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From: Mike Stark <michael.e.stark@gsfc.nasa.gov>
Subject: Applet compiled with AppletMagic 1.6
Date: 1996/10/22
Message-ID: <326CD1EC.27B9@gsfc.nasa.gov>#1/1
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organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA
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Date: 1996-10-22T00:00:00+00:00
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An applet which generates a satellite ground track can be accessed at
   http://fdd.gsfc.nasa.gov/orb_prop/version1/orbit_propagator.html

This page can also be reached via the Intermetric's page
   http://www.inmet.com/javadir/download/demo.html

or the Goddard Flight Dynamics division home page
   http://fdd.gsfc.nasa.gov/

This applet reuses Ada 83 code for orbit propagation, with minor 
additions to compute latitude and longitude.  The graphics part of
the code is implemented in Java, and calls the Ada code to get the
value of longitude and latitude to be plotted.

The Intermetrics AppletMagic tool has pretty much worked as advertised.
We had a few places where the Ada code needed to be modified to pass
the byte-code verifier, but this did not take much effort to fix.  We
also ran into a few places where no documentation existed -- we will
be sending stuff to Intermetrics to incorporate into a future version
of the applet writer's guide.

The current tool doesn't do much more than draw a pretty picture, and
it also takes some mathematical liberties (for those who care about the
difference between siderial and solar days, send e-mail!).  Over the
next several months this tool will be enhanced to get initial orbit
data for actual spacecraft and to generate the corresponding ground 
track.  We will also be adding more text to the web page at some point
describing what we did in more detail.

Mike