QUESTION:
In order to facilitate more similar missions, wouldn't
it make more sense to construct a space station with
facilities to build probes such as the one being sent to
Jupiter?

ANSWER FROM Jim Erikson on Dec. 21, 1995:  
There is a large "startup" cost involved in designing, building and using
a space station with the facilities needed to manufacture outer planets
probes.  The current plan for space station Freedom (which will be in
orbit around the Earth) will cost upwards of $10 Billion.  A space station
with large manufacturing capabilities would be at least 2 to 3 times as
expensive. 

Putting something out in the asteroid belt, and having transportation that
can take humans back and forth, is going to be a LOT more expensive.  The
current costs for planetary missions, including operations and data
processing range in the $100 Million to $1 Billion range.  The advantages
of developing a planetary mission on a space station would involve the
cheaper launch costs, which are only a fraction of the total (10% or so). 
Clearly, we shouldn't build a space station for thais reason. 

But there are valid reasons for building large, capable space stations. 
Being free of the Earth's gravity will enable missions that we haven't
even begun planning for, particularly large unmanned or manned missions. 
As has been said,

"low Earth orbit is halfway to anywhere."

I don't know of any currently planned missions to either Uranus or
Neptune.  However, JPL and NASA have many projects in development, from
the Cassini mission to Saturn, the Mars Pathfinder (Lander) and Mars
Global Surveyor, to the Pluto Express mission.  Other missions are also
planned, to numerous to mention. 

The next fifteen years will be a great time to be alive!