Core2SA:

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   Transforms a vector from the core frame to the solar array frame
   when the sun sensor is attached to a solar array that is rotated
   an angle a with respect to the core. When a = 0 the +z array axis
   is aligned with the +z core axis

   Since version 1.
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   Form:
   v = Core2SA( a, u )
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   ------
   Inputs
   ------
   a            (1,1)      Angle (rad)
   u            (3,1)     Vector in the core frame

   -------
   Outputs
   -------
   v             (3,1)    Vector in the array frame

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