DynAstVO - Asteroid orbital database and ephemerides

Abstract

This page presents the description of the parameters and ephemeris in the DynAstVO database. This service provides orbital elements of Near-Earth objects. The database is available on the VESPA datacenter.

The database provides for each asteroid, orbital elements and their uncertainty, the state-vector, information about the observations, Minimum Orbital Intersection distance (MOID), and the covariance matrix of the system, as well as general information on their magnitude. Osculating orbital elements are given as elliptic and cartesian coordinates, in the ecliptic J2000 reference frame. A link gives also the ephemeris file (in bsp format) usable with the SPICE library (NASA/JPL).

The database is daily updated in an automatic process for objects with new observations. The observations comes from the Minor Planet Center.

Database computation

The orbital elements are computed based on a fit to the astrometric data available at IAU/MPC, with outlier rejection and weighting according to Farnocchia et al. (2015). Osculating orbital elements are given as elliptic and cartesian coordinates, in ecliptic J2000 reference frame. Computation are done by considering 8 perturbing planets, and 4 biggest asteroids (Ceres, Vespa, Pallas, Hygiea), relativistic effects, and TDB time scale, with masses and positions taken from the INPOP13c solution. Numerical integration is performed with an Radau adaptive-step integrator.

The magnitude is given with two parameters: absolute magnitude H and the slope parameter G. H is determined by fitting to observations whereas G is fixed and taken from MPC.

For every object, the orbital elements (semi major axis, eccentricity, inclination, longitude of ascending node, argument of perihelion and mean anomaly) are provided for two different epochs: one is specific to the object and corresponds approximately to the middle of the observational period, the other one (with the suffix 'standard') is common to every object and corresponds to the 1st of July of the current year.

A short description of DynAstVO is also given in Desmars et al. (2017)

Description of the table

column index type unit description
target_name char Name of object (number or designation)
creation_date char Date of first entry of this granule
modification_date char Date of last modification
release_date char Start of public access period
access_url char URL of the ephemeris bsp file
publisher char A short string identifying the entity running the data service used.
bib_reference char Bibliographic reference of the service
semi_major_axis double au Semi major axis at epoch
eccentricity double Eccentricity at epoch
inclination float deg Inclination at epoch, referred to Ecliptic J2000
long_asc float deg Longitude of ascending node at epoch, J2000.0
arg_perihel float deg Argument of Perihelion at epoch, J2000.0
mean_anomaly float deg Mean anomaly at epoch
epoch double Epoch of the osculating elements
semi_major_axis_error float au Semimajor axis error
eccentricity_error float Eccentricity error
inclination_error float deg Inclination error
long_asc_error float deg Longitude of ascending node error
arg_perihel_error float deg Argument of Perihelion error
mean_anomaly_error float deg Mean anomaly error
moid float au Minimum Orbital Intersection Distance with Earth orbit
spu float arcsec Sky-plane uncertainty at epoch
magnitude float Absolute magnitude of the object from HG magnitude system
slope float G slope parameter from HG magnitude system
id_mpc int MPC number of the object (if object is numbered)
id_spk int NAIF integer ID code (used for bsp file)
id_gaia long Gaia integer ID code
alt_target_name char Alternative target name (number, name, designations)
covar_mat char Coefficient of covariance matrix in json format (Note that only the triangular matrix is provided with 21 coefficients c1,1,c1,2,...,c1,6, c2,2, ..., c2,6, ...,c6,6).
cartesian_x double au State-vector x position component
cartesian_y double au State-vector y position component
cartesian_z double au State-vector z position component
cartesian_vx double au/d State-vector vx velocity component
cartesian_vy double au/d State-vector vy velocity component
cartesian_vz double au/d State-vector vz velocity component
pha char Potentially hazardous asteroid
dynamical_class char Dynamic class of object (Apollo, Aten, Amor, Atira)
dynamical_type char Class of the object
fit_nb_obs_used int Number of observations used in the fit
fit_nb_obs_rejected int Number of observations rejected in the fit
fit_nb_obs_ranging int Number of radar ranging measurement
fit_nb_obs_doppler int Number of radar doppler measurement
fit_jd_initial double Julian date of first observation used in the fit
fit_jd_final double Julian date of last observation used in the fit
lastdou char Last Daily Orbit Update used for orbit determination
rms_obs double arcsec Root mean square of observations
semi_major_axis_standard double au Semi major axis at standard epoch
eccentricity_standard double Eccentricity at standard epoch
inclination_standard float deg Inclination at standard epoch
long_asc_standard float deg Longitude of ascending node (J2000.0) at standard epoch
arg_perihel_standard float deg Argument of perihelion (J2000.0) at standard epoch
mean_anomaly_standard float deg Mean anomaly at standard epoch
epoch_standard double Standard epoch of orbital elements (identical for every object, first of July of the current year)
cartesian_x_standard double au State-vector x position component at standard epoch
cartesian_y_standard double au State-vector y position component at standard epoch
cartesian_z_standard double au State-vector z position component at standard epoch
cartesian_vx_standard double au/d State-vector vx velocity component at standard epoch
cartesian_vy_standard double au/d State-vector vy velocity component at standard epoch
cartesian_vz_standard double au/d State-vector vz velocity component at standard epoch

Other parameters visible on VESPA and not listed above are used for VESPA purpose only.


Credits:
Creators: J. Desmars
Contributors: J. Desmars, W. Thuillot, D. Hestroffer, P. David, P. Le Sidaner, PADC
Publisher: Paris Astronomical Data Centre - IMCCE
Last update: 2019.02.19