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jsonformat.txt
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# Detailed info on input JSON file parameters:
----------------------------------------------
Note: All the paths mentioned below are relative to $MEQS_DIR.
outdirname: Name of the output directory in which to write all the products of MeqSilhouette.
Format: string
e.g.: 'output/EHT230_TEST'
input_fitsimage: Name of the directory containing input fits images named using the following convention (samples can be found in input/sky_models):
Format: string
e.g.: No time-variability or polarisation -- 't0000-model.fits'
Time-variable sky -- 'txxxx-model.fits', where, xxxx = 0000, 0001, 0002...
Time-variable polarised sky -- 'txxxx-I-model.fits', 'txxxx-Q-model.fits', 'txxxx-U-model.fits', and 'txxxx-V-model.fits'
Non-FITS ASCII/Tigger LSM file -- <filename-without-extension>. A valid ASCII input LSM has extensions '.txt' or '.lsm.html'
for MeqTrees compatible Tigger LSMs.
Note: The total number of unique times (i.e., correlator dumps) will be divided evenly between the input fits images which are
simulated into the column indicated by 'ms_datacolumn'. Since wsclean can predict visibilities only into the MODEL_DATA column,
MeqSilhouette will retain the values in MODEL_DATA, while copying the same into <ms_datacolumn>, after which the corruptions are
applied to <ms_datacolumn>.
input_fitspol: Toggle 0 or 1 for polarisation simulation.
Format: integer or boolean
Note: This does not apply when <input_fitsimage> is an ASCII LSM, since any polarisation info is read by MeqTrees automatically.
output_to_logfile: Toggle 0 or 1 -- create 'logfile.txt' within <outdirname>.
Format: integer or boolean
add_thermal_noise: Toggle 0 or 1 -- add baseline-dependent thermal noise, calculated using station SEFDs obtained from <station_info>.
Format: integer or boolean
make_image: Toggle 0 or 1 -- make a dirty image using lwimager. Other imagers such as WSClean and PyMORESANE to be used in the future.
Format: integer or boolean
exportuvfits: Toggle 0 or 1 -- export MS to UVFITS.
Format: integer or boolean
station_info: Name of the file containing individual station info such as SEFD, coherence time, primary beam model etc.,
Samples can be found in input/station_info.
Format: string
e.g.: 'input/station_info/EHT2017_station_info.txt'
bandpass_enabled: Toggle 0 or 1 -- add bandpass corruptions.
Format: integer or boolean
bandpass_table: ASCII file to read bandpass info from. The input file must contain bandpass gain amplitudes for each station for a set of frequencies.
Samples can be found in input/jones_info.
Format: integer or boolean
e.g.: 'input/jones_info/bandpass.txt'
bandpass_freq_interp_order: Order of spline interpolation.
Format: integer
e.g.: 3
bandpass_makeplots: Toggle 0 or 1 -- make bandpass plots.
Format: integer or boolean
elevation_limit: Flag visibilities below this elevation limit.
Format: float
Units: radians
e.g.: 0.174
corr_quantbits: Number of bits used for quantization by the correlator -- for instance, 2 bits for 4 level quantization.
Format: integer
Units: bits
e.g.: 2
ms_antenna_table: Input CASA antenna table to use for creating the Measurement Set. Samples can be found in input/antenna_tables
Format: string
e.g.: 'input/antenna_Tables/EHT2017_ANTENNA'
ms_datacolumn: Specify the column in the Measurement Set in which to write the output visibilities.
Format: string
e.g.: 'DATA'
ms_RA: Right Ascension of the pointing centre of the observation.
Format: float
Units: Degrees
e.g.: 266.416837
ms_DEC: Declination of the pointing centre of the observation.
Format: float
Units: Degrees
e.g.: -29.000781
ms_polproducts: Indicate how to interpret the polarization information of the 2 x 2 complex visibilities, based on whether the polarization feeds
are circular or linear.
Format: string
e.g.: 'RR RL LR LL' or 'XX XY YX YY'
ms_nu: Specify the centre frequency of the bandpass.
Format: float
Units: GHz
e.g.: 230.0
ms_dnu: Specify the bandwidth of the spectral window.
Format: float
Units: GHz
e.g.: 2.56
ms_nchan: Specify the number of channels into which the bandwidth <ms_dnu> is divided.
Format: integer
e.g.: 8
ms_obslength: Specify the duration of the observation.
Format: float
Units: hours
e.g.: 4
ms_tint: Specify the integration time (i.e. the correlator dump time).
Format: float
Units: seconds
e.g.: 60
ms_StartTime: Specify the starting time of the observation to be input to the CASA simulator via simms.
Format: string
e.g.: 'UTC,2017/04/01/00:00:00.00'
ms_nscan: Specify the number of scans in the observation.
Format: integer
e.g.: 1
ms_scan_lag: Specify the lag time between scans.
Format: float
Units: hours
e.g.: 0
ms_makeplots: Toggle 0 or 1 -- generate MS-related plots such as uv-coverage, uv-distance sensitivity bins etc.,
Format: integer or boolean
im_cellsize: Specify the cell size to be used for imaging. Used only if <make_image> is enabled.
Format: string
e.g.: '3e-6arcsec'
im_npix: Specify image size in pixels. Used only if <make_image> is enabled.
Format: integer
e.g.: 64
im_stokes: Specify the the Stokes parameter to image (I, Q, U, or V). Used only if <make_image> is enabled.
Format: string
e.g.: 'I'
im_weight: Specify the weighting to use for imaging. Used only if <make_image> is enabled.
Format: string
e.g.: 'uniform'
trop_enabled: Toggle 0 or 1 -- enable tropospheric corruptions.
Format: integer or boolean
trop_wetonly: Toggle 0 or 1 -- simulate wet component only (from the output obtained from AATM). Used only if trop_enabled=1.
Format: integer or boolean
trop_attenuate: Toggle 0 or 1 -- enable tropospheric attenuation. Used only if trop_enabled=1.
Format: integer or boolean
trop_noise: Toggle 0 or 1 -- include tropospheric (i.e. sky) noise. Used only if trop_enabled=1.
Format: integer or boolean
trop_turbulence: Toggle 0 or 1 -- add Kolmogorov turbulence to the visibility phases. Used only if trop_enabled=1.
Format: integer or boolean
trop_mean_delay: Toggle 0 or 1 -- add mean (i.e. non-turbulent) delay errors due to both dry and wet components. Used only if trop_enabled=1.
Format: integer or boolean
trop_percentage_calibration_error: Unused.
trop_fixdelays: Toggle 0 or 1 -- Insert time-invariant delay errors for testing purposes. Used only if trop_enabled=1.
Format: integer or boolean
trop_fixdelay_max_picosec: Specify the maximum absolute value of the constant delay errors. Used only if trop_enabled=1 and trop_fixdelays=1.
Format: float
Units: picoseconds
e.g.: 200
trop_makeplots: Toggle 0 or 1. Plot troposphere-related quantities such as zenith opacity, elevation-dependent transmission, zenith sky temperature against frequency
and turbulent phase errors and delays against time.
Format: integer or boolean
pointing_enabled: Toggle 0 or 1 -- enable pointing error simulation. Station-based pointing error info must be present in <station_info>.
Format: integer or boolean
pointing_time_per_mispoint: Specify the number of minutes per mispointing.
Format: float
Units: minutes
e.g.: 10
pointing_makeplots: Toggle 0 or 1 -- plot pointing offset against time.
Format: integer or boolean
uvjones_d_on: Switch on polarization leakage effects (D-Jones). The station-based complex leakage terms are specified in the station-info file.
The 2x2 D-Jones matrix takes the form [[1 dR_real+1j*dR_imag], [dL_real+1j*dL_imag 1]]. When switched on, the parallactic angle (P-Jones)
effects are added automatically.
uvjones_g_on: Switch on complex gains (G-Jones). The station-based complex gain terms are specified in the station-info file.
The 2x2 G-Jones matrix takes the form [[gR_real+1j*gR_imag 0], [0 gL_real+1j*gL_imag]].
parang_corrected: Toggle 0 or 1 -- If 0, then parallactic angle rotation will be performed while computing the D-Jones terms;
if 1, then it will be assumed that parallactic angle correction has already been performed and twice the field angle
rotation will be performed while computing the D-Jones terms.