StellarNavigation:

Path: SpacecraftEstimation/OrbitEstimation

% Demonstrate stellar navigation.
   Generates the spacecraft position vector given a star catalog and 
   a range measurement from a ground station. The landmark is assumed
   to be the ground station. If rEst is entered it will use a 
   recursive Kalman Filter. The least squares is unweighted.
   The estimator estimates the unit vector from the ground station to the
   spacecraft. The range is used directly. This routine implements
   the measurement update alone. In practice, you would also use the
   state update.

   This system does not estimate velocity. Normally, range rate would be
   an additional measurement. With the addition of the state update,
   this would give estimates of rate better than differencing position.

   Normally, it would also be necessary to estimate the clock error.
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   Form:
   [r, p] = StellarNavigation( d, range, angleMeas, kAngle, rEst )
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   ------
   Inputs
   ------
   d           (1,1)   Database
                       .rG   (3,1) Ground station position in ECI frame
                       .uS   (3,:) Star unit vectors referred to the origin
                                   of the ECI frame
                       .rho  (1,:) Measurement uncertainty
                       .p    (3,3) Initial state covariance
   range        (1,1)  Range from the ground station to the spacecraft
   angleMeas    (1,:)  Measured star angles from between the star
                       vector and the ground station
   kAngle       (1,:)  Index relating angleMeas to d.uS
   rEst         (3,1)  Initial estimate

   -------
   Outputs
   -------
   r            (3,1)   Position vector
   p            (3,3)   Covariance (Kalman Filter only)

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Children:

Math: Linear/Unit

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