Indication of Perturbing Bodies¶
The Minor Planet Center maintains files of perturbed orbital elements that specifically identify the source of planetary ephemerides and additional perturbing bodies beyond Mercury through Neptune.
One-Line Format Changes¶
Changes affect the one-line format for orbit submissions to the Minor Planet Center. Columns 1-201 and 210-220 remain unaffected. The "Extended Computer Service" includes this information, though printed MPCs omit it for simplicity.
Column 202: Planetary Ephemerides Descriptor¶
This column identifies the system used for perturbing planets:
| Code | Ephemeris |
|---|---|
| (space) | Undefined/unknown; assumes JPL DE200 positions + masses |
| d | JPL DE200 positions + masses |
| f | JPL DE245 positions + masses |
| h | JPL DE403 positions + masses |
| j | JPL DE405 positions + masses |
| k | JPL DE431 positions + masses |
| l | JPL DE441 positions + masses |
New codes are assigned only under exceptional circumstances, as consistency in perturbation schemes takes priority over frequent updates.
Columns 204-206: Coarse Perturbing Bodies Indicator¶
Minor planets use lowercase letters, distinguishing between M-P (includes Pluto) and M-p (includes Pallas and likely Ceres).
Columns 208-209: Precise Perturbers (Hexadecimal)¶
A two-digit hexadecimal number indicates specific perturbers:
Low digit:
| Perturber | Bit | Value |
|---|---|---|
| Hygiea | 0 | 1 |
| Earth | 1 | 2 |
| Moon | 2 | 4 |
| Ceres | 3 | 8 |
High digit:
| Perturber | Bit | Value |
|---|---|---|
| Pallas | 0 | 1 |
| Vesta | 1 | 2 |
| Eunomia | 2 | 4 |
Note: Low-digit bits 1 and 2 must both be set or both be unset (Earth and Moon constraint).
Examples¶
| Coarse | Precise | Perturbers |
|---|---|---|
| M-c | 08 | Ceres, EM barycenter |
| M-c | 0E | Ceres, Earth, Moon |
| M-p | 16 | Pallas, Earth, Moon (NOT RECOMMENDED) |
| M-p | 18 | Ceres, Pallas, EM barycenter |
| M-p | 1E | Ceres, Pallas, Earth, Moon |
| M-v | 38 | Ceres, Pallas, Vesta, EM barycenter |
| M-v | 3E | Ceres, Pallas, Vesta, Earth, Moon |
| M-e | 78 | Ceres, Pallas, Vesta, Eunomia, EM barycenter |
| M-e | 7E | Ceres, Pallas, Vesta, Eunomia, Earth, Moon |
| M-h | 39 | Ceres, Pallas, Vesta, Hygiea, EM barycenter |
Default Settings¶
The default for Minor Planet Center orbits is k (DE431), M-v (coarse) and 38 or 3E (precise, depending on whether the object is an Earth-approacher or not). Additional perturbers are incorporated as needed.