1

Data Inspection: The Good, the Bad, and the Ugly

2

Getting the Data

cd /lustre/aoc/users/yourusername/cp -r /lustre/aoc/ftp/e2earchive/stage/QM0129/* .importevla(asdm='12B-211.sb12168671.eb13834174.56240.03889960648',vis='L1157.ms', applyflags=True)

3

Data Inspection - Phases

plotms(vis='CB230.ms',xaxis='time',yaxis='phase',field='J2009+7229',correlation='RR',spw='5',iteraxis='baseline',avgchannel='64')

4

Data Inspection - Phases

plotms(vis='CB230.ms',xaxis='time',yaxis='phase',field='J2009+7229',correlation='RR',spw='5',iteraxis='baseline',avgchannel='64')

5

Data Inspection - Phases

● Calibrator data are ok, but source should be flagged between phase jumps

6

Data Inspection - Phases

● Sometimes phase jump is present in the same scans for a particular antenna, EA11 in this case

7

Data Inspection - Phases

● Phase jump for first two scans on EA11 again, but another one in the middle of track

8

Data Inspection - Amps

plotms(vis='CB230.ms',xaxis='time',yaxis='amp',field='J2009+7229',correlation='RR',spw='5',iteraxis='baseline',avgchannel='64')

9

Data Inspection - Amps

● Amplitude drops at beginning of scans reflect antennas not on source, flag with mode=quack● In general, look for amplitudes that are consistently low compared to overall trend

10

Data Inspection - Deformatter

plotms(vis='CB230.ms',xaxis='frequency',yaxis='amp',field='J2009+7229',correlation='RR',spw='0~15',iteraxis='baseline',avgtime='120')

plotms(vis='CB230.ms',xaxis='frequency',yaxis='amp',field='J2009+7229',correlation='LL',spw='0~15',iteraxis='baseline',avgtime='120')

GOOD

11

Data Inspection - Deformatter

plotms(vis='CB230.ms',xaxis='frequency',yaxis='amp',field='J2009+7229',correlation='RR',spw='0~15',iteraxis='baseline',avgtime='120')

plotms(vis='CB230.ms',xaxis='frequency',yaxis='amp',field='J2009+7229',correlation='LL',spw='0~15',iteraxis='baseline',avgtime='120')

BAD

12

Calibration Inspection – Gain Amps

plotcal('L1157.ms.gaincal',yaxis='amp',xaxis='time',iteration='baseline',field='J2006+6424',subplot=321,plotrange=[-1,-1,0,2])● Gain amplitudes should be ~1, values significantly different indicate possible bad data

13

Calibration Inspection – Gain Amps

plotcal('L1157.ms.gaincal',yaxis='amp',xaxis='time',iteration='baseline',field='J2006+6424',subplot=321,plotrange=[-1,-1,0,2])

14

Calibration Inspection – Gain Amps

plotcal('L1157.ms.gaincal',yaxis='amp',xaxis='time',iteration='baseline',field='J2006+6424',subplot=321,plotrange=[-1,-1,0,2])

15

Calibration Inspection – Gain Phases

plotcal('L1157.ms.gaincal',yaxis='phase',xaxis='time',iteration='antenna',field='J2006+6424',subplot=111)● Complex because point for each spw and polarization, should be able to connect dots

16

Post Calibration Inspection

plotms(vis='L1157.ms',xaxis='time',yaxis='phase',field='J2006+6424',correlation='RR',spw='5',iteraxis='baseline',avgchannel='64',ydatacolumn='corrected')● Phase should be distributed around zero, otherwise there was a problem

17

Post Calibration Inspection

plotms(vis='L1157.ms',xaxis='time',yaxis='phase',field='J2006+6424',correlation='RR',spw='5',iteraxis='baseline',avgchannel='64',ydatacolumn='corrected')● Amplitude should be distributed around the flux density derived, otherwise there was a problem

18

Post Calibration Inspection

plotms(vis='L1157.ms',xaxis='uvwave',yaxis='amp',field='J2006+6424',correlation='RR',spw='5',iteraxis='none',avgchannel='64',ydatacolumn='corrected')● Calibrator should have constant amplitude vs. uv distance, deviations due to problems/poor coherence, or resolved calibrator

19

Post Calibration Inspection

plotms(vis='L1157.ms',xaxis='time',yaxis='amp',field='L1157',correlation='RR',spw='5',iteraxis='none',avgchannel='64',ydatacolumn='corrected')● Look for points that are significantly outside the mean distribution

20

C-Band RFI

● Some persistent, some intermittent● Pipeline doesn’t catch persistent RFI

● Must flag affected channels out manually