calibrater¶

class calibrater[source]¶

Synthesis calibration (self- and cross-)

The calibrater tool (cb) provides for synthesis calibration operations within CASA.

Methods Summary

`accumulate`	This function enables cumulative calibration using `calibrater`.
`activityrec`	This funtion enables returning generic information about recent activity.
`calibrater`	Create a `calibrater` tool.
`close`	Close the `calibrater` tool, which is hardly ever necessary.
`correct`	This function applies the calibration components specified via one or more invocations of the setapply function to the observed visibility data and writes the result to the CORRECTED_DATA column of the Measurement Set.
`corrupt`	This function applies the calibration components specified via one or more invocations of the setapply function to the model visibility data and (over-)writes the result to the MODEL_DATA column of the Measurement Set.
`createcaltable`	Creates an empty calibration table that can subsequently be filled with by using the table tool.
`delmod`	This method can be used to delete the model visibility data representations in the MS.
`done`	This function is redundant with the close method.
`fluxscale`	This function is used to bootstrap the amplitude scale the calibration solutions according to specified reference calibrator(s) of known flux density.
`initcalset`	This function re-initializes the calibration scratch columns: MODEL_DATA to unity (in total intensity, and unpolarized), and CORRECTED_DATA to (observed) DATA.
`initweights`	This function initializes the MS weight info in various ways.
`linpolcor`	THIS METHOD IS CURRENTLY DISABLED.
`listcal`	calibrater.listcal() lists antenna gain solutions in tabular form.
`modelfit`	This method fits single-component models (points, elliptical Gaussians or elliptical Disks_ to the CORRECTED_DATA of the selected field.
`open`	Attaches a MeasurementSet to the `calibrater` tool for further processing with other methods.
`parsecallibfile`	TBD
`plotcal`	This function plots a calibration table either to a plotter or to a file.
`posangcal`	This function is used to apply position angle calibration for observations made using circularly polarized feeds.
`rerefant`	TBD
`reset`	Resets the apply and/or solve components previously set by setapply and setsolve.
`returndict`	Return a dictionary containing information about the current calibrater tool state.
`selectvis`	This function provids for selection of the visibility data from the MS which will be treated by subsequent execution of the solve and correct functions.
`setapply`	This function is used to specify the calibration components which should be applied during subsequent execution of the solve and correct functions.
`setcallib`	TBD
`setcorrdepflags`	TBD
`setmodel`	Name of the model image to be used as a sky model for model visibility computations.
`setptmodel`	Set a global point source model Stokes parameters to use in solving operations.
`setsolve`	This function specifies the calibration component that will be solved for by the solve function.
`setsolvebandpoly`	This function is a specialization of the setsolve method which should be used to arrange for bandpass solving when polynomial solutions for B are desired, e.g., when per-channel SNR on calibrators is too low to obtain a useful sampled bandpass.
`setsolvegainspline`	This function is a specialization of the setsolve method which should be used when cubic spline G solutions are desired, e.g., when SNR on calibrators is very low.
`setvi`	Use this method to control whether the modern (old=False) or old-style (old=True) VisibilityIterator is used by the calibration application.
`smooth`	This function provides for time-dependent smoothing of sampled calibration solutions.
`solve`	Execution of this function initiates a solve for the calibration component specified in a previous setsolve execution.
`specifycal`	This function enables specifying calibration parameters externally.
`state`	Request the apply/solve state of the calibrater tool.
`updatecaltable`	This method can be used to update a caltable (from v3.4 or later) to the current version of CASA.
`validatecallib`	TBD

accumulate(tablein='', incrtable='', tableout='', field='', calfield='', interp='linear', t=- 1.0, spwmap=[- 1])[source]¶

This function enables cumulative calibration using calibrater. It is the analog of the task “CLCAL” in classic AIPS.

The accumulate function is useful when:

a calibration solution of a particular type already exists,
an incremental calibration solution of the same type is desired (an incremental solution in this context means derived independently from, or determined with respect to, the first)
the first calibration cannot be implicitly recovered in the course of obtaining the incremental solution

For example, a phase-only “G” self-calibration on a target source may be desired to tweak the full amplitude and phase “G” calibration already obtained from a calibrator. The initial calibration (from the calibrator) contains amplitude information, and so must be carried forward, yet the phase-only solution itself cannot (by definition) recover this information, as a full amplitude and phase self-calibration would. In this case, the initial solution must be applied while solving for the phase-only solution, then the two solutions combined to form a cumulative calibration embodying the net effect of both. In terms of the Measaurement Equation, the net calibration is the product of the initial and incremental solutions.

The analog of accumulate in classic AIPS is the use of CLCAL to combine a series of (incremental) SN calibration tables to form successive (cumulative) CL calibration tables.

Cumulative calibration tables also provide a means of generating carefully interpolated calibration, on variable user-defined timescales, that can be examined prior to application to the data with setapply and correct. The solutions for different fields and/or spectral windows can be interpolated in different ways, with all solutions stored in the same table.

The only difference between incremental and cumulative calibration tables is that incremental tables are generated directly from the data via solve or (in the near future) from other ancilliary data (e.g. weather information), and cumulative tables are generated from other cumulative and incremental tables via accumulate. In all other respects (internal format, application to data via setapply and correct, plotting with plotcal, etc.), they are the same, and therefore interchangable. Thus, accumulate and cumulative calibration tables need only be used when circumstances require it.

The accumulate function represents a generalization on the classic AIPS CLCAL model of cumulative calibration in that its application is not limited to accumulation of “G” solutions (SN/CL tables classic AIPS are the analog of “G” (and, implicitly, “T”) in aips++). In principle, any basic calibration type can be accumulated (onto itself), as long as the result of the accumulation (matrix product) is of the same type. This is True of all the basic types, except “D”. Accumulation is currently supported for “B”, “G”, and “T”, and, in future, “F” (ionospheric Faraday rotation), “J” (generic full-polarization calibration), fringe-fitting, and perhaps others. Accumulation of certain specialized types (e.g., “GSPLINE”, “TOPAC”, etc.) onto the basic types will be supported in the near future. The treatment of various calibration from ancilliary data (e.g., system temperatures, weather data, WVR, etc.), as they become available, will also make use of accumulate to achieve the net calibration.

Note that accumulation only makes sense if treatment of a uniquely incremental solution is required (as described above), or if a careful interpolation or sampling of a solution is desired. In all other cases, re-solving for the type in question will suffice to form the net calibration of that type. For example, the product of an existing “G” solution and an amplitude and phase “G” self-cal (solved with the existing solution applied), is equivalent to full amplitude and phase “G” selfcal (with no prior solution applied), as long as the timescale of this solution is at least as short as that of the existing solution.

Use of accumulate is straightforward:

The tablein parameter is used to specify the existing cumulative calibration table to which an incremental table is to be applied. Initially, no such table exists, and accumulate will generate one from scratch (on-the-fly), using the timescale (in seconds) specified by the parameter t. These nominal solutions will be unit-amplitude, zero-phase (i.e., unit matrix) calibration, ready to be adjusted by accumulation. When t is negative (the default), the table name specified in tablein must exist and will be used.

The incrtable parameter is used to specify the incremental table that should be applied to tablein. The calibration type of incrtable sets the type assumed in the operation, so tablein must be of the same type. If it is not, accumulate will exit with an error message. (Certain combinations of types and subtypes will be supported by accumulate in the future.)

The tableout parameter is used to specify the name of the output table to write. If un-specified (or ), then tablein will be overwritten. Use this feature with care, since an error here will require building up the cumulative table from the most recent distinct version (if any).

The field parameter specifies those field names (standard selection syntax) in tablein to which the incremental solution should be applied. The solutions for other fields will be passed to tableout unaltered. If the cumulative table was created from scratch in this run of accumulate, then these solutions will be unit-amplitude, zero-phase, as described above.

The calfield parameter is used to specify the fields (standard selection syntax) to select from incrtable to use when applying to tablein. Together, use of field and calfield permit completely flexible combinations of calibration accumulation with respect to fields. Multiple runs of accumulate can be used to generate a single table with many combinations. In future, a “self” mode will be enabled that will simplify the accumulation of field-specific solutions.

The interp parameter is used to specify the interpolation type to use on the incremental solutions, as in setapply. The currently available interpolation types are “nearest”, “linear”, and “aipslin”. See the setapply URM documentation for more details.

The spwmap parameter enables accumulating solutions from differing spectral windows. See setapply for details on how spwmap works.

Pending improvements:

Implement a “self” mode (independent of interpolation type), to simplify or eliminate use of the field and calfield parameters in some contexts (e.g., self-cal)
More interpolation modes, e.g., “cubic”, and interpolation timescale (timerange to permit interpolation)
Handle propogation (or not) of bad/flagged solutions
Support of specialized types (e.g., TOPAC) onto the basic types
Smoothing (probably a separate function)

Parameters

tablein (string='') - Input cumulative calibration table name
incrtable (string='') - Input incremental calibration table name
tableout (string='') - Output cumulative calibration table name. Default is input table name.
field (variant='') - List of fields (names) to update in input cumulative table. Default is all.
calfield (variant='') - List of fields (names) in incremental table to use. Default is use all.
interp (string='linear') - Interpolation mode to use on incremental solutions
t (double=-1.0) - Cumulative table timescale when creating from scratch
spwmap (intVec=[-1]) - Spectral windows to apply

Returns

bool

Examples

cb.open('ap366.sim');

# obtain G solutions from calibrator
cb.selectvis(msselect='FIELD_ID IN [9,11]');
cb.setsolve(type='G',table='cal.G0',t=300);
cb.solve()

# obtain proper flux density scale
cb.fluxscale (tablein='cal.G0', tableout='cal.G1',
             reference='1328+307', transfer="0917+624");

# generate cumulative table for target source on 20s timescale
cb.accumulate(tablein='',incrtable='cal.G1',tableout='cal.cG0',
             field='0957+561',calfield='0917+624',
             interp='linear',t=20);

# apply this calibration to target
cb.selectvis(msselect='FIELD_ID==10');
cb.setapply(type='G',table='cal.cG0',interp='linear')
cb.correct();

#    (image target with imager tool)

# phase-selfcal target on 60s timescale 
cb.selectvis(msselect='FIELD_ID==10');
cb.setapply(type='G',table='cal.cG0',interp='linear')
cb.setsolve(type='G',table='cal.G2',t=60,phaseonly=T);
cb.solve();

# accumulate new solution onto existing one
cb.accumulate(tablein='cal.cG0',incrtable='cal.G2',tableout='cal.cG1',
             field='0957+561',calfield='0957+561',
             interp='linear');

# apply new cumulative solution to data
cb.setapply(type='G',table='cal.cG1',interp='linear')
cb.correct();

#   (another round of imaging, etc.)

cb.close();

activityrec()[source]¶

This funtion enables returning generic information about recent activity.

Pending improvements:

??

calibrater()[source]¶: Create a calibrater tool. The casapy environment provides a standard calibrater tool for general use (cb), but additional calibrater tools may be created if needed. Calibrater tools created in this way are independent of the standard calibrater tool.

close()[source]¶: Close the calibrater tool, which is hardly ever necessary.

correct(applymode='')[source]¶

This function applies the calibration components specified via one or more invocations of the setapply function to the observed visibility data and writes the result to the CORRECTED_DATA column of the Measurement Set.

Parameters

applymode (string='') - Correction cal/flag mode: ‘’=’calflag’,’cal’,’flag’,’trial’

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.selectvis(field='1445*')
cb.setapply ('G', 10.0, 'gcal_1')
cb.correct();
cb.close();

corrupt()[source]¶: This function applies the calibration components specified via one or more invocations of the setapply function to the model visibility data and (over-)writes the result to the MODEL_DATA column of the Measurement Set.

createcaltable(caltable='', partype='', caltype='', singlechan='')[source]¶

Creates an empty calibration table that can subsequently be filled with by using the table tool.

Parameters

caltable (string='') - Calibration table name
partype (string='') - Parameter type name
caltype (string='') - Calibration type name
singlechan (bool='') - Create a calibration table with frequency-independent parameters?

Returns

bool

Examples

cb.open('ngc5921.ms',F,F,F)   # don't add MODEL_DATA, etc.
cb.createcaltable('ngc5921.gcal', 'Complex', 'G Jones', True)
cb.close()

delmod(otf=False, field='', spw='', scr=False)[source]¶

This method can be used to delete the model visibility data representations in the MS. The ’otf’ representation is the new (as of v3.4) ’scratch-less’ model data, stored as keywords in the MS header containing model data formation instructions. It is generated by the im tool (setjy, ft, and clean methods; usescratch=F in im.open), and if present, overrides the old-fashioned MODEL_DATA column (if present). If a user wishes to use the MODEL_DATA column _after_ having operated with the ’otf’ representation, this method can be used to delete the ’otf’ represenatation to make the MODEL_DATA column visible. (Create the MODEL_DATA column by using usescratch=T in the im tool, or by running the cb.open with addmodel=T.)

If otf=T, the user may selectively remove only a selection of fields model from the MS by specifying the field parameter. Similarly if the field parameter is specified, selected spws model for those fields may be deleted by specifying the spw.

For convenience, this method also provides a means for deleting the MODEL_DATA column by setting scr=T.

Parameters

otf (bool=False) - If T, delete the otf model data keywords
field (variant='') - Select on field
spw (variant='') - Select on spw only if field is defined
scr (bool=False) - If T, delete the MODEL_DATA column

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.delmod(otf=T,scr=F);   # delete only the otf model for all fields
cb.solve();

cb.open('n4826.ms')
cb.delmod(otf=T, field='1') 
#delete otf model of field 1 only, all other fields model are untouched
#if present
cb.open('n4826.ms')
cb.delmod(otf=T, field='1', spw='2') 
#delete otf model of field 1 and spectralwindow 2  only.

####NOTE doing:
cb.delmod(otf=T, field='', spw='2')

#will delete all otf models and spw will be ignored 

done()[source]¶: This function is redundant with the close method.

fluxscale(tablein='', reference='', tableout='', transfer='', listfile='', append=False, refspwmap=[- 1], gainthreshold=- 1.0, antenna='', timerange='', scan='', incremental=False, fitorder=1, display=False)[source]¶

This function is used to bootstrap the amplitude scale the calibration solutions according to specified reference calibrator(s) of known flux density. This is necessary when the flux densities of some of your calibrators were unknown (and thus were assumed to be 1 Jy) during G solving.

The bootstrapping is achieved by comparing the median gain norm of the calibration solutions derived for the calibrators specified in reference (one or more sources with known flux densities at the time of G solving) with that of the calibrators specified in transfer, and enforcing the assumption that the antenna gains are constant, on average. The gain solutions for the transfer sources are then re-scaled accordingly. The reference and transfer parameters may be specified using the general field selection syntax (as in field in selectvis).

If no transfer fields are specified, then the solutions for all non-reference fields in tablein will be re-scaled.

If no tableout is specified the input table will be overwritten with the scaled solutions. Note that the resulting table will only contain solutions for those fields implicit in the reference and transfer specifications. Use append=T to append the scaled solutions to an existing table.

Use the refspwmap parameter to indicate how data for different spectral windows should be matched in calculating the flux density scale factor for transfer fields. The default behavior for refspwmap is to insist on precisely matching spectral windows for reference and transfer fields. When specified, the refspwmap parameter takes a vector of integers indicating which spectral window solutions to use as the reference for others, such that refspwmap[j]=i causes solutions (from reference fields) observed in the i-th spectral window to be used to reference solutions (from transfer fields) observed in the j-th spectral window. For example, for the case of a total of 4 spectral windows: if the reference fields were observed only in spw=2 & 4, and the transfer fields were observed variously in all 4 spws, specify refspwmap=[2,2,4,4]. This will ensure that transfer fields observed in spws 1,2,3,4 will be referenced to reference field data from spws 2,2,4,4, respectively. Note that if the transfer fields were observed only in spws 1 & 3, the same specification would work, but refspwmap=[2,2,4] would suffice. In this case, nothing need be specified for the 4th spw (there are no transfer fields there), and specifying 2 for the 2nd spw is actually inconsequential (though required so that the specification of 4 for spw 3 is properly interpretted).

The gain values used in the flux scaling determination skewed by outliers. The parameters, gainthreshold and antenna can be used to limit the input gain solutions to be included in the flux scale determination. Use the gainthreshold is a threshold in % from the median values of the gain solutions to be used. Use the antenna to select or de-selesect (using the MSSelection syntax) antenna(s). Futher refinements on the selection based on timerange and scan are possible.

The derived flux densities for the transfer fields will be reported in the logger, and returned to the Python dictionary specified in fluxd. This will be an 2D array of shape [number-of-spectral-windows X number-of-fields]. When mulitple spectral windows are involved the spectral index will also be reported by fitting the determined flux densities across the freuquencies. The order of a polynomcial to be fitted can be specified with fitorder.

Note that elevation-dependent gain effects may render the basic assumption used here invalid, and so should be corrected for prior to solving for G, using types ’TOPAC’ or ’GAINCURVE’ in setapply.

Note that the visibility data itself is not used directly by this function.

Pending improvements:

Allow antenna and uv-distance selection to improve results for resolved calibrators
Set the visibility model according to the flux density results
An option to use the data to derive the relative flux densities

Parameters

tablein (string='') - Input calibration table name
reference (variant='') - Reference calibrator field names (comma-separated)
tableout (string='') - Output calibration table name. Default is input calibration table name.
transfer (variant='') - Transfer source field names (comma-separated). Default is all other fields.
listfile (string='') - Name of listfile that contains the fit information. Default is ‘’ (no file).
append (bool=False) - Append to existing table?
refspwmap (intVec=[-1]) - List of alternate spw for referencing
gainthreshold (float=-1.0) - Threshold of gain amplitudes with respect to the median value to be used in flux scale calculation. Default: -1.0 (no threshold)
antenna (string='') - antenna selection/de-selection in flux scale calculation. Default: “”(include all antennas)
timerange (string='') - timerage sub-selection with antenna selection in flux scale calculation. Default: “”(include all)
scan (string='') - scan sub-selection with antenna selection in flux scale calculation. Default: “”(include all)
incremental (bool=False) - create a incremental caltable
fitorder (int=1) - order for spectral fitting for multiple spws
display (bool=False) - display statistics of the flux ratios

Returns

record

Examples

cb.open('ngc5921.ms')
cb.selectvis(field='1331*,1445*')
cb.setsolve(type='G',table='gcal',t='inf')
cb.solve()
cb.fluxscale (tablein='gcal', tableout='flxcal', 
              reference='1331*', transfer='1445*');
cb.close();


This example generates a calibration table containing {\tt G}
solutuions ('gcal') and then writes a re-scaled version, using
1335+305 as the reference calibrator, to derive properly scaled
amplitude calibration for the transfer source, 1445+099.  We have
assumed that 1331+305 has already had its MODEL\_DATA set to
the correct flux density.

initcalset(calset=0)[source]¶

This function re-initializes the calibration scratch columns: MODEL_DATA to unity (in total intensity, and unpolarized), and CORRECTED_DATA to (observed) DATA. Optionally if calset is set to 1 any model saved in the MS header to for calibration purposes is deleted

Parameters

calset (int=0) - if it set to 1 the model saved in the header is removed

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.initcalset();
cb.solve();

initweights(wtmode='nyq', dowtsp=False, tsystable='', gainfield='', interp='', spwmap='')[source]¶

This function initializes the MS weight info in various ways.

If wtmode=’ones’, SIGMA and WEIGHT will be initialized with 1.0, globally.

If wtmode=’nyq’ (the default), SIGMA and WEIGHT will be initialized according to bandwidth and integration time. This is the theoretically correct mode for raw normalized visibilities.

If wtmode=’sigma’, WEIGHT will be initialized according to the existing SIGMA column.

If mode=’weight’, WEIGHT_SPECTRUM will be initialized according to the existing WEIGHT column; dowtspec=T must be specified in this case.

For the above wtmodes, if dowtspec=T (or if the WEIGHT_SPECTRUM column already exists), the WEIGHT_SPECTRUM column will be initialized (uniformly in channel), in a manner consistent with the WEIGHT column. If the WEIGHT_SPECTRUM column does not exist, dowtsp=T will force its creation.

The follow modes should be used with extreme care: If wtmode=’delwtsp’, the WEIGHT_SPECTRUM column will be deleted (if it exists). If wtmode=’delsigsp’, the SIGMA_SPECTRUM column will be deleted (if it exists). Note that creation of SIGMA_SPECTRUM is not supported via this method.

Note that this method does not support any prior selection. Intialization of the weight information must currently be done globally or not at all. This is to maintain consistency.

Parameters

wtmode (string='nyq') - Initialization mode
dowtsp (bool=False) - Initialize WEIGHT_SPECTRUM column
tsystable (string='') - Tsys calibration table to apply on the fly
gainfield (string='') - Select a subset of calibrators from Tsys caltable
interp (string='') - Interp type in time[,freq]. default==linear,linear
spwmap (intVec='') - Spectral windows combinations to form for gaintables(s)

Returns

bool

Examples

cb.open('ngc5921.ms')
cb.initweights()
cb.close()

linpolcor(tablein='', tableout='', fields='')[source]¶

THIS METHOD IS CURRENTLY DISABLED.

This function can be used to correct the gains derived from secondary calibrators with unknown or variable polarization. It should only be used for arrays with linear (X/Y) feeds and an Alt-Az mount for which the observed polarization varies with feed position angle on the sky.

The function fits the gains with a sine and cosine term in feed position angle and extracts the Q and U components of the secondary calibrator. This is only possible if there is sufficient range in the position angle (i.e., minimum of about 6 scans spanning at least 90 degrees in position angle). Check the error of the fit to judge if the fit was succesfull, it should generally be smaller than 0.5%.

Use the fields argument to select calibrator fields to be fitted. The function takes a calibration table as input, and can write the adjusted gain solutions to the same table on output, or create a new table containing these results. The function also prints the derived polarization for each field for each spectral window.

Parameters

tablein (string='') - Input calibration table name
tableout (string='') - Output calibration table name
fields (stringVec='') - Calibrator field names

Returns

bool

Examples

cb.open('atca.ms');
cb.linpolcor(tablein='atca.gcal', tableout='atca.gcal2', 
             fields='2254-367');
cb.close();


This example takes an existing calibration table containing {\tt G}
Jones matrices, and writes a corrected output table, correcting only
gains derived from 2254-367 for linear polarization.

listcal(caltable='', field='', antenna='', spw='', listfile='', pagerows=50)[source]¶

calibrater.listcal() lists antenna gain solutions in tabular form. The table is organized as follows. Solutions are output by

Spectral window,
Antenna,
Time,
Channel,
and Polarization.

The inner-most loop is over polarization. A “Spw Header” row is printed each time the spectral window changes. In addition to listing the spectral window ID (SpwID), the Spw Header also lists the date of observation (Date), the calibration table name (CalTable), and the measurement set name (MS name). A lower-level “antenna header” is printed each time the antenna names change or every ‘pagerows’ of output, whichever comes first. The antenna header column are described here:

ll Column Name & Description Ant & Antenna name Time & Visibility timestamp corresponding to gain solution Field & Field name Chn & Channel number Amp & Complex solution amplitude Phs & Complex solution phase F & Flag

Elements of the “F” column contain an ‘F’ when the datum is flagged, and (whitespace) when the datum is not flagged.

Presently, the polarization mode names (for example: R, L) are not given, but the ordering of the polrization modes (left-to-right) is equivalent to the order output by task listobs (see “Feeds” in listobs output).

Parameters

caltable (string='') - Calibration table to list
field (variant='') - Field names or indices to list: ‘’==>all
antenna (variant='') - Antenna/Baseline to list: ‘’==>all
spw (variant='') - Spectral windows and channels: ‘’==>all, spw=’10:8~20’
listfile (string='') - Send output to file: ‘’==>send to terminal)
pagerows (int=50) - Rows per page

Returns

bool

Examples

Input:

The following example imports a UVFITS file, performs a bandpass calibration, 
and displays a subset of the resulting calibration table.

pathname=os.environ.get('CASAPATH').split()[0] # Get path to CASA home dir
fitsdata=pathname+'/data/demo/NGC5921.fits' # Select uv-data (FITS) file
msdata='NGC5921.ms' # MS name; write to current directory
importuvfits(fitsfile=fitsdata, vis=msdata) # import FITS data to MS
setjy(vis=msdata) # Create model data for flux calibrator
caldata=msdata+'.bcal' # Calibration table name
bandpass(vis=msdata, caltable=caldata) # Bandpass calibration
cb.open(msdata) # Open MS in cb
cb.listcal(caltable=caldata, field='N5921_2, 0, 1', antenna='1~5;10~13;20~22', spw='0:4~6', pagerows=0) # List a subset of calibration factors

Output:

SpwID = 0, Date = 1995/04/13,  CalTable = NGC5921.ms.bcal (B Jones), MS name = /users/jcrossle/NRAO/casa/NGC5921.ms                                    
-------------------------------------------------------------------------------------------------------------------------------------------------------
                              | Ant = 1                     | Ant = 2                     | Ant = 3                     | Ant = 4                     |
Time       Field           Chn|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|
----------|---------------|---|--------------|--------------|--------------|--------------|--------------|--------------|--------------|--------------|
09:21:46.0 1331+30500002_0   4|0.294    5.3   0.264    3.5   0.296  105.9   0.287 -111.9   0.276  -66.0   0.264  -24.5   0.269  165.8   0.281 -108.6   
09:21:46.0 1331+30500002_0   5|0.303    5.3   0.279    0.6   0.305  107.0   0.298 -111.6   0.283  -64.2   0.274  -23.3   0.280  166.8   0.291 -108.9   
09:21:46.0 1331+30500002_0   6|0.307    5.6   0.287   -1.6   0.309  107.5   0.303 -111.5   0.287  -63.2   0.280  -22.6   0.284  167.8   0.296 -108.8   
10:05:27.9 1445+09900002_0   4|0.467    7.6   0.419    2.7   0.473  107.7   0.455 -112.3   0.437  -63.5   0.413  -24.8   0.427  168.2   0.446 -108.8   
10:05:27.9 1445+09900002_0   5|0.472    7.3   0.440    0.0   0.486  109.1   0.471 -111.8   0.451  -62.6   0.436  -23.1   0.435  169.4   0.453 -108.5   
10:05:27.9 1445+09900002_0   6|0.486    8.4   0.453   -2.4   0.482  110.0   0.478 -111.4   0.452  -60.7   0.443  -23.1   0.446  169.6   0.468 -108.6   
10:09:05.3         N5921_2   4|0.082   50.0   0.074   34.7   0.097  -74.5   0.083   54.4   0.070  131.3   0.080  150.7   0.085   81.0   0.095  150.6   
10:09:05.3         N5921_2   5|0.074   62.7   0.084   24.3   0.114  -73.1   0.093   47.3   0.066  119.9   0.069  154.9   0.099   81.2   0.085  147.4   
10:09:05.3         N5921_2   6|0.079   44.4   0.081   21.7   0.092  -66.3   0.101   48.0   0.089  125.6   0.060  154.0   0.099   83.1   0.097  152.7   
                              | Ant = 5                     | Ant = 10                    | Ant = 11                    | Ant = 12                    |
Time       Field           Chn|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|
----------|---------------|---|--------------|--------------|--------------|--------------|--------------|--------------|--------------|--------------|
09:21:46.0 1331+30500002_0   4|0.261  -26.0   0.285 -107.1   0.279 -149.5   0.263    2.9   0.274 -102.5   0.257   -7.0   0.289  174.3   0.309 -139.2   
09:21:46.0 1331+30500002_0   5|0.269  -26.1   0.295 -107.2   0.288 -148.8   0.274    2.3   0.283 -100.9   0.271   -6.8   0.307  173.1   0.319 -138.2   
09:21:46.0 1331+30500002_0   6|0.272  -26.1   0.300 -107.0   0.293 -148.7   0.281    2.0   0.287  -99.7   0.280   -6.7   0.312  171.2   0.326 -137.2   
10:05:27.9 1445+09900002_0   4|0.416  -24.0   0.450 -106.4   0.437 -147.3   0.414    3.2   0.433  -99.6   0.412   -6.8   0.456  175.9   0.477 -140.0   
10:05:27.9 1445+09900002_0   5|0.421  -22.6   0.478 -106.1   0.453 -147.4   0.433    2.0   0.453  -98.1   0.433   -6.7   0.481  174.4   0.491 -138.9   
10:05:27.9 1445+09900002_0   6|0.436  -22.7   0.478 -106.7   0.459 -146.6   0.443    2.4   0.457  -97.1   0.450   -7.0   0.486  173.5   0.510 -137.7   
10:09:05.3         N5921_2   4|0.074   95.0   0.085   -4.2   0.083  109.6   0.084 -116.6   0.081   63.2   0.071  131.2   0.050  -55.4   0.083  -27.4   
10:09:05.3         N5921_2   5|0.071   96.8   0.084  -13.7   0.086  104.3   0.100 -116.4   0.099   61.7   0.084  145.1   0.091  -76.1   0.087  -33.6   
10:09:05.3         N5921_2   6|0.082   84.9   0.078   -5.3   0.101  109.1   0.102 -109.9   0.087   60.1   0.107  130.4   0.085  -75.5   0.080  -31.2   
                              | Ant = 13                    | Ant = 20                    | Ant = 21                    | Ant = 22                    |
Time       Field           Chn|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|  Amp    Phs F   Amp    Phs F|
----------|---------------|---|--------------|--------------|--------------|--------------|--------------|--------------|--------------|--------------|
09:21:46.0 1331+30500002_0   4|0.285 -169.5   0.277  -90.4   0.254  -36.0   0.290   70.9   0.286  -97.8   0.305  108.8   0.273  -84.6   0.224 -124.2   
09:21:46.0 1331+30500002_0   5|0.296 -168.9   0.287  -90.5   0.269  -38.6   0.300   71.0   0.296  -97.8   0.317  108.2   0.284  -85.8   0.243 -127.6   
09:21:46.0 1331+30500002_0   6|0.301 -168.7   0.291  -90.3   0.278  -39.9   0.306   70.9   0.302  -97.8   0.326  107.2   0.289  -86.6   0.255 -129.7   
10:05:27.9 1445+09900002_0   4|0.448 -167.2   0.434  -90.7   0.401  -34.4   0.456   70.8   0.457  -95.5   0.485  108.9   0.431  -82.1   0.361 -123.9   
10:05:27.9 1445+09900002_0   5|0.466 -166.5   0.457  -91.1   0.423  -36.6   0.470   70.8   0.471  -96.6   0.506  108.1   0.448  -83.2   0.393 -126.7   
10:05:27.9 1445+09900002_0   6|0.473 -166.9   0.464  -91.1   0.436  -37.8   0.485   70.2   0.476  -96.6   0.521  108.0   0.447  -83.2   0.410 -130.0   
10:09:05.3         N5921_2   4|0.097   83.0   0.087  143.5   0.080   43.1   0.094  144.2   0.087  168.7   0.092    1.4   0.111   76.1   0.079   18.9   
10:09:05.3         N5921_2   5|0.100   87.4   0.094  137.0   0.061   54.7   0.098  153.3   0.094  178.6   0.096   -3.7   0.101   64.6   0.091    9.5   
10:09:05.3         N5921_2   6|0.099   93.3   0.122  140.5   0.077   51.3   0.090  151.7   0.083 -179.6   0.100    2.2   0.095   61.3   0.108    0.4   

Listed 108 antenna solutions.

modelfit(vary='', niter=0, compshape='P', par=[1.0, 0.0, 0.0], file='')[source]¶

This method fits single-component models (points, elliptical Gaussians or elliptical Disks_ to the CORRECTED_DATA of the selected field. A first guess for the component parameters may be specified in the par parameter.

Parameters

vary (boolVec='') - If specified where T, let this parameter (in par) vary in fit
niter (int=0) - Number of non-linear fitting iterations
compshape (string='P') - Component shape, P=point G=gaussian
par (doubleVec=[1.0, 0.0, 0.0]) - Initial guess for fit parameters (default is for “P)”I flux, rel RA, rel Dec, 1,0, 0.0, 0.0 are defaults
file (string='') - If specified, output componentslist file name, if empty don’t write componentslist file

Returns

doubleVec

Examples

cb.open('ngc5921.ms');
cb.selectvis(field='1331*')
cb.modelfit(compshape='P',par=[15.0,0.0,0.0]) 
cb.close();


This example fits a point source mode using 15.0 Jy at the origin (phase center)
as a first guess.



cb.open('ngc5921.ms');
cb.selectvis(field='1331*')
cb.modelfit(compshape='G',par=[15.0,0.0,0.0,2.0,1.0,0.0]) 
cb.close();


This example fits a Guassian model with a starting
guess of 15 Jy at the phase center (0,0), with 2.0 arcsec major axis,
1.0 axial ratio, at position angle 0.0 deg.

open(filename='', compress=False, addcorr=True, addmodel=True)[source]¶

Attaches a MeasurementSet to the calibrater tool for further processing with other methods.

Parameters

filename (string='') - MeasurementSet file name. No default
compress (bool=False) - Compress calibration columns?
addcorr (bool=True) - Add scratch columns?
addmodel (bool=True) - Add MODEL_DATA column along with CORRECTED_DATA ?

Returns

bool

Examples

cb.open('ngc5921.ms');

parsecallibfile(filein='')[source]¶

TBD

Parameters

filein (string='') - Input cal library file name

Returns

record

Examples

TBD

plotcal(antennas='', fields='', spwids='', plottype='1/AMP', tablename='', polarization=1, multiplot=False, nx=1, ny=1, psfile='')[source]¶

This function plots a calibration table either to a plotter or to a file.

The argument plottype can take the following values for all types of solutions:

AMP: Gain Amplitude vs. Time
1/AMP: Inverse Gain Amplitude vs. Time (useful for comparing with classic AIPS)
PHASE: Gain Phase vs. Time
RI: Gain Real vs. Imaginary
RLPHASE: Right/Left Gain phase difference (if polarizations are R,L)
XYPHASE: X/Y Gain phase difference (if polarizations are X,Y)

The argument plottype can take the following values for D tables

DAMP: Cross-polarized Gain Amplitude vs. Time
DPHASE: Cross-polarized Gain Phase vs. Time
DRI: Cross-polarized Gain Real vs. Imaginary

The quality of the solutions can be examined with the following plottype choices:

FIT: Fit per spectral window
FITWGT: Fit weight per spectral window
TOTALFIT: Total fit

By default, all antennas (as specified in the antennas argument) will appear on the same plot. Separate plots (all with the same scale) for each antenna can be activated by setting multiplot=T. The multiplot argument only separates plots by antenna (not, e.g., by the field_id(s) specified in the fields argument). If multiplot=T, the nx and ny arguments can be used to specify the number of plots per page.

At the moment, only one polarization can be plotted per execution. This restriction will be relaxed in the near future.

For B solutions, the plotting will loop over timestamps (if more than one).

A hardcopy plot can be created by specifying the psfile argument (which is especially useful for batch processing when a display screen is not available). This will cause the plot to be written to a PostScript file which can be subsequently sent to a printer.

Parameters

antennas (intVec='') - Antennas to plot. Default is none.
fields (intVec='') - Fields to plot. Default is none.
spwids (intVec='') - Spectral windows id.’s to plot. Default is none.
plottype (string='1/AMP') - Plot type
tablename (string='') - Calibration table name
polarization (int=1) - Polarization to plot
multiplot (bool=False) - Turn on separate antenna plots
nx (int=1) - If multiplot=T, number of plots on horizontal axis
ny (int=1) - If multiplot=T, number of plots on vertical axis
psfile (string='') - Name of output PostScript file to write plot to. Default is to send plot to the screen.

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.plotcal(plottype='PHASE', tablename="gcal", antennas=[1,3], polarization=2);
cb.close();

posangcal(posangcor='', tablein='', tableout='')[source]¶

This function is used to apply position angle calibration for observations made using circularly polarized feeds. According to the Measurement Equation formalism, this correction should be applied to a D (instrumental polarization) calibration table.

If no D calibration is performed (and thus no such table is available), the correction can be applied to a G table, but it should NEVER be applied to both, and always applied to a D table if one is available. An input table must be specified. If no output table is specified, then the input table will be modified in place.

Specify, as a vector of values, a position angle adjustment (in degrees) for each spectral window. If only one value is specified, it will be duplicated to all spectral windows; otherwise, the number of values specified must match the number of spectral windows. The sign convention for the position angle adjustment is such that the specified value is the that which, when added to the position angle implied by the data, will yield the correct position angle. For example, if G-, D-, and P-calibrated data for 3c286 suggests a position angle of 45 degrees, the posangcor value should be -12 degrees as this will yield the correct position angle of 33 degrees when added. In general, posangcor equals correct position angle minus observed position angle.

A future version of this function will have an option to recognize standard position angle calibrators and determine the correction automatically.

(NB: It may be desirable to use solutions for ’X’ to handle position angle calibration, rather than this method.)

Parameters

posangcor (doubleVec='') - Position angle corrections (degrees)
tablein (string='') - Input calibration table name
tableout (string='') - Output calibration table name. Default is input table name.

Returns

bool

Examples

cb.open('polcal.ms');
cb.posangcal(tablein='3C286.dcal', tableout='3C286.dpacal', 
             posangcor=[-12.0, 54.0]);
cb.close();


This example takes an existing calibration table containing {\tt D}
Jones matrices, and applies a position angle calibration of 45 and 54
degrees to spectral windows 1 \& 2, respectively, writing the result
to a new table.  The observed position angles for 3C286 must have been
45 and -21 degrees; the corrections specified yield the correct value
of 33 degrees when added to the observed values.

rerefant(tablein='', tableout='', refantmode='strict', refant='')[source]¶

TBD

Pending improvements:

TBD

Parameters

tablein (string='') - Input calibration table
tableout (string='') - Output calibration table
refantmode (string='strict') - The refant application mode
refant (variant='') - Reference antenna. Default is none.

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.rerefant(tablein='in.gcal',tableout='out.gcal',
            refantmode='median',refant='4')
cb.close();

reset(apply=True, solve=True)[source]¶

Resets the apply and/or solve components previously set by setapply and setsolve.

Parameters

apply (bool=True) - If True, unset all apply settings
solve (bool=True) - If True, unset all solve settings

Returns

bool

Examples

cb.open('ngc5921.ms')
cb.setapply ('P', 5.0)
cb.setsolve ('G', 300.0, F, 3, 'gcal_1', T)
cb.state()
cb.reset(apply=T,solve=F);
cb.state()
cb.reset()

returndict()[source]¶

Return a dictionary containing information about the current calibrater tool state. This dictionary contains the following keys: ’antennas’, ’apply tables’, ’field’, ’intents’, ’observation’, ’scan’, ’solve table’, ’spw’.

Each of these keys will show which values for each of these parameters are selected. By default all of the MS is selected when opened by the calibrater tool.

The values of each of these keys is an array of either strings or integers.

selectvis(time='', spw='', scan='', field='', intent='', observation='', baseline='', uvrange='', chanmode='channel', nchan=1, start=0, step=1, mstart=0.0, mstep=0.0, msselect='')[source]¶

This function provids for selection of the visibility data from the MS which will be treated by subsequent execution of the solve and correct functions. Note that data selection is not cumulative, i.e., any selection made in a previous call to selectvis will be overridden by the the current call.

Most of the selectvis parameters use the standardized MS Selection syntax.

The parameters are described below. The selected data will satisfy the logical AND of all non-trivially specified parameters. Note that the old-fashioned strided channel selection parameters are deprecated (and will soon be removed); use spw instead. Running selectvis with no specified parameters restores selection of the entire MS.

time: is used to specify time ranges in a stardard format
spw: is used to specify spectral window and channel selection. Currently, only a single channel range can be specified per spw.
scan: is used to specify scan numbers and ranges
observation: is used to specify observation ID(s).
field: is used to specify field names or indices
baseline: is used to specify antenna and baseline combinations
uvrange: is used to specify baseline length ranges
chanmode: is deprecated (use spw)
nchan: is deprecated (use spw)
start: is deprecated (use spw)
step: is deprecated (use spw)
mstart: is deprecated (use spw)
mstep: is deprecated (use spw)
msselect: is used to specify a subselection of data according to Measurement Set columns in conditional combinations not possible with the standard parameters above. This parameter should be specified as a valid expression. If both msselect and the standard selection parameter are used together, they are combined with a logical AND, i.e., the data must jointly satisfy all selectvis parameters.

Parameters

time (variant='') - Select on time
spw (variant='') - Select on spectral window
scan (variant='') - Select on scan
field (variant='') - Select on field
intent (variant='') - Select on intent or state
observation (variant='') - Select by observation ID(s)
baseline (variant='') - Select on antennas/baselines
uvrange (variant='') - Select by uvrange
chanmode (string='channel') - Type of data selection: channel or velocity
nchan (int=1) - Number of channels to select (mode=’channel’)
start (int=0) - Start channel (0-relative) (mode=’channel’)
step (int=1) - Step in channel number (mode=’channel’)
mstart (double=0.0) - Start velocity (e.g. ‘20Km/s’)
mstep (double=0.0) - Step in velocity (e.g. ‘100m/s’)
msselect (string='') - TAQL selection string. Default (empty) is no specific selection.

Returns

bool

Examples

Open and select a field:

cb.open('ngc5921.ms');
cb.selectvis(field='N5921_2');  # by complete name
cb.selectvis(field='N5921*');   # with wildcard
cb.selectvis(field='2');        # by index

Select a field and a channel range:

cb.selectvis(spw='0:10~40',field='N5921*');

Select using all MS Selection parameters (these parameters are
over-specified somewhat, i.e., scan 6 contains only field N5921_2,
etc.):

cb.selectvis(time='>1995/04/13/10:40:00',   # times greater than this
             spw='0:20~40',                 # channels 20-40 in spw 0
             scan='6',                      # scan 6 only
             field='N59*',                  # fields matching N59*
             baseline='1 \& *',              # baselines to antenna 1
             uvrange='>0.0klambda')         # baselines greater than zero length

Reset selection to the entire dataset

cb.selectvis()

setapply(type='B', t=0.0, table='', field='', interp='aipslin', select='', calwt=False, spwmap=[- 1], opacity=[0.0])[source]¶

This function is used to specify the calibration components which should be applied during subsequent execution of the solve and correct functions. This function should be executed as many times as necessary to specify all desired calibration components.

Each calibration component represents a separate calibration matrix correction included in the measurement equation. The different types correspond to different instrumental and atmospheric effects. Calibration components are available as calibration tables generated by previous solve executions (types ’B’,’BPOLY’,’G’,’GSPLINE’, ’D’,’DF’,’T’,’M’,’MF’,’X’), or are calculated analytically on the fly (types ’P’, ’TOPAC’, ’GAINCURVE’). Upon execution of solve or correct, the group of specified calibration components will be applied in the order prescribed by the Measurement Equation formalism.

The parameters are as follows:

type

The calibration type being specified. This is only required for analytic types (’P’,’TOPAC’,’GAINCURVE’). When specifying an existing pre-solved calibration table, it is not necessary to explicitly specify the type; this will be discerned from the table. (Specifying the type as well as the table will force a check that the table contains solutions of the specified type.

For type=’GAINCURVE’, an elevation-dependent correction will be applied using parameters read from the data repository. Currently, this is only supported for the VLA.

t

This parameter will be used in a future release to control the range of applicability of the specified calibration. Currently, it is ignored.

table

For pre-solved calibration, the file name of the table to apply.

field

The fields to select from the specified table, using MS Selection syntax (as in selectvis).

interp

The desired type of time-dependent interpolation. Use interp=’nearest’ to calibrate each datum with the calibration value nearest in time. Use interp=’linear’ to calibrate each datum with calibration phases and amplitudes linearly interpolated from neighboring (in time) values. In the case of phase, this mode will assume that phase jumps greater than 180 degrees between neighboring points indicate a cycle slip, and the interpolated value will follow this change in cycle accordingly (i.e., the implied rate will always be less than 180 degrees per sample). Use interp=’aipslin’ to emulate the basic interpolation mode used in classic AIPS, i.e., linearly interpolated amplitudes, with phases derived from linear interpolation of the complex calibration values. While this method avoids having to track cycle slips (which is unstable for solutions with very low SNR), it will yield a phase interpolation which becomes increasingly non-linear as the spanned phase difference increases. The non-linearity mimics the behavior of interp=’nearest’ as the spanned phase difference approaches 180 degrees (the phase of the interpolated complex calibration value initially changes very slowly, then rapidly jumps to the second value at the midpoint of the interval). If the uncalibrated phase is changing this rapidly, a ’nearest’ interpolation is not desirable. Usually, interp=’linear’ is the best choice. The interp parameter is applicable to any calibration type, as long as there are sufficient solutions available to perform the interpolation. Note that calibration solutions which have been determined for only one timestamp will default to ’nearest’. More interpolation options (e.g., ’cubic’) will be added in the future.

select

Used to specify general selection of a subset of calibration measurements from the table to be applied to the visibility data. Arbitrary cross-calibration is possible by combining this function with the setdata function. The string specified must be a valid expression.

spwmap

This parameter is used to indicate how solutions derived from different spectral windows should be applied to other spectral windows. Nominally, data in each spectral window will be corrected by solutions derived from the same spectral window. This is the default behavior of spwmap, i.e., if spwmap is not specified, calibrater will insist that data be corrected by solutions from the same spw. Otherwise, spwmap takes a vector of integers indicating which spectral window solutions to apply to which spectral window data, such that spwmap[j]=i causes solutions derived from the i-th spectral window to be used to correct the j-th spectral window. For example, if (say) bandpass solutions are available for spws 0 & 2, and it is desired that these be applied to spws 1 & 3 (as well as 0 & 2), respectively, use spwmap=[0,0,2,2]. Even if some spws do not require an explicit spwmap setting, yet one or more does, it is safest to specify it explicitly for all, e.g., spwmap=[0,1,3,3] indicates that spw 2 will be corrected with solutions from spw 3, and the others will behave nominally. Note that if no solutions exist for any of the spws specified in spwmap, an error message will result.

calwt

If set True, the data weights will be calibrated along with the data. This is usually desirable.

opacity

For type=’TOPAC’, an elevation-dependent opacity correction will be applied according to the zenith opacity value supplied in the opacity parameter. Currently, only one zenith opacity value can be supplied, and it is used for all antennas.

Use the state function to review the list of calibration components that have been set for application.

Pending improvements:

Enable variety of interpolation modes and timescales
Allow for antenna- and time-dependent opacities

Parameters

type (string='B') - Component type
t (double=0.0) - Interpolation interval (seconds)
table (string='') - Calibration table name
field (variant='') - Select on field
interp (string='aipslin') - Interpolation type (in time)
select (string='') - TAQL selection string. Default is no selection.
calwt (bool=False) - Calibrate weights?
spwmap (intVec=[-1]) - Spectral windows to apply
opacity (doubleVec=[0.0]) - Array-wide zenith opacity per antenna (for type=’TOPAC’)

Returns

bool

Examples

cb.open('ngc5921.ms')
cb.selectvis(field='N5921*')            
cb.setapply (type='G', table='gcal', field='1445*') 
cb.setapply (type='P')     
cb.correct();
cb.close();


In this example, we apply parallactic angle corrections and a gain
calibration derived from a field whose name matches '1445*' in a caltable
called 'gcal' to data for a field matching 'N5921*'

setcallib(callib='')[source]¶

TBD

Parameters

callib (record='') - A calibration library record

Returns

bool

Examples

TBD

setcorrdepflags(corrdepflags='')[source]¶

TBD

Parameters

corrdepflags (bool='') - Turn correlation dependent flags on/off (True/False)

Returns

bool

Examples

TBD

setmodel(modelimage='')[source]¶

Name of the model image to be used as a sky model for model visibility computations. For now, this is used only by EP-Jones solver.

Parameters

modelimage (string='') - Name of the model image.

Returns

bool

Examples

cb.setmodel("mymodel");

setptmodel(stokes=[0.0, 0.0, 0.0, 0.0])[source]¶

Set a global point source model Stokes parameters to use in solving operations.

Parameters

stokes (doubleVec=[0.0, 0.0, 0.0, 0.0]) - Vector of Stokes parameters.

Returns

bool

Examples

cb.setmodel([1,1,0,0]);

setsolve(type='G', t='', table='', append=False, preavg=- 1.0, phaseonly=False, apmode='AP', refant='', refantmode='flex', minblperant=4, solnorm=False, normtype='median', minsnr=0.0, combine='', fillgaps=0, cfcache='', painc=360.0, fitorder=0, fraction=0.1, numedge=- 1, radius='', smooth=True, zerorates=False, globalsolve=True, niter=100, delaywindow='', ratewindow='', paramactive='', solmode='', rmsthresh='')[source]¶

This function specifies the calibration component that will be solved for by the solve function. Currently, only one type can be solved for at one time.

Each calibration component represents a separate calibration matrix correction included in the measurement equation. The different types correspond to different instrumental and atmospheric effects. Currently, the solvable calibration components are types ’G’,’T’,’B’, ’D’ and ’DF’, which are antenna-based, and, ’M’ and ’MF’, which are baseline-based. Arrange to pre-apply any existing calibration components (of types other than the solved-for one) using the setapply function.

The parameters are:

type: Specify the calibration type you want to solve for, from ’G’,’T’,’B’,’D’,’DF’,’M’,’MF’.
t: Specify the solution interval. This can be specified as an integer (units of seconds assumed) or as a string containing a value and units (e.g., ’30s’, ’45min’, ’2h’) or ’inf’ (infinite) or ’int’ (per data integration). A solution interval of 0 (with or without units) is the same as ’int’ (per integration), and negative solution intervals are treated as ’inf’ (infinite).
table: Specify the output calibration table name in which to store the calibration solve result. Existing tables will be deleted and replaced.
append: Append the solutions to an existing table.
preavg: Specify the amount of pre-average (in time) within the solution interval. By default, data are averaged up to the solution interval (or up to 5 minutes for ’D’ solving).
phaseonly: This parameter is deprecated, use apmode.
apmode: Control generation of amplitude-only (’a’), phase-only (’p’), or amplitude-and-phase (’ap’, the default) solutions.
refant: Specify an antenna (using data selection syntax) for referencing the solutions.
solnorm: Normalize the solutions by their mean post-solve. For ’B’, and ’MF’, this is a complex normalization per solution spectrum. For other types, this is a global (per-spw) normalization of the amplitudes only.
minsnr: Specify the SNR below which solution are rejected.
combine: Specify which data axes (spw, field, scan, or some combination) on which the data should be combined to generate a single solution. E.g., combine=’spw’ will force combination of many spws to form a single solution (per solution interval). Similarly, combine=’scan’ with a long solution interval will force the combination of scans to yield individual solutions (per field and spw). Ordinarily, solutions are always broken at scans boundaries. Separate multiple combine options with commas.
fillgaps: For ’B’ solutions, specify the largest solution channel gap (which arise due to flagged data) that will be filled post-solve via interpolation. Such solution gaps remain flagged by default.

Pending improvements:

Change t to solint?
Permit flexible specification of preavg (as for t)

Parameters

type (string='G') - Component type
t (variant='') - Solution interval (units optional)
table (string='') - Output calibration table name
append (bool=False) - Append to existing table?
preavg (double=-1.0) - Pre-averaging interval (in sec)
phaseonly (bool=False) - Solve only for phase?
apmode (string='AP') - Solve for ‘AP’, ‘A’ (amp-only) or ‘P’ (phase-only)
refant (variant='') - Reference antenna. Default is none.
refantmode (string='flex') - Reference antenna mode
minblperant (int=4) - Minimum number of baselines per ant for solving
solnorm (bool=False) - Normalize solution after solve
normtype (string='median') - Solution normalization type
minsnr (float=0.0) - SNR threshold for accepting solutions
combine (string='') - Data axes on which to combine solving (scan, spw, and/or field)
fillgaps (int=0)
cfcache (string='') - Name of the directory to be used for convolution function disk cache. This is used when type=EP.
painc (float=360.0) - Parallactic Angle increment used to trigger computation of a new convolution function. This is used when type=EP. Default value implies that only one convolution function will be computed for the entire range of observation.
fitorder (int=0) - Order of the polynomial fit, used when type=’A’.
fraction (float=0.1) - [SINGLE-DISH SPECIFIC] Edge detection parameter for otfraster/otf calibration. This is a number of edge points as a fraction of total number of points.
numedge (int=-1) - [SINGLE-DISH SPECIFIC] Edge detection parameter for otfraster calibration. This is a number of edge points. The value specified here comes before fraction. Note that edge points will be detected from both side of each raster row so that number of edge points is effectively twice of the specified value in each raster row. Default (-1) is to use fraction.
radius (string='') - [SINGLE-DISH SPECIFIC] Specifies radius of the central region of double circle gain calibration for fast scanning data. The value must be either empty or quantum string (numeric value with unit). Default (“”) is to use a radius of primary beam.
smooth (bool=True) - [SINGLE-DISH SPECIFIC] Whether or not applying smoothing during double circle gain calibration for fast scanning data. Default is True.
zerorates (bool=False) - [FRINGE-FIT SPECIFIC] Zero delay-rates in fringe fitting solution tables.
globalsolve (bool=True) - [FRINGE-FIT SPECIFIC] Use global least-squares solver to improve fringe-fitting parameter estimates
niter (int=100) - [FRINGE-FIT SPECIFIC] Maximum number of iterations for global least-squares solver
delaywindow (doubleVec='') - [FRINGE-FIT SPECIFIC] Constrain FFT delay search to a window; a two-element list, units of nanoseconds
ratewindow (doubleVec='') - [FRINGE-FIT SPECIFIC] Constrain FFT rate search to a window; a two-element list, units of seconds per second
paramactive (boolVec='') - An array of three booleans to control whether to sove for delay, fringe-rate and dispersive delay
solmode (string='') - Solving mode: ‘’, ‘L1’; add ‘R’ for iterative outlier excision.
rmsthresh (doubleVec='') - RMS threshold sequence.

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.setapply (type='P');
cb.setsolve (type='G',t='300s', refant=3, table='gcal');
cb.solve();
cb.close();


In this example, analytic (non-solvable) parallactic angle corrections
are pre-applied before G solutions are obtained on a timescale of 300 
seconds.  The resulting solutions are phase-referenced to antenna 3, 
and stored in a calibration table called 'gcal'.


cb.reset();
cb.setapply (type='P',t=5.0);
cb.setapply (type='G',table='gcal');
cb.setsolve (type='D',t=86400.0, preavg=60.0, refant=3, table='dcal');
cb.solve();
cb.close();


In this example, the solve/apply state of the calibrater tool is reset
and then the P and G corrections (from above) are applied before
solving for D solutions on a diurnal timescale.  Note that the data
will be averaged only to 60 seconds before the solution.  The resulting
D solutions are stored in a table called 'dcal'.

setsolvebandpoly(table='', append=False, t='', combine='', degamp=3, degphase=3, visnorm=False, solnorm=True, maskcenter=0, maskedge=5.0, refant='')[source]¶

This function is a specialization of the setsolve method which should be used to arrange for bandpass solving when polynomial solutions for B are desired, e.g., when per-channel SNR on calibrators is too low to obtain a useful sampled bandpass.

Prior to the solution, the visibility data are averaged in time, and the solution is performed for both phase and amplitude.

This method uses most of the same parameters as the generic setsolve, with a few unique additions:

degamp and degphase: The parameters permit specification of the polynomial order to use in amp and phase. Specifying 0 (zero) yields constant solutions.
visnorm: This parameter is used to normalize the assembled spectral data, in a per baseline manner. If set True, this will have the effect of removing any non-frequency-dependent closure errors (e.g., as caused by source structure, or introduced by the instrument) from the data, and should be used with caution. The resulting solutions will be effectively normalized as well. When visnorm=F is used, closure errors in the data (as supplied to the solver) may be visible in the form of offsets between the data and solutions. For bandpass calibration, this is usually ok, as the shape of the bandpass is the most important aspect of the solution. In future this parameter will be generalized and made available for other solve types. (NB: Use of solnorm=True still provides for post-solve normalization of the solutions.)
maskcenter and maskedge: These parameters control how many channels are ignored on-the-fly, at the center and edges of each input spectral window, respectively. To avoid edge channels, it is almost always better to flag these channels directly, or select against them in setdata. Aggressive use of maskedge (large values), will yield polynomial solutions which will tend to diverge at the edges (especially when the polynomial degree is also high), because maskedge does not change the frequency domain of the solutions. Such solutions should be used with caution in subsequent operations. (It is best to avoid use of maskedge.)

The BPOLY solution is performed for both phase and amplitude, and the result will be stored in the same table. The frequency domain of the solutions is limited to only the range of frequencies selected in selectvis. When correcting data with these solutions (for other solves or with correct), only data within this domain will be corrected. Data outside (e.g., edge channels avoided in setdata for the solve), will not be corrected. Therefore, the same (or narrower) channel selection is recommended for all operations using solutions produced by this function and solve().

Note that the combine parmaeter can be used meaningfully with the BPOLY solver. When combine=’spw’, the data from multiple spws will be combined on a common frequency axis, and a single polynomial will be determined spanning them all. This is different than for ordinary sampled ’B’ solutions, for which combine=’spw’ causes the bandpass to be combined on a common channel axis, effectively yielding a mean bandpass for the set of spws.

Parameters

table (string='') - Output calibration table name
append (bool=False) - Append to existing table?
t (variant='') - Solution interval (units optional)
combine (string='') - Data axes on which to combine solving (scan, spw, and/or field)
degamp (int=3) - Polynomial degree for amplitude solution
degphase (int=3) - Polynomial degree for phase solution
visnorm (bool=False) - Normalize data prior to solution
solnorm (bool=True) - Normalize result?
maskcenter (int=0) - Number of channels to avoid in center of each band
maskedge (double=5.0) - Fraction of channels to avoid at each band edge (in %)
refant (variant='') - Reference antenna

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.selectvis(field='1331*')
cb.setsolvebandpoly(table='bpoly',degamp=5,degphase=7);
cb.solve();
cb.close();


In this example, amplitude (degree 5) and phase (degree 7) Chebychev
polynomial bandpasses are determined using the default parameters.

setsolvegainspline(table='', append=False, mode='AMP', splinetime=10800, preavg=0.0, npointaver=10, phasewrap=250, refant='')[source]¶

This function is a specialization of the setsolve method which should be used when cubic spline G solutions are desired, e.g., when SNR on calibrators is very low. Currently, this solving mode treats dual polarization data on a per-polarization basis. The option to obtain a joint solution (a la ’T’) will be provided in the future.

The visibility data are averaged in frequency (for multi-channel data) prior to the solution.

This method uses many of the basic parameters as the generic setsolve. Parameters unique to the spline solver are:

mode: For phase solutions only, use mode=’PHAS’. For amplitude solutions only, use mode=’AMP’. If both are desired, use mode=’PHASAMP’, and both will be solved for using the same spline timescale (this mode also assumes that all calibrators have the correct relative flux densities). If solving for phase and amplitude separately (usually in this order), it is usually desirable to apply the first one when solving for the second one. Spline solution so obtained will be stored in separate calibration tables. In the near future, the mode parameter will be consolidated with the generic apmode parameter.
splinetime: The spline timescale (time between knots) is specified here. The default is 10800 seconds (3 hours). In future this parameter will be consolidated with the generic t parameter. The preavg parameter should be set to a value at least 4X shorter than the spline time (an error will occur if there is insufficient sampling within the splinetime timescale), and consistent with the expected coherence. Consistent with these constraints, use the largest possible value for preavg to optimize the SNR of the pre-solve phase-tracking algorithm.
npointaver and phasewrap: These parameters tune the phase-unwrapping algorithm when mode \(=\) ’PHAS’. Cycle slips are detected (and removed before the spline solve) when the median phase a sequence of length npointaver (in integrations) differs by more than phasewrap degrees from the previous sequence.

Pending improvements:

Consolidate more parameters with the generic setsolve
Introduce the generic combine options
Improve phase-tracking algorithm

Parameters

table (string='') - Output calibration table name
append (bool=False) - Append to existing table?
mode (string='AMP') - Phase or Amplitude mode?
splinetime (double=10800) - Spline timescale (sec)
preavg (double=0.0) - Pre-averaging interval (in sec)
npointaver (int=10)
phasewrap (double=250)
refant (variant='') - Reference antenna. Default is none.

Returns

bool

Examples

cb.open('ngc5921.ms')
cb.selectvis(field='1445*')
cb.setsolvegainspline (table='gcalph',mode='PHAS',splinetime=3600.0,preavg=60.0)cb.solve()

cb.setsolvegainspline (table='gcalamp',mode='AMP',splinetime=10800.0);
cb.solve();
cb.close();


In this example, a spline solution is first found for phase on a hourly timescale, then for amplitude on a three-hour timescale.

setvi(old=False, quiet=False)[source]¶

Use this method to control whether the modern (old=False) or old-style (old=True) VisibilityIterator is used by the calibration application. General users should avoid use of this function unless they understand what this means.

This method will be removed from the calibrater tool in v5.1.

Parameters

old (bool=False) - Use old-style VI, if old=True, else use new VI2
quiet (bool=False) - Warn in logger, if quiet=False

Returns

bool

Examples

cb.setvi(True)   
cb.open('ngc5921.ms')

smooth(tablein='', tableout='', field='', smoothtype='mean', smoothtime=60.0)[source]¶

This function provides for time-dependent smoothing of sampled calibration solutions. Currently supported types are ’G’, ’B’, and ’T’. (Smoothing on the frequency axis for ’B’ will be supported in the near future.)

Two (sliding) smoothing types are currenlty supported: ’median’ or ’mean’, one of these options should be specified in smoothtype. The full width (in seconds) of the smoothing filter should be specified in smoothtime. Amplitude and (ambiguity-corrected) phase are smoothed separately.

Use field to limit the smoothing operation to a subset of the fields (standard selection syntax) found in the calibration table (other fields will pass to the output table unsmoothed). If field is left blank, all fields in the table will be smoothed.

The smoothing is always done independently for each field, but scan boundaries are not observed. Thus, if the smoothtime is large enough, smoothing may occur over many boundaries.

Flagged solutions in the input table will not participate in the smoothing calculation, but will be replaced with smoothed values if the smoothing window covers one or more unflagged solutions when centered on the flagged point.

Pending improvements:

Add other smoothtypes?
Add spw and other selection on input table
Add A/P toggle

Parameters

tablein (string='') - Input calibration table
tableout (string='') - Output calibration table
field (variant='') - Limit smoothing to these fields (default is all fields)
smoothtype (string='mean') - The smoothing type: ‘mean’ or ‘median’
smoothtime (double=60.0) - Smoothing filter time constant (sec)

Returns

bool

Examples

cb.open('ngc5921.ms');
cb.smooth(tablein='in.gcal',tableout='out.gcal',
         smoothtype='median',smoothtime=60);
cb.close();


In this example, 'G' solutions for all fields in the table 'in.gcal' are 
smoothed using a median filter with a full-width of 60 seconds,
and the result written to 'out.gcal'.

solve()[source]¶: Execution of this function initiates a solve for the calibration component specified in a previous setsolve execution. Existing calibration components (as specified in one or more setapply executions) will be appropriately applied to the observed and model data according to their position in the Measurement Equation, and their commutation properties.

specifycal(caltable='', time='', spw='', antenna='', pol='', caltype='', parameter=[1.0], infile='', uniform=True)[source]¶

This function enables specifying calibration parameters externally.

Parameters

caltable (string='') - The calibration table name
time (string='') - Calibration timestamp
spw (string='') - Calibration spw(s)
antenna (string='') - Calibration antenna(s)
pol (string='') - Calibration polarization
caltype (string='') - Calibration timestamp
parameter (doubleVec=[1.0]) - Calibration parameters
infile (string='') - Ancillary input file
uniform (bool=True) - Assume uniform calibration values across the array

Returns

bool

Examples

cb.open('ap366.sim');

(TBD)

cb.close();

state()[source]¶: Request the apply/solve state of the calibrater tool. A listing of all calibration components that have been set for application or solving is written to the logger.

updatecaltable(caltable='')[source]¶

This method can be used to update a caltable (from v3.4 or later) to the current version of CASA.

The following updates are currently supported.

o At CASA v4.1.0, the OBSERVATION subtable and OBSERVATION_ID column were added to caltables. This method adds trivial versions of these elements to pre-v4.1 caltables.

Parameters

caltable (string='') - Name of the caltable.

Returns

bool

Examples

cb.updatecaltable("mycaltable");

validatecallib(callib='')[source]¶

TBD

Parameters

callib (record='') - A calibration library record

Returns

bool

Examples

TBD