Brouwer-Lydanne conversion between mean and osculating Elements

I am trying to convert between osculating orbital elements and specifically Brouwer-Lydanne mean elements. I have thus far tried using the FiniteDifferentPropagatorConverter to create both a TLEPropagator and KeplerianPropagator based on the osculating elements I have, but neither has produced the Brouwer-Lydanne mean elements. I’ve also attempted to use the OsculatingToMeanElementsConverter, though that also did not produce the desired results.

This reference provides a first-order mapping algorithm to directly convert from osculating to specifically Brouwer-Lydanne mean elements. Is there anything currently like that in the Orekit library that I am missing?

Hi @rclubb ,

Using the propagator convertor to get the mean elements as you did is a proper way. Did you tried using the DSST propagator ?

Concerning the Brouwer-Lyddane method, we do not have yet this orbit propagator in Orekit. Implementing it is not really a complex task. Indeed, the reference paper for the Lyddane model is only 4 pages long. Adding this algorithm in Orekit would be a good addition.

If you would like to have it included, please open a feature request on the issue tracker.

Kind regards,


Thanks for the response. I had tried the DSST propagator before, and I gave it another go today, both times I did not get the desired results. I am comparing my results against the output from an STK model, and I think there is just no getting around the fact that I need to use the Brouwer-Lydanne method. I will open a ticket to request this feature. Thanks for the help!