RE: Lacrosse elset

From: Ted Molczan (
Date: Sat Apr 30 2005 - 03:31:41 EDT

  • Next message: Paul Henney: "RE: Lacrosse elset"

    Thank you to all who reported observations. I enjoyed reading every one of your
    It was a nice way for Titan IV to end its east coast career, and I am pleased
    that quite a few list members were able to see it. 
    This preliminary elset is derived from 6 of 9 positional observations by Russell
    Eberst, Alan Pickup, Bjoern Gimle and myself, over about a 15 minute arc
    immediately following orbit insertion:
    Lacrosse 5
    1 71001U 05016A   05120.05269919  .00001335  00000-0  10000-3 0    09
    2 71001  56.9932 133.2207 0153942  13.3598  97.7461 14.93250618    09
    WRMS residuals = 0.114 deg
    Perhaps some of the outliers can be salvaged with the aid of he preliminary
    0501501 2420 20050430 010932.04 100900+324200 1.0 1.0 0 S
    71001 05 620A   5919 G 20050430011441090 17 25 1649682+041623 29 S
    71001 05 620A   5919 G 20050430011553210 17 25 1818182-044451 29 S
    I allowed all elements to vary except for drag; epoch is that of the final
    observation in the arc.
    This orbit will be revised somewhat with further observations, but it is very
    believable. Without a doubt, this is the initial orbit of a Lacrosse in a 57 deg
    inclination orbit.
    The argument of perigee results in apogee passes at the latitude of Diego
    Garcia, which is where I expect the orbit to be circularized about 48 h after
    launch, early on 2005 May 02, probably at 01:50 UTC (perhaps one rev earlier).
    That would be in keeping with the pattern established by Lacrosses 2, 3 and 4.
    Finally, I note that Lacrosse 5's plane is about 59 deg east of Lacrosse 3's,
    similar to Lacrosse 4's initial plane spacing 69.3 deg east of Lacrosse 2. One
    month ago, I argued that this approximate spacing was optimal, and expressed
    doubt that this mission was a Lacrosse, because the April 7 UTC launch period
    would not have supported it:
    But then Lacrosse 3's planar precession during the subsequent 23 day launch
    delay brought about the optimal spacing (at least my idea of it) apparently by
    chance. The delay was due to problems with ground support systems, as reported
    in detail by Spaceflight Now:
    This is a great example of how easy it is to read meaning into relationships
    that are merely coincidental.
    Ted Molczan
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