I've finished the implementation of the OEMWriter, and the corresponding unit tests. They are ready for review on branch 259-OEMWriter. I also created an OrekitEphemerisFile object for easier serialization to an external ephemeris format, with corresponding unit test for showing to/from OEM file. That is in a separate branch called 259-OrekitEphemerisPropagator off of the original 259-OEMWriter branch. Both should be ready for review.
Hank