Hills2Frenet:

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   Rotate the Hills frame state to the Frenet frame, where x is along-track

   Since version 7.
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   Usage:
   xF = Hills2Frenet( xH, e, nu );

   Note: The number of columns of "nu" and "xH" must be equal if they both
           have more than ONE column.
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   ------
   Inputs
   ------
   xH            (M,:)  Relative state in Hills frame [km] (M = 3 or 6)
   e             (1,1)  Eccentricity
   nu            (1,:)  True anomaly [rad] 
   n             (1,1)  Orbit rate [rad/s]. Optional. 
                          Uses time-derivatives if provided.
                          Uses nu-derivatives is NOT provided.

   -------
   Outputs
   -------
   xF            (M,N)   Local-vertical / Local-horizontal 
                            N = number of columns of nu or xH, whichever
                                is greater
   
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Children:

Common: Transform/RotMat
FormationFlying: Utility/NuDot
Math: Linear/Cross