poliastro.ephem

Module Contents

Classes

InterpolationMethods

Interpolation methods to sample the ephemerides.

Ephem

Time history of position and velocity of some object at particular epochs.

Functions

build_ephem_interpolant(body, period, t_span, rtol=1e-05)

Interpolates ephemerides data

_interpolate_splines(epochs, reference_epochs, coordinates, *, kind='cubic')

_interpolate_sinc(epochs, reference_epochs, coordinates)

_sinc_interp(x, s, u)

Interpolates x, sampled at "s" instants, at "u" instants.

_get_destination_frame(attractor, plane, epochs)

poliastro.ephem.EPHEM_FORMAT = Ephemerides at {num} epochs from {start} ({start_scale}) to {end} ({end_scale})
class poliastro.ephem.InterpolationMethods

Bases: enum.Enum

Interpolation methods to sample the ephemerides.

SINC
SPLINES
poliastro.ephem.build_ephem_interpolant(body, period, t_span, rtol=1e-05)

Interpolates ephemerides data

Parameters
  • body (Body) – Source body.

  • period (Quantity) – Orbital period.

  • t_span (list(Quantity)) – Initial and final epochs.

  • rtol (float, optional) – Relative tolerance. Controls the number of sampled data points, defaults to 1e-5.

Returns

intrp – Interpolated function.

Return type

interp1d

poliastro.ephem._interpolate_splines(epochs, reference_epochs, coordinates, *, kind='cubic')
poliastro.ephem._interpolate_sinc(epochs, reference_epochs, coordinates)
poliastro.ephem._sinc_interp(x, s, u)

Interpolates x, sampled at “s” instants, at “u” instants.

poliastro.ephem._INTERPOLATION_MAPPING
poliastro.ephem._get_destination_frame(attractor, plane, epochs)
class poliastro.ephem.Ephem(coordinates, epochs, plane)

Time history of position and velocity of some object at particular epochs.

Instead of creating Ephem objects directly, use the available classmethods.

Parameters
__str__(self)

Return str(self).

__repr__(self)

Return repr(self).

property epochs(self)

Epochs at which the ephemerides was originally sampled.

property plane(self)

Reference plane of the ephemerides.

classmethod from_body(cls, body, epochs, *, attractor=None, plane=Planes.EARTH_EQUATOR)

Return Ephem for a SolarSystemPlanet at certain epochs.

Parameters
  • body (SolarSystemPlanet) – Body.

  • epochs (Time) – Epochs to sample the body positions.

  • attractor (SolarSystemPlanet, optional) – Body to use as central location, if not given the Solar System Barycenter will be used.

  • plane (Planes, optional) – Fundamental plane of the frame, default to Earth Equator.

classmethod from_horizons(cls, name, epochs, *, attractor=None, plane=Planes.EARTH_EQUATOR, id_type='smallbody')

Return Ephem for an object using JPLHorizons module of Astroquery.

Parameters
  • name (string) – Name of the body to query for.

  • epochs (Time) – Epochs to sample the body positions.

  • attractor (SolarSystemPlanet, optional) – Body to use as central location, if not given the Solar System Barycenter will be used.

  • plane (Planes, optional) – Fundamental plane of the frame, default to Earth Equator.

  • id_type (str, optional) – Use “smallbody” for Asteroids and Comets (default), and “majorbody” for Planets and Satellites.

classmethod from_orbit(cls, orbit, epochs, plane=Planes.EARTH_EQUATOR)

Return Ephem from an Orbit at certain epochs.

Parameters
  • orbit (Orbit) – Orbit.

  • epochs (Time) – Epochs to sample the orbit positions.

  • plane (Planes, optional) – Fundamental plane of the frame, default to Earth Equator.

sample(self, epochs=None, *, method=InterpolationMethods.SPLINES, **kwargs)

Returns coordinates at specified epochs.

Parameters
  • epochs (Time, optional) – Epochs to sample the ephemerides, if not given the original one from the object will be used.

  • method (InterpolationMethods, optional) – Interpolation method to use for epochs outside of the original ones, default to splines.

Returns

Sampled coordinates with velocities.

Return type

CartesianRepresentation

rv(self, epochs=None, **kwargs)

Position and velocity vectors at given epochs.

Parameters

epochs (Time, optional) – Epochs to sample the ephemerides, default to now.