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  Collision monitoring algorithm. Discretizes orbit according to input
  time and anomaly vectors. Handles high eccentricity and maneuvers input
  through accel.
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  Form:
  [prob, dMin, Shat, xhat] = CollisionMonAlg( y, t, M, nu, accel, aDiff, d )
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   Inputs
   ------
   y      (6,m)   Relative state(s)
   t      (1,n)   Time vector, s
   M      (1,n)   Mean anomaly vector
   nu     (1,n)   True anomaly vector
   accel   {m}    Accelerations due to maneuvers
   aDiff          Differential acceleration
   d        :     Algorithm data structure
                  .el0
                  .eRef          Eccentricity
                  .MRef          Mean anomaly
                  .initBounds    Error in measurement (6,1) [km, km/s]
                  .scalev        Sigma for measurement noise
                  .lenSC         Spacecraft length [m]
                  .Pmin          Probability of scalev
                  .Ssc           Spacecraft hard-body sphere
                  .S0            Initial ellipsoid

   Outputs
   --------
   prob   {n}(1,:)     probability of collision    
   d      {n}(1,:)     minimum distance between spacecraft position ellipsoids
   xhat   {n}(6,:)     xhat, ellipsoid centers
   Shat   {n}(6,6,:)   Shat, ellipsoid size matrices
 
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