Re: Missed Daytime Iridium Flare

From: Thomas A. Troszak (tom@bullhammer.com)
Date: Thu Mar 29 2001 - 06:16:03 PST

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    Tom Wagner wrote: 
    > I have found that sometimes there are no predictions for a flare in my town
    > of 70,000 yet some close neighboring small towns have a bright pass
    > predicted.
    
    I believe that there are at least three Iridium satellites above the
    local horizon at any given moment of the day or night ("handing off"
    signals to provide contimuous coverage), but the probability of seeing a
    flare is small due to the many constraining variables of sun angle etc.,
    and the local population density is not a factor ;-)
    
    I quote from an earlier message from Paolo Bussola:
    
    The maximum brightness of an Iridium Flare at the center line depends on
    satellite elevation upon the horizon because of its distance from us. An
    Iridium Flare at the Zenith point will be at maximum brightness and it
    plots on the ground concentric circles where the flare becomes dimmer as
    we go away from center line. In most cases the plots on the ground will
    be
    concentric ellipses more elongated when the satellite are lower upon the
    horizon. So, a "high elevation flare" has a small "corridor" where
    there'smaximum brightness (60 elevation = +/- 3 km) and a "low
    elevation
    flare"at 10 can be observed at maximum in +/- 15 km. In my page about
    Iridium Flares at:
    
    http://www.geocities.com/pbussola/iridium.html
    
    I drawed two graphs about the brightness of 2 flares at 60 and 10 of
    elevation. They are very interesting!
    Bye!
    Paolo Bussola
    
    I hope this is helpful.
    -- 
    Tom Troszak, Asheville, NC, USA
    35.601 N, -82.554 W
    mailto:tom@bullhammer.com
    
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