Thanks for your answers.
Writing the OEM file works well indeed !
However I would have modified the format of the exported data in OEMWriter.writeEphemeris() in order to respect the CCSDS recommended standard for OEM files. Today, the format is set to « %16.16e » which means 16 digits after the decimal point (for example : -2.9007962960875825e+03) while the CCSDS recommends a mantissa of 16 digits (https://public.ccsds.org/
Pubs/502x0b2c1.pdf , §6.5.5).A better format may then be « %21.14e ». 14 will allow to have a mantissa of 16 digits (1 before the point, the point and 14 after the point) while 21 allows to have a place for the sign (« - » or a blank space), the 16-digit mantissa and the 4 digit exponent (a character, the sign and a 2-digits integer).
With this format, the previous example would look that way : -2.90079629608758e+03
What do you think about it ?
Regarding the covariance : thanks, I’ll take a look at those pages !
Best Regards,
Nicolas