USA193 decay and flux values clarified

From: George Roberts (gr@gr5.org)
Date: Wed Jan 30 2008 - 14:58:15 UTC

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    Okay - I read what Vossinakis and Ted wrote about solar flux and decay and I 
    looked at the web page and I was very confused but I think I understand what Ted 
    is saying - I'm not really adding anything to what Ted said but I didn't 
    understand it until now and figure other people as dumb as me had just as much 
    trouble.
    
    The Flux value entered is used to determine the area to mass ratio (A/m).  This 
    needs to be known before satevo can predict how quickly a satellite will come 
    down.  This means that the Flux value entered was for *the past*.  So higher 
    values of Flux in *the past* for the same rate of decay in the past implies the 
    satellite has a high area to mass ratio (like a feather - it's gonna slow down 
    quickly).  Lower Flux values in the past result in a higher A/m (like a rock - 
    it will take longer to succumb to drag).  This (A/m) factor changes the 
    prediction more than potential future flux which has the opposite effect.
    
    Does that make sense?
    
    Again: low flux in the past implies it will come down sooner, low flux in the 
    future implies it will come down later.  The "past" affect has a stronger weight 
    in the equation.
    
    Maybe satevo should ask for two different flux values - past and future.
    
    - George Roberts
    http://gr5.org
    
    ----- Original Message ----- 
    From: "Ted Molczan" <ssl2molcz@rogers.com>
    To: <seesat-l@satobs.org>
    
    
    > Vossinakis Andreas wrote:
    >> the bigger the value (which means strongest solar activity),
    >> the decay time moves later.
    >
    
    Ted Molczan wrote:
    > The program uses the solar flux to estimate atmospheric density at the 
    > altitude of
    > the satellite at the epoch of the initial elements, then combines this
    > information with the object's rate of decay to estimate its ballistic
    > coefficient, which is its cross-sectional area divided by its mass, denoted by
    > A/m. 
    
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