`CelestialBody`#

class CelestialBody(name: str, mass: ArrayWUnits, mean_radius: ArrayWUnits, grav_param: ArrayWUnits, base_frame: Frame, spice_id: int | str = None, barycenter_id: int | str = None, gs_list: list = [])#

Bases: Body

Defines an astronomical body such as a planet, moon, asteroid, or comet.

Parameters:

name (str) – The written name of the CelestialBody.
mass (ArrayWUnits) – The mass of the CelestialBody. Recommend expressed in units of kilograms.
mean_radius (ArrayWUnits) – The mean radius of the CelestialBody. Recommend expressed in units of kilometers.
grav_param (ArrayWUnits) – The gravitational parameter of the CelestialBody. Recommend expressed in units of \(\frac{km^3}{s^2}\).
base_frame (Frame) – The body-centered, body-fixed reference frame attached to the CelestialBody.
spice_id (int or str, optional) – The NAIF ID code of the object. May be given as an integer ID or as a string. Defaults to None.
gs_list (list, optional) – A list containing all of the ground stations on the surface of the CelestialBody. Defaults to [].

See also

scarabaeus.constants: Scarabaeus’ constants library, including planetary constants.
scarabaeus.Frame: Scarabaeus’ representation of reference frames.

Notes

The gravitational parameter \(\mu\) is defined as

\[\mu = GM\]

where \(G = 6.674\times10^{-20}\ \mathrm{km}^3\,\mathrm{kg}^{-1}\,\mathrm{s}^{-2}\) is the universal gravitational constant and \(M\) is the body mass. The circular orbital velocity at distance \(r\) and surface escape velocity are

\[v_{circ} = \sqrt{\frac{\mu}{r}}, \qquad v_{esc} = \sqrt{\frac{2\mu}{R_{mean}}}\]

Use grav_param (\(\mu = GM\)) rather than mass for orbital computations to avoid rounding errors from \(G\).

Examples

Create a CelestialBody object with numerical values that are half that of Jupiter.

>>> import scarabaeus as scb
>>> jov_constants = scb.constants.JUPITER
>>> half_jupiter = scb.CelestialBody(
...     name        = "HALF JUPITER",
...     mass        = jov_constants.mass / 2,
...     mean_radius = jov_constants.mean_radius / 2,
...     grav_param  = jov_constants.GM / 2,
...     base_frame  = jov_constants.ref_frame,
...     spice_id    = 50000,
...     gs_list     = []
... )

Attributes:

base_frame: The reference frame attached to the CelestialBody.
grav_param: The gravitational parameter of the CelestialBody given, by convention, in units of \(\frac{km^3}{s^2}\).
gs_list: All GroundStation objects attached to the surface of the CelestialBody.
mass_profile: Stored constant or polynomial mass profile.
mean_radius: The mean radius of the CelestialBody.
name: The name of the Body object.
spice_id: The SPICE ID of the Body object.

Methods

`disp_properties`()	Displays all properties of the CelestialBody object in a readable format.
`fit_mass_profile_from_data`(t_array, m_array, ...)	Fits a polynomial to a mass time history and sets it as the new mass profile.
`from_constants`(cb_name)	Creates a CelestialBody object from a given name using its respective values as defined in `constants`.
`get_mass`(t)	Evaluates the time-varying mass profile at specified epochs.
`get_state`(epoch_0[, reference_frame, origin])	Retrieves the state of the body relative to a given origin in a specified reference frame.
`mass`([t])	Returns the mass of the body.
`set_mass_profile`(poly, units)	Sets the mass profile of the body using a polynomial function and associated units.

classmethod from_constants(cb_name: str) → Self#

Creates a CelestialBody object from a given name using its respective values as defined in constants.

Parameters:: cb_name (str) – The name of the desired celestial body to create a Scarabaeus CelestialBody object for.
Returns:: cb_out – A CelestialBody object initialized with all relevant values as defined by the given constant value.
Return type:: CelestialBody
Raises:: not_def_err – Raised when the given cb_name does not match an object in Scarabaeus’ constants library.

CelestialBody#

`CelestialBody`#