RE: Old Unknown Identified as a Re-entry

From: Ted Molczan (
Date: Wed May 02 2012 - 05:39:23 UTC

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    Thank you Harro Zimmer, for propagating the orbit of 1996-069B / 24671 to decay, using your special perturbations
    program - and for sharing the detailed trajectory data relative the Earth's surface, and the sky as seen from several of
    the Yukon eyewitness locations:
    Harro has an excellent track record on SeeSat-L estimating decays, and his results are among the standards against which
    I evaluate my own.
    Harro's analysis confirms my Satana/Satevo-based finding that the final descent was in progress as 1996-069B passed
    within visual range of the locations of the UFO sightings, on 1996 Dec 12, from about 04:25 to 04:27 UTC (Dec 11, 8:25
    to 8:27 PM PST). He estimated that during that period, the object descended from about 83 km to 68 km. I do not have the
    means to estimate the altitude during the final descent as precisely, but my guess of about 90 km (average) was not too
    far off, and the difference does not invalidate my initial report:
    Harro's analysis adds to our understanding of the decay. Within a couple minutes after the object passed out of range of
    the Yukon eyewitnesses, it had descended to 30 km altitude, and lost nearly all of its forward velocity. This was at
    about 4:29:18 UTC (8:29:18 PM PST) over 64.88 N, 117.02 W.
    From that point, its descent was almost completely vertical, and Harro estimated arrival at 10 km altitude as 04:31:06
    UTC (8:31:06 PM PST). The corresponding location, 64.86 N, 116.68 W, would be the approximate "toe" of any debris
    "footprint", where the heaviest pieces would have fallen. Most authorities that issue decay estimates, e.g. USSTRATCOM,
    define 10 km altitude as the point of decay. It was about 1000 km east of the zone of the Yukon sightings, but it is
    doubtful whether much of anything survived re-entry, so this is mostly of academic interest. Of greater interest is what
    more we can learn about the Yukon sightings from Harro's precise estimate of the descent.
    New Information
    The most important new information is that the final break-up probably occurred during the period of the sightings, at
    about the time the object came into view.
    Decaying objects orient themselves with the heavy end forward, like a shuttlecock, which in the case of a rocket body,
    exposes the engine and related structures to the greatest heat. The rocket body began to experience significant heating
    about 4.5 min prior to reaching Yukon, as it descended below 96 km, over the Bering Sea, just north of the Aleutians.
    The heating intensified as it crossed Alaska and into Yukon, but it would have remained largely intact, except for
    sporadic separation of debris - probably from the engine - that would have fallen behind the main object.
    Soon after it came into view of the Yukon eyewitnesses, the rocket body reached the altitude at which the combination of
    intense heat and rapid deceleration brings about the final break-up of re-entering objects, between 75 and 80 km. The
    sudden structural failure and disintegration would have created a swarm of bright objects. Their differing ballistic
    coefficients would have caused them to decay at different rates, resulting in an elongated trail of plasma and glowing
    pieces of debris.
    I had been in some doubt as to the timing of the final breakup, and suspected it to have occurred a bit after the Yukon
    sightings, so I am pleased to have this more precise information. To facilitate further discussion - and independent
    analysis - I have used Harro's trajectory data to tabulate ephemerides for several of the eyewitness locations, and to
    plot a few graphs:
    The file opens to the first graph, which shows the change in altitude during the couple of minutes or so that the object
    was within range of the Yukon sighting zone. The next graph shows the altitude vs. downrange distance travelled after it
    passed below 100 km. It traveled about 5,000 km during this period, until its demise. Note the near-vertical descent
    below 40 km. The final graph shows altitude vs. time below about 100 km.
    The ephemerides are on the first sheet. The data is at 6 s intervals. The first five columns list the date and time -
    both UTC and PST. Columns 7-9 list Harro Zimmer's trajectory data, consisting of the rocket body's latitude, longitude
    and altitude. The remaining columns present the ephemerides for several locations of interest. The first (cols 11-14),
    is near the south end of Fox Lake, at the location of FOX4 and 5's sightings. Azimuth is stated in degrees clockwise
    from north (north is zero, east is 90 deg, south is 180 deg, etc.). Elevation is in degrees; positive values are above
    the horizon, which is the minimum condition required for visibility.
    Atmospheric extinction typically is severe near the horizon, so practical visibility begins well above the horizon.
    Since the sky was reportedly clear, I have assumed that the brilliant decay would have been readily visible from about 8
    deg elevation and higher, which I have colour coded in green. If the conditions were exceptionally good, then visibility
    below 8 deg to about 5 deg might have been possible; that data is in red.
    The final two columns list the angular velocity in deg/s and the range in kilometres.
    From Fox4 and 5's vantage point, the object reached the altitude of final breakup - a little below 80 km - just as it
    rose above 8 deg elevation. Investigator, Martin Jasek asked both witnesses to sketch the apparent size and location of
    the UFO on three photographs:,5estimates.htm
    Jasek reports that from top to bottom, the angular size was 12.8 deg, 8.44 deg and 3.95 deg. The mountain peak in the
    photo is about 8 km distant, and its azimuth is about 322 deg. The ephemeris places the decaying rocket body at that
    direction at about 4:25:48 UTC (8:25:48 PM PST), at just 7.6 deg elevation. Jasek reported, "FOX5 made a mental note of
    the time; she looked at the car clock; it was 8:23 pm.", which is in excellent agreement, as is the elevation - at least
    for the sketch in the top photo.
    In the lower two photos the object seems to be almost on the horizon or the lake itself, but the text of the report is
    unclear about the exact trajectory, except to say that the object headed east and disappeared behind trees. They
    reported seeing the object for about 1 min, which is roughly the duration it spent above about 7 deg elevation. Little
    wonder it was lost in the trees, given its low elevation. What is clear is that the rocket's brilliant debris trail was
    in the sky at about the same time and in the same direction as the UFO.
    Fox 3 was about 8 km north of FOX4 and 5. The ephemeris reveals about the same path across the sky, culminating a
    fraction of a degree higher, at 9 deg. Jasek photographed Fox3's finger pointing toward the location of the bottom of
    the UFO:
    Jasek determined "angular height of 6.5 degrees above the ground". With the aid of Google Maps, I have determined that
    the position was a bit west of due north. The ephemeris reports that the decaying rocket was in that direction just
    after 8:26 PM PST, between 8 and 9 deg above the horizon. According to Jasek, "FOX3 made a note of the time and date, it
    was 8:30 pm December 11, 1996 immediately after the UFO was gone." Temporal and positional agreement between the rocket
    body and the UFO is excellent.
    I will conclude this section by revisiting the report of Pelly Crossing witness PEL2, who observed the UFO pass below
    the Big Dipper, which she sketched:
    In my initial report, I presented this computer-plotted estimate of the decay trajectory from PEL2's location, which I
    estimated to be accurate in elevation to within 1 or 2 deg:
    In fact, Harrow's trajectory puts it about 3 deg lower, but the agreement with PEL2 remains excellent:
    The ephemeris puts the rocket body below the Big Dipper about 8:26:30 PM PST. The time of PEL2 and 3's sighting is not
    known as precisely as those of Fox4,5 and Fox3. Jasek reported, "PEL3 along with his sister PEL2 left Whitehorse around
    6:00 pm and therefore PEL3 reasons that it must have been close to 9:00 pm when they were arriving in the Village of
    Pelly Crossing." Also, "PEL2's husband arrived home from work at about 9:10 pm and recalls his wife being home thereby
    indicating that the sighting occurred sometime before 9:00 pm."
    Based on official mile-marker and speed limit data published in 2008, I estimate that they could have arrived at the
    point of the initial sighting by about 8:26 PM, by departing at about 5:30 PM, and exceeding the speed limit by 2 km.
    Departure at 5:48 PM plus 10 km/h over the speed limit would also work. The actual time of the sighting can never be
    known, but it could plausibly have occurred at the time of the re-entry, which is what I believe happened.
    In closing, I offer an ephemeris generator to enable researchers to evaluate the visibility of the decay from other
    locations in the region. Harro Zimmer's trajectory data is hard-wired into the spreadsheet. Simply enter the site's
    latitude, longitude and height above mean sea-level, and the topocentric coordinates of the trajectory will be
    re-calculated. Celestial coordinates are also included.
    Ted Molczan
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