Next version of IRIDFLAR to be released today

From: Matson, Robert (
Date: Tue Jun 12 2001 - 13:42:44 PDT

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    Hi All,
    I observed a nice solar array flare from Iridium 30 last
    night (Tuesday, June 12th) at 21:02:40 PDT from Newport
    Coast, CA.  Peak brightness was a little brighter than
    Vega -- perhaps -0.5.  My Iridium solar array glint model
    was predicting about +0.0, which is well within the
    expected error of +/- 2 visual magnitudes.
    I feel I'm ready to release the current version of the
    program so as to allow a wider data-collecting audience
    for these solar array flares.  More people watching means
    more observations can be reported, allowing me to improve
    on the preliminary magnitude curve that I've put in
    I will be sending the code to Ed Cannon and Mike McCants
    later today so that they can host it.  If anyone else
    wants to host a copy of the program on their website,
    please contact me.
    I want to emphasize that we will never be able to predict
    solar array flare magnitudes as accurately as the regular
    MMA flares since the pointing requirements for the articulating
    solar arrays are far less stringent than those for the MMAs
    (which are tied to the orientation of the satellite itself).
    The solar arrays are always pointed to within 25 degrees
    of the sun; if the pointing error was as much as 3 degrees,
    the worst case loss in energy collecting efficiency would
    only be 2.6% relative to the 25-degree-angle case.  In
    other words, no big deal from a power-generating standpoint.
    When the solar arrays are supposed to be pointed 10 degrees
    away from the sun, they could be off-pointed by 6 degrees
    with a power loss of only 2.4%.
    However, that same 3-degree (or greater) error can have
    a huge impact on the predicted flare brightness, and can
    also shift the flare time by 15 seconds or more depending
    on how low in the sky the flare is expected to occur.
    The bottom line is, don't expect too much accuracy from
    IRIDFLAR's solar array flare predictions -- treat them
    as extra opportunities to see Iridium satellites at
    brightnesses far greater than their typical appearance
    from purely diffuse solar reflectance.
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