RE: Video of Yaogan 17 rocket fuel dump

From: Ted Molczan (
Date: Sat Sep 07 2013 - 02:42:56 UTC

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    In my previous post, I showed that the trajectory of the object in Lou20764's video correlates with the trajectory of
    the objects from the Yaogan 17 launch. In this message, I elaborate on why I believe that a fuel dump and/or the
    aftermath of a fuel depletion burn was in progress.
    The first step is to determine whether evidence of such a manoeuvre exists in the orbital elements. Below is a table of
    the perigee and apogee of each Yaogan 17 object, derived from USSTRATCOM orbital elements. All have the same apogee, but
    the rocket's CZ-4C stage has a nearly 200 km lower perigee, consistent with its having made a fuel-depletion manoeuvre. 
    Int'l         Per  Apo
    Desig   SSN   km   km   Object
    13046A 39239 1082 1117 payload 1
    13046B 39240 1083 1117 payload 2
    13046C 39241 1086 1117 payload 3
    13046D 39242  896 1117 CZ-4C stage
    13046E 39243 1084 1117 debris 1
    13046F 39244 1084 1117 debris 2
    The two previous Yaogan launches of NOSS-like payloads resulted in the same initial number of objects, with very similar
    orbital dimensions, indicating that a fuel dump and/or fuel-depletion burn is standard procedure for these launches. In
    fact, it has become standard procedure for most launch agencies, mainly to prevent rocket stages from eventually
    exploding and adding to the orbital debris population. A secondary purpose is to remove the stage from the orbit of its
    payload(s), to eliminate any risk of re-contact, i.e. collision.
    The next step is to determine the time of the depletion burn and/or fuel dump. In order to have reduced the perigee but
    not the apogee, the orbit manoeuvre must have occurred at or close to an apogee, but which one? Since the rocket stage
    was in the same orbit as its payloads at the time of the manoeuvre, I looked for the point of intersection between the
    post-manoeuvre orbit of the rocket and the orbits of the payloads. Due to the imperfect precision of the orbital data
    and other factors, such intersections are seldom exact, but often it is possible to find a point where the orbits pass
    within a reasonably close distance.
    I computed the point of intersection between a few TLEs of Yaogan 17's rocket and a few of its presumed payloads and
    debris, issued not long after launch. The four intersections occurred between 19:45:36 and 19:46:01 UTC, which is the
    approximate time of the manoeuvre. The orbits typically intersected to within 1 to 2 km, which is excellent agreement
    for this type of calculation. At the time, the objects were very close to their first apogee passage after launch, which
    satisfies the constraint that the event must have occurred at an apogee.
    Twenty-four (24) seconds into Lou20764's video, a statement appears that confirms that the "exact time" of his initial
    sighting was at 5:47 local time = 19:47 UTC. The few independent accounts I have seen agree with that approximate time.
    The portion of the trajectory in Lou20764's video that I identified yesterday, began just after 19:49:30 UTC. I chose
    that portion because it showed a reasonably large number of bright stars that would aid in the identification. I have
    since reviewed the video to try to spot the earliest scene recorded by both cameras. For the first camera, this occurs
    45 s into the video, just after the screen that introduced the "Complete Footage". Yaogan 17 position in the star field
    places the time at about 19:47:19 UTC. The earliest scene of the second camera - the image-intensified one - occurs at
    04:02 of the video, just after the screen that states "2nd camera view," which based on the position of Yaogan 17
    relative the stars, occurred at about 19:46:17 UTC.
    Both times are in good agreement with Lou20764's statement that he spotted the event at 19:47 UTC. The earliest of the
    two times, 19:46:17 UTC, is less than one minute after the point of intersection between the pre and post-manoeuvre
    orbits, which defined the approximate time of the orbit-change manoeuvre.
    Yaogan 17 was in sunlight at that time (in fact, for the entire pass), which satisfies another key visibility
    constraint. The plumes of gas from fuel dumps and significant rocket burns briefly grow to a large size, such that when
    they are illuminated by sunlight and seen against a dark sky, they are readily visible to the unaided eye as brilliant,
    extended objects. Gas clouds from Centaur stages have been observed with the unaided eye at geo-synchronous orbit range,
    i.e. ~40,000 km.
    Many such events have been identified here on SeeSat-L, some of which first came to our attention as UFOs. We have even
    predicted them prior to certain launches, and have received confirming reports.
    Having established that Lou20764's video correlates with the time and trajectory of Yaogan 17, and that its rocket's
    fuel depletion burn and/or fuel dump must have occurred at just about that time, while in sunlight, I can conclude
    beyond reasonable doubt that is what was captured on the video, and seen by other witnesses in the region. Lou20764 did
    a nice job capturing the event.
    Ted Molczan
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