Custom Observations 
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Custom observations provide a scriptlevel interface via the CustomObservation object that allows the user to leverage FreeFlyer's orbit determination capability and inject their own unique measurement model to be used by FreeFlyer's estimators. All estimators support the processing of custom observations. To run orbit determination using custom observations, two separate parts of the measurement model must be computed by the user:
The computed value is the predicted value of the measurement based on the propagated states, and is set with the SetComputedValue() method. The partial derivatives from the matrix which maps the measurement information to the estimated state is set by the SetPartialDerivatives() method(1).
Uniform Gravity Field Trajectory
Sample CalculationsFrom the image above, the range and rangerate can be computed with the following expressions and set as the SetComputedValues(), where Xs, Ys, Xdots, and Ydots are the position and velocity components, respectively, of the tracking station.
This can be configured in script as follows:
The matrix is a mapping matrix that relates the observation deviation vector, y = [delta row, delta row_dot], to the state deviation vector, x = [deltaX deltaY deltaX_dot deltaY_dot], and can be set with the SetPartialDerivatives() method.
This can be configured in script as follows:
References:
See Also
