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How can I correct for improperly flagged shadowed data in CASA 3.4 ?
26 February 2013 02:40 PM

A small fraction of Cycle 0 data sets have been found to be impacted by a bug in the CASA 3.4 task 'tflagdata'. When 'tflagdata' in CASA 3.4 was used to flag shadowed antennas, instead the shadowing antennas were flagged. The impact of this bug on delivered data sets has been found to be minimal, but the correction to flag the correct antennas is easy to apply. Simply rerun the calibration script(s) in CASA 3.4, changing the 'tflagdata' command to 'flagdata' in step 8 or 9 (for the shadow flagging only).

Reversing only the flagging related to the improperly flagged data, with the goal of recovering data from the shadowing antenna, is not always possible with the products delivered to PIs. Instead, one can request the original ASDM, import that into a measurement set, and run the corrected calibration script on that measurement set.

CASA 3.4 became the standard release for data reduction in September 2012, when the array was in an extended configuration. This bug was not present in CASA 3.3, which was used to reduce data when ALMA when in a compact configuration. The bug was corrected in CASA 4.0.1.

CASA can be downloaded here.

All PIs of affected projects have been contacted via the ALMA Helpdesk. Futhermore, a note will be added to the README file included in archive packages before the data become public.


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