[from website]
This dockapp shows you the actual distance of Jupiter in astronomical
units (AE) and when the red spot crosses (which is a weather feature
on jupiter).  The four Gallileo Moons are displayed too but only
when they are near the planet (Io, Europa, Ganymede, and Callisto).
The position of the red spot changes on the surface so you need to
change that value within few months or so. The current position can
be found on the internet. It was 80 deg. as of 11th Jan 2002.

WWW: http://www.inxsoft.net/wmjupiter/
Author: Thomas Kuiper <tkuiper@inxsoft.net>
