FRotatingSun:

--------------------------------------------------------------------------
   Sail orbit equations in a sun-centered cylindrical rotating frame.
   The equations are nondimensionalized. Sail angle control is included.
   Either sail pitch (angle fron the sun vector) or elevation from the 
   ecliptic plane may be held constant.
   See also SphOrb and FOrb.

   Since version 7.
--------------------------------------------------------------------------
   Form:
   xDot = FRotatingSun( t, x, theta, beta, control )
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   t                (1,1) Time
   x                (6,1) state [rho;theta;z;drho/dt;dtheta/dt;dz/dt]
   theta            (1,1) Sail control angle
   beta             (1,1) Sail lightness number
   control          (1,1) Control type: (1) pitch angle (2) elevation

   -------
   Outputs
   -------
   xDot             (6,1) state derivative

--------------------------------------------------------------------------