bandpass – Calculates a bandpass calibration solution – calibration task
Description
Determines the amplitude and phase as a function of frequency for each spectral window containing more than one channel. Strong sources (or many observations of moderately strong sources) are needed to obtain accurate bandpass functions. The two solution choices are: Individual antenna/based channel solutions ‘B’; and a polynomial fit over the channels ‘BPOLY’. The ‘B’ solutions can determined at any specified time interval, and is recommended if each channel has good signal-to-noise.
Parameters
Parameter |
Default |
Description |
|---|---|---|
vis |
|
Name of input visibility file |
caltable |
|
Name of output bandpass calibration table |
field |
|
Select field using field id(s) or field name(s) |
spw |
|
Select spectral window/channels |
intent |
|
Select observing intent |
selectdata |
|
Other data selection parameters |
timerange |
|
Select data based on time range |
uvrange |
|
Select data within uvrange (default units meters) |
antenna |
|
Select data based on antenna/baseline |
scan |
|
Scan number range |
observation |
|
Select by observation ID(s) |
msselect |
|
|
solint |
|
Solution interval in time[,freq] |
combine |
|
Data axes which to combine for solve (obs, scan, spw, and/or field) |
refant |
|
Reference antenna name(s) |
minblperant |
|
Minimum baselines _per antenna required for solve |
minsnr |
|
Reject solutions below this SNR (only applies for bandtype = B) |
solnorm |
|
Normalize average solution amplitudes to 1.0 |
bandtype |
|
Type of bandpass solution (B or BPOLY) |
smodel |
|
Point source Stokes parameters for source model. |
append |
|
Append solutions to the (existing) table |
fillgaps |
|
Fill flagged solution channels by interpolation |
degamp |
|
Polynomial degree for BPOLY amplitude solution |
degphase |
|
Polynomial degree for BPOLY phase solution |
visnorm |
|
Normalize data prior to BPOLY solution |
maskcenter |
|
Number of channels to avoid in center of each band |
maskedge |
|
Fraction of channels to avoid at each band edge (in %) |
docallib |
|
Use callib or traditional cal apply parameters |
callib |
|
Cal Library filename |
gaintable |
|
Gain calibration table(s) to apply on the fly |
gainfield |
|
Select a subset of calibrators from gaintable(s) |
interp |
|
Interpolation mode (in time) to use for each gaintable |
spwmap |
|
Spectral windows combinations to form for gaintables(s) |
parang |
|
Apply parallactic angle correction |
Parameter Explanations
vis
''
- Name of input visibility file
default: non
Example: vis=’ngc5921.ms’
caltable
''
- Name of output bandpass calibration table
default: none
Example: caltable=’ngc5921.bcal’
field
''
- Select field using field id(s) or field name(s)
default: ‘’ –> all fields
Use ‘go listobs’ to obtain the list id’s or names. If field string is a non-negative integer, it is assumed a field index, otherwise, it is assumed a field name.
Examples: field=’0~2’; field ids 0,1,2 field=’0,4,5~7’; field ids 0,4,5,6,7 field=’3C286,3C295’; field named 3C286 and 3C295 field = ‘3,4C*’; field id 3, all names starting with 4C
spw
''
Select spectral window/channels
Examples: spw=’0~2,4’; spectral windows 0,1,2,4 (all channels) spw=’<2’; spectral windows less than 2 (i.e. 0,1) spw=’0:5~61’; spw 0, channels 5 to 61, INCLUSIVE spw=’*:5~61’; all spw with channels 5 to 61 spw=’0,10,3:3~45’; spw 0,10 all channels, spw 3, channels 3 to 45. spw=’0~2:2~6’; spw 0,1,2 with channels 2 through 6 in each. spw=’0:0~10;15~60’; spectral window 0 with channels 0-10,15-60. (NOTE ‘;’ to separate channel selections) spw=’0:0~10^2,1:20~30^5’; spw 0, channels 0,2,4,6,8,10, spw 1, channels 20,25,30 type ‘help par.selection’ for more examples.
intent
''
- Select observing intent
default: ‘’ (no selection by intent)
Example: intent=’BANDPASS’ (selects data labelled with BANDPASS intent)
selectdata
True
- Other data selection parameters
default: True
timerange
''
- Select data based on time range
Subparameter of selectdata=True default = ‘’ (all)
Examples: timerange = ‘YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss’ (Note: if YYYY/MM/DD is missing date defaults to first day in data set.) timerange=’09:14:0~09:54:0’ picks 40 min on first day timerange= ‘25:00:00~27:30:00’ picks 1 hr to 3 hr 30min on NEXT day timerange=’09:44:00’ pick data within one integration of time timerange=’>10:24:00’ data after this time
uvrange
''
- Select data within uvrange (default units meters)
Subparameter of selectdata=True default: ‘’ (all)
Examples: uvrange=’0~1000klambda’; uvrange from 0-1000 kilo-lambda uvrange=’>4klambda’;uvranges greater than 4 kilolambda
antenna
''
- Select data based on antenna/baseline
Subparameter of selectdata=True default: ‘’ (all)
Examples: antenna=’5&6’; baseline between antenna index 5 and index 6. antenna=’VA05&VA06’; baseline between VLA antenna 5 and 6. antenna=’5&6;7&8’; baselines with indices 5-6 and 7-8 antenna=’5’; all baselines with antenna index 5 antenna=’05’; all baselines with antenna number 05 (VLA old name) antenna=’5,6,10’; all baselines with antennas 5,6,10 index numbers
Note: just for antenna selection, an integer (or integer list) is converted to a string and matched against the antenna ‘name’ first. Only if that fails, the integer is matched with the antenna ID. The latter is the case for most observatories, where the antenna name is not strictly an integer.
scan
''
- Scan number range
Subparameter of selectdata=True default: ‘’ = all
Check ‘go listobs’ to insure the scan numbers are in order.
observation
''
- Select by observation ID(s)
Subparameter of selectdata=True default: ‘’ = all
Example: observation=’0~2,4’
msselect
''
Optional complex data selection (ignore for now)
solint
'inf'
- Solution interval in time[,freq]
default: ‘inf’ (~infinite, up to boundaries controlled by combine, with no pre-averaging in frequency) Options for time: ‘inf’ (~infinite), ‘int’ (per integration), any float or integer value with or without units Options for freq: an integer with ‘ch’ suffix will enforce pre-averaging by the specified number of channels. A numeric value suffixed with frequency units (e.g., ‘Hz’,’kHz’,’MHz’) will enforce pre-averaging by an integral number of channels amounting to no more than the specified bandwidth.
Examples: solint=’1min’; solint=’60s’, solint=60 –> 1 minute solint=’0s’; solint=0; solint=’int’ –> per integration solint=’-1s’; solint=’inf’ –> ~infinite, up to boundaries enforced by combine solint=’inf,8Mhz’ –> ~infinite in time, with 8MHz pre-average in freq solint=’int,32ch’ –> per-integration in time, with 32-channel pre-average in freq
combine
'scan'
- Data axes to combine for solving
default: ‘scan’ –> solutions will break at obs, field, and spw boundaries but may extend over multiple scans (per obs, field and spw) up to solint. Options: ‘’,’obs’,’scan’,’spw’,field’, or any comma-separated combination in a single string.
Example: combine=’scan,spw’ –> extend solutions over scan boundaries (up to the solint), and combine spws for solving.
refant
''
Reference antenna name(s); a prioritized list may be specified
default: ‘’ (no reference antenna)
Examples: refant=’13’ (antenna with index 13) refant=’VA04’ (VLA antenna #4) refant=’EA02,EA23,EA13’ (EVLA antenna EA02, use EA23 and EA13 as alternates if/when EA02 drops out)
Use ‘go listobs’ for antenna listing
minblperant
int(4)
- Minimum baselines _per antenna required for solve
default: 4
Antennas with fewer baselines are excluded from solutions. Amplitude solutions with fewer than 4 baselines, and phase solutions with fewer than 3 baselines are only trivially constrained, and are no better than baseline-based solutions.
example: minblperant=10 –> Antennas participating on 10 or more baselines are included in the solve.
minsnr
float(3.0)
Reject solutions below this SNR (only applies for bandtype = B)
default: 3.0
solnorm
False
Normalize bandpass amplitudes and phase for each spw, pol, ant, and timestamp
default: False (no normalization)
bandtype
'B'
- Type of bandpass solution (B or BPOLY)
default: ‘B’
‘B’ does a channel by channel solution for each specified spw. ‘BPOLY’ is somewhat experimental. It will fit an nth order polynomial for the amplitude and phase as a function of frequency. Only one fit is made for all specified spw, and edge channels should be omitted. Use taskname=plotcal in order to compare the results from B and BPOLY.
Example: bandtype=’BPOLY’
smodel
numpy.array( [ ] )
Point source Stokes parameters for source model.
append
False
- Append solutions to the (existing) table
default: False (overwrite existing table or make new table)
Append solutions to the (existing) table. Appended solutions must be derived from the same MS as the existing caltable, and solution spws must have the same meta-info (according to spw selection and solint) or be non-overlapping.
fillgaps
int(0)
- Fill flagged solution channels by interpolation
Subparameter of bandtype=’B’ default: 0 (don’t interpolate)
Example: fillgaps=3 (interpolate gaps 3 channels wide and narrower)
degamp
int(3)
- Polynomial degree for BPOLY amplitude solution
Subparameter of bandtype=’BPOLY’ default: 3
Example: degamp=2
degphase
int(3)
- Polynomial degree for BPOLY phase solution
Subparameter of bandtype=’BPOLY’ default: 3
Example: degphase=2
visnorm
False
- Normalize data prior to BPOLY solution
Subparameter of bandtype=’BPOLY’ default: False
Example: visnorm=True
maskcenter
int(0)
- Number of channels to avoid in center of each band
Subparameter of bandtype=’BPOLY’ default: 0
Example: maskcenter=5 (BPOLY only)
maskedge
int(5)
- Fraction of channels to avoid at each band edge (in %)
Subparameter of bandtype=’BPOLY’ default: 5
Example: maskedge=3 (BPOLY only)
docallib
False
- Control means of specifying the caltables
default: False –> Use gaintable, gainfield, interp, spwmap, calwt.
If True, specify a file containing cal library in callib
callib
''
- Cal Library filename
Subparameter of callib=True
If docallib=True, specify a file containing cal library directives
gaintable
numpy.array( [ ] )
- Gain calibration table(s) to apply on the fly
Subparameter of callib=False default: ‘’ (none)
Examples: gaintable=’ngc5921.gcal’ gaintable=[‘ngc5921.ampcal’,’ngc5921.phcal’]
gainfield
numpy.array( [ ] )
- Select a subset of calibrators from gaintable(s)
Subparameter of callib=False default:’’ –> all sources in table
gaintable=’nearest’ –> nearest (on sky) available field in table. Otherwise, same syntax as field
Examples: gainfield=’0~2,5’ means use fields 0,1,2,5 from gaintable gainfield=[‘0~3’,’4~6’] (for multiple gaintables)
interp
numpy.array( [ ] )
- Interpolation mode (in time[,freq]) to use for each gaintable
Subparameter of callib=False default: ‘’ –> ‘linear,linear’ for all gaintable(s)
When frequency interpolation is relevant (B, Df, Xf), separate time-dependent and freq-dependent interp types with a comma (freq _after_ the comma). Specifications for frequency are ignored when the calibration table has no channel-dependence. Time-dependent interp options ending in ‘PD’ enable a “phase delay” correction per spw for non-channel-dependent calibration types. For multi-obsId datasets, ‘perobs’ can be appended to the time-dependent interpolation specification to enforce obsId boundaries when interpolating in time.
Examples: interp=’nearest’ (in time, freq-dep will be linear, if relevant) interp=’linear,cubic’ (linear in time, cubic in freq) interp=’linearperobs,splineflag’ (linear in time per obsId, spline in freq with channelized flagging) interp=’,spline’ (spline in freq; linear in time by default) interp=[‘nearest,spline’,’linear’] (for multiple gaintables)
spwmap
numpy.array( [ ] )
- Spectral windows combinations to form for gaintables(s)
Subparameter of callib=False default: [] (apply solutions from each spw to that spw only)
Examples: spwmap=[0,0,1,1] means apply the caltable solutions from spw = 0 to the spw 0,1 and spw 1 to spw 2,3. spwmap=[[0,0,1,1],[0,1,0,1]] (for multiple gaintables)
parang
False
- Apply parallactic angle correction
default: False
If True, apply the parallactic angle correction (required for polarization calibration)