->  DW> So 1/2 is not a significant fraction?  
 
-> i dunno... i hear "significant fraction" as "more than
half" ;) 
  
I think most people hear it as "more than a few percent". 
  
->  DW> So the length of the  tangent from the surface to the station would 
->  DW> be sqr(400 * 13400),   
 
-> where do you get 13400 from? the diameter of the earth plus the station's 
-> altitude above the earth? wouldn't that be 13800 then? if the station is in  
-> perfectly circular orbit, that is... not that its going to make that much 
-> difference in the math... what's a few kms, here and there out of several 
-> hundred ;) 
  
There's a geometrical theorem. If you have some point, P, which is 
outside a circle, and you draw a line through P which intersects the 
circle at two points, A and B, and you draw another line through P that 
intersects the circle at C and D, then: 
  
PA . PB = PC . PD 
  
(PA, for example, means the distance from P to A.) 
  
In the limiting case, if the line is tangential to the circle, touching 
it at point T, then: 
  
PA . PB = (PT)^2 
  
So, if the ISS is 400 km perpendicularly above the surface of the 
earth, its distance from the point on the opposite side of the earth is 
13400 km, i.e. the diameter plus the 400 km height. So (PT)^2 is 
400*13400. 
  
No. I didn't bother with nitpicking details. 
  
-> mmmmm... i think you may be on to something, too... i'm seeing a SUN LOS of 
-> 21:00 and a SUN AOS of 52:12... subtract the LOS from the AOS and we get a n 
-> 31 minutes, 12 seconds of "no sun"... since i was figuring
45 minutes and i/ 
-> see that it is actually 31 minutes, that gives us 59 minutes in sunlight...  
-> figure 60/30 ... 2/3rds of the time is spent in the sunlight... 
  
I guess that's when the sun is well away from the ISS's orbital plane. 
In the extreme case, if the orbit were perpendicular to the direction 
toward the sun, the station would spend 100% of the time in sunlight. 
However, this never actually happens, since the orbit is nowhere near 
polar. 
  
-> now to continue on with the quest as to why the station rotates from
"pushin 
-> the shuttle when it docks to "pulling" it and then back to
"pushing" it when 
-> the time comes to undock ;) 
  
I already explained that... 
  
                                dow 
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