Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE) Solar System Services (astroquery.imcce/astroquery.solarsystem.imcce)

Overview

IMCCE provides a number of Solar System-related services, two of which are currently implemented here:

• SkyBoT: search for and identify Solar System objects that are present in a given area of the sky at a given time

• Miriade: ephemerides service

Use cases for both services are detailed below.

SkyBot - Solar System Body Identification Service

Cone Search

astroquery.imcce.SkybotClass provides an interface to the cone search offered by SkyBoT.

A simple cone search for Solar System objects in a circular field looks like this:

>>> from astroquery.imcce import Skybot
>>> from astropy.coordinates import SkyCoord
>>> from astropy.time import Time
>>> import astropy.units as u
>>> field = SkyCoord(0*u.deg, 0*u.deg)
>>> epoch = Time('2019-05-29 21:42', format='iso')
>>> Skybot.cone_search(field, 5*u.arcmin, epoch)  
<QTable length=2>
Number    Name            RA         ...      vy          vz       epoch
                         deg         ...    AU / d      AU / d       d
int64    str10         float64       ...   float64     float64    float64
------ ---------- ------------------ ... ----------- ----------- ---------
516566  2007 DH36           0.005535 ... 0.008556458 0.002875929 2458630.0
163149 2002 CV106 359.98691791666664 ... 0.009078103  0.00267749 2458630.0

cone_search produces a QTable object with the properties of all Solar System bodies that are present in the cone at the given epoch.

The required input arguments for cone_search are the center coordinates of the cone, its radius, as well as the epoch of the observation. Field center coordinates coo should be provided as a SkyCoord object, the radius of the cone rad should be provided as a Quantity object. Note that the maximum cone radius is limited to 10 degrees by the SkyBoT service. The epoch of the observation should be provided as Time object.

The following optional parameters are available:

• location: the location of the observer on Earth using the official list of IAU codes. If no location is provided, the center of the Earth is used as location.

• position_error: the maximum positional uncertainty of each body at the given epoch. This option can be used to improve the reliability of associations with detected sources in the field. If not provided, the maximum positional uncertainty of 120 arcsec is used.

• find_planets, find_asteroids, find_comets: these flags control what types of Solar System objects are identified. By default, each of the flags is True.

For diagnostic purposes, the query payload or raw response from the service can be returned instead of the parsed results using the flags get_query_payload and get_raw_response, respectively.

The resulting QTable contains all available information provided by SkyBoT with corresponding units. The following properties are obtained:

Column Name	Definition
'Number'	Target Number (-1 if none provided, int)
'Name'	Target Name (str)
'RA'	Target RA (J2000, deg, float)
'DEC'	Target declination (J2000, deg, float)
'Type'	Target dynamical/physical type (str)
'V'	Target apparent brightness (V-band, mag, float)
'posunc'	Positional uncertainty (arcsec, float)
'centerdist'	Angular distance of target from cone center (arcsec, float)
'RA_rate'	RA rate of motion (arcsec/hr, float)
'DEC_rate'	Declination rate of motion (arcsec/hr, float)
'geodist'	Geocentric distance of target (au, float)
'heliodist'	Heliocentric distance of target (au, float)
'alpha'	Solar phase angle (deg, float)
'elong'	Solar elongation angle (deg, float)
'x'	Target equatorial vector x (au, float)
'y'	Target equatorial vector y (au, float)
'z'	Target equatorial vector z (au, float)
'vx'	Target velocity vector x (au/d, float)
'vy'	Target velocity vector y (au/d, float)
'vz'	Target velocity vector z (au/d, float)
'epoch'	Ephemerides epoch (JD, float)

Miriade - Ephemeris Service

The Miriade service enable the query of Solar System object ephemerides. The most minimalistic get_ephemerides query looks like this:

>>> from astroquery.miriade import Miriade
>>> Miriade.get_ephemerides('Ceres')
<Table masked=True length=1>
 target        epoch                 RA        ...  DEC_rate   delta_rate
                 d                  deg        ... arcs / min    km / s
bytes20       float64             float64      ...  float64     float64
------- -------------------- ----------------- ... ---------- ------------
  Ceres    2458519.315165116 242.1874308333333 ...   -0.14926  -20.9668673

This query will return ephemerides for asteroid Ceres, for the current epoch, and for a geocentric location. The query output is formatted as a Table.

Ephemerides Queries

Miriade queries are highly customizable.

Epochs and Location

get_ephemerides is able to query a range of epochs starting at epoch epoch in steps of epoch_step for a total of epoch_nsteps. epoch has to be provided as a Time object, a float (interpreted as Julian Date), or a string (interpreted as iso date YYYY-MM-DD HH-MM-SS). Time steps epoch_step are provided as string that consist of a floating point number followed by a single character: d refers to days, h to hours, m to minutes, s to seconds; e.g., '1.23d' defines a time step of 1.23 days. epoch_nsteps defines the number of steps between the individual ephemerides. By default, epoch_nsteps = 1, which means that only a single epoch epoch will be queried.

Consider the following example, which queries ephemerides for asteroid Pallas over an entire year with a time step of 1 day:

>>> from astroquery.miriade import Miriade
>>> Miriade.get_ephemerides('Pallas', epoch='2019-01-01',
>>>                         epoch_step='1d', epoch_nsteps=365) 
<Table masked=True length=365>
 target        epoch                 RA         ...  DEC_rate   delta_rate
                 d                  deg         ... arcs / min    km / s
bytes20       float64             float64       ...  float64     float64
------- -------------------- ------------------ ... ---------- ------------
 Pallas            2458484.5  200.5865645833333 ...    0.15854  -19.3678422
 Pallas            2458485.5 200.92699458333328 ...    0.16727  -19.4137907
 Pallas            2458486.5 201.26416541666663 ...    0.17613  -19.4552649
 Pallas            2458487.5 201.59800958333332 ...    0.18511  -19.4921113
 Pallas            2458488.5  201.9284608333333 ...    0.19421  -19.5241972
 Pallas            2458489.5 202.25545124999996 ...    0.20344  -19.5514101
    ...                  ...                ... ...        ...          ...
 Pallas            2458843.5  261.1308308333333 ...   0.025007   -2.2916737
 Pallas            2458844.5  261.5084158333333 ...   0.029542   -2.5107013
 Pallas            2458845.5 261.88534958333327 ...   0.034077   -2.7290895
 Pallas            2458846.5        262.2616025 ...   0.038612   -2.9467393
 Pallas            2458847.5  262.6371470833333 ...   0.043144   -3.1635784
 Pallas            2458848.5         263.011955 ...   0.047672   -3.3795565

The observer location is defined through the location keyword, expecting a string containing the official IAU observatory code, a spacecraft name, or a set of coordinates (see the Miriade manual for details).

Coordinate Types

The Miriade system offers a range of different coordinate types - sets of coordinates and properties that can be queried. In agreement with the Miriade webform query, the coordinate type in get_ephemerides is defined through an integer value. For a full discussion of the different coordinate types we refer to this section of the Miriade website. The keyword coordtype controls which set of coordinates and properties are queried.

Here, we list the different coordinates and properties as returned by get_ephemerides for the different coordinate types available (the item numbers refer to the integer code to be provided to the keyword coordtype to use these sets) :

1. Spherical coordinates (default):

Column Name	Definition
target	Target name (str)
epoch	Ephemerides epoch (JD, float)
RA	Target RA at ephtype (deg, float)
DEC	Target declination at ephtype (deg, float)
delta	Distance from observer (au, float)
delta_rate	Rate in observer distance (km/s, float)
V	Apparent visual magnitude (mag, float)
alpha	Solar phase angle (deg)
elong	Solar elongation angle (deg)
RAcosD_rate	Rate of motion in RA * cos(DEC) (arcsec/min, float)
DEC_rate	Rate of motion in DEC (arcsec/min, float)

2. Rectangular coordinates:

Column Name	Definition
target	Target name (str)
epoch	Ephemerides epoch (JD, float)
delta	Distance from observer (au, float)
V	Apparent visual magnitude (mag, float)
alpha	Solar phase angle (deg)
elong	Solar elongation angle (deg)
x	X position state vector (au, float)
y	Y position state vector (au, float)
z	Z position state vector (au, float)
vx	X velocity state vector (au/d, float)
vy	Y velocity state vector (au/d, float)
vz	Z velocity state vector (au/d, float)
rv	Radial velocity (km/s, float)
heldist	Target heliocentric distance (au, float)
x_h	X heliocentric position vector (au, float)
y_h	Y heliocentric position vector (au, float)
z_h	Z heliocentric position vector (au, float)
vx_h	X heliocentric vel. vector (au/d, float)
vy_h	Y heliocentric vel. vector (au/d, float)
vz_h	Z heliocentric vel. vector (au/d, float)

3. Local coordinates:

Column Name	Definition
target	Target name (str)
epoch	Ephemerides epoch (JD, float)
AZ	Target azimuth (deg, float)
EL	Target elevation (deg, float)
delta	Distance from observer (au, float)
V	Apparent visual magnitude (mag, float)
alpha	Solar phase angle (deg)
elong	Solar elongation angle (deg)

4. Hour angle coordinates:

Column Name	Definition
target	Target name (str)
epoch	Ephemerides epoch (JD, float)
DEC	Target declination at ephtype (deg)
delta	Distance from observer (au, float)
V	Apparent visual magnitude (mag, float)
alpha	Solar phase angle (deg)
elong	Solar elongation angle (deg)
hourangle	Target hour angle (deg, float)

5. dedicated to observations:

Column Name	Definition
target	Target name (str)
epoch	Ephemerides epoch (JD, float)
DEC	Target declination at ephtype (deg)
RAJ2000	Target RA at J2000 (deg, float)
DECJ2000	Target declination at J2000 (deg, float)
AZ	Target azimuth (deg, float)
EL	Target elevation (deg, float)
delta	Distance from observer (au, float)
delta_rate	Rate in observer distance (km/s, float)
V	Apparent visual magnitude (mag, float)
alpha	Solar phase angle (deg)
elong	Solar elongation angle (deg)
RAcosD_rate	Rate of motion in RA * cos(DEC) (arcsec/min, float)
DEC_rate	Rate of motion in DEC (arcsec/min, float)
heldist	Target heliocentric distance (au, float)
hourangle	Target hour angle (deg, float)
siderealtime	Local sidereal time (hr, float)
refraction	Atmospheric refraction (arcsec, float)
airmass	Target airmass (float)
posunc	Positional uncertainty (arcsec, float)

6. dedicated to AO observations:

Column Name	Definition
target	Target name (str)
epoch	Ephemerides epoch (JD, float)
RAJ2000	Target RA at J2000 (deg, float)
DECJ2000	Target declination at J2000 (deg, float)
delta	Distance from observer (au, float)
delta_rate	Rate in observer distance (km/s, float)
V	Apparent visual magnitude (mag, float)
alpha	Solar phase angle (deg)
elong	Solar elongation angle (deg)
RAcosD_rate	Rate of motion in RA * cos(DEC) (arcsec/min, float)
DEC_rate	Rate of motion in DEC (arcsec/min, float)
heldist	Target heliocentric distance (au, float)
siderealtime	Local sidereal time (hr, float)
refraction	Atmospheric refraction (arcsec, float)
airmass	Target airmass (float)
posunc	Positional uncertainty (arcsec, float)

Other parameters

A range of additional parameters is available in get_ephemerides to modify the query results:

• timescale: switch between UTC (default) and TT

• planetary_theory: use planetary ephemerides other than INPOP

• ephtype: switch between J2000 ephemerides (default) and other coordinates

• refplane: switch from equatorial coordinates (default) to ecliptical coordinates

• elements: switch to MPCORB ephemerides instead of ASTORB

• radial_velocity: provides additional information on target’s radial velocity

Acknowledgements

This submodule makes use of IMCCE’s SkyBoT VO tool and the IMCCE Miriade service. Additional information on SkyBoT can be obtained from Berthier et al. 2006.

Please consider the following notes from IMCCE:

• If SkyBoT was helpful for your research work, the following acknowledgment would be appreciated: “This research has made use of IMCCE’s SkyBoT VO tool”, or cite the following article 2006ASPC..351..367B.

• If Miriade was helpful for your research work, the following acknowledgment would be appreciated: “This research has made use of IMCCE’s Miriade VO tool”

The development of this submodule is funded through NASA PDART Grant No. 80NSSC18K0987 to the sbpy project.

Reference/API

astroquery.imcce Package

IMCCE

author

Michael Mommert (mommermiscience@gmail.com)

Classes

MiriadeClass()	A class for querying the IMCCE/Miriade service.
SkybotClass()	A class for querying the IMCCE SkyBoT service.
Conf()	Configuration parameters for astroquery.imcce.