Faster State Vector processing (SPG4/Skyfield vs ideal Keppler vs...)

[hornig]

the SGP4 Skyfield libs are really cool. Also they have more realistic models.
but they seem a bit slow by a magnitude.

So adding a faster state vector processing would be great! :)

[kerel-fs]

Related:
@astrojuanlu published the "SPG4 implementations benchmark report" (full text) which describes an “Evaluation of available[open source] Python libraries for multi-satellite propagation” as part of a sub-activity of the OpenSatCom activity.

In this report a comparison of multiple SGP4 implementations is performed, specifically thoses: