RE: Iridium double-flare

From: Matson, Robert (
Date: Tue Mar 06 2001 - 20:20:08 PST

  • Next message: Patrick McNally: "Iridium 36 Double Flare"

    Hi Rod (and list),
    Thanks for your latest report observation on the double
    flare from Iridium 35 (#24966) on the evening of 05 March.
    I'm beginning to get the impression that these extra
    flares are solar-panel related, as the LVLH pointing
    vector for whatever surface (or surfaces) that are causing
    the extra flare is changing from night to night.
    For example, the following list gives the satellite's
    local pointing normals corresponding to the observed
    extra flares for Rod's location:
    2 Mar 2001 IR36 19:40:30 m-3.4 az 129.7, el -35.9
    3 Mar 2001 IR 7 19:34:10 m+3   az 127.1, el -36.0
    3 Mar 2001 IR51 19:34:30 m-2   az 126.7, el -35.9
    4 Mar 2001 IR61 19:37:05 m+1   az 128.4, el -38.5
    5 Mar 2001 IR35 19:30:40 m+0   az 124.1, el -39.5
    Michael Gill also observed this last flare from Iridium 35
    from a slightly different location:
    5 Mar 2001 IR35 19:30:50 m-3   az 123.3, el -38.3
    From these 6 data points, there is no direct correlation
    between the secondary glint brightness and the derived
    az/el of the "effective" surface normal.  This means one
    of two things: either the surface causing the glint is
    not stationary from night to night with respect to the
    satellite body coordinate system (e.g. a moving solar
    panel, or crosslink antenna), or the glint is caused by
    a multiple reflection.
    So keep those extra glint observations coming!  In the
    meantime, I'll work on some double-bounce geometries to
    see if any reasonable solutions pop out.
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