Beam model modules¶

Beamformer¶

class arts_localisation.beam_models.beamformer.BeamFormer(dish_pos, freqs, ntab=12, lon=<Longitude 6.60894465 deg>, ref_pos=None, itrf=True)¶

Bases: object

ARTS tied-array beamformer simulation

Parameters:

dish_pos (array) – dish positions with shape (ndish, 3), with unit
freqs (array) – Observing frequencies (with unit)
ntab (int) – Number of TABs (Default: NTAB from constants)
lon (Quantity) – longitude of observatory (Default: WSRT)
ref_pos (Quantity) – Observatory reference position relative to dish_pos (Default: None)
itrf (bool) – Dish positions and ref position are ITRF coordinates (Default: True)

_get_uvw(ha, dec)¶

Convert sky coordinates to uvw

Parameters:

ha (Quantity) – hour angle
dec (Quantity) – declination

Returns:

array of uvw with shape (ndish, nfreq, 3)

static _itrf_to_xyz(dish_pos, lon, ref_pos=None)¶

Convert ITRF to local XYZ coordinates

Parameters:

dish_pos (array) – dish positions with shape (ndish, 3), with unit
lon (Quantity) – longitude of observatory (Default: WSRT)
ref_pos (Quantity) – Observatory reference position relative to dish_pos (Default: None)

Returns:

XYZ positions of dishes

static _phase_to_pbeam(phases)¶

Convert an array of phase offsets to a power beam

Parameters:: phases (array) – complex phase offsets
Returns:: power beam

beamform(tab=0)¶

Beamform a tied-array beam

Parameters:: tab (int) – tied-array beam index
Returns:: power beam

set_coordinates_and_phases(grid_ha, grid_dec, ha0, dec0)¶

Calculate the geometric phases at each point in the coordinate grid, given a phase centre

Parameters:

grid_ha (array) – hour angle grid
grid_dec (array) – declination grid
ha0 – hour angle of phase centre
dec0 – declination of phase centre

Compound Beam¶

class arts_localisation.beam_models.compound_beam.CompoundBeam(freqs, theta=<Quantity 0. deg>, phi=<Quantity 0. deg>, rot=<Quantity 0. deg>)¶

Bases: object

Generate a compound beam pattern :param freqs: observing frequencies :param theta: E-W offsets (default: 0) :param phi: N-S offsets (default: 0) :param rot: rotation applied to model (parallactic angle, default 0)

_airy()¶

Airy disk beam pattern

Returns:: beam pattern

_gaussian()¶

Gaussian beam pattern

Returns:: beam pattern

_real(cb, thresh=0.5)¶

Measured beam pattern

Parameters:

cb (int) – beam number
thresh (flaot) – max NaN fraction, reverts to default gaussian above this (Default: 0.5)

Returns:

beam pattern

beam_pattern(mode, cb=None)¶

Return beam pattern for given mode

Parameters:

mode (str) – gauss, airy, or real
cb (int) – beam number (only used for real beam)

Returns:

beam pattern

arts_localisation.beam_models.compound_beam.gauss_2d(xy, x_mean, x_sig, y_mean, y_sig, rho)¶

Construct a 2D Gaussian

Parameters:

xy (array) – 2xN array of x, y values
x_mean (float) – mean of x
x_sig (float) – sigma of x
y_mean (float) – mean of y
y_sig (float) – sigma of y
rho (float) – correlation between x and y

Returns:

An NxN array with the Gaussian distribution

Synthesised Beam Generator¶

class arts_localisation.beam_models.sb_generator.SBGenerator(fname=None, science_case=None)¶

Bases: object

Synthesised beam layout and generator

Parameters:

fname (str) – path to SB table
science_case – ARTS science case (3 or 4)

_load_table()¶: Load the SB table

classmethod from_science_case(science_case)¶

Initalize default table for given science cases

Parameters:: science_case (int) – science case (3 or 4)
Returns:: SBGenerator object

classmethod from_table(fname)¶

Initalize with provided SB table

Parameters:: fname (str) – Path to SB table
Returns:: SBGenerator object

get_map(sb)¶

Return mapping of requested SB

Parameters:: sb (int) – beam to return mapping for
Returns:: SB mapping for requested beam

property reversed¶

Whether or not the SB table is reversed for use on filterbank data

Returns:: reversed (bool)

synthesize_beam(data, sb)¶

Synthesise beam

Parameters:

data (array) – TAB data with shape [TAB, freq, others(s)]
sb (int) – SB index

Returns:

SB data with shape [freq, other(s)]

exception arts_localisation.beam_models.sb_generator.SBGeneratorException¶: Bases: Exception