UVCal Parameters

These are the standard attributes of UVCal objects.

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

Required

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

Nants_data

Number of antennas that have data associated with them (i.e. length of ant_array), which may be smaller than the numberof antennas in the telescope (i.e. length of antenna_numbers).

Nants_telescope

Number of antennas in the antenna_numbers array. May be larger than the number of antennas with gains associated with them.

Nfreqs

Number of frequency channels

Njones

Number of Jones calibrationparameters (Number of Jones matrix elements calculated in calibration).

Nspws

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

Ntimes

Number of times with different calibrations calculated (if a calibration is calculated over a range of integrations, this gives the number of separate calibrations along the time axis).

ant_array

Array of integer antenna numbers that appear in self.gain_array, with shape (Nants_data,). This array is ordered to match the inherent ordering of the zeroth axis of self.gain_array.

antenna_names

Array of antenna names with shape (Nants_telescope,). Ordering of elements matches ordering of antenna_numbers.

antenna_numbers

Array of all integer-valued antenna numbers in the telescope with shape (Nants_telescope,). Ordering of elements matches that of antenna_names. This array is not necessarily identical to ant_array, in that this array holds all antenna numbers associated with the telescope, not just antennas with data, and has an in principle non-specific ordering.

cal_style

Style of calibration. Values are sky or redundant.

cal_type

cal type parameter. Values are delay, gain or unknown.

channel_width

Channel width of of a frequency bin. Units Hz.

freq_array

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

gain_convention

The convention for applying the calibration solutions to data.Values are “divide” or “multiply”, indicating that to calibrate one should divide or multiply uncalibrated data by gains. Mathematically this indicates the alpha exponent in the equation: calibrated data = gain^alpha * uncalibrated data. A value of “divide” represents alpha=-1 and “multiply” represents alpha=1.

history

String of history, units English

integration_time

Integration time of a time bin, units seconds.

jones_array

Array of antenna polarization integers, shape (Njones). linear pols -5:-8 (jxx, jyy, jxy, jyx).circular pols -1:-4 (jrr, jll. jrl, jlr).

spw_array

Array of spectral window numbers, shape (Nspws).

telescope_name

Name of telescope. e.g. HERA. String.

time_array

Array of calibration solution times, center of integration, shape (Ntimes), units Julian Date

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)

Optional

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

Nsources

Number of sources used.

antenna_positions

Array giving coordinates of antennas relative to telescope_location (ITRF frame), shape (Nants_telescope, 3), units meters. See the tutorial page in the documentation for an example of how to convert this to topocentric frame.

baseline_range

Range of baselines used for calibration.

delay_array

Required if cal_type = “delay”. Array of delays with units of seconds. Shape: (Nants_data, Nspws, 1, Ntimes, Njones), type = float.

diffuse_model

Name of diffuse model.

extra_keywords

Any user supplied extra keywords, type=dict. Keys should be 8 character or less strings if writing to calfits files. Use the special key “comment” for long multi-line string comments.

flag_array

Array of flags to be applied to calibrated data (logical OR of input and flag generated by calibration). True is flagged. Shape: (Nants_data, Nspws, Nfreqs, Ntimes, Njones), type = bool.

freq_range

Required if cal_type = ‘delay’. Frequency range that solutions are valid for. list: [start_frequency, end_frequency] in Hz.

gain_array

Required if cal_type = “gain”. Array of gains, shape: (Nants_data, Nspws, Nfreqs, Ntimes, Njones), type = complex float.

gain_scale

The gain scale of the calibration, which indicates the units of the calibrated visibilities. For example, Jy or K str.

git_hash_cal

Commit hash of calibration software (from git_origin_cal) used to generate solutions.

git_origin_cal

Origin (on github for e.g) of calibration software. Url and branch.

input_flag_array

Array of input flags, True is flagged. shape: (Nants_data, Nspws, Nfreqs, Ntimes, Njones), type = bool.

lst_array

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

observer

Name of observer who calculated solutions in this file.

quality_array

Array of qualities of calibration solutions. The shape depends on cal_type, if the cal_type is ‘gain’ or ‘unknown’, the shape is: (Nants_data, Nspws, Nfreqs, Ntimes, Njones), if the cal_type is ‘delay’, the shape is (Nants_data, Nspws, 1, Ntimes, Njones). The type is float.

ref_antenna_name

Required if cal_style = “sky”. Phase reference antenna.

sky_catalog

Required if cal_style = “sky”. Name of calibration catalog.

sky_field

Required if cal_style = “sky”. Short string describing field center or dominant source.

telescope_location

Telescope location: xyz in ITRF (earth-centered frame). Can also be accessed using telescope_location_lat_lon_alt or telescope_location_lat_lon_alt_degrees properties

time_range

Time range (in JD) that cal solutions are valid for.list: [start_time, end_time] in JD. Should only be set in Ntimes is 1.

total_quality_array

Array of qualities of the calibration for entire arrays. The shape depends on cal_type, if the cal_type is “gain” or “unknown”, the shape is: (Nspws, Nfreqs, Ntimes, Njones), if the cal_type is “delay”, the shape is (Nspws, 1, Ntimes, Njones), type = float.

last updated: 2021-10-21