XPost: sci.astro, sci.physics, sci.space.policy   
   From: willner@cfa.harvard.edu   
      
   > >The [JWST] telescope is folded, not only the solar arrays.   
      
   In particular the 6.5-m primary mirror is folded as well as many   
   other pieces.  It's frightening to watch the deployment videos.   
      
   In article ,   
    Fred J. McCall  writes:   
   > And THAT is because you cannot make a single mirror that large to   
   > adequate precision,   
      
   At least three observatories with seven telescopes in active use will   
   be surprised to learn that.  Not to mention additional ones planned.   
      
   Every JWST presentation I've seen that mentioned the subject said   
   that using a deployable (folding) mirror is because the Ariane 5   
   shroud is too small to fit a 6.5-m mirror.  I wouldn't be surprised   
   if there are "black" programs with the same difficulty.   
      
   That said, this particular use case doesn't necessarily justify a   
   rockoon approach, which will be difficult at best for large boosters.   
      
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   Steve Willner            Phone 617-495-7123     swillner@cfa.harvard.edu   
   Cambridge, MA 02138 USA   
      
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