These parameters govern all processing used for the calibrator observation. The requested measurement set is split up by beam and scan, assuming that a given beam points at 1934-638 in the correspondingly-numbered scan. While it is possible to use the BEAM_MIN and BEAM_MAX parameters to specify a given range of beams to process for the science field, only the BEAM_MAX parameter is applied to the bandpass calibrator processing. All beams up to BEAM_MAX are split & flagged, and have their bandpass solved for. This is due to the particular requirements of cbpcalibrator.
If the bandpass calibration observation is long, and you just wish to use a portion of it for bandpass calibration, then you can specify a time range through SPLIT_TIME_START_1934 and SPLIT_TIME_END_1934. If either is not given, the start or end time are taken to be the start or end of the observation respectively.
The default behaviour is to flag the data with cflag (Flagging Utility). In this case, the MS is flagged in two passes. First, a combination of selection rules (allowing flagging of channels, time ranges, antennas & baselines, and autocorrelations) and (optionally) a simple flat amplitude threshold are applied. Then a sequence of Stokes-V flagging and dynamic flagging of amplitudes is done, integrating over individual spectra. Each of these steps is selectable via input parameters.
There is an option to use the AOFlagger tool (written by Andre Offringa) to do the flagging. This can be turned on by FLAG_WITH_AOFLAGGER, or FLAG_1934_WITH_AOFLAGGER (to just do it for the bandpass calibrator). You can provide a strategy file via AOFLAGGER_STRATEGY or AOFLAGGER_STRATEGY_1934, with access to some of the aoflagger parameters provided - see the table below.
Then the bandpass table is calculated with cbpcalibrator, which requires MSs for all beams to be given. This is a parallel job, the size of which is configurable through NUM_CPUS_CBPCAL.
If a second processing job is run with a higher BEAM_MAX (and hence wanting to use beams not included in a previous bandpass solution), the bandpass table is deleted and re-made once the new beams are split and flagged.
The cbpcalibrator job can make use of one of two scripts developed in the commissioning team. The first, plot_caltable.py from ACES both plots the bandpass solutions (as a function of antenna, beam and polarisation), and smooths the bandpass table so that outlying points are interpolated over. This produces a second table (with ”.smooth” appended to the name), which will then be applied to the science data instead of the original. There are a number of parameters that may be used to tweak the smoothing - this is intended to be an interim solution until this functionality is implemented in ASKAPsoft.
The second script, smooth_bandpass.py, does the smoothing of the bandpass via harmonic fitting, in a way that is robust to portions of the spectra being flagged.
If either of these options are used, a bandpass validation script is run, producing plots that can describe the quality of the bandpass solutions.
Finally, the bandpass solutions can be applied back to the 1934 datasets themselves. This will permit possible diagnostic analysis of the quality of the bandpass solution.
Additionally, we now have the option to derive instrumental on-axis polarisation leakages from the 1934-638 data. The bandpass calibrated 1934-638 measurement sets are further flagged, spectrally-averaged to 1MHz resolution, flagged again, and then leakages derived. To turn this on, use DO_LEAKAGE_CAL_CONT=true. The derived solutions can then be applied to continuum averaged, and self-calibrated science data using DO_APPLY_LEAKAGE=true. The derivation and application of leakage calibration is done indepdendently on each continuum channel.
| Variable | Default | Parset equivalent | Description |
|---|---|---|---|
| DO_SPLIT_1934 | true | none | Whether to split a given beam/scan from the input 1934 MS |
| JOB_TIME_SPLIT_1934 | JOB_TIME_DEFAULT (24:00:00) | none | Time request for splitting the calibrator MS |
| DO_FLAG_1934 | true | none | Whether to flag the splitted-out 1934 MS |
| JOB_TIME_FLAG_1934 | JOB_TIME_DEFAULT (24:00:00) | none | Time request for flagging the calibrator MS |
| DO_FIND_BANDPASS | true | none | Whether to fit for the bandpass using all 1934-638 MSs |
| JOB_TIME_FIND_BANDPASS | JOB_TIME_DEFAULT (24:00:00) | none | Time request for finding the bandpass solution |
| Preparing the calibrator datasets | |||
| MS_BASE_1934 | 1934_SB%s_%b.ms | none | Base name for the 1934 measurement sets after splitting. The wildcard %b will be replaced with the string “beamBB”, where BB is the (zero-based) beam number, and the %s will be replaced by the calibration scheduling block ID. |
| CHAN_RANGE_1934 | "" | channel (mssplit (Measurement Splitting/Averaging Utility)) | Channel range for splitting (1-based!). This range also defines the internal variable NUM_CHAN_1934 (which replaces the previously-available parameter NUM_CHAN). The default is to use all available channels in the MS. |
| FLAG_DO_DYNAMIC_AMPLITUDE_1934 | true | none | Whether to do the dynamic flagging, after the rule-based and simple flat-amplitude flagging is done. |
| FLAG_THRESHOLD_DYNAMIC_1934 | 4.0 |
|
Dynamic threshold applied to amplitudes when flagging 1934 data [sigma] |
| FLAG_DYNAMIC_1934_INTEGRATE_SPECTRA | true | amplitude_flagger.integrateSpectra (cflag (Flagging Utility)) | Whether to integrate the spectra in time and flag channels during the dynamic flagging task. |
| FLAG_THRESHOLD_DYNAMIC_1934_SPECTRA | 4.0 | amplitude_flagger.integrateSpectra.threshold (cflag (Flagging Utility)) | Dynamic threshold applied to amplitudes when flagging 1934 data in integrateSpectra mode [sigma] |
| FLAG_DYNAMIC_1934_INTEGRATE_TIMES | false | amplitude_flagger.integrateTimes (cflag (Flagging Utility)) | Whether to integrate across spectra and flag time samples during the dynamic flagging task. |
| FLAG_THRESHOLD_DYNAMIC_1934_TIMES | 4.0 | amplitude_flagger.integrateTimes.threshold (cflag (Flagging Utility)) | Dynamic threshold applied to amplitudes when flagging 1934 data in integrateTimes mode [sigma] |
| FLAG_DO_STOKESV_1934 | true | none | Whether to do Stokes-V flagging, after the rule-based and simple flat-amplitude flagging is done. |
| FLAG_USE_ROBUST_STATS_STOKESV_1934 | true | stokesv_flagger.useRobustStatistics (cflag (Flagging Utility)) | Whether to use robust statistics (median and inter-quartile range) in computing the Stokes-V statistics. |
| FLAG_THRESHOLD_STOKESV_1934 | 4.0 |
|
Threshold applied to amplitudes when flagging Stokes-V in 1934 data [sigma] |
| FLAG_STOKESV_1934_INTEGRATE_SPECTRA | true | stokesv_flagger.integrateSpectra (cflag (Flagging Utility)) | Whether to integrate the spectra in time and flag channels during the Stokes-V flagging task. |
| FLAG_THRESHOLD_STOKESV_1934_SPECTRA | 4.0 | stokesv_flagger.integrateSpectra.threshold (cflag (Flagging Utility)) | Threshold applied to amplitudes when flagging Stokes-V in 1934 data in integrateSpectra mode [sigma] |
| FLAG_STOKESV_1934_INTEGRATE_TIMES | false | stokesv_flagger.integrateTimes (cflag (Flagging Utility)) | Whether to integrate across spectra and flag time samples during the Stokes-V flagging task. |
| FLAG_THRESHOLD_STOKESV_1934_TIMES | 4.0 | stokesv_flagger.integrateTimes.threshold (cflag (Flagging Utility)) | Threshold applied to amplitudes when flagging Stokes-V in 1934 data in integrateTimes mode [sigma] |
| FLAG_DO_FLAT_AMPLITUDE_1934 | false | none | Whether to apply a simple (“flat”) amplitude threshold to the 1934 data. |
| FLAG_THRESHOLD_AMPLITUDE_1934 | 0.2 | amplitude_flagger.high (cflag (Flagging Utility)) | Simple amplitude threshold applied when flagging 1934 data. If set to blank (FLAG_THRESHOLD_AMPLITUDE_1934=""), then no minimum value is applied. [value in hardware units - before calibration] |
| FLAG_THRESHOLD_AMPLITUDE_1934_LOW | "" | amplitude_flagger.low (cflag (Flagging Utility)) | Lower threshold for the simple amplitude flagging. If set to blank (FLAG_THRESHOLD_AMPLITUDE_1934_LOW=""), then no minimum value is applied. [value in hardware units - before calibration] |
| ANTENNA_FLAG_1934 | "" | selection_flagger.<rule>.antenna (cflag (Flagging Utility)) | Allows flagging of antennas or baselines. For example, to flag out the 1-3 baseline, set this to "ak01&&ak03" (with the quote marks). See the documentation for further details on the format. |
| CHANNEL_FLAG_1934 | "" | selection_flagger.<rule>.spw (cflag (Flagging Utility)) | Allows flagging of a specified range of channels. For example, to flag out the first 100 channnels, use "0:0~16" (with the quote marks). See the docuemntation for further details on the format. |
| TIME_FLAG_1934 | "" | selection_flagger.<rule>.timerange (cflag (Flagging Utility)) | Allows flagging of a specified time range(s). The string given is passed directly to the timerange option of cflag’s selection flagger. For details on the possible syntax, consult the MS selection documentation. |
| UVRANGE_FLAG_1934 | "" | selection_flagger.<rule>.uvrange (cflag (Flagging Utility)) | Allows flagging of a specified UV range(s). The string given is passed directly to the uvrange option of cflag’s selection flagger. For details on the possible syntax, consult the MS selection documentation. |
| FLAG_AUTOCORRELATION_1934 | false | selection_flagger.<rule>.autocorr | If true, then autocorrelations will be flagged. |
| SPLIT_TIME_START_1934 | "" | timebegin (mssplit (Measurement Splitting/Averaging Utility)) | The starting time for data to be used from the 1934 SB. If blank, the start of the observation will be used. The formatting must conform to requirements of mssplit (Measurement Splitting/Averaging Utility). |
| SPLIT_TIME_END_1934 | "" | timeend (mssplit (Measurement Splitting/Averaging Utility)) | The starting time for data to be used from the 1934 SB. If blank, the start of the observation will be used. The formatting must conform to requirements of mssplit (Measurement Splitting/Averaging Utility). |
| Using AOFlagger for flagging | |||
| FLAG_WITH_AOFLAGGER | false | none | Use AOFlagger for all flagging tasks in the pipeline. This overrides the individual task level switches. |
| FLAG_1934_WITH_AOFLAGGER | false | none | Use AOFlagger for the flagging of the bandpass calibrator. This allows differentiation between the different flagging tasks in the pipeline. |
| AOFLAGGER_STRATEGY | "" | none | The strategy file to use for all AOFlagger tasks in the pipeline. Giving this a value will apply this one strategy file to all flagging jobs. The strategy file needs to be provided by the user. |
| AOFLAGGER_STRATEGY_1934 | "" | none | The strategy file to be used for the bandpass calibrator. This will be overridden by AOFLAGGER_STRATEGY. |
| AOFLAGGER_VERBOSE | true | none | Verbose output for AOFlagger |
| AOFLAGGER_READ_MODE | auto | none | Read mode for AOflagger. This can take the value of one of “auto”, “direct”, “indirect”, or “memory”. These trigger the following respective command-line options for AOflagger: “-auto-read-mode”, “-direct-read”, “-indirect-read”, “-memory-read”. |
| AOFLAGGER_UVW | false | none | When true, the command-line argument “-uvw” is added to the AOFlagger command. This reads uvw values (some exotic strategies require these). |
| Solving for the bandpass | |||
| DIRECTION_1934 | "[19h39m25.036, -63.42.45.63, J2000]" | sources.field1.direction (cbpcalibrator) | Location of 1934-638, formatted for use in cbpcalibrator. |
| TABLE_BANDPASS | calparameters_1934_bp_SB%s.tab | calibaccess.table (cbpcalibrator and ccalapply (Calibration Applicator)) | Name of the CASA table used for the bandpass calibration parameters. If no leading directory is given, the table will be put in the BPCAL directory. Otherwise, the table is left where it is (this allows the user to specify a previously-created table for use with the science field). The %s will be replaced by the calibration scheduling block ID. |
| BANDPASS_SCALENOISE | false | calibrate.scalenoise (ccalapply (Calibration Applicator)) | Whether the noise estimate will be scaled in accordance with the applied calibrator factor to achieve proper weighting. |
| NCYCLES_BANDPASS_CAL | 50 | ncycles (cbpcalibrator) | Number of cycles used in cbpcalibrator. |
| NUM_CPUS_CBPCAL | 216 | none | The number of cpus allocated to the cbpcalibrator job. The job will use all 20 cpus on each node (the memory footprint is small enough to allow this). |
| BANDPASS_MINUV | 200 | MinUV (Data Selection) | Minimum UV distance [m] applied to data prior to solving for the bandpass (used to exclude the short baselines). |
| BANDPASS_CAL_SOLVER | SVD | solver (Calibration solvers) | Selection of solver - either “SVD” or “LSQR” |
| BANDPASS_REFANTENNA | 1 | refantenna (cbpcalibrator) | Antenna number to be used as reference in the bandpass calibration. Ignored if negative, or if provided as a blank string (BANDPASS_REFANTENNA=""). |
| Smoothing and plotting the bandpass | |||
| DO_BANDPASS_SMOOTH | true | none | Whether to produce a smoothed version of the bandpass table, which will be applied to the science data. |
| BANDPASS_SMOOTH_TOOL | plot_caltable | none | Which tool to use. Possible values here are “plot_caltable” (the default) or “smooth_bandpass”. Relevant parameters for each tool follow. |
| BANDPASS_SMOOTH_F54 | "" | none | Integer value which if >0, the fitting is done within the beam-forming intervals assumed to be a multiple of 54 channels. For eg., for 54-channel beamforming interval set BANDPASS_SMOOTH_F54=1 For 216-channel interval, set BANDPASS_SMOOTH_F54=4 |
| plot_caltable | Options for the script “plot_caltable.py” | ||
| DO_BANDPASS_PLOT | true | none | Whether to produce plots of the bandpass |
| BANDPASS_SMOOTH_AMP | true | none | Whether to smooth the amplitudes (if false, smoothing is done on the real and imaginary values). |
| BANDPASS_SMOOTH_OUTLIER | true | none | If true, only smooth/interpolate over outlier points (based on the inter-quartile range). |
| BANDPASS_SMOOTH_FIT | 1 | none | The order of the polynomial (if >=0) or the window size (if <0) used in the smoothing. |
| BANDPASS_SMOOTH_THRESHOLD | 1.0 | none | The threshold level used for fitting to the bandpass. |
| smooth_bandpass | Options for the script “smooth_bandpass.py” | ||
| BANDPASS_SMOOTH_POLY_ORDER | "" | none | The polynomial order for the fit - the value for the -np option. Ignored if left blank. |
| BANDPASS_SMOOTH_HARM_ORDER | "" | none | The harmonic order for the fit - the value for the -nh option. Ignored if left blank. |
| BANDPASS_SMOOTH_N_WIN | "" | none | The number of windows to divide the spectrum into for the moving fit - the value for the -nwin option. Ignored if left blank. |
| BANDPASS_SMOOTH_N_TAPER | "" | none | The width (in channels) of the Gaussian Taper function to remove high-frequency components - the value for the -nT option. Ignored if left blank. |
| BANDPASS_SMOOTH_N_ITER | "" | none | The number of iterations for Fourier-interpolation across flagged points - the value for the -nI option. Ignored if left blank. |
| Applying the bandpass solution | |||
| DO_APPLY_BANDPASS_1934 | true | none | Whether to apply the bandpass solution to the 1934 datasets. |
| KEEP_RAW_1934_DATA | true | none | If true, the 1934 MSs will be copied prior to having the bandpass solution applied. This means you will have copies of both the raw and calibrated datasets. |
| Deriving leakage solutions | |||
| DO_LEAKAGE_CAL_CONT | true | none | Whether to derive leakage solutions from the bandpass calibrated 1934 datasets. |
| TIME_FLAG_1934_AV | "" | selection_flagger.<rule>.timerange (cflag (Flagging Utility)) | Allows flagging of a specified time range(s). The string given is passed directly to the timerange option of cflag’s selection flagger. For details on the possible syntax, consult the MS selection documentation. This option is for flagging spectrally averaged data before leakage solutions are derived. |
| UVRANGE_FLAG_1934_AV | "" | selection_flagger.<rule>.timerange (cflag (Flagging Utility)) | Allows flagging of a specified UV range(s). The string given is passed directly to the uvrange option of cflag’s selection flagger. For details on the possible syntax, consult the MS selection documentation. This option is for flagging spectrally averaged data before leakage solutions are derived. |