Re: Atlantis and ISS

From: Jonathan T Wojack (tlj18@juno.com)
Date: Thu Apr 18 2002 - 16:45:16 EDT

  • Next message: Sebastian Stabroth: "COSMOS 2388"

    Hello,
    
    > Last evening clouds rolled in that were dense enough to totally
    > obscure the moon but had enough openings to catch the end of
    > the pass.   At 20:49 EDT (00:49 UTC, 18 April) Atlantis led the
    > ISS by about 7 seconds or about 3 degrees of arc.   They were
    > descending in the due south at an elevation of about 40
    > degrees.  Both were about -2 mag.
    
    I saw the same pass a bit north of you.  I was also able to get a
    telescopic lock onto both the Space Shuttle and the International Space
    Station, at 47x.  The Space Shuttle was a ball of whitish light - it was
    featureless.  The ISS, on the other hand, was yellowish, appeared
    slightly brighter than STS-110, and definitely showed structure !!  I
    could make out the solar panels/truss structures.  This is the most
    plainly obvious I've seen structure on the ISS.
    
    I could visually, through the eyepiece, distinguish between the Orbiter
    and the Space Station.  Twice, realizing that I had the Shuttle in the
    eyepiece, I waited, and several seconds later the ISS showed up.  Both
    objects were following the same arc across the sky.  Question: ignoring
    the obvious answer (they were both joined recently), did both objects
    essentially follow the same path across the sky because they both crossed
    the equator at the same angle (38.4d; the supplemental (or complemental,
    I can't remember which) angle to the angle of inclination), and at about
    the same point and time?  After seeing the pass, I suddenly had a vision
    of sorts concerning the mathematics of orbital mechanics.  I then began
    to consider what conditions had to exist for to objects to follow the
    same path across the sky.  Just because I saw the two spacecrafts pass
    by, I understood things I had never understood before....
    
    Would I be correct in calculating that the diamter of the Earth is
    assumed to be 12,827.5 kilometers (or 7970.6 miles) ?
    
    ------------------------------
    Jonathan T. Wojack                 tlj18@juno.com
    39.706d N   75.683d W            4 hours behind UT (-4)
    
    
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