0000220: Low-level baseline-dependent calibration errors
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ID Category Severity Reproducibility Date Submitted Last Update
0000220 [DZB] 0.unknown/unspecified major always 20-01-10 12:22 23-02-11 19:19
Reporter Gyula Jozsa View Status public  
Assigned To Hans van der Marel
Priority low Resolution open  
Status progressing  
Summary 0000220: Low-level baseline-dependent calibration errors
Description For L-band line observations using 1 band, after calibration, baseline-dependent amplitude calibration errors of the order of 1-2 percent on a few baselines become evident. The consequence is that a reliable calibration of those baselines cannot be achieved using antenna gains only, which may seriously affect deep observations requiring a high dynamical range. From measurement to measurement those baselines can vary, but the pattern can be constant over a large number of repeated measurements (hence the errors are enhanced and do not enter as noise).

Since the problem occurs quite often, the reproducibility is set to always, not sometimes (there's nothing in-between).

Most probably this is a backend problem.
Additional Information The viewgraph shows crosscorrelations from an observation of 3C147, after a (self)calibration. Obviously, the amplitude of RT1-3 is high.
nr subbands 1
nr polarisations 2
nr channels 1024
bandwidth 10 MHz
multi-subarray no
recirculation no
Attached Files  baseline_errors.pdf [^] (23,930 bytes) 20-01-10 12:22

- Relationships
related to 0000329feedback  Baseline dependent gain errors (closure errors) 

- Notes
(0000233)
Gyula Jozsa
20-01-10 12:26

 G. Heald states that deleting affected baselines help the problem (this means data loss), while a baseline-dependent calibration does not solve it. This indicates a time-dependent variability of the baseline gains.
 
(0000331)
Gyula Jozsa
23-02-11 19:18

 A recent inspection showed that the issue is severely reduced in one observation since issue 329 has been solved. Monitoring continues, but with low priority.
 

- Issue History
Date Modified Username Field Change
20-01-10 12:22 Gyula Jozsa New Issue
20-01-10 12:22 Gyula Jozsa File Added: baseline_errors.pdf
20-01-10 12:22 Gyula Jozsa nr subbands  => 1
20-01-10 12:22 Gyula Jozsa nr polarisations  => 2
20-01-10 12:22 Gyula Jozsa nr channels  => 1024
20-01-10 12:22 Gyula Jozsa bandwidth  => 10 MHz
20-01-10 12:22 Gyula Jozsa multi-subarray  => no
20-01-10 12:22 Gyula Jozsa recirculation  => no
20-01-10 12:26 Gyula Jozsa Note Added: 0000233
25-01-10 09:49 Harm Munk Status new => assigned
25-01-10 09:49 Harm Munk Assigned To  => Hans van der Marel
27-01-11 18:37 Gyula Jozsa Relationship added related to 0000329
23-02-11 19:18 Gyula Jozsa Note Added: 0000331
23-02-11 19:19 Gyula Jozsa Priority high => normal
23-02-11 19:19 Gyula Jozsa Status assigned => progressing
23-02-11 19:19 Gyula Jozsa Priority normal => low