Estimated covariance

1

Hello everyone!

I have a few very simple questions: when performing OD using a BatchLSEstimator what are the frame and units of the covariance obtained via the .getPhysicalCovariance(threshold) method? I presume that the frame is the one used to input the observations, but I’m not sure about the units. Is it in m and m/s or km2 and km2/s2? I also presume that the type of covariance is consistent with the type of orbit used inside the estimator, correct? Also, to which date is the covariance associated? The one of the initial orbit?

Best regards,
Emiliano

2

Hi Emiliano,

Apart from a few exceptions maybe, quantities in Orekit are always given in SI units.
You’re right, an orbital covariance is given using the parameters that were used in the propagation, in the frame associated with it. In the least squares case, its epoch is set to the initial time passed to the builder.

Cheers,
Romain.

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