This record contains the technical preprint for OPM, a compact deployable ephemeris representation for major Solar-System bodies. OPM represents DE441-derived ephemerides with segmented Chebyshev series, body-dependent local coordinates and reference shapes, integer quantization, and bit-level packing. The accompanying preprint reports a 600-year production instance covering approximately 1800--2400, validates OPM against DE441 on a deterministic dense grid with 6,757,597 geocentric test samples, and compares the resulting angular errors with Swiss Ephemeris under the same geometric geocentric J2000 ICRS convention. The English PDF is the primary version. A Chinese version is included as supplementary material. The associated GitHub repository contains Python reference tools, validation scripts, generated figures, and 600-year OPM sample artifacts: https://github.com/RedSC1/opm-ephemeris Code in the repository is licensed under Apache-2.0. Paper sources, PDFs, figures, plots, and generated OPM release artifacts are licensed under CC BY 4.0, unless otherwise noted. Third-party materials such as JPL/NAIF ephemeris data, Swiss Ephemeris, and pyswisseph are governed by their own licenses and are not redistributed as part of this record.
Rz Liu (Thu,) studied this question.