RM sign flipping issue for VCS observation in early 2018

I beam formed on PSR J0630-2834, J0742-2822 with obs 1202130016 (Feb 2018); PSR J0630-2834, J0742-2822, and J0737-3039A with obs 1205063600 (Mar 2018). All of them shows negtive RM value, while they all should be positive. The same pulsar beamformed with previous observation (e.g. 1165080856) do not have this problem when processing with the same method.

The circular polarisation and PA curve also sign-flipped.

The causition is still unknown. Might be useful to check with imaging people.

For detailed info: https://docs.google.com/document/d/1DREA2dXqSzoM7ee2K03ySNdG6qQI6HbsAXy8RW8aV8g/edit?usp=sharing

==depol_Gum notes 2021==

beamform.nf --obsid 1165080856 --calid 1165092496 --all --pointings 06:30:49.40_-28:34:42.76 #(without pol corrections)

cat /pawsey/mwa/software/profiles/mwavcs_pulsar.profile
module use /pawsey/mwa/software/python3/modulefiles
module load vcstools/smcsweeney
process_vcs.py -m beamform -o 1165080856 -O 1165092496 -a -p "06:30:49.40_-28:34:42.75" --UV_phase 5.6e-09,-0.06283 --vcstools_version smcsweeney --DI_dir /astro/mwavcs/vcs/1165080856/cal/1165092496/rts/ --flagged_tiles /astro/mwavcs/vcs/1165080856/cal/1165092496/rts/flagged_tiles.txt

#!/bin/bash -l
#SBATCH --export=NONE
#SBATCH --job-name=DOdspsr
#SBATCH --account=mwavcs
#SBATCH --partition=gpuq
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=1
#SBATCH --cpus-per-task=1
#SBATCH --mem=370gb
#SBATCH --gres=gpu:1
#SBATCH --time=08:55:00

module use /pawsey/mwa/software/python3/modulefiles
module load vcstools/master
module load mwa_search/master
module load pgplot
module load psrcat
module load singularity

Nbin=128
OBID=1165080856
PSRJ=J0630-2834
FITS_dir=/group/mwaops/xuemy/depol_Gum/${OBID}/pointing/${PSRJ}

psrcat -e ${PSRJ} > ${PSRJ}.par
/pawsey/mwa/singularity/dspsr/dspsr.sif dspsr -cont -t 16 -E ${PSRJ}.par -K -b ${Nbin} -L 10 -O ar_files/${PSRJ}/${PSRJ}_n${Nbin}_ch109-132 ${FITS_dir}/${OBID}_00??.fits