Re: searching for USA 129

From: Björn Gimle (
Date: Fri Dec 26 2003 - 07:44:07 EST

  • Next message: Ed Davies: "O/T HearSat-L, was: ISS on the radio"

    IMHO, it seems that a small manoeuver by 161 is unusual, and probably done
    only to correct inclination or track timing in preparation for the next one
    by 129. OTOH it is more likely that when 161 is raised, it is by a large
    amount (to reach 14.72 or so), although it did not reach the normally
    significant MM=14.84 yet.
    But it may be that they prefer to change the orbit while it is most
    difficult for amateurs to discover. Tony has only occasional passes around
    20 deg elev, usually just above 10 deg. I may spot it in the afternoon
    twilight, low in NW.
    129 is usually raised alone when the pass time reaches 2h 45m before 161,
    to a MM lower than that of 161, by an amount that causes the drag to reduce
    the pass time difference to 2h 20m by the time their MMs are equal.
    Roughly, this means that its new MM differs from that of 161 by the same
    amount as before, but with opposite sign.
    In this case, it would mean a change from 14.8456 to 14.8113, since 161 had
    By coincidence, or more likely careful planning, this 2h 45m diff was
    reached on the same day that USA 161 had its perigee on the equator !
    Since it has not been found on any of Ted's search elsets, I would propose
    that the large raise was made, probably on the evening of Dec.19, when USA
    161 perigee was on the equator. You can make search elsets by just adding
    small +- increments to MM, eg 14.719 14.739  and 14.733 14.753
    USA 129 +19 m/s
    1 24680U 96072A    3353.75010000  .00027406  00000-0  28356-3 0    11
    2 24680  97.7982  53.4604 0545501 117.4163 359.3733 14.72878899   207
    USA 161 +14 m/s
    1 26934U 01044A   03353.84324512  .00002200  00000-0  90000-4 0    28
    2 26934  97.9250 105.5870 0354827   0.1152   0.0078 14.74316830    15
    ----- Original Message ----- >
    > The last time USA 161 manoeuvred, its mean motion went from about 14.834
    > to 14.82 rev/d. This time, its mean motion likely had not quite reached
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