Covariance Propagation with Ephemeris Propagator

Hi guys,

I am currently dealing with the covariance propagation coming from an ephemeris file.
The CCSDS OEM format might have only one covariance matrix sample in it, which then I would like to propagate during the whole arc of the ephemeris file.

I tried to use the new MatricesHarvester interface that was introduced in the last releases, however it triggers an unsupported exception when coupled with an ephemeris propagator.
So, to be able to propagate the covariance I thought of spawning a NumericalPropagatorBuilder, fitting the trajectory in the ephemeris propagator and then use the harvester to compute the covariance matrix at each step during the propagation with the newly created NumericalPropagator.

However I was wondering if there could be a simpler approach with the current release (v 11.2.1) or if you plan to provide a different solution in the future to deal with this particular case?

Thank you

Leonardo

Hi @Leonardo,

“It is normal” (or not :slight_smile:)
With the current version of Orekit, the Ephemeris propagator doesn’t have a matrix harvester. Therefore, it is not able to compute a state transition matrix and then it can’t propagate a covariance matrix. That’s why you have the unsupported exception.
Adding the harvester is a new feature we must add. It is straightforward to do since we already have a lot of matrix harvester implementations that can be used as example.

We implemented for the next version (i.e. 11.3) a new class able to propagate a state covariance matrix using the common used linear model. Its name is StateCovarianceMatrixProvider. The class uses the concept of AdditionalState, so it can be easy to configure and to add to an orbit propagator. It works for all propagators having a matrix harverster. So, it works for the numerical propagator.
Once the harvester added for the Ephemeris, it will also work with it.

I don’t know if we will have time to implement the Ephemeris harvester for the next release… However, because it is a very interesting new feature we will probably add it very soon.

Best regards,
Bryan

Hi @bcazabonne ,

thank you really much for the prompt reply!

Good to know about the StateCovarianceMatrixProvider and that you plan to add an harvester also for the Ephemeris.
Well at this point I am looking forward for the next release/s :wink:

Kind Regards,
Leonardo