SafeEllipsePosVel:

% Compute the relative SLO-frame position and velocity that corresponds to
  a "safe ellipse" trajectory at a phase angle of alpha.

--------------------------------------------------------------------------
   Usage:
   [rSLO,vSLO] = SafeEllipsePosVel( x0, aE, yA, yR, alpha, n );
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   x0            (1)   Center of along-track motion 
   aE            (1)   Semi-major axis of relative ellipse 
   yA            (1)   Cross-track offset at along-track axis crossing 
   yR            (1)   Cross-track offset at radial axis crossing 
   alpha         (1)   Center of along-track motion [rad]
   n             (1)   Mean orbit rate [rad/s]

   -------
   Outputs
   -------
   rSLO         (3,1)  Relative position in SLO frame
   vSLO         (3,1)  Relative velocity in SLO frame
--------------------------------------------------------------------------