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calibrater.setsolvegainspline - Function

	Package	synthesis
	Module	calibrater
	Tool	calibrater

Specialization of setsolve for cubic spline G (time-dependent gain) solving

Synopsis
setsolvegainspline(table, append, mode, preavg, splinetime, refant, npointaver, phasewrap, unset)

Arguments

table	in	Output calibration table name
		Allowed:	String
		Default:	' '
append	in	Append to existing table?
		Allowed:	Bool
		Default:	F
mode	in	Phase or Amplitude mode?
		Allowed:	String from 'PHAS', 'AMP', or 'PHASAMP'
		Default:	'PHAS'
preavg	in	Pre-averaging interval (in sec)
		Allowed:	Float
		Default:	0.0
splinetime	in	Spline timescale (sec)
		Allowed:	Float
		Default:	10800
refant	in	Reference antenna. Default is none.
		Allowed:	Int
		Default:	-1
npointaver	in
		Allowed:	Int
		Default:	10
phasewrap	in
		Allowed:	Float
		Default:	250
unset	in	If T, unset solve of this type
		Allowed:	Bool
		Default:	F

Returns
Bool

Description

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 is available only for single polarization data.

The visibility data are averaged in frequency (for multi-channel data) prior to the solution. The spline timescale (time between knots) is specified in the splinetime paramter, which defaults to 10800 seconds (3 hours).

The solution is performed for phase and/or amplitude according to the mode parameter. 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), be sure run setapply to specify application of the first one when solving for the second one. The combined solution will be stored in the table specified for the second solve. If it is desired that the first solution table be preserved, use a new table name.

Different spline timescales may be used for phase and amplitude. If multiple fields are present, they will be used together to obtain a single solution. In mode='AMP', it is important that the model flux densities of each fields be correct, so that a single, consistent gain function can be properly determined.

The parameters npointaver and phasewrap 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.

When solve is run, the solutions are obtained, and postscript plot of baseline data and solutions is generated and deposited in your working directory. Its name is the same as table, with .ps appended.

At this time, it is not yet possible to plot the antenna-based solutions themselves using plotcal.

After obtained, these solutions should be applied using type='GSPLINE' in setapply.

Pending improvements:

• Generalize to dual polarization
• Enable plots of antenna-based solutions (currently, only plots of baseline data and solutions are produced)

Example

c:=calibrater('3C273XC1.MS');
c.setsolvegainspline (table='gcal',mode='PHAS');
c.solve();

c.reset();
c.setsolvegainspline (table='gcal',mode='AMP');
c.solve();
c.done();

In this example, a spline solution is first found for phase, then for amplitude.