QUESTION:
Knowing what has happened to the main dish communication antenna,what are
the changes in hardware that we must take in considerations for future
projects in order to keep a good communication link almost all the time?
In other words,what lesson do we learn from Galileo's state of the art
hardware communication equipment?

ANSWER from Byron Yetter on March 19, 1997:
The main "Lesson Learned" from the Galileo High Gain Antenna problems
was that solid HGAs would be used where ever possible.
     
-Nearly all Deep Space Missions since Galileo have gone to a "fixed"
or solid dish design. This eliminates the need to open or deploy an
umbrella type antenna. Mars Pathfinder as an example, will use a 
solid dish type antenna for its High Gain communications 
requirements. This antenna will still need to be pointed (slightly)
each day as the Mars orbit/rotation changes the line of sight to 
Earth.
     
-Also, since non-Shuttle type launch vehicles have come back into
service, Shuttle bay size constraints no longer drive the need for
a deployable HGA. At the time Galileo was launched NASA was working
hard at making the Shuttle the only Earth to space vehicle. 
     
-Advances in Spacecraft antenna, transmitters, and receivers 
technology, as well as the ground based tracking hardware, has also
reduced the overall size requirements of HGAs. We can effectively
communicate with spacecraft with smaller HGAs.