Re: Milstar 5 Titan 4/Centaur Launch

From: Michael McCants (
Date: Wed Jan 16 2002 - 15:29:08 EST

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    As Ed Cannon wrote, I arrived at BCRC about 01:45UT (all times
    Jan 16, 2002 UT) and I spotted the combined Milstar 5/Centaur Rk
    object about 02:01UT about 1 minute late on an elset that I
    generated for the transfer orbit (based on an elset that Ted Molczan
    sent me for the original target launch time).  The 02:00 prediction
    from BCRC (30.315N, 97.866W, 280m) was altitude 48, azimuth 263,
    range 3000 miles.  My estimated magnitude at this point was 5.5,
    but my magnitude estimates are always too bright.  A magnitude of
    6.0 would produce a Quicksat intrinsic magnitude of 1.5 and a
    Molczan intrinsic magnitude of about 2.5.
    I tracked the object for 15 minutes as it rose rapidly to altitude
    81 and went just to the south of my zenith.  At 02:30UT it was alt 69,
    azi 121, range 7300 miles and estimated magnitude 6.7 (probably about
    7.0).  Ed saw a flash at 02:33 through the 8-inch and I looked through
    the 12x80 finder scope.  We saw a flash at 02:33:25 that I estimated at
    about -2 magnitude.  Ed saw another minor flash at 2:37:30.
    At 02:46:34, I saw a flash that I estimated was magnitude 4.5.
    I estimated the object magnitude as 7.2.  This was alt 63, azi 117,
    range 9500 miles.
    We tracked the object for the next few hours.  We noted flashes
    at 03:43:40, 03:49:40, 03:55:39, 04:10:03, 04:12:25, 04:36:40,
    04:39:42, 04:42:39, 04:45:38, 04:48:57.  The object was changing
    from magnitude 7.5 to 8.5 during this time and the flashes were
    about 2 magnitudes brighter than the object.  Note periods of
    3 minutes and 6 minutes in the above data.
    We were hampered by some clouds off-and-on from 05:05 to 05:45 and
    again from 06:15 to 06:35.
    I switched from a 50x eyepiece to a 90x eyepiece for the 8-inch
    during this time.
    The "action" started at 06:47.  We saw three very similar operations.
    Each one started with symmetric fan-shaped plumes going north and south
    from the object.  Then the plumes expanded into faint crescent-shaped
    "shells".  These started at 06:47, 06:48:05, and 06:48:55.
    Then at 06:53:55, the Centaur orbit circularization burn started.
    This was a fan-shaped plume going back to the west.  At 06:54:45,
    the burn ended and a "gap" became visible between the plume and
    the object.  At 06:56 I estimated that the plume appeared to be
    about 5th magnitude in the 12x80 finder scope.
    At 06:56:30, the object brightened to magnitude 5 very briefly and
    another plume appeared to the west.  This was a very short event
    and a gap between the plume and the object appeared almost immediately.
    At 06:59 I noted that this second plume was very faint, but Ed said
    he could still see the first plume in his binoculars.  The object
    was moving away from the plumes.  Probably a 1 degree gap between
    them after only 5 minutes.
    At 07:22:56, there was a single event very much like the original
    three events at 06:47.  Two plumes were emitted north and south for
    a few seconds and they moved away from the object and formed two
    crescents and dissipated over the next 2 minutes.
    At 07:26, I believed I could see a second object "in front of"
    (east of) the brighter object.  The two objects separated very slowly.
    At 07:30:25, the "main event" (Centaur fuel dump) started.
    A fan-shaped plume was emitted to the north.  This gradually grew
    in size and brightness.  At 07:37 it was estimated to be 0.2 degrees
    in diameter and magnitude 2.5.  It was easily visible to our unaided
    eyes.  At 07:39, the size was 0.3 degrees and there was a gap between
    the bright object and the plume, so the fuel dump had ended.
    The plume continued with the two objects.  The fainter object remained
    at the "base" of the plume.  The brighter object gradually moved away
    from the fainter object (moving to the south and east).  I continued
    to obtain star passage timings for the two objects to allow me to determine
    orbits for each.  By the time I stopped at 08:21, the two objects
    were about 0.3 degrees apart and the plume was only very faintly
    visible in the 8-inch about 0.3 degrees noth of the faint object.
    The bright object was about magnitude 9.0 and the faint object was
    about magnitude 10.0.  I assume that the bright object was the Centaur
    and the faint object was the Milstar 5.
    Spacecom has assigned catalog numbers 27168 to the Milstar 5 and
    27169 to the Centaur.
    Mike McCants
    Austin, TX
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    This archive was generated by hypermail 2b29 : Wed Jan 16 2002 - 15:35:55 EST