Re: Can Someone Predict This?

From: Edward S Light (light@argoscomp.com)
Date: Tue Apr 16 2002 - 09:47:27 EDT

  • Next message: Ted Molczan: "RE: Can Someone Predict This?"

    Earlier this morning, Art Glick asked: 
    > 
    > I have just learned that approximately 6 hours and 14 minutes after the
    > Shuttle is scheduled to undock from the ISS, it will make a very nearly
    > overhead pass here, and I'm wondering what the apparent distance will be
    > between them at this time.
    > 
    < ... stuff deleted ... >
    > 
    > In particular, I'd be very interested in knowing what some of you would
    > expect to see in terms of the amount of separation between the two objects.
    > 
    
    The problem is that we don't know exactly what the ISS and STS' orbital
    elements will be like 1.5 days in the future. The NASA website:
       http://spaceflight.nasa.gov/realdata/elements 
    has predicted elements for the remainder of the STS-110 mission and
    gives, for tomorrow evening (EDT):
    STS110
    1 27413U 02018A   02107.88245779  .00071000  00000-0  10050-3 0  9041
    2 27413  51.6357 355.8819 0009603 343.5190  16.5651 15.58512204  1433
    ISS
    1 25544U 98067A   02108.07491017  .00070138  00000-0  83646-3 0  9045
    2 25544  51.6360 354.9209 0007701 352.0218   8.0813 15.58001937  4699
    
    Using these elements, and Rob Matson's SkyMap program for your assumed
    coordinates, I find (all times being EDT on Wednesday 2002 April 17):
      20:48:23 Shuttle at 85 degs elevation, 222 degs azimuth (SW)
      20:48:29 ISS     at 85 degs elevation, 223 degs azimuth,
    the two objects being six degrees apart.
    
    Using the same input data, Mike McCants' quicksat program gives essentially
    the same result:
      20:48:24 Shuttle at 86/218
      20:48:30 ISS at 86/218
    
    Of course, when just 4-5 degrees from the zenith, "differences" of
    5-6 degrees in azimuth are insignificant :)
    
    In all, the biggest uncertainty is the lack of an accurate crystal
    ball to give the future orbital elements.
    
    Clear and dark skies!
       Ed Light
    
    Lakewood, NJ, USA
    N 40.1075, W 074.2312, +24 m (80 ft)
    
    PS: From my location, the same passes described above will be just
        33 degrees above my SW horizon; Art should have a spectacular
        view!
    
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