geosat flaring season

From: George Roberts (
Date: Tue Sep 04 2007 - 11:36:54 EDT

  • Next message: George Roberts: "Re: geosat flaring season"

    I have a question for you guys out there.  I'm a very visual person so 
    I will try to explain my question visually.  First of all, if you aren't familiar 
    with geosat flare season (yay!  it's here already!), then read this 
    posting (posting 1):
    If geosats solar arrays face the sun, then the brightest flare should be when 
    I am on or close to a line drawn from the sat to the sun.  The problem with 
    this is that I don't know how to get off this big ball we call the earth and the 
    earth blocks the light to the sat.  Observing at dusk helps because I am 
    nearer the edge of the earth with respect to this line from the sun to the 
    satellite whereas at midnight - not so good (but doesn't mean you can't 
    see flares - these arrays aren't aligned perfectly and aren't perfectly flat).
    Although tonight I think midnight would be better.
    Now I live at lat 42N and so according to this (posting 2):
    the best date to observe is around October 7.  Reading posting 1 
    above it seems I can observe already.  
    Okay - now for my question/point:
    If I could see the earth's shadow at geosynch distance, it would be 
    a circle about 20 degrees in diameter.  At this time in early September 
    according to posting 1, the top of that shadow will just graze the 
    location of all the geostationary satellites (for me at about -7 degrees).  
    This is great because just before the satellites enter that shadow they 
    should get bright.  Now if you project my location on the earth onto 
    that shadow at various times during the night, my position within that 
    shadow will move from the right edge at sunset towards the middle at 
    midnight and towards the left edge at sunrise so I would expect better 
    flares to the right side of the shadow (sats move right to left with respect 
    to stars) in the early evening and better flares left of the shadow in the 
    early morning, right?  Note that this line isn't horizontal nor is it parallel 
    to the ecliptic but would be due east west along the declination line.  
    However, I don't live on the equator or north pole.  If you project my 
    position on the earth back to that shadow again, there is a date when 
    42N right at sunset puts my projected point on the -7 degree declination 
    line.  If I lived on the equator then that date in the postings (sep 23)
    seems correct, but since I am north in the shadow, that date should be 
    quite a bit before the date listed in posting 2 - probably around mid or 
    late september rather than October 7 exactly.  Does this make sense?  
    Can someone come up with a table just like that in posting 2 that takes 
    this into account?  Of course the table should include the spring also.  
    Posting 2 kind of takes this all into account when it metions that the 
    satellite should enter the earth's shadow when that point in the sky 
    is less than 20 degrees from the horizon.  But it seems to give me 
    the wrong 'ideal' date.
    - George Roberts
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