imap_processing.spice.geometry.basis_vectors#

imap_processing.spice.geometry.basis_vectors(et: float | ndarray[tuple[int, ...], dtype[_ScalarType_co]], from_frame: SpiceFrame, to_frame: SpiceFrame) → ndarray[tuple[int, ...], dtype[_ScalarType_co]]#

Get the basis vectors of the from_frame expressed in the to_frame.

The rotation matrix defining a frame transform are the basis vectors of the from_frame expressed in the to_frame. This function just transposes each rotation matrix retrieved from the get_rotation_matrix function so that basis vectors can be indexed 0 for x, 1 for y, and 2 for z.

Parameters:

  • et (float or np.ndarray) – Ephemeris time(s) for which to get the rotation matrices.

  • from_frame (SpiceFrame) – Reference frame to transform from.

  • to_frame (SpiceFrame) – Reference frame to transform to.

Returns:

basis_vectors – If et is a float, the returned basis vector matrix is of shape (3, 3). If et is a np.ndarray, the returned basis vector matrix is of shape (n, 3, 3) where n matches the number of elements in et and basis vectors are the rows of the 3 by 3 matrices.

Return type:

np.ndarray

Examples

>>> from imap_processing.spice.geometry import basis_vectors
... from imap_processing.spice.time import ttj2000ns_to_et
... et = ttj2000ns_to_et(dataset.epoch.values)
... basis_vectors = basis_vectors(
...     et, SpiceFrame.IMAP_SPACECRAFT, SpiceFrame.ECLIPJ2000
... )
... spacecraft_x = basis_vectors[:, 0]
... spacecraft_y = basis_vectors[:, 1]
... spacecraft_z = basis_vectors[:, 2]
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