Re: Possible re-entry observation

From: Alan Pickup (
Date: Mon Mar 11 2002 - 15:04:53 EST

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    Dwayne Crow reports...
    >On Monday March 4, 2002 my wife observed what sounds to me like a possible
    >satellite reentry and I'm hoping some of you might have the expertise to
    >help us determine what it was she saw.
    >Observation occurred in Plano, Texas.  She was driving west at 6:35 pm local
    >time (00:35 UTC which would be 03/05/2002).  The sun had just set below the
    >horizon and she was admiring the pink color in the western sky when she
    >noticed 8 fireballs in the sky.  From her description, they were spread in
    >an irregular pattern over an area with about a 10 degree diameter, with the
    >lowest one about 25 degrees over the western horizon.  Each of the objects
    >looked like a long, streaming fireball, and one of them had a dark-colored
    >smoke trail.  She pulled over to watch them and estimates that they were
    >visible for about 5 minutes, all disappearing at about the same time.  She
    >said they were moving extremely slowly, almost imperceptibly from left to
    >right (northerly).   I occasionally drag her out of the house to see the ISS
    >or something, so she's familiar with the speed that you normally see visible
    >satellites moving, and she was amazed at how slow these objects were.  I
    >asked her how far they moved from left to right during the entire 5 minutes,
    >and she couldn't say, it was such a small amount.
    >First question:  Does this sound like a satellite re-entry?
    No. There is no way that any re-entry fireball (let alone eight of them) 
    could be visible in the same area of sky for about 5 minutes. While a 
    re-entry might be observable for 90 seconds, or perhaps even longer, on 
    an overhead transit from horizon to horizon, the only way you might see 
    it for much longer would be by viewing it from an aircraft at high 
    altitude, or from orbit. And no re-entry could appear to move "extremely 
    slowly, almost imperceptibly" since the near-orbital velocity is 
    essential to generate the frictional heating that leads to the fireball.
    On the other hand, I see several reports (and sometimes photos too) each 
    year of slow-moving "fireballs" in the western sky at dusk that are 
    undoubtedly due to aircraft and their short-lived condensation trails 
    being illuminated by the Sun, although the latter may be below the 
    observer's horizon. In such a circumstance, the trail can shine brightly 
    by forward scattering while, because of its distance and altitude, the 
    aircraft itself is inaudible and, unless it glints in the sunlight, 
    might be invisible too. The darkening sky may also increase the contrast 
    and makes the observation even more startling. The disappearance is most 
    likely to be due to the sunlight disappearing as seen from the aircraft, 
    either because it has set or passed behind a cloud, or it might be due 
    to a change in the local atmospheric conditions that give rise to the 
    trail or (possible the same thing) the aircraft climbing above or 
    falling below the critical altitude.
    >OIG's "Query decay by date" returned one object for March 4 and four on
    >March 5.    Can anyone refer me to some software that would let me plug in
    >the tle's for these 5 objects to see if any of them coincide with the
    >time/location of the observation?
    A first pass might be to run the elsets through a prediction program 
    that gives you a ground track for the period in question - Mike McCants'
    LATLONG will do that, but there are several others. In most cases you 
    will find that the orbit could pass nowhere near the observing location 
    (sometimes even the continent!) at the time in question, which rules out 
    any possibility of that object being responsible. Surviving candidate 
    decayers need closer analyses, including more detailed prediction and 
    comparison with the direction and altitude of the observation
    Alan Pickup / COSPAR 2707:  55.8968N   3.1989W   +208m   (WGS84 datum)
    Edinburgh  / SatEvo & elsets:
    Scotland  / Decay Watch:
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