(588) Achilles
This object has a more recent orbit available here
Object
Object | (588) Achilles |
Diameter(1) | 130 km |
Dynamic class(1) | trojan |
Absolute magnitude | 8.26 |
G slop | 0.15 |
(1) Data from the johnston archive list.
Orbital elements
Epoch (Julian date) | 2456468.249406684 |
Semi major axis | 5.199067 ± 0.000001 au |
Eccentricity | 0.148169636 ± 0.000000057 |
Inclination | 10.317133259 ± 0.000006667 ° |
Longitude of ascending node | 316.593823 ± 0.000031 ° |
Argument of perihelia | 133.112313 ± 0.000072 ° |
Mean anomaly | 61.516921 ± 0.000046 ° |
Orbital period | 11.85 yr |
Ephemeris & Observations
Ephemeris version | NIMAv4 |
Observation file |
omc_ast_NIMAv4.txt |
bsp file | 588_Achilles_nima_v4.bsp |
Date of first observation | 1906-02-22 |
Date of last observation | 2020-11-14 |
Number of observations used in the fit | 2368 |
Number of rejected observations | 34 |
Number of DES observations | 0 |
Number of MPC observations | 2354 |
Number of unpublished observations | 48 |
RMS of observations | 4.874 arcsec |
Residuals

Residuals in right ascension and declination compared to NIMAv4 ephemeris.
Colours indicate the estimated precision in arcsec used as weights in the fitting process.
Orbit quality
date | σα (arcsec) | σδ (arcsec) |
2021-01 | 0.008 | 0.009 |
2021-07 | 0.019 | 0.015 |
2022-01 | 0.025 | 0.024 |
2022-07 | 0.036 | 0.023 |
2023-01 | 0.060 | 0.036 |
2023-07 | 0.048 | 0.024 |
2024-01 | 0.075 | 0.042 |
2024-07 | 0.049 | 0.028 |
2025-01 | 0.060 | 0.038 |
Ephemeris comparison

Difference between NIMAv4 and JPL88 in right ascension (weighted by cos δ) and in declination.
Gray area represents the 1-σ uncertainty of NIMA ephemeris. Green dots represent the DES observations.