UARS: Evolution of Decay Predictions

From: Ted Molczan (
Date: Fri Sep 23 2011 - 03:16:32 UTC

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    I have plotted the evolution of the decay predictions, to show the gradual convergence on the actual date and time.
    Most of the data consists of Satevo 0.51 propagations of USSTRATCOM TLEs, but it also includes those of USSTRATCOM, The
    Aerospace Corporation, and Harro Zimmer. All were in reasonably close agreement, most of the time.
    The first plot shows the past two weeks. Two weeks ago, it appeared that the decay would occur during Sep 29 - Oct 01
    UTC, but the increased drag associated with high geomagnetic activity during Sep 9-13, advanced the decay by about one
    The second version focuses in on the past four days, during which the predicted decay ranged between Sep 23, 14 h and
    Sep 24, 07 h UTC. It now seems to have narrowed to Sep 23, 21 h - Sep 24, 03 h UTC.
    Ted Molczan
    Seesat-l mailing list

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