2. Antenna#

class Antenna(name: str, turn_ratio: float = 1.1748998664886516, pos_craft_centrd: ArrayWFrame = None, spice_id: int | str = None)#

Bases: Instrument

Class defining the antenna, to receive and transmit radiometric data for navigation.

Parameters:

  • name (str) – The name of the Antenna object.

  • turn_around_ratio (float, optional) – Transponder ratio between received and transmitted frequencies. Defaults to Xband value from Moyer: 880.0 / 749.0.

  • pos_craft_cntrd (ArrayWFrame, optional) – Antenna shift position-vector. Defaults to None.

  • 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.

Attributes

area

The cross-sectional area of the spacecraft.

body_fixed_frame_id

The SPICE ID assigned to the spacecraft's body-fixed frame.

instrument_list

The list of instruments attached to the spacecraft.

mass_profile

Stored constant or polynomial mass profile.

measurement_type

Description.

n_plate_model

The N-Plate model representing the spacecraft's geometry.

name

The name of the spacecraft.

ref_coeff

The reflectivity coefficient of the spacecraft.

spice_id

The SPICE ID of the Body object.

thruster

DEF :base: Spacecraft :type:

turn_ratio

Store the turn-around-ratio between transmitted and received frequency a the transponder.

Methods

add_instrument(instruments)

Adds an instrument or instruments to the spacecraft.

field_of_view()

Placeholder for Field of View functionality.

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.

get_attitude(from_frame, epoch[, tol])

Computes the Direction Cosine Matrix (DCM) to transform vectors from a given inertial frame to the spacecraft-fixed frame.

get_dependent_spice_ids()

Collects the SPICE ID's of all attached frames and instruments into a dictionary.

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.

inertial_to_body_DCM_nadir_pointing_to_sun(...)

Computes the Direction Cosine Matrix (DCM) that points the body frame's -X axis toward the Sun (nadir-to-sun), using inertial quantities.

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.
add_instrument(instruments) → None#

Adds an instrument or instruments to the spacecraft.

Parameters:

instruments (Instrument or list of Instrument) – The instrument or instruments to be attached to the spacecraft.

Return type:

None

field_of_view()#

Placeholder for Field of View functionality.

Returns:

None

fit_mass_profile_from_data(t_array: ndarray, m_array: ndarray, domain: tuple, units: Units)#

Fits a polynomial to a mass time history and sets it as the new mass profile.

Parameters:

  • t_array (np.ndarray) – Time values in seconds (ephemeris time).

  • m_array (np.ndarray) – Corresponding mass values.

  • deg (int) – Degree of the polynomial.

  • domain (tuple) – Domain [t0, tf] for the polynomial conversion.

  • units (ArrayWUnits) – Units to assign to the mass profile. If None, uses existing mass profile units.

Return type:

None

get_attitude(from_frame: Frame, epoch: EpochArray, tol: int = 0) → ndarray#

Computes the Direction Cosine Matrix (DCM) to transform vectors from a given inertial frame to the spacecraft-fixed frame.

Parameters:

  • from_frame (Frame) – The intertial reference frame for which the spacecraft-fixed frame will be transformed from.

  • epoch (EpochArray) – The epoch at which the transformation will be performed. Given in ephemeris time (seconds past J2000).

  • tol (int, optional) – The time tolerance for retrieving attitude and angular velocity from the specified spacecraft clock time, given in sclock ticks. Defaults to 0.

Returns:

DCM – The DCM for transforming inertial vectors to spacecraft-fixed coordinates.

Return type:

numpy.ndarray

Notes

The epoch argument is converted from ephemeris time in seconds to continuous encoded spacecraft clock ticks.

get_dependent_spice_ids()#

Collects the SPICE ID’s of all attached frames and instruments into a dictionary.

Parameters:

None

Returns:

ids – A dictionary containing the keys:

  • 'instruments' : list The SPICE ID’s of all attached Instrument objects.

  • 'plates' : list The SPICE ID’s of all C-frames for CK type panels defined in the nPlateModel if one has been assigned to the Spacecraft.

Return type:

dict

get_mass(t: EpochArray) → ArrayWUnits#

Evaluates the time-varying mass profile at specified epochs.

Parameters:

t (EpochArray) – Time(s) in ephemeris seconds (TDB).

Returns:

Evaluated mass at each input epoch.

Return type:

ArrayWUnits

get_state(epoch_0, reference_frame: str = 'J2000', origin: str = 'EARTH')#

Retrieves the state of the body relative to a given origin in a specified reference frame.

Parameters:

  • epoch_0 (EpochArray) – The epoch times for which the state is to be computed.

  • reference_frame (str) – The reference frame in which the state is desired. Defaults to ‘J2000’.

  • origin (str) – The origin body relative to which the state is computed. Defaults to 'EARTH'.

Returns:

state_vector – The state vector of the body relative to the origin.

Return type:

ArrayWUnits

inertial_to_body_DCM_nadir_pointing_to_sun(origin_name, frame, sun2body_pos, current_state: dict, epoch, body)#

Computes the Direction Cosine Matrix (DCM) that points the body frame’s -X axis toward the Sun (nadir-to-sun), using inertial quantities.

Parameters:

  • origin_name (str) – Name of the origin at which current_state is defined (e.g., ‘EARTH’, ‘SUN’).

  • frame (Frame or str) – Frame in which current_state is expressed (e.g., J2000).

  • sun2body_pos (ArrayWUnits) – Position of the body w.r.t. SUN (km).

  • current_state (dict) –

    State of the body w.r.t. the origin. Accepts either: - {(‘velocity’, spice_id): Array/ArrayWUnits or ‘velocity’: Array/ArrayWUnits}

    (and similarly for ‘position’ if ever needed)

  • epoch (float) – Epoch (TDB seconds past J2000) at which the state is computed.

  • body (CelestialBody or Spacecraft) – The body whose state we are extracting from current_state (used for spice_id lookup).

Returns:

DCM_inertial_to_body – DCM that rotates inertial vectors into the body-fixed frame realizing the nadir-to-sun pointing.

Return type:

(3,3) ndarray

mass(t: EpochArray | float | ndarray = None) → ArrayWUnits#

Returns the mass of the body. If the mass is time-varying, evaluates it at time t. If the mass is constant, returns the same value regardless of t.

Parameters:

t (EpochArray, float, or np.ndarray, optional) – Time(s) in ephemeris seconds (TDB) at which to evaluate the mass. Or None for constant mass.

Returns:

Mass at time t or constant mass.

Return type:

ArrayWUnits

set_mass_profile(poly: SCBPolynomial, units: Units)#

Sets the mass profile of the body using a polynomial function and associated units. :param poly: A polynomial object representing the mass profile. :type poly: SCBPolynomial :param units: The units associated with the mass profile. :type units: Units

Returns:

None

property area: ArrayWUnits#

The cross-sectional area of the spacecraft. Expressed in units of square meters.

property body_fixed_frame_id: int#

The SPICE ID assigned to the spacecraft’s body-fixed frame.

property instrument_list: list#

The list of instruments attached to the spacecraft.

property mass_profile: ArrayWUnits | SCBPolynomial#

Stored constant or polynomial mass profile.

property measurement_type#

Description.

property n_plate_model: nPlateModel#

The N-Plate model representing the spacecraft’s geometry.

property name: str#

The name of the spacecraft.

property ref_coeff: float#

The reflectivity coefficient of the spacecraft.

property spice_id: int | str#

The SPICE ID of the Body object.

property thruster#

DEF :base: Spacecraft :type:

property turn_ratio: float#

Store the turn-around-ratio between transmitted and received frequency a the transponder.