Version 2 (modified by 15 years ago) (diff) | ,
---|
Instructions for operating the Parkes continuum polarimetry software.
The data are acquired from the pulsar Digital Filter Bank correlator in "rpfits" format and are written to the area /DATA/PKCCC2_1/corr/dat/.
Sequence of Operations
Three files are necessary before the process can begin.
- freqtab.dat lists the centre frequencies (in MHz) of channels in the final output data.
- feed.dat is used to transform raw data to Stokes vectors (in the telescope frame). It defines the transformation in terms of reordering and sign changes.
- 0637Flux.dat tabulates the frequency dependence of the flux and polarization characteristics of the polarized calibrator (3c138, B0637-75, ...).
These files should be in the working directory. Copies will be assigned to each data file being processed.
Reduce the bandpass calibrator data
- Load the rpfits file into "parkespol" format.
pload 1934.rpf # # This will create a directory 1934/ and # with contents # -rw-r--r-- 1 mcc381 atculg 2355200 Feb 1 22:23 data.rpf # -rw-r--r-- 1 mcc381 atculg 204 Feb 2 11:06 feed.dat # -rw-r--r-- 1 mcc381 atculg 646 Feb 2 11:06 freqtab.dat
The original rpfits file is maintained so you will have two copies of the data.
- Perform the bandpass calibration
bpass 1934
Reduce the phase calibrator data
- Load the rpfits file
pload 2006-11-20_1401_3c138_Cal_DEC.rpf
- Copy the bandpass tables
gcopy 2006-11-20_1401_3c138_Cal_DEC 1934
- Extract the phase vs parallactic angle information from scans of the polarised calibrator
polcalr 2006-11-20_1401_3c138_Cal_DEC
- Determine polarisation parameters (leakages and phase difference between the signals from the two polarization channels) of the system from the phase data
psolve 2006-11-20_1401_3c138_Cal_DEC 3c138 /xs
To get a consistent pair of output files, the procedure needs to be executed twice. An example follows.
polcalr 2006-11-20_1401_3c138_Cal_DEC 3c138 psolve 2006-11-20_1401_3c138_Cal_DEC 3c138 3c138 /xs polcalr 2006-11-20_1401_3c138_Cal_DEC 3c138 psolve 2006-11-20_1401_3c138_Cal_DEC 3c138 3c138 /xs
Reduce the astronomical data
- Load the rpfits file
pload source.rpf
- Copy the bandpass tables and polarisation corrections
gcopy source 1934 3c138
- Apply the calibrations and write results as a single-dish FITS file.
calscans.pl list
where list is a list of the data files to be calibrated.
If calscans is executed successively with the same outfile named it appends data from each execution into that file.
What calscans does: (check that this desription is correct)
- Reads the rpfits file;
- apply the bandpass calibration;
- transform to Stokes vectors;
- correct for instrumental phase;
- reorder the DFB output bins;
- properly label scan data with interpolated sky positions;
- average into final frequency channels;
- apply leakage calibration (if file polparams.dat is present);
- write out in sdfits format.
What calscans does not do (but could with some small software changes):
- Subtract baselines scan data;
- rotate Q,U from telescope to sky coordinates.