LVLH2Hills:

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   Converts a state vector from the LVLH to the Hills coordinate frame.

   Since version 7.
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   Form:
   xH = LVLH2Hills( xL )
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   Inputs
   ------
   xL               (6,:) [r;v] LVLH frame

   -------
   Outputs
   -------
   xH               (6,:) [r; v] Hills frame

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