RE: Non obs report dec 23 (USA 129)

From: Ted Molczan (
Date: Tue Dec 23 2003 - 11:30:39 EST

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    Tony Beresford reported:
    > Used Ted's search elements looking for USA 129, bracketed the 
    > time 1 minute before earliest to 1 minute after latest 
    > prediction. This was a pass at 31 degrees maximum elevation 
    > in the West. Used 7x50 binoculars. Saw nothing Tony Beresford
    USA 129 (96072A / 24680) could have been fainter than predicted, putting it just
    beyond the reach of 7x50's. I have experienced many faint low west passes,
    difficult to see even with 11x80's, so I suggest trying again on a better pass.
    If it still fails to show, then we must consider other possibilities:
    1. The magnitude of the manoeuvre could have much different than expected, but
    its mean motion was ripe for the size of manoeuvre that I estimated.
    2. Perigee could have been raised, and apogee lowered, to produce a low drag
    orbit similar to those of the two KH's in the eastern planes (95066A and
    01044A). This would be unprecedented for a KH while still in the operational
    western plane, but not shocking. Reducing drag to conserve propellant now (at
    the expense of some resolution), might be a sensible hedge against the potential
    failure of the replacement launch on the final Titan IVB, believed to be
    scheduled for 2005 Feb.
    3. It could have been de-orbited. At 7.01 years of age, it is nearing its end of
    life, and has spent the second longest duration in a primary KH plane (the
    longest was 7.52 years). If USA 129 remains otherwise healthy, but is low on
    propellant, then the drag-reducing manoeuvres discussed above make sense, and
    could extend life by up to several years. The two longest KH missions (total
    time in orbit, including time in s secondary plane) lasted 8 and 10 years,
    Ted Molczan
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