Changes between Initial Version and Version 1 of Instructions

Timestamp:

06/25/08 17:43:48 (16 years ago)

Author:

DavidMcConnell

Comment:

--

Instructions

@@ +1 @@
+[wiki:WikiStart Up to main page]
+
+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.
+
+ 1. freqtab.dat lists the centre frequencies (in MHz) of channels in the final output data.
+ 1. 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.
+ 1. 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 ===
+ 1. 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
+}}}
+
+ 1. Perform the bandpass calibration
+{{{
+bpass 1934
+}}}
+
+=== Reduce the phase calibrator data ===
+ 1. Load the rpfits file
+{{{
+pload 3c138.rpf
+}}}
+ 1. Copy the bandpass tables
+{{{
+gcopy 3c138 1934
+}}}
+ 1. Extract the phase vs parallactic angle information from scans of the polarised calibrator
+{{{
+polcalr 3c138
+}}}
+ 1. Determine polarisation parameters (leakages and phase difference between the signals from the two polarization channels) of the system from the phase data
+{{{
+psolve 3c138
+}}}
+To get a consistent pair of output files, the procedure needs to be executed twice. An example follows.
+
+{{{
+   polcalr 3c138
+   psolve 3c138 /xs
+   polcalr 3c138
+   psolve 3c138 /xs
+
+}}}
+
+
+=== Reduce the astronomical data ===
+ 1. Load the rpfits file
+{{{
+pload source.rpf
+}}}
+ 1. Copy the bandpass tables and polarisation corrections
+{{{
+gcopy source 1934 3c138
+}}}
+ 1. 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) ''
+ 1. Reads the rpfits file;
+ 2. apply the bandpass calibration;
+ 3. transform to Stokes vectors;
+ 4. correct for instrumental phase;
+ 5. reorder the DFB output bins;
+ 6. properly label scan data with interpolated sky positions;
+ 7. average into final frequency channels;
+ 8. apply leakage calibration (if file polparams.dat is present);
+ 9. write out in sdfits format.
+
+What calscans does not do (but could with some small software changes):
+1. Subtract baselines scan data;
+2. rotate Q,U from telescope to sky coordinates.
+
+