# poliastro.core.util¶

## Module Contents¶

### Functions¶

 rotation_matrix(angle, axis) alinspace(start, stop=None, num=50, endpoint=True) Return increasing, evenly spaced angular values over a specified interval. Compute cartesian coordinates from spherical coordinates (norm, colat, long). This function is vectorized. planetocentric_to_AltAz(theta, phi) Defines transformation matrix to convert from Planetocentric coordinate system
poliastro.core.util.rotation_matrix(angle, axis)
poliastro.core.util.alinspace(start, stop=None, num=50, endpoint=True)

Return increasing, evenly spaced angular values over a specified interval.

poliastro.core.util.spherical_to_cartesian(v)

Compute cartesian coordinates from spherical coordinates (norm, colat, long). This function is vectorized.

$\begin{split}v = norm \cdot \begin{bmatrix} \sin(colat)\cos(long)\\ \sin(colat)\sin(long)\\ \cos(colat)\\ \end{bmatrix}\end{split}$
Parameters

v () – Spherical coordinates in 3D (norm, colat, long). Angles must be in radians.

Returns

v – Cartesian coordinates (x,y,z)

Return type

poliastro.core.util.planetocentric_to_AltAz(theta, phi)

Defines transformation matrix to convert from Planetocentric coordinate system to the Altitude-Azimuth system.

$\begin{split}t\_matrix = \begin{bmatrix} -\sin(theta) & \cos(theta) & 0\\ -\sin(phi)\cdot\cos(theta) & -\sin(phi)\cdot\sin(theta) & \cos(phi)\\ \cos(phi)\cdot\cos(theta) & \cos(phi)\cdot\sin(theta) & \sin(phi) \end{bmatrix}\end{split}$
Parameters
• theta (float) – Local sidereal time

• phi (float) – Planetodetic latitude

Returns

t_matrix – Transformation matrix

Return type