Old Unknown Identified as a Re-entry

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Mon Apr 30 2012 - 02:24:47 UTC

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    Jim Oberg relayed to me a query from British journalist Ian Ridpath, about a UFO sighting in Yukon, on 1996 Dec 12 UTC
    (evening of Dec 11 PST), described in this 2000 Feb report by Martin Jasek: http://www.ufobc.ca/yukon/22index.htm. Jim
    wondered whether the reported phenomena could have been related to a satellite launch or decay, so I had a look.
    A quick check of USSTRATCOM's Space Track database revealed a single decay on the date in question. The final set of
    orbital elements placed the trajectory sufficiently near the location and time of the sightings to merit more detailed
    analysis. As a result, I am confident that the observed phenomena were due to the re-entry of the 2nd stage of the
    rocket that placed Cosmos 2335 into orbit earlier the same day. I estimate that the re-entry was in progress at the most
    probable time of the sightings, and that it was visible from each of the widely separated locations from which they were
    reported. The reported path of the phenomena across the sky is consistent with the trajectory of the decay, and its
    general description is consistent with a satellite re-entry debris trail.
    1. Second Stage Rocket of Cosmos 2335 
    Jonathan McDowell's launch log reports that Cosmos 2335 lifted off from Baykonur, Kazakstan on 1996 Dec 11 at 12:00 UTC,
    on a Tsiklon-2 launch vehicle. Novosti Kosmonavtiki is cited. 
    Russian Space Web reports that the 2nd stage is 9.4 m long, 3 m in diameter, and its empty mass is 3700 kg - sufficient
    to produce a spectacular re-entry light show for anyone fortunate to see it:
    The rocket body has the international designation 1996-069B, and the U.S. Strategic Command catalogue number 24671.
    USSTRATCOM's Space Track website contains seven (7) 2-line element sets (TLEs), with epochs spanning 1996 Dec 11, 16:19
    UTC to Dec 12, 02:39 UTC. Jonathan McDowell's archive contains the same TLEs:
    Analysis of the TLEs reveals that Cosmos 2335 and its 2nd stage rocket entered an approximately 119 km x 409 km, 65 deg
    orbit. Cosmos 2335 manoeuvred at apogee to circularize its orbit to approximately 402 X 414 km. (These altitudes are the
    TLE mean values, relative Earth's equatorial radius.) The rocket stage was doomed to a very rapid decay, by its low
    altitude and especially its very low perigee height. Space Track's satellite catalogue lists the date of decay as 1996
    Dec 12 UTC. The TLE record is in agreement, and is sufficient to confidently estimate the time and location.
    2. Decay Estimate
    I estimated the date and time of decay using the combination of Alan Pickup's Satevo and Satana decay propagators.
    Satevo is based on the published research of Dr. Desmond King-Hele, who was among the leading investigators into the
    mathematics and physics of Earth satellite orbits during the first three decades of the space age. Satevo quickly and
    reliably propagates any given TLE to decay, reports the estimated date and time, and generates propagated TLEs for each
    revolution up to decay. As a rule of thumb, decay estimates are accurate to within about 20 percent of the time
    remaining until decay.
    Satana is a pre-processor for Satevo, that uses the same decay algorithms to fit more accurate decay rates to
    USSTRATCOM's TLEs, which I have found helps to improve the accuracy of decay estimates. The user specifies three TLEs,
    ideally spanning several revolutions, and the program generates improved versions. Alan recommends feeding the Satana
    result to Satevo to make the final decay estimate. I fed USSTRATCOM's final three TLEs to Satana, which yielded this
    improved estimate of the final TLE:
    96069B                                                    210 x 99 km
    1 24671U 96069B   96347.11017787  .73113739  21233+1  46128-3 0 90080
    2 24671  65.0090 293.1409 0084762  53.5911 307.1878 16.44383208    93
    Feeding it into Satevo yielded the TLE for the final ascending node crossing (Dec 12, about 04:06 UTC) prior to decay:
    96069B                                                    145 x 95 km
    1 24671U 96069B   96347.17072022 1.96922529  50000+2  55689-3 0 90087
    2 24671  65.0049 292.9047 0038551  53.5611 306.7936 16.57513813   107
    Satevo estimated "Final decay at 96347.184950" which is Dec 12, 04:26 UTC = Dec 11, 8:26 PM PST. Uncertainty is about
    10, perhaps 20 min. 
    To help judge the reliability of this estimate, I extended my analysis to include all ten (10) combinations of TLEs,
    from the 3rd to the 7th and final TLE issued. I excluded the first two TLEs issued, since they appeared to be less
    accurate than the subsequent ones, as is common immediately after a new launch, due to the shortness of the
    observational time span, and the still small number of observations.
    Processing the remaining ten (10) combinations of three TLEs through Satana/Satevo resulted in 10 estimates of time of
    decay on 1996 Dec 12, ranging between 03:34 UTC and 05:13 UTC, eight (8) of which were between 04:10 UTC and 04:33 UTC.
    Mean and median estimated time of decay of the 10 estimates is 1996 Dec 12 at 04:22 UTC = Dec 11 8:22 PM PST. This is
    strong support for the aforementioned 04:26 UTC (8:26 PM PST) result, based on the final three TLEs.
    As an additional check, I estimated the time of final passage below the altitude near which the final descent typically
    begins - about 100 km - and found that seven of the ten TLE combinations placed it within about one (1) minute of 8:08
    PM PST. The final descent would have begun about one (1) minute or so after this time, and was highly likely to have
    remained in progress as the trajectory passed within sight of the zone of the Yukon observations, during the period from
    about 04:25 UTC to 04:27 UTC (8:25 PM PST to 8:27 PM PST).
    3. Agreement With Reported Time and Sighting Locations
    For the decay hypothesis to be correct, it must have been observable from the locations from which the suspected
    sightings were reported, close to the reported time.
    The event times reported by the eye-witnesses span the period from Dec 12, 03:00 UTC to 06:00 UTC (Dec 11, 7 PM PST to
    10 PM PST), with several reports clustered at or near the apparent median time of Dec 12 04:30 UTC (Dec 11 8:30 PM PST).
    A couple of the reports tend to lend weight to that time. 
    The witness identified as FOX5 reported 8:23 PM PST, based on having read her car's clock at the time. Fox3 reportedly
    made a note of the date, with the time 8:30 PM PST. Local news reports following the events reportedly gave that time.
    The decay estimate is in very good agreement with this time.
    The report linked at the top of this message, documents eyewitness accounts from the vicinity of Fox Lake, Carmacks and
    Pelly Crossing. It also mentions reports of sightings at Mayo, from which eyewitness reports were added to a subsequent
    version of the report by the same investigator, which I have not read. 
    The decay was readily visible from all of those locations, which lie along a roughly north-south line, spanning about
    270 km. I estimate that during this period the object was no more than about 90 km above the geoid on average (higher at
    the beginning and lower by the end). Breakup and terminal descent probably occurred soon after the Yukon sightings,
    somewhat farther to the east.
    Due to my lack of software to accurately propagate the final minutes of the descent, I had to rely on the standard SGP4
    orbit propagator. Using it with the TLE from Section 2, put the altitude about 10 km too high over the Yukon. It is
    important to use a realistic altitude to properly assess whether the decay could have been visible from the location of
    each sighting. Allowing an unrealistically high value, would have somewhat overestimated the maximum elevation, hence
    the potential visibility. Therefore, I made a lower altitude version of the TLE by propagating to the time of interest,
    and adjusting the mean motion to yield a more realistic altitude:
                                                              74 X 112 km
    1 24671U 96069B   96347.18472222 1.96922529  00000-0  55689-3 0    01
    2 24671  65.0049 292.8493 0029249  53.5540  30.4833 16.67000000    02
    I used this TLE for all of the remaining analyses of this report.
    The time and circumstances of rise, culmination (i.e. maximum elevation), and set, of the decay trajectory are listed
    below. Sites appear in order of increasing north latitude.
                       Coordinates    Rise >8 deg     Culmination    Set <8 deg  Dur
                       Deg N  Deg W     PST    AZ     PST    AZ EL    PST    AZ  min
    Fox Lake (FOX4,5)  61.17 135.39  20:25:29 312  20:26:09 349 11  20:26:50 28  1.4
    Carmacks           62.10 136.28  20:25:11 293  20:26:06 349 16  20:27:00 45  1.8
    Pelly Crossing     62.78 136.58  20:25:05 282  20:26:06 349 22  20:27:07 56  2.0
    Mayo               63.6  135.9   20:25:08 274  20:26:12 347 35  20:27:17 66  2.2
    The rise and set times are arbitrarily stated for 8 deg elevation. From vantage points with a clear view to the horizon,
    and exceptionally good atmospheric conditions, the brightest debris from a decay might be seen several degrees lower,
    with the unaided eye. Many of the eyewitnesses were driving on a highway surrounded by low, rolling hills, with a good
    view of the horizon for long stretches; therefore, the decay was readily observable from all of the above locations.
    The duration above 8 deg elevation ranged from 1.4 min at Fox Lake to 2 min at Pelly Crossing. Most eyewitnesses
    probably saw it for a shorter time; however, the eight (8) who reported the duration, gave values ranging between 30 s
    and 5 to 10 min. The approximate mean and median values of 4.7 min and 4 min, respectively, are 2 to 5 times longer than
    the decay was actually observed; however, such after-the-fact estimates are notoriously inaccurate, especially after
    events as impressive as described. Allowing for that reality, I find the prediction and observations to be in reasonable
    4. Agreement With Trajectory
    For the decay hypothesis to be correct, it must be consistent with the trajectory observed from the locations from which
    the suspected sightings were reported. 
    Below is the ground track of the decay, spanning the period of the table of Section 3:
       PST      Lat        Long
    20:25:00  63.338 N  147.170 W
    20:25:10  63.573 N  145.750 W
    20:25:20  63.793 N  144.306 W
    20:25:30  63.997 N  142.840 W
    20:25:40  64.185 N  141.353 W
    20:25:50  64.358 N  139.845 W
    20:26:00  64.513 N  138.319 W
    20:26:10  64.652 N  136.777 W
    20:26:20  64.774 N  135.219 W
    20:26:30  64.878 N  133.647 W
    20:26:40  64.964 N  132.065 W
    20:26:50  65.033 N  130.472 W
    20:27:00  65.084 N  128.873 W
    20:27:10  65.117 N  127.268 W
    20:27:20  65.132 N  125.661 W
    The decay ground track passed far to the north of all four eyewitness locations, moving from west to east, at an
    altitude of about 90 km. Witnesses at the three locations for which I have seen the detailed sighting reports,
    overwhelmingly agreed that the observed phenomena moved from west to east (sometimes expressed as left to right), fairly
    close to the northern horizon. The initial sighting typically was in the NNW or North, and the final sighting was in the
    NE or East.
    Six (6) of the nine (9) individuals or groups made their initial sighting from within moving vehicles, which tended to
    restrict the field of view to the lower elevations, which happened to be ideal to spot the decaying rocket body, which
    varied in maximum elevation between approximately 11 deg and 22 deg, depending on the observer's location.
    All six (6) of the sightings from moving vehicles occurred while driving north. It's a small sample, but the lack of
    reported sightings while driving south is consistent with the known path of the decaying rocket, 200 to 400 km to the
    north, depending on the observer's location.
    The Pelly Crossing witness identified as PEL2, made the especially useful observation that the unidentified object
    passed below the Big Dipper, and was about its length, as depicted in the following drawing attributed to her: 
    My computer-plotted estimate of the decay trajectory from PEL2's location, accurate in elevation to within 1 or 2 deg,
    is in substantial agreement:
    The orientation of the Big Dipper in PEL2's sketch, which has it roughly horizontal, is not quite correct; in reality it
    was tilted, with the bowl somewhat above the handle, but overall the agreement is excellent considering that the sketch
    was made from memory, probably long after the fact.
    The decay trajectory was about 233 km slant range from PEL2; therefore, the 25 deg angle subtended by the reported
    phenomenon represents a length of about 100 km, which probably consisted of the plasma trail and debris.
    Fox4 and 5, who were nearly twice as far from the decay trajectory as PEL2, drew a much shorter object (variously
    estimated by Jasek as 3.95 deg, 8.44 deg and 12.8 deg), as would be expected, since the angular size varies inversely
    with distance. 
    The lack of exact proportionality with range probably is due in part to the inherent imprecision of all of the angular
    estimates, and to reduced brightness of the trail from the position of Fox4 and 5, due to the greater range
    (inverse-square law), and to atmospheric extinction due to the lower elevation.
    5. Agreement With Appearance
    For the decay hypothesis to be correct, it must be reasonably consistent with the observed appearance and other relevant
    physical characteristics of the phenomena.
    Jasek's 2000 Feb report includes detailed eyewitness reports of 20 persons, in 9 groups, who observed from the vicinity
    of Fox Lake, Carmacks or Pelly's Crossing. Below is the first description of the appearance of the phenomenon attributed
    to each observer. Double quotes denote a direct quote of the eyewitness; single quotes are attributable to the report's
    author, with links to the corresponding illustration.
    The consistent theme across nearly all of the descriptions is of a row or formation of lights, which is strongly
    consistent with the known appearance of a re-entry debris trail. This is strongly reinforced by many of the sketches.
    For example, the first sketch attributed to FOX1 depicts a bright light followed by a bright tail. It looks very much
    like the one and only decay that I observed, in which the object was still mostly intact and glowed brilliantly,
    followed by a long plasma trail, looking like a surreal comet. Even the drawing under the Fox3 heading (below) that
    looks like a spacecraft, has some resemblance to the formation of lights in a decay.
    Fox1   "shining light down a smooth gentle curve"
           'three rows of rectangular lights'
    Fox2   'a huge object with a row of lights'
    Fox3   'a huge object out over the Lake'
           'lighting up the entire valley!'
           "We could see our shadows"
    Fox4   'recalls two very long rows of rectangular lights in the distance'
    Fox5   'noticed lights out over the lake'
           'a huge row of rectangular lights'
           like a 'a long truck on a road in the distance'
    Fox6   'a large arrangement of multicolored lights'
    CRM1   'about 3 dark orange flashing lights in a horizontal row'
           'spread out a considerable distance apart'
    CRM2   'initially thought was a formation of three airplanes flying'
    CRM3   'consisted of three lights'
    CRM4   not yet interviewed
    CRM5-9 'a long row of lights moving in the distance'
    PEL1   'huge row of lights'
    PEL2   "whole big cluster of stars"; white, blue & green; "same length as the Big Dipper!"
    PEL3   'a huge row of lights'; mostly white, with some blue and some red
    PEL4   not yet interviewed
    PEL5,6 'a row of lights in the distance'
    PEL7   'a large oval shape that was lit up with rows of lights along the side of it'
    No observer reported hearing a sound from the observed phenomenon; six stated that it made no noise or sound. This is as
    expected of a decay.
    Several observers reported that the lights disappeared one by one as the object moved out of view, or disappeared from
    view, in the east, which is consistent with passage behind an unseen obstruction near the horizon.
    6. Conclusion and Comments
    The estimated time of decay of 1996-069B / 24671 is strongly consistent with the time and location of the Yukon
    sightings of 1996 Dec 12 UTC, as well as the observed trajectory and visual appearance, after allowing for fading of
    memory with time, and the misperception that frequently attends this type of phenomenon.
    Of course, much depends on the accuracy of my decay estimate. I am confident in my work, but make no claim to
    infallibility, so I welcome and encourage alternative analyses. I would be especially interested to know the results of
    semi-analytic or numerically integrated propagations. It would also be worth obtaining a copy of USSTRATCOM's TIP
    (tracking and impact prediction) message, which may take a FOIA request, unless someone has retained a copy in his or
    her archives.
    Experienced sky watchers on SeeSat-L may find it difficult to believe that anyone could misidentify a re-entry as a
    spaceship, but human perception is notoriously fallible, and no one is immune. Much depends on the circumstances and
    personal experience. Driving through the wilderness under a pitch black sky, and suddenly faced with a slowly moving
    formation of brilliant lights can be awe-inspiring and even terrifying. The human mind races to make sense of the
    unfamiliar, drawing on experience that may be inadequate. Depth perception can play tricks, such that something 200 km
    away, 100 km long, and moving at 7 km/s, seems to be just 200 m away, 100 m long, and moving 7 km/h - the angular
    velocity is roughly the same. 
    Taking these considerations into account, the eyewitnesses did a pretty good job, and need not be embarrassed for having
    perceived more than was there.
    Ted Molczan
    Seesat-l mailing list

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