A new comet ephemerides file in XEPH format is now available on our distribution server. The new file covers the time span from 1989-12-01 to 2030-12-27 and includes 3040 comets from the official JPL comets database with data retrieved on 2024 June 24. This XEPH file can be used to compute high-precision ephemerides with our solar system ephemerides engine and the Ephemerides script, as well as to generate comet annotations for plate-solved images with our standard AnnotateImage script.
The new XEPH file provide Chebyshev polynomial expansions for position in barycentric rectangular coordinates coherent with fundamental JPL planetary and lunar DE440 ephemerides (ICRS), with maximum truncation errors below 1e–10 au (about 15 meters) for all objects during most of the covered time span.
This XEPH file has been generated by numerical integration of perturbed orbital motion with our standard EphemerisGenerator process. The initial conditions and physical parameters have been obtained using the JPL Small–Body Database Query system. The implemented physical model includes the following:
Some bodies from JPL comet databases have not been included in this XEPH file. Missing objects include historical comets with unreliable data, for which a numerical integration like this one doesn't make sense, and more importantly, objects passing too close to the Sun (mostly SOHO sungrazers), and comets that collided with other solar system bodies, including Shoemaker-Levy 9 fragments (Jupiter, 1994) and some SOHO comets (Sun). For these objects, if the user is interested in calculating ephemerides for a specific time span, the EphemerisGenerator process can be executed directly to compute accurate collision times and coordinates and maximum approaches to the Sun.
The numerical integration executed to generate this XEPH file required about 5 hours on our MARS-1 server: a GIGABYTE R263-Z33 (rev. AAF1) server with an AMD EPYC 9654 96-core processor and 768 GiB of RAM running Kubuntu 22.04 LTS Linux. The integration was performed by a single instance of the PixInsight core 1.8.9-3 application limited to 80 worker threads.
We hope you enjoy this new release.
The new XEPH file provide Chebyshev polynomial expansions for position in barycentric rectangular coordinates coherent with fundamental JPL planetary and lunar DE440 ephemerides (ICRS), with maximum truncation errors below 1e–10 au (about 15 meters) for all objects during most of the covered time span.
This XEPH file has been generated by numerical integration of perturbed orbital motion with our standard EphemerisGenerator process. The initial conditions and physical parameters have been obtained using the JPL Small–Body Database Query system. The implemented physical model includes the following:
- Perturbations from Mercury, Venus, Earth, Moon, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. State vectors and constants are provided by XEPH fundamental ephemerides (currently JPL DE440).
- Perturbations from the 343 most massive asteroids used in DE440 numerical integrations. State vectors and constants are provided by XEPH asteroid ephemerides (currently JPL DE441 asteroid ephemerides).
- Perturbations from the 30 most massive Kuiper belt objects (KBOs). State vectors and constants are provided by XEPH asteroid ephemerides (currently JPL DE441 asteroid ephemerides).
- Direct acceleration perturbation terms caused by oblateness. Zonal harmonics J2 are computed for Sun, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
- Relativistic perturbation terms (DE440's parametrized post-Newtonian (PPN) formulation) up to O(1/c^2) for the point–mass accelerations induced by all planets, Moon, Pluto, and the five most massive asteroids.
- Non-gravitational perturbations. We implement the standard asymmetric model of D.K. Yeomans and P.W. Chodas (Astron. J. 98 (3), 1989). This applies only to comets with available non-gravitational acceleration parameters, which include (optionally) the A1, A2, A3 and DT parameters (respectively, the radial, transverse and normal acceleration components in au/day^2, and the perihelion time offset in days).
Some bodies from JPL comet databases have not been included in this XEPH file. Missing objects include historical comets with unreliable data, for which a numerical integration like this one doesn't make sense, and more importantly, objects passing too close to the Sun (mostly SOHO sungrazers), and comets that collided with other solar system bodies, including Shoemaker-Levy 9 fragments (Jupiter, 1994) and some SOHO comets (Sun). For these objects, if the user is interested in calculating ephemerides for a specific time span, the EphemerisGenerator process can be executed directly to compute accurate collision times and coordinates and maximum approaches to the Sun.
The numerical integration executed to generate this XEPH file required about 5 hours on our MARS-1 server: a GIGABYTE R263-Z33 (rev. AAF1) server with an AMD EPYC 9654 96-core processor and 768 GiB of RAM running Kubuntu 22.04 LTS Linux. The integration was performed by a single instance of the PixInsight core 1.8.9-3 application limited to 80 worker threads.
We hope you enjoy this new release.