Covariance in local orbital frame for position (velocity) measurement

Orekit development
1

Hi all,

In PVBuilder and PositionBuilder, I can’t find the possibility to define the noise in a local orbital frame. Is there something I’m missing or is it actually a missing feature?
For the latter, is there an architecture obstacle for that? I think that a priori uncertainty is way easier to define let’s say in TNW than in inertial.

Cheers,
Romain.

2

Hi @Serrof,

True, this is a missing feature.
I don’t think there’s an architectural obstacle to it.

Cheers,
Maxime

3

Thanks for your reply Maxime.
I’ll open an issue then.

Cheers,
Romain.

4

Hi again Maxime,

Actually another limitation of the position(velocity) builder is the fact that the frame must be the same as used by the orbit propagation within OD. This might be for historical reasons because measurement models in Orekit are biased by the estimation layer, but I think it’d be good to lift it. Does opening an issue on that sounds reasonable?

Cheers,
Romain.

5

Hi Romain,

Yes, it’s a good idea.
I think the thing we tried to avoid (for performance reasons) is to change the frame dynamically during an OD, so in the PV or Position class directly.
But if it’s in the builder it’s not an issue.

Cheers,
Maxime

6

Hi Maxime,

Actually I think that the only option to choose the frame without breaking APIs would be to add a modifier.
But I think to make the covariance system more generic the builder and the measurement classes need a revamp. So maybe this needs to wait for a major release.

Cheers,
Romain.