UVFlag Parameters

These are the standard attributes of UVFlag objects.

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

Required

These parameters are required to have a sensible UVFlag object and are required for most kinds of uv data files.

Nants_data

Number of antennas with data present. Only available for “baseline” or “antenna” type objects.May be smaller than the number of antennas in the array

Nants_telescope

Number of antennas in the array. Only available for “baseline” type objects. May be larger than the number of antennas with data.

Nbls

Number of baselines. Only Required for “baseline” type objects.

Nblts

Number of baseline-times (i.e. number of spectra). Not necessarily equal to Nbls * Ntimes

Nfreqs

Number of frequency channels

Npols

Number of polarizations

Nspws

Number of spectral windows (ie non-contiguous spectral chunks). More than one spectral window is not currently supported.

Ntimes

Number of times

ant_1_array

Array of first antenna indices, shape (Nblts). Only available for “baseline” type objects. type = int, 0 indexed

ant_2_array

Array of second antenna indices, shape (Nblts). Only available for “baseline” type objects. type = int, 0 indexed

baseline_array

Array of baseline indices, shape (Nblts). Only available for “baseline” type objects. type = int; baseline = 2048 * (ant1+1) + (ant2+1) + 2^16

freq_array

Array of frequencies, center of the channel, shape (Nspws, Nfreqs), units Hz

history

String of history, units English

label

String used for labeling the object (e.g. ‘FM’). Default is empty string.

lst_array

Array of lsts, center of integration, shape (Nblts), units radians

metric_array

Floating point metric information, only availble in metric mode. shape (Nblts, Nspws, Nfreq, Npols).

mode

The mode determines whether the object has a floating point metric_array or a boolean flag_array. Options: {“metric”, “flag”}. Default is “metric”.

polarization_array

Array of polarization integers, shape (Npols). AIPS Memo 117 says: pseudo-stokes 1:4 (pI, pQ, pU, pV); circular -1:-4 (RR, LL, RL, LR); linear -5:-8 (XX, YY, XY, YX). NOTE: AIPS Memo 117 actually calls the pseudo-Stokes polarizations “Stokes”, but this is inaccurate as visibilities cannot be in true Stokes polarizations for physical antennas. We adopt the term pseudo-Stokes to refer to linear combinations of instrumental visibility polarizations (e.g. pI = xx + yy).

time_array

Array of times, center of integration, shape (Nblts), units Julian Date

type

The type of object defines the form of some arrays and also how metrics/flags are combined. Accepted types:”waterfall”, “baseline”, “antenna”

weights_array

Floating point weight information, shape (Nblts, Nspws, Nfreq, Npols).

Optional

These parameters are defined by one or more type but are not always required. Some of them are required depending on the type (as noted below).

ant_array

Array of antenna numbers, shape (Nants_data), Only available for “antenna” type objects. type = int, 0 indexed

extra_keywords

Any user supplied extra keywords, type=dict.Use the special key ‘comment’ for long multi-line string comments.Default is an empty dictionary.

flag_array

Boolean flag, True is flagged, only availble in flag mode. shape (Nblts, Nspws, Nfreq, Npols).

weights_square_array

Floating point weight information about sum of squares of weights when weighted data converted from baseline to waterfall mode.

x_orientation

Orientation of the physical dipole corresponding to what is labelled as the x polarization. Options are “east” (indicating east/west orientation) and “north” (indicating north/south orientation)

last updated: 2021-10-21