-------------------------------------------------------------------------------
   Computes the orbit velocity in the perifocal plane.
-------------------------------------------------------------------------------
   Form:
   vPQ = VPQ( e, p, nu, mu )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   e                     Eccentricity
   p                     The parameter
   nu              (:)   True anomaly (rad)
   mu                    Gravitational parameter

   -------
   Outputs
   -------
   vPQ             (3,:) Velocity

-------------------------------------------------------------------------------
   References:	 Wiesel, W. E., Spaceflight Dynamics, McGraw-Hill, 1988,
                pp. 63-64.
-------------------------------------------------------------------------------