1. Bplane

class Bplane(epoch: EpochArray, bplane_name: str, bplane_spice_id: int | str, sc_name: str, sc_spice_id: int | str, target_name: str, target_spice_id: int | str, fk_file: str, v_hat: bool = True, new_bplane: bool = True)

Bases: object

Bplane and Bvector definition and targeting.

Represents a Bplane and Bvector used for targeting purposes. Provides methods to compute the b-vector from spacecraft state and create a b-plane frame kernel.

Attributes

bplane_name	The name of Bplane.
bplane_spice_id	The SPICE ID of the Bplane.
br_ref	The \(B_r\) component of the B vector.
bt_ref	The \(B_t\) component of the B vector.
epoch	The current epoch.
fk_file	The filepath to the given fk file.
ltof_ref	The inearized time of flight expressed in seconds.
name	Name corresponding to the b-plane.
new_bplane	The new Bplane
rot_to_bplane	Rotation matrix from J2000 to the b-plane.
rot_to_j2000	Rotation matrix from the b-plane to J2000.
rotmat_to_bplane	DCM to the Bplane.
rotmat_to_j2000	DCM from the current frame to J2000.
sc_name	The name of the spacecraft.
sc_spice_id	The SPICE ID of the spacecraft.
spice_id	Spice ID corresponding to the b-plane.
target_name	The name of the target.
target_spice_id	The SPICE ID of the target.
time_close_approach_ref	The current epoch plus the ltof expressed in seconds.
v_hat	The unit vector pointing in the direction of the velocity.

Methods

compute_jacobian(sc_rel_state_j2000)	Given a perturbed state in J2000, compute Jacobian with respect to velocity and linearized time of flight.
compute_parameters(sc_rel_state_j2000)	Compute from a spacecraft state relative to the target and in J2000, the b-vector and the linearized time-of-flight.
create_kernel()	If not already given, creates the b-plane frame kernel.
linear_targeting(sc_rel_state_j2000[, err, ...])	Given a perturbed state in J2000, compute TCM to correct trajectory through STMs.
nonlinear_targeting(sc_rel_state_j2000[, err])	Given a perturbed state in J2000, compute TCM to correct trajectory through Prediction-Correction.
target_covariance(sc_cov, sc_rel_state_j2000)	Given a state and its covariance (at the time of close approach) in J2000, compute B-plane parameters covariance.
target_spacecraft_covariance(sc_targ_cov, ...)	Given a spacecraft, a target and their covariance (at the time of close approach, in J2000, compute B-plane parameters covariance.

compute_jacobian(sc_rel_state_j2000: ndarray) → ArrayWUnits

Given a perturbed state in J2000, compute Jacobian with respect to velocity and linearized time of flight.

Parameters:

sc_rel_state_j2000 (numpy.ndarray) – The perturbed state in J2000.

Returns:

jacobian – The Jacobian matrix.

Return type:

ArrayWUnits

compute_parameters(sc_rel_state_j2000: ndarray)

Compute from a spacecraft state relative to the target and in J2000, the b-vector and the linearized time-of-flight.

Parameters:

sc_rel_state_j2000 (numpy.ndarray) – Spacecraft state relative to the target in J2000.

Returns:

b_vec – The b-vector and the linearized time-of-flight.

Return type:

numpy.ndarray

create_kernel() → None

If not already given, creates the b-plane frame kernel.

Return type:

None

linear_targeting(sc_rel_state_j2000: ndarray, err: float = 1e-08, max_iterations: int = 100) → ndarray

Given a perturbed state in J2000, compute TCM to correct trajectory through STMs.

Parameters:

• sc_rel_state_j2000 (numpy.ndarray) – The perturbed state in J2000.

• err (float, optional) – Error tolerance for convergence. Defaults to 1e-8.

• max_iterations (int, optional) – The maximum number of iterations for computing the error. Defaults to 100.

Returns:

tcm_vec – The TCM vector.

Return type:

numpy.ndarray

nonlinear_targeting(sc_rel_state_j2000: ndarray, err: float = 1e-10) → ndarray

Given a perturbed state in J2000, compute TCM to correct trajectory through Prediction-Correction.

Parameters:

• sc_rel_state_j2000 (numpy.ndarray) – The erturbed state in J2000.

• err (float, optional) – Tolerance for the optimization algorithm. Defaults 1e-10.

Returns:

tcm_vec – The TCM vector.

Return type:

numpy.ndarray

target_covariance(sc_cov: ndarray, sc_rel_state_j2000: ndarray) → ndarray

Given a state and its covariance (at the time of close approach) in J2000, compute B-plane parameters covariance.

Assumes no correlation between position in the B-plane and linearized time of flight.

Parameters:

• sc_cov (numpy.ndarray) – The covariance matrix of the spacecraft state in J2000.

• sc_rel_state_j2000 (numpy.ndarray) – The relative state of the spacecraft in J2000.

Returns:

covar – Covariance B-plane parameters matrix.

Return type:

numpy.ndarray

target_spacecraft_covariance(sc_targ_cov: ndarray, sc_rel_state_j2000: ndarray) → ndarray

Given a spacecraft, a target and their covariance (at the time of close approach, in J2000, compute B-plane parameters covariance.

Assumes no correlation between position in the B-plane and linearized time of flight.

Parameters:

• sc_targ_cov (numpy.ndarray) – Covariance matrix of the spacecraft and target.

• sc_rel_state_j2000 (numpy.ndarray) – Relative state of the spacecraft and target in J2000.

Returns:

covar – Covariance B-plane parameters matrix.

Return type:

numpy.ndarray

property bplane_name: str

The name of Bplane.

property bplane_spice_id: int | str

The SPICE ID of the Bplane.

property br_ref: float

The \(B_r\) component of the B vector.

property bt_ref: float

The \(B_t\) component of the B vector.

property epoch: EpochArray

The current epoch.

property fk_file: str

The filepath to the given fk file.

property ltof_ref: ArrayWUnits

The inearized time of flight expressed in seconds.

property name: str

Name corresponding to the b-plane.

property new_bplane

The new Bplane

property rot_to_bplane: str

Rotation matrix from J2000 to the b-plane.

property rot_to_j2000: str

Rotation matrix from the b-plane to J2000.

property rotmat_to_bplane: ndarray

DCM to the Bplane.

property rotmat_to_j2000: ndarray

DCM from the current frame to J2000.

property sc_name: str

The name of the spacecraft.

property sc_spice_id: int | str

The SPICE ID of the spacecraft.

property spice_id: int

Spice ID corresponding to the b-plane.

property target_name: str

The name of the target.

property target_spice_id: int | str

The SPICE ID of the target.

property time_close_approach_ref: ArrayWUnits

The current epoch plus the ltof expressed in seconds.

property v_hat: ndarray

The unit vector pointing in the direction of the velocity.