Phase jump on CA03
Posted: Fri Feb 06, 2015 8:28 pm
Hi all,
I've encountered a problem in the calibration for the secondary (2333-528) on our 21cm continuum data taken on 2014-12-28. After I calibrated the data, I checked the calibration solutions by typing the following command:
gpplt vis=2014-12-28/2333-528.2100 yaxis=phase options=xygains device=/xs
I see the plots as shown in the image attached (2014-12-28_phase_2333-528.tiff). The large, sudden jump in the XY phase for CA03 worries me. When the jump occurred (UT ~4:00), there weren't any problems going on with the array. Is that normal? And given that we are only interested in stokes I, will it matter? I didn't see this phenomenon on any of our 20 other observation days. There has been a phase drift problem on CA03 ever since sometime in November/December 2014 (see the attached vis screenshots). Could this be part of the problem? Is the data for CA03 going to be recoverable if its phases were drifting, as seen in the screenshots?
You can also see less severe phase offsets for CA01, CA05 and CA06 after UT ~11:00 (there was a problem with the array at around UT ~10:00-11:00, but another pcal wasn't necessary after the problem occurred). Is this normal? These phase offsets may be due to bad data that hasn't been flagged yet, so I will look into that...
Thanks,
Andrew
I've encountered a problem in the calibration for the secondary (2333-528) on our 21cm continuum data taken on 2014-12-28. After I calibrated the data, I checked the calibration solutions by typing the following command:
gpplt vis=2014-12-28/2333-528.2100 yaxis=phase options=xygains device=/xs
I see the plots as shown in the image attached (2014-12-28_phase_2333-528.tiff). The large, sudden jump in the XY phase for CA03 worries me. When the jump occurred (UT ~4:00), there weren't any problems going on with the array. Is that normal? And given that we are only interested in stokes I, will it matter? I didn't see this phenomenon on any of our 20 other observation days. There has been a phase drift problem on CA03 ever since sometime in November/December 2014 (see the attached vis screenshots). Could this be part of the problem? Is the data for CA03 going to be recoverable if its phases were drifting, as seen in the screenshots?
You can also see less severe phase offsets for CA01, CA05 and CA06 after UT ~11:00 (there was a problem with the array at around UT ~10:00-11:00, but another pcal wasn't necessary after the problem occurred). Is this normal? These phase offsets may be due to bad data that hasn't been flagged yet, so I will look into that...
Thanks,
Andrew