I would like
    > to "learn fishing" insteag of simply "obtain a fish".  Excuse me for
    > my non-perfect English.
    Your English is excellent, as is your grasp of English metaphors!
    Happy fishing!  Let me know if you need more pointers...  --Rob
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