# What are all the elements of the expression returned by KalmanEstimator used for?

The first "Application" in the documentation for KalmanEstimator is copied below with additional variables for clarity.

Clear["Global*"];
a={{0.5,0.07869},{0,-0.60653}};
b={{0.0042,0.0104},{0.0786,0.00786}};
c={{1,0}};
d={{0,0}};
antenna=StateSpaceModel[{a,b,c,d},SamplingPeriod->0.1]


processVariance=0.07;
measurementVariance=0.001;
processCovariance={{processVariance}};
measurementCovariance={{measurementVariance}};
kalmanEstimate=KalmanEstimator[{antenna,All,1},
{processCovariance,measurementCovariance}]


The dimensions of the lower submatricies in kalmanEstimate have three rows. In the next line (SystemsModelExtract) is used to ensure we only use the third row from the lower submatrices. What are each of the rows in the lower submatrices (kalmanEstimate) above used for?

kalmanFilter=SystemsModelExtract[kalmanEstimate,All,{3}]
`