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   Computes the dipole vector needed to produce a torque t
   given the magnetic field b. This minimizes the weighted sum
   of the following cost functional:

   J = (t + Cross(b,m))'(t + Cross(b,m))' + m'm

   Only two elements of t can be constrained. These axes are selected
   using the vector a. The other component of t will be uncontrolled. Any time
   the components of b corresponding to the constrained components of t are
   aligned this algorithm will demand very large dipoles.

   If b is not entered it computes the magnetic field for an orbit 
   whose radius is 7000 km and inclination is 28.4 deg. The default t is
   [1e-5;1e-5] and the default a is [1;2]. The demo is run by typing:

   MagControlTwoAxis

   The dipole results are in ATM^2.
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   Form:
   [m, e] = MagControlTwoAxis( t, b, a )
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   ------
   Inputs
   ------
   t               (2,1)   Torque
   b               (3,:)   Magnetic field vector in the torque frame
   a               (2,1)   Axes corresponding to the values in t

   -------
   Outputs
   -------
   m               (3,:)   Magnetic dipole vector needed
   e               (3,:)   Torque error

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