ms.tofits - Function

Convert a measurement set to a UVFITS file

Synopsis
tofits(fitsfile, column, fieldid, spwid, start, nchan, width, writesyscal, multisource, combinespw, writestation)

Arguments

fitsfile	in	Name of the new UVFITS file
		Allowed:	String
		Default:	no default
column	in	Data column to write, see above for options
		Allowed:	String
		Default:	corrected
fieldid	in	selection of fields to write out
		Allowed:	Vector of ints
		Default:	[]
spwid	in	selection of spectral windows to write out
		Allowed:	Vector of ints
		Default:	[]
start	in	First channel at output
		Allowed:	Int
		Default:	-1
nchan	in	number of channel to output
		Allowed:	Int
		Default:	-1
width	in	number of input channels to average for output
		Allowed:	Int
		Default:	-1
writesyscal	in	Write GC and TY tables
		Allowed:	Boolean
		Default:	F
multisource	in	Write in multisource format
		Allowed:	Boolean
		Default:	F
combinespw	in	Handle spectral window as IF
		Allowed:	Boolean
		Default:	F
writestation	in	Write station name instead of antenna name
		Allowed:	Boolean
		Default:	F

Description
This functions writes a UVFITS file that contains the data in the measurement set associated with this tool. The FITS file is always written in floating point format and the data is always stored in the primary array of the FITS file.

If the measurement set has been processed by many of the imaging tools, including imager and calibrator, it may contain additional data columns. You need to select which of these data columns will be written to the FITS file. The possible options are:

observed: This is the raw data as collected by the telescope. All interferometric measurement sets must contain this column. A synonym for 'observed' is 'data'.
corrected: This is the calibrated data. A synonym for 'corrected' is 'corrected_data'.
model: This is the visibilites that would be measured using the current model of the sky. A synonym for 'model' is 'model_data'.

The parsing of these strings is case insensitive. If any other option is specified then the observed data will be written.

By default a single-source UVFITS file is written, but if the measurement set contains more than one field or if you set the multisource argument to T a multi-source UVFITS file will be written. Because of limitations in the UVFITS format you have to ensure that the data shape is fixed for all the data you intend to write to one FITS file. See the general description of this tool for how you can select data to meet this condition.

The combinespw argument is used to control whether data from different spectral windows will be written as different entries in the FITS FQ (frequency) table or combined as different IF's within one entry in the FQ table. You should set this to T only if you know that the data from different spectral windows was observed simultaneously, and the data in the measurement set can be equally divided between all the spectral windows. Use of this switch is recommended for data to be processed in classic AIPS (if possible, e.g., standard dual IF observations).

The FITS GC (gain curve) and TY (system temperature) tables can be optionally written by setting the writesyscal argument to T. This is a rather WSRT-specific operation at the moment and may not work correctly for measurement sets from other telescopes.

The three parameters 'start', 'nchan', 'width' are for channel averaging while outputing the data to the fits file. The default values of -1 will copy the channels of the input as is. 'start' is input channel number that will be the first channel of the output. 'nchan' is the number of channel wanted in the output data. 'width' is the number of channels of the input data to make 1 channel of the output data. Hence (nchan*width+start-1) should not be larger than the number of channels in the original data.

Example

      include 'ms.g'
      myms := ms('3C273XC1.ms')
      myms.tofits('3C273XC1.fits', column='DATA'); 
      myms.done()

This example writes the observed data of a measurement set to a UVFITS file.

      include 'ms.g'
      myms := ms('big.ms')
      myms.tofits('part.fits', column='CORRECTED', fieldid=[1,2], spwid=[3]); 
      myms.done()

This example writes part (the first 2 fields and for the third spectral window) of the corrected data to the fits file.

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	Package	general
	Module	ms
	Tool	ms