QUESTION:
My question is did you ever have a problem writing
the computer programs for the exposures?

ANSWER from Wayne Baggett May 16, 1996:
Yes, there have been problems with the computer programs which set up and 
take the exposures with the Hubble.  There are millions (really!) of lines 
of code in these computer programs, and as good as the programmers are 
(I'm only one of several hundred), problems will always be present in 
programs as large as these.  Programmers cannot possibly anticipate all 
of the conditions a program is ever going to encounter, so sooner or later 
a problem will be discovered.  

Hopefully, the problem is found on the ground and no science exposures 
are hurt by it, but sometimes they only happen when an exposure is being 
taken.  When a problem is discovered, the programmers have to analyse the 
conditions and then search the right part of the program to find out why 
it happened, then figure how to fix the problem without making more.  
It's really like a big detective story.  After I discoved a particularly 
bad problem, I had someone ask if there were any more waiting to hurt us, 
and I answered without hesitating, "Yes!"  Needless to say, he wasn't very 
happy with my answer, but it really is just a part of working with 
huge programs.

Thanks for the questions.  I hope you have enjoyed the Live from HST program,
and have learned some interesting things about how these kinds of projects
really work.  Have a good summer!

Wayne Baggett
Computer Sciences Corporation
Space Telescope Science Institute