UVBeam Parameters

These are the standard attributes of UVBeam objects.

Under the hood they are actually properties based on UVParameter objects.

Required

These parameters are required to have a sensible UVBeam object and are required for most kinds of beam files.

Naxes_vec
Number of directions in vector_coordinate_system, options are 2 or 3 (or 1 if beam_type is “power”)
Nfreqs
Number of frequency channels
Nspws
Number of spectral windows (ie non-contiguous spectral chunks). More than one spectral window is not currently supported.
antenna_type
String indicating antenna type. Allowed values are “simple”, and “phased_array”
beam_type
String indicating beam type. Allowed values are “efield”, and “power”.
data_array
Depending on beam type, either complex E-field values (“efield” beam type) or power values (“power” beam type) for beam model. units are linear normalized to either peak or solid angle as given by data_normalization. The shape depends on the beam_type and pixel_coordinate_system, if it is “healpix”, the shape is: (Naxes_vec, Nspws, Nfeeds or Npols, Nfreqs, Npixels), otherwise it is (Naxes_vec, Nspws, Nfeeds or Npols, Nfreqs, Naxes2, Naxes1)
data_normalization
Normalization standard of data_array, options are: “peak” and “solid_angle”. Peak normalized means each frequency is separately normalized such that the peak is 1 and the beam is dimensionless. Solid angle normalized means the peak normalized beam is divided by the integral of the beam over the sphere, giving the beam dimensions of 1/stradian.
feed_name
Name of physical feed (string)
feed_version
Version of physical feed (string)
freq_array
Array of frequencies, shape (Nspws, Nfreqs), units Hz
history
String of history, units English
model_name
Name of beam model (string)
model_version
Version of beam model (string)
pixel_coordinate_system
Pixel coordinate system, options are: healpix, az_za, sin_zenith
spw_array
Array of spectral window Numbers, shape (Nspws)
telescope_name
Name of telescope (string)

Optional

These parameters are defined by one or more file standard but are not always required. Some of them are required depending on the beam_type, antenna_type and pixel_coordinate_systems (as noted below).

Naxes1
Number of elements along the first pixel axis. Not required if pixel_coordinate_system is “healpix”.
Naxes2
Number of elements along the second pixel axis. Not required if pixel_coordinate_system is “healpix”.
Nelements
Required if antenna_type = “phased_array”. Number of elements in phased array
Nfeeds
Number of feeds. Not required if beam_type is “power”.
Npixels
Number of healpix pixels. Only required if pixel_coordinate_system is “healpix”.
Npols
Number of polarizations. Only required if beam_type is “power”.
axis1_array
Coordinates along first pixel axis. Not required if pixel_coordinate_system is “healpix”.
axis2_array
Coordinates along second pixel axis. Not required if pixel_coordinate_system is “healpix”.
basis_vector_array
Beam basis vector components – directions for which the electric field values are recorded in the pixel coordinate system. Not required if beam_type is “power”. The shape depends on the pixel_coordinate_system, if it is “healpix”, the shape is: (Naxes_vec, 2, Npixels), otherwise it is (Naxes_vec, 2, Naxes1, Naxes2)
coupling_matrix
Required if antenna_type = “phased_array”. Matrix of complex element couplings, units: dB, shape: (Nelements, Nelements, Nfeed, Nfeed, Nspws, Nfreqs)
delay_array
Required if antenna_type = “phased_array”. Array of element delays, units: seconds, shape: (Nelements)
element_coordinate_system
Required if antenna_type = “phased_array”. Element coordinate system, options are: N-E or x-y
element_location_array
Required if antenna_type = “phased_array”. Array of element locations in element coordinate system, shape: (2, Nelements)
extra_keywords
Any user supplied extra keywords, type=dict
feed_array
Array of feed orientations. shape (Nfeeds). options are: N/E or x/y or R/L. Not required if beam_type is “power”.
gain_array
Required if antenna_type = “phased_array”. Array of element gains, units: dB, shape: (Nelements)
loss_array
Array of antenna losses, shape (Nspws, Nfreqs), units dB?
mismatch_array
Array of antenna-amplifier mismatches, shape (Nspws, Nfreqs), units ?
nside
Healpix nside parameter. Only required if pixel_coordinate_system is “healpix”.
ordering
Healpix ordering parameter, allowed values are “ring” and “nested”. Only required if pixel_coordinate_system is “healpix”.
pixel_array
Healpix pixel numbers. Only required if pixel_coordinate_system is “healpix”.
polarization_array
Array of polarization integers, shape (Npols). AIPS Memo 117 says: stokes 1:4 (I,Q,U,V); circular -1:-4 (RR,LL,RL,LR); linear -5:-8 (XX,YY,XY,YX). Only required if beam_type is “power”.
s_parameters
S parameters of receiving chain, shape (4, Nspws, Nfreqs), ordering: s11, s12, s21, s22. units ?
system_temperature_array
Array of system temperatures, shape (Nspws, Nfreqs), units K

last updated: 2017-07-26