Demixer

Demix bright sources, i.e. calibrate in the direction of the birght sources and subtract the bright sources from the data. Note that the calibration solution is assumed to be constant over the entire frequency range, so this will only work on relatively small bandwidth (e.g. a single sub-band).

inputs

type

type:: string
default:: demixer
doc:: Case-insensitive step type; must be ‘demixer’ (or ‘demix’) .

baseline

type:: string
default:: ""
doc:: Baselines to demix. See Description of baseline selection parameters

blrange

type:: double[]

default

doc:: Baselines to demix. See Description of baseline selection parameters

corrtype

type:: string
default:: cross
doc:: Baselines to demix. Correlation type to match? Must be auto, cross, or an empty string .

defaultgain

type:: double
default:: 1
doc:: The default and initial gain for the directional gains that are computed internally .

demixfreqresolution

type:: float
default:: 0
doc:: Frequency resolution to use when demixing, in Hz (or append “MHz” or “kHz” to specify it in those units). If this is given, and is greater than zero, it overrides <step>.demixfreqstep. This will not exceed the bandwidth of a subband, even if a larger value is given .

demixfreqstep

type:: int
default:: 0
doc:: Number of channels to average when demixing. It is truncated if exceeding the actual number of channels. It defaults to the averaging used for the subtract .

demixtimeresolution

type:: float
default:: 0
doc:: Time resolution to use when demixing, in seconds. If this is given, and is greater than zero, it overrides <step>.demixtimestep .

demixtimestep

type:: int
default:: 0
doc:: Number of time slots to average when demixing. It is truncated if exceeding the actual number of times. It defaults to the averaging used for the subtract .

freqstep

type:: int
default:: 1
doc:: Number of channels to average when subtracting. It is truncated if exceeding the actual number of channels. Note that the data itself will also be averaged by this amount .

ignoretarget

type:: boolean
default:: False
doc:: false = project the target source away; true = ignore the target .

instrumentmodel

type:: string
default:: instrument
doc:: The name of the ParmDB to use. The ParmDB does not need to exist. If it does not exist it will be created .

lbfgs.historysize

type:: int
default:: 10
doc:: If using the LBFGS solver, the history size, specified as a multiple of the parameter vector, to use to approximate the inverse Hessian .

lbfgs.robustdof

type:: double
default:: 2.0
doc:: If using the LBFGS solver, the degrees of freedom (DOF) given to the noise model. The larger this becomes (more than 30), the noise model behaves as a Gaussian. The smaller values make the noise model more robust to outliers in the data .

maxiter

type:: int
default:: 50
doc:: Maximum number of iterations used in the LM solve .

modelsources

type:: string[]
default:: []
doc:: Names of sources with models to take into account when solving. the sources must exist as patches in the SourceDB. Note that the target should NOT be part of this parameter. If a model of the target has to be used, it has to be given in parameter targetsource.

ntimechunk

type:: int
default:: 0
doc:: Number of demix time slots (after averaging) that are processed jointly in as much a parallel way as possible. If subtract uses different time averaging, it has to fit integrally .

othersources

type:: string[]
default:: []
doc:: Names of sources of which the direction is taken into account when demixing by projecting the directions away. The direction needs to be specified if the source is unknown (which is usually the case). It can be done using parameters <step>.<sourcename>.phasecenter.

propagatesolutions

type:: boolean
default:: True
doc:: If set to true, solutions of a time slot are used as initial values for the next time slot. If set to false, the diagonal elements of the Jones matrix are initialized to one and the off-diagonal elements to zero .

skymodel

type:: string
default:: sky
doc:: Sourcedb (created with makesourcedb) with the sky model to calibrate on. When the path ends with .skymodel or .txt DP3 expects a skymodel file as used by makesourcedb. This makes it possible to directly use a skymodel file without using makesourcedb to convert the file.

step_name

type:: string
default:: demix
doc:: unique name for the step .

subtractsources

type:: string[]?
default:: []
doc:: Names of the sources to subtract. If none are given, demixing comes down to averaging. The sources must exist as patches in the SourceDB .

targetsource

type:: string
default:: ""
doc:: This setting can be used to specify the name of the source model of the target. If given, the target source model (its patch in the SourceDB) is taken into account when solving; in this case parameter othersources cannot be given. It cannot be given if ignoretarget=true. If not given, the target is projected away or ignored (depending on parameter ignoretarget).

timestep

type:: int
default:: 1
doc:: Number of time slots to average when subtracting. It is truncated if exceeding the actual number of times. Note that the data itself will also be averaged by this amount .

uselbfgssolver

type:: boolean
default:: False
doc:: If true, use LBFGS solver instead of the LM solver (or LSQfit) .