NoMetadataSource

NoMetadataSource is a source task which does not depend on the metadata stream from the Telescope Operating System (TOS). It uses the same classes to receive visibility datagrams and decode the content as the main MergedSource task, but takes additional information, which is normally supplied via the metadata, from the configuration parameters. This is often handy for debugging because one could have the ingest pipeline loosely coupled to the rest of the system, and, therefore, being started and stopped manually at any time (as opposed to being started by TOS when the observations start with the data ingest commencing only when the appropriate metadata are received). As this task does not use the metadata stream at all, the metadata-specific Ice configuration (see the main page on Ingest pipeline for further details) is ignored. Note, the metadata supplied via the parset essentially lead to a static configuration with a single scan which cannot be changed without stopping the ingest pipeline. This unlike MergedSource, which receives the same information via the metadata and, therefore, can start new scans dynamically. Another consequence of this is inability to stop based on the special end of observation flag in the metadata. If NoMetadataSource task is used, the ingest pipeline has to be stopped via Ctrl+C or a signal.

Configuration Parameters

Ingest pipeline requires a configuration file to be provided on the command line. This section describes the valid parameters applicable to this particular task. These parameters need to be defined only if this 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. The type of the task defined by tasks.name.type should be set to NoMetadataSource. As mentioned above, this task is different from MergedSource in the way the information normally supplied in the metadata stream is obtained. Therefore, almost all configuration parameters of the MergedSource are understood by NoMetadataSource, and the exceptions are clearly mentioned in the parameter table for that task. The table below contains additional parameters understood by this task which fill in for the metadata content. Note, NoMetadataSource requires beam arrangement parameters to be defined in parset (see the section in Ingest pipeline).

Parameter	Type	Default	Description
centre_freq	quantity string	None	The central frequency of the observed band. This is the same value which is specified in the scheduling block parset and distributed via the metadata when MergedSource is used. Note, in the parallel mode, this is the centre of the band corresponding to the first correlator card (rather than the centre of the combined band).
target_name	string	None	Name of the target. This information is used just to fill the appropriate field in the measurement set.
target_direction	quantity string	None	Direction to the observed field. It is used to fill the appropriate field in the measurement set and can be treated as a phase centre if ingest pipeline does fringe rotation.
correlator_mode	string	None	Correlator mode (see main Ingest pipeline configuration) used for observations.

Example

########################## NoMetadataSource ##############################

tasks.tasklist = [NoMetadataSource, CalcUVWTask, TCPSink]

# record only 9 beams, discard the rest (determined by the
# beam configuration (see the main ingest pipeline documentation page)
tasks.NoMetadataSource.params.maxbeams = 9
# channel distribution - assuming serial mode, i.e. only value for
# rank zero is defined
tasks.NoMetadataSource.params.n_channels.0 = 216
# visibility source details
# do not reject any beams
tasks.NoMetadataSource.params.vis_source.max_beamid = 36
# reject slices with ID of 1 and above, for ASKAP it means
# baselines up to antenna 16. We use this for tests at MRO
tasks.NoMetadataSource.params.vis_source.max_slice = 0
# port to receive visibility data from (for rank 0, other ranks would listen
# port number equal to this parameter + rank, if we used this setup in the parallel mode)
tasks.NoMetadataSource.params.vis_source.port = 16384
# UDP receive buffer size in bytes (the value we used for ASKAP6 as in Nov2015)
tasks.NoMetadataSource.params.vis_source.receive_buffer_size = 67108864
# frequency of the band centre
tasks.NoMetadataSource.params.centre_freq = 0.9175GHz
# field name, this is just written to the FIELD table
tasks.NoMetadataSource.params.target_name = test-field1
# field centre/phase centre: Virgo
# in the task configuration as above (i.e. without ingest controlled phase tracking),
# this is just a piece of metadata to be written into the FIELD table
tasks.NoMetadataSource.params.target_direction = [12h30m49.43, +12d23m28.100, J2000]
# correlator mode
tasks.NoMetadataSource.params.correlator_mode = standard
# circular buffer size (in datagrams). We used this value in August 2014 commissioning run
tasks.NoMetadataSource.params.buffer_size = 15552
# type of the task
tasks.NoMetadataSource.type = NoMetadataSource