API Reference¶
Read array layout from txt file. |
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Convert from local E, N, H to X, Y, Z coordinates. |
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Convert local XYZ to UVU coordinates. |
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Create 2D gaussian kernel. |
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Degrid continuous uv baselines onto regular uv grid. |
Imaginary Interferometers.
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radio_dreams.interferometer.read_layout(layout_path=None)¶ Read array layout from txt file.
Antenna positions are defined with respect to the array centre.
E - East of the center in metres N - North of center in metres H - Height above sea level in metres
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radio_dreams.interferometer.enh_xyz()¶ Convert from local E, N, H to X, Y, Z coordinates.
Antenna positions are defined with respect to the array centre.
E - East of the center in metres N - North of center in metres H - Height above sea level in metres
Convert these coordinates to a Earth Centered Earth Fixed (ECEF) cartesian system with axes pointing towards
X - (h = 0, δ = 0) Y - (h = -6, δ = 0) Z - (δ = 90)
h - hour angle δ - declination
- Parameters
layout (
ndarray) – object fromread_layout()latitude (float) – Latitude of array in radians
- Returns
Array of shape [3, n], for X, Y, Z respectively
- Return type
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radio_dreams.interferometer.xyz_uvw()¶ Convert local XYZ to UVU coordinates.
U, V, W are coordinates used to represent interferometric baselines
\[\begin{split}\begin{bmatrix} u \\ v \\ w \end{bmatrix} = \begin{bmatrix} \sin(H_0) & \cos(H_0) & 0 \\ -\sin(\delta_0)\cos(H_0) & \sin(\delta_0)\sin(H_0) & \cos(\delta_0) \\ \cos(\delta_0)\cos(H_0) & -\cos(\delta_0)\sin(H_0) & \sin(\delta_0) \end{bmatrix} \begin{bmatrix} X_\lambda \\ Y_\lambda \\ Z_\lambda \end{bmatrix},\end{split}\]
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radio_dreams.interferometer.gauss_kernel()¶ Create 2D gaussian kernel.
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radio_dreams.interferometer.uv_degrid()¶ Degrid continuous uv baselines onto regular uv grid.
- Parameters
max_lambda (int) – Maximum baseline to evaluate, defaults to [1400]
nside (int) – Number of pixels per side, defaults to [511]
sigma (float) – Standard deviation of gaussian kernel, defaults to [3]
kernel (str) – Kernel size in pixel, Must be odd number for symmetry, defaults to [21]
kernel – Kernel type, gaussian or None, defaults to [“gaussian”]
- Returns
UV grid of size [nside, nside]
- Return type
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radio_dreams.interferometer.radec_lmn()¶ Calculate LMN direction cosines from Ra/Dec with respect to a phase center.
\begin{eqnarray} & l =& \, \cos \, \delta \sin \, \Delta \alpha \\ & m =& \, \sin \, \delta \cos \, \delta 0 - \cos \delta \sin \delta 0 \cos \Delta \alpha \\ & n =& \, \sin \, \delta \sin \, \delta 0 + \cos \delta \cos \delta 0 \cos \Delta \alpha \\ & =& \, \sqrt{1 - l^2 - m^2} - 1 \end{eqnarray}Here \(\Delta \alpha = \alpha - \alpha 0\) is the difference between the Right Ascension of each coordinate and the phase centre and \(\delta 0\) is the Declination of the phase centre.