ShadowFlagTask

ShadowFlagTask is an experimental task to detect and flag shadowed antennas on the fly. It supports only basic interferometry mode. For example, cases where off-axis beams are shadowed during offset pointings of the holography run will not be treated correctly. Even in the standard mode there are limitations with regard to off-axis beams: the algorithm uses the phase tracking centre and, therefore, would treat all beams the same if no fringe tracking per beam is done and if executed without distribution by beam (the latter limitation may be lifted in the future, if necessary). Note, antennas excluded from data recording may cause shadowing, but would not be detected. Antennas which ingest pipeline knows about (i.e. data are recorded) are treated as tracking the same source regardless whether they are participating in the observations at all or point somewhere else. The task requires uvw information to be present and, therefore, should be in the appropriate position in the task chain.

Configuration Parameters

The program requires a configuration file be provided on the command line. This section describes the valid parameters. In addition to mandatory parameters which are always required, individual tasks often have specific parameters which need to be defined only if a particular task is used. As for all tasks, parameters are taken from keys with tasks.name.params prefix (not shown in the table below) where name is an arbitrary name assigned to this task and used in tasklist (this allows us to run the same task more than once with different parameters). The type of the task defined by tasks.name.type should be set to ShadowFlagTask.

Parameter Type Default Description
dry_run boolean false If true, the task will only report when antennas are shadowed or unshadowed without actually flagging affected baselines.
dish_diamter float 12 Dish diamter in metres for shadowing calculations. Note, antennas sesne each other a bit earlier before geometrical shadowing occurs. In addition, increasing it by about a metre ensures the most offset beams are also flagged for the shortest separation between antennas if fringe tracking is not done per beam.

Example

########################## FlagTask ##############################

tasks.tasklist = [MergedSource, Merge, FringeRotationTask, ShadowGlagger, MSSink, FlagTask, TCPSink]

# dish diameter for flagging calculations
tasks.ShadowFlagger.params.dish_diamter = 15
# type of the task
tasks.ShadowFlagger.type = ShadowFlagTask