QHillsToBody:

Path: FormationFlying/Coord

% Compute the Hills-to-Body quaternion
 Compute the Hills-to-Body quaternion given the ECI position and velocity, and
 the ECI-to-Body quaternion.

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   Form:
   qHB = QHillsToBody( r, v, qEB )
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   ------
   Inputs
   ------
   r                (3,:)     ECI position [km]
   v                (3,:)     ECI velocity [km/s]
   qEB              (4,:)     ECI-to-Body quaternion

   -------
   Outputs
   -------
   qHB              (4,:)     Hills-to-Body quaternion

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