sora.ephem

The EphemPlanete Class

class sora.EphemPlanete(ephem, name=None, spkid=None, **kwargs)[source]

Class used to simulate former Fortran programs ephem_planete and fit_d2_ksi_eta.

ephem

Input file with JD (UTC), geocentric RA (deg), DEC (deg), and distance (AU).

Type:

file, required

name

Name of the object to search in the JPL database.

Type:

str, optional, default=None

radius

Object radius, in km.

Type:

int, float, optional, default: online database

error_ra

Ephemeris RA*cosDEC error, in arcsec.

Type:

int, float, optional, default: online database

error_dec

Ephemeris DEC error, in arcsec.

Type:

int, float, optional, default: online database

mass

Object mass, in kg.

Type:

int, float, optional. default=0

H

Object absolute magnitude.

Type:

int, float, optional, default=NaN

G

Object phase slope.

Type:

int, float, optional, default=NaN

fit_d2_ksi_eta(star, verbose=True)[source]

Fits the projected position (orthographic projection) of the object in the tangent sky plane relative to a star.

Parameters:

  • star (str, astropy.coordinates.SkyCoord) – The coordinate of the star in the same reference frame as the ephemeris.

  • verbose (bool, optional, default=True) – Enable log printing.

get_ksi_eta(time, star=None)[source]

Returns the projected position (orthographic projection) of the object in the tangent sky plane relative to a star.

Parameters:

  • time (str, astropy.time.Time, required) – Reference time to calculate the position. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.

  • star (str, astropy.coordinates.SkyCoord, optional, default=None) – The coordinate of the star in the same reference frame as the ephemeris.

Returns:

ksi, eta – Projected position (orthographic projection) of the object in the tangent sky plane relative to a star. ksi is in the North-South direction (North positive). eta is in the East-West direction (East positive).

Return type:

float array

get_position(time, observer='geocenter')[source]

Returns the object’s geocentric position.

Parameters:

  • time (str, astropy.time.Time) – Reference time to calculate the object position. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.

  • observer (any) – This parameter is present in EphemPlanete for compatibility with the remaining ephem classes. The returned positions are based on the given ephemeris despite the observer.

Returns:

coord – Astropy SkyCoord object with the object coordinates at the given time.

Return type:

astropy.coordinates.SkyCoord

The EphemHorizons Class

class sora.EphemHorizons(name, id_type='smallbody', spkid=None, **kwargs)[source]

Obtains the ephemeris from Horizons/JPL service.

Note

Web tool URL: https://ssd.jpl.nasa.gov/horizons.cgi

name

Name of the object to search in the JPL database.

Type:

str, required

id_type

Type of object options: smallbody, majorbody (planets but also anything that is not a small body), designation, name, asteroid_name, comet_name, id (Horizons id number), or smallbody (find the closest match under any id_type).

Type:

str, default=’smallbody’

radius

Object radius, in km.

Type:

int, float, default: online database

error_ra

Ephemeris RA*cosDEC error, in arcsec.

Type:

int, float, default: online database

error_dec

Ephemeris DEC error, in arcsec.

Type:

int, float, default: online database

mass

Object mass, in kg.

Type:

int, float, default=0

H

Object absolute magnitude.

Type:

int, float, default=NaN

G

Object phase slope.

Type:

int, float, default=NaN

get_position(time, observer='geocenter')[source]

Returns the ICRS position of the object for observer.

Parameters:

  • time (str, astropy.time.Time) – Reference time to calculate the object position. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.

  • observer (str, sora.Observer, sora.Spacecraft) – IAU code of the observer (must be present in given list of kernels), a SORA observer object or a string: [‘geocenter’, ‘barycenter’]

Returns:

coord – Astropy SkyCoord object with the object coordinates at the given time.

Return type:

astropy.coordinates.SkyCoord

The EphemKernel Class

class sora.EphemKernel(kernels, spkid, name=None, **kwargs)[source]

Gets the ephemeris from BSP kernels.

Parameters:

  • name (str, optional, default=None) – Name of the object to search in the JPL database.

  • spkid (str, required) – spkid of the targeting object. Former ‘code’ (v0.1).

  • kernels (list, required) – List of paths for kernels files.

  • radius (int, float, optional, default: online database) – Object radius, in km.

  • error_ra (int, float, optional, default: online database) – Ephemeris RA*cosDEC error, in arcsec .

  • error_dec (int, float, optional, default: online database) – Ephemeris DEC error, in arcsec.

  • mass (int, float, optional, default=0) – Object Mass, in kg.

  • H (int, float, optional, default=NaN) – Object Absolute Magnitude.

  • G (int, float, optional, default=NaN) – Object Phase slope.

get_position(time, observer='geocenter')[source]

Returns the object geocentric position.

Parameters:

  • time (str, astropy.time.Time) – Reference time to calculate the object position. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.

  • observer (str, sora.Observer, sora.Spacecraft) – IAU code of the observer (must be present in given list of kernels), a SORA observer object or a string: [‘geocenter’, ‘barycenter’]

Returns:

coord – Astropy SkyCoord object with the object coordinates at the given time.

Return type:

astropy.coordinates.SkyCoord

Complementary functions

sora.ephem.utils.ephem_horizons(time, target, observer, id_type='smallbody', output='ephemeris')[source]

Calculates the ephemeris from Horizons.

Parameters:

  • time (str, astropy.time.Time) – Reference instant to calculate ephemeris. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.

  • target (str) – IAU (kernel) code of the target.

  • observer (str) – IAU (kernel) code of the observer.

  • id_type (str) – Type of target object options: smallbody, majorbody (planets but also anything that is not a small body), designation, name, asteroid_name, comet_name, id (Horizons id number), or smallbody (find the closest match under any id_type).

  • output (str) – The output of data. ephemeris will output the observed position, while vector will output the Cartesian state vector, without light time correction.

Returns:

coord – ICRS coordinate of the target.

Return type:

astropy.coordinates.SkyCoord

Notes

If the interval of time is larger than 30 days or so, a timeout error may be raised. The maximum interval will depend on the user connection.

sora.ephem.utils.ephem_kernel(time, target, observer, kernels, output='ephemeris')[source]

Calculates the ephemeris from kernel files.

Parameters:

  • time (str, astropy.time.Time) – Reference instant to calculate ephemeris. It can be a string in the ISO format (yyyy-mm-dd hh:mm:ss.s) or an astropy Time object.

  • target (str) – IAU (kernel) code of the target.

  • observer (str) – IAU (kernel) code of the observer.

  • kernels (list, str) – List of paths for all the kernels.

  • output (str) – The output of data. ephemeris will output the observed position, while vector will output the Cartesian state vector, without light time correction.

Returns:

coord – ICRS coordinate of the target.

Return type:

astropy.coordinates.SkyCoord

sora.ephem.utils.getBSPfromJPL(identifier, initial_date, final_date, email, directory='./')[source]

Downloads BSP files from JPL database.

BSP files, which have information to generate the ephemeris of the objects, will be downloaded and named as (without spaces): ‘[identifier].bsp’.

Important

It is not possible to download BSP files for Planets or Satellites.

Parameters:

  • identifier (str, list) –

    Identifier of the object(s). It can be the name, number or SPK ID. It can also be a list of objects.

    Examples: '2137295', '1999 RB216', '137295', ['2137295', '136199', '1999 RC216', 'Chariklo'].

  • initial_date (str) –

    Date the bsp file is to begin, within span 1900-2100.

    Examples: '2003-02-01', '2003-3-5'.

  • final_date (str) –

    Date the bsp file is to end, within span [1900-2100]. Must be more than 32 days later than initial_date.

    Examples: '2006-01-12', '2006-1-12'.

  • email (str) –

    User’s e-mail contact address. Required by JPL web service.

    Example: username@user.domain.name.

  • directory (str) – Directory path to save the bsp files.