QProp:

Path: SC/Sensor

% Propagates a quaternion based on updated angular increment measurements.
   The integration order can be specified but only correction terms up to and
   including the fourth order terms are included. The third order correction
   terms require the measurements from the previous time step. The fourth order
   correction terms require the measurements from the two previous time steps.

   Note that the sign of all correction terms is opposite that given in the
   Wong and Breckenridge reference. Testing has not shown this to be an issue.

   Since version 3.
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   Form:
   q = QProp( qLast, theta, n )	
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   qLast           (4,1)  Quaternion at last time step
   theta           (3,k)  Angular increments from gyro
                            The first column is the most recent output.
                            The second column is the previous output.
                            The third column is the output from 2 time steps ago.
   n               (1,1)  The order of the propagator. Terms up to theta^n
                            will be included.

   -------
   Outputs
   -------
   Q3              (4,1)  Updated quaternion

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	References: Wong, E.C. and W.G. Breckenridge, "Inertial Attitude Determination
             for a Dual-Spin Planetary Spacecraft", AIAA Journal of Guidance
             Navigation, and Control Vol. 6, No. 6, Nov-Dec 1983, pp. 491-8.

             Iwens, R.P. and R.L. Farrenkopf, "Performance Evaluation of a
             Precision Attitude Determination System", AIAA Paper 71-964, 1971.
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Children:

Common: Quaternion/QMult
Common: Quaternion/QPose
Math: Linear/Factorl
Math: Linear/Unit

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