 > 
 > 
 > SOmebody mentioned  a re-boost of HST during this mission,  meaning
 > that Weight is a very tight  margin on this  mission.
 >  

I haven't heard any hint of a re-boost, or that any is needed.

 > 
 > why not  grapple,  do all said fixes,   bolt a small  liquid  fueled
 > thruster module  to  HST,   then let it make the re-boost.  it has to be
 > cheaper on mass then usingthe shuttle as a tug.   

Nasty, dirty combustion products!  People have gone to monumental efforts to
keep HST clean.  We certainly aren't going to bolt any thrusters to it.