QXToAlphaDelta:

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   Cone and clock angles (alpha,delta) to inertial quaternion.

   delta is defined with respect to the osculating orbital plane, where
   k_hat is the unit vector orbit normal.
   The sail normal is defined along the X axis in the body frame.
   n = (cos alpha) r_hat + (sin alpha sin delta) theta_hat + (sin alpha cos delta) k_hat

   When the angles are zero, then
     n_hat = r_hat = Xbody
     theta_hat = Ybody
     k_hat = Zbody

   Since version 7.
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   Form:
   [alpha, delta] = QToAlphaDelta( q, x )
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   ------
   Inputs
   ------
   q      (4,1)   Inertial quaternion in the solar ecliptic frame
   x      (6,1)   [r;v] Cartesian state

   -------
   Outputs
   -------
   alpha  (1,1)   Cone angle
   delta  (1,1)   Clock angle

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   Reference: Bong Wie, Propellantless AOCS Design for a 160-m, 450-kg 
   Sailcraft of the Solar Polar Imager Mission, AIAA 2005-3928, p. 11
------------------------------------------------------------------------

Children:

Common: Quaternion/QTForm
Math: Linear/Cross
Math: Linear/Unit