From: jrfrank@ibm-pc.borg.retro.com   
      
   "Duram" <"danur@"@ig.com.br> wrote in news:c9dkl601f1k@news4.newsguy.com:   
      
   > How is the Hubble positioned in space?   
      
   The word you are probably looking for here is "oriented", not "positioned".   
   HST's position describes where it is, which changes constantly since it is   
   in orbit around the Earth. HST's orientation describes which way it is   
   pointing.   
      
   > parallel to earth?   
   > pointed up?   
      
   HST's orientation is controlled with respect to the stars (i.e.   
   inertially), not with respect to the Earth.   
      
   > Is it possible for the space telescope to change position?   
      
   No. HST's position is entirely dictated by orbital mechanics; it has no   
   capability to change its orbit. HST *can* change its orientation.   
      
   > How they move it to see a star they want to look?   
   > It has rockets?   
      
   HST has no rockets. It controls its orientation with a set of momentum   
   wheels. Spin the wheel one way, HST spins the other way. With at least   
   three wheels it is possible to point the telescope in any direction   
   desired. To keep the wheels from spinning too fast, HST also has a set of   
   magnetic torquers that work against the Earth's magnetic field to allow HST   
   to slow the wheels down without losing control.   
      
   > Can it look down to earth?   
      
   It can. However, in its low orbit, the surface of the Earth moves by too   
   quickly for HST to get good pictures of it.   
      
      
   --   
   JRF   
      
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