A familiar number

From: Matson, Robert (ROBERT.D.MATSON@saic.com)
Date: Thu Apr 10 2003 - 14:32:22 EDT

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    Hi All,
    I've followed the discussion of the STS-107 co-orbiting "mystery debris"
    interest, but not 'til today did something REALLY grab my eye.
    Ted wrote:
    "Last night, I analysed the OIG elset using the same method as in Section 3
    my report, and found that A/m was 0.049 m^2/kg - about 20 percent greater
    the value derived from my estimated elset, well within the uncertainty in
    rate of decay. One of my correspondents has obtained a value of 0.051
    using a different, probably more accurate method."
    This was the first time I had seen a number for the A/m ballistic
    for the co-orbiting STS-107 debris.  Now here's the interesting part -- I
    recognized that number.  You see, I spent several hundred hours doing a
    detailed analysis of Columbia debris piece #6 -- the largest of the pieces
    of debris shed by Columbia as it was flying over California and Nevada.  The
    key piece of evidence in this analysis was John Sanford's video of the
    which he recorded from Springville, CA.  John was kind enough to send me a
    copy of his video, which I poured over frame by frame, extracting separation
    distances between Columbia and the bright debris piece at 25 time points
    during the ~10 seconds that the debris was in the camera's field of view.
    A very complicated analysis followed, folding in the geometry of the pass,
    optical characteristics of John's camera, truth data of Columbia's path,
    and the density of the upper atmosphere as a function of altitude.  Pixel
    separation distances were successively converted into angles, then projected
    linear distances, real linear distances, and ultimately real positions.  The
    end result is that I could derive a ballistic coefficient for the debris
    based on its deceleration.
    The 25 data points I measured from John's video all fall on a nice smooth
    curve; the least-squares fit to the BC that produces this curve is .0491
    Look familiar??!  Perhaps it's merely an amazing coincidence.
    When I completed this analysis a month ago, my assumption was that debris
    #6 was an RCC panel from the left wing leading edge.  There was no way it
    was a shuttle tile or group of shuttle tiles -- the mass-to-area ratio
    was far too high.  Propagation of the debris down to the ground, folding
    in the jet stream and surface winds (based on radiosonde data), resulted
    in an impact point very close to the Nevada/Utah border near 114.00 W,
    37.45 N.  I sent my analysis to several NASA contacts, partly out of
    concern that debris searchers in Nevada were concentrating their efforts
    northeast of Panaca, NV -- an area that no Columbia debris could possibly
    have reached.  To this day, I still have no confirmation that search
    efforts were redirected southeast to the area I indicated.
    Unfortunately, the area in question is a nasty place to have to look for
    debris -- forested and mountainous.  It may be months or years before the
    debris is found, if it ever is.  Still, it would be an important find --
    perhaps THE most important find, since it was the earliest known piece
    of significant debris to come off Columbia (aside from the unrecoverable
    co-orbiting debris).  --Rob
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